Ozone Reactions with Organic Compounds (Advances in Chemistry Series 112)

Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.fw001 Ozone Reactions with Organic Compounds In Ozone React...

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Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.fw001

Ozone Reactions with Organic Compounds

In Ozone Reactions with Organic Compounds; Bailey, P.; Advances in Chemistry; American Chemical Society: Washington, DC, 1972.



Ozone Reactions with Organic Compounds

A symposium sponsored by Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.fw001

the D i v i s i o n of Petroleum Chemistry at the 161st Meeting of the American Chemical Society, Los Angeles, Calif., M a r c h 29-30, 1 9 7 1 . Philip

S. B a i l e y ,

Symposium Chairman

ADVANCES

IN

CHEMISTRY

SERIES

AMERICAN CHEMICAL SOCIETY WASHINGTON, D. C. 1972


112


A D C S A J 112 1-129 (1972)

Copyright © 1972 American Chemical Society A l l Rights Reserved

Library of Congress Catalog Card 72-88560 I S B N 8412-0152-8 PRINTED I N T H E UNITED STATES O F AMERICA


Advances in Chemistry Series


Robert F. Gould, Editor

Advisory Board Bernard D. Blaustein P a u l N. Craig Gunther Eichhorn Ellis K. Fields Fred W. McLafferty Robert W. Parry A a r o n A. Rosen Charles N. Satterfield Jack W e i n e r



FOREWORD

A D V A N C E S I N C H E M I S T R Y SERIES was

founded i n 1 9 4 9

by

the

American Chemical Society as an outlet for symposia and collections of data i n special areas of topical interest that could not be accommodated i n the Society's journals. It provides a medium for symposia that would otherwise be fragmented, their papers distributed among several journals or not published at all. Papers are refereed critically according to A C S editorial standards and receive the careful attention and processing characteristic of A C S publications. Papers published in A D V A N C E S I N C H E M I S T R Y SERIES are original contributions

not published elsewhere i n whole or major part and include reports of research as well as reviews since symposia may embrace both types of presentation.


Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.pr001

PREFACE

'T'he nine chapters which comprise this volume are based on papers presented at the symposium on Ozone Chemistry—Reactions with Organic Compounds. This, to my knowledge, was the fifth symposium or conference which was devoted (or included sessions which were devoted) exclusively to the ozone chemistry of organic compounds. The first was the broadly based International Ozone Conference i n Chicago in November 1956. This was followed by symposia or sessions at the September 1959 A C S meeting i n Atlantic City, the December 1963 Southwest Regional A C S meeting in Houston (both of which were either arranged or coarranged by the undersigned), and the August 1967 International Oxidation Symposium in San Francisco. It is hoped that these meetings w i l l continue to be held every three to four years. Interest i n ozone-organic chemistry remains strong, not only because of its use and potential use i n industrial synthetic chemistry and i n the space program, but, perhaps more importantly today, its role in air pollution and its potential utilization in water pollution problems. More and more, ozone appears to be the brightest hope of the future for purifying sewage and industrial waste water. This is at least partially the result of research during the last 20 years which has called attention to the fact that ozone is much more versatile in its reactions than was supposed when it was earlier thought of purely as a double-bond reagent. Although Harries reported upon the versatility of ozone, this was almost forgotten until recently because of the emphasis placed by Harries and others upon the ozonolysis reaction. Ozone can be described as a resonance hybrid of the following canonical structures: : 0 = 0 — O " : +

:&—6 =6: 6— 6—O": +

:6 — 6—6 . +

As such, it should be

able to function as a 1,3-dipole, an electrophile, or a nucleophile. In the ozonolysis of olefins, acetylenic compounds, and aromatic groupings ozone is thought to behave predominantly as a 1,3-dipole although it is possible that it sometimes behaves initially as an electrophile in these reactions. It is likely that it also behaves as a 1,3-dipole in its reactions with various carbon-hydrogen bonds, which are thought to involve insertion. A n insertion reaction of some description is also thought to occur in the ozonehydrosilane and the organomercurial ozonations reported in this volume. ix


M u c h of the versatility of ozone in its reactions is the result of its electrophilic character. As an electrophile it reacts with certain olefins to give epoxides or rearrangement products thereof, with certain aromatics and heterocyclics, and with nucleophiles such as amines, sulfides, phosphines, phosphites, and others, perhaps including ethers. Regarding the reactions of ozone with carbon ir systems, evidence is presented here that the initial attraction between ozone and the ir system involves the formation of ir complexes, examples of which have been observed and characterized for the first time. Reactions of ozone with amines and certain other nucleophiles are often as fast or faster than those with carbon-carbon double bonds. This book includes one such study involving aromatic amines. The reactions with sp systems (carbon- or silicon-hydrogen bonds, etc.) are much slower but can occur readily when more reactive systems are not present. Examples of ozone as a nucleophile are few and are not included. There is no evidence that ozone can react as a radical at ordinary ozonation temperatures (room temperature or below). It is not paramagnetic, and any initiation of radical reactions via ozonation is probably caused by decomposition of hydrotrioxides (insertion products) rather than by ozone itself. In addition to the reactions mentioned, ozone reacts with carbon-nitrogen, nitrogen-nitrogen, and other unsaturated groupings.


3

Although interest is increasing i n the versatility of ozone in its reactions with systems other than carbon IT systems, there is still much to be learned concerning the ozonolysis reaction and other reactions between ozone and sp carbon-carbon systems. Thus, six of the nine papers in this volume deal with such reactions. Four of these deal primarily with mechanistic aspects of these reactions, while the other two have more to do with the utility of ozonolysis although they also discuss mechanistic ideas. 2

The revival of interest in ozone-organic chemistry during the past 20 years, which has led to the five symposia or conferences mentioned above, is generally credited to Prof. Rudolf Criegee, Emeritus Director of the Institute of Organic Chemistry of the University of Karlsruhe, Germany. His extraordinarily detailed and precise investigations into the mechanism of the ozonolysis reaction transformed this classical reaction from an art into a science, dispelling unwarranted fears concerning it (based on misconceptions regarding the nature of the peroxidic ozonolysis products), and pointing the way to a host of additional theoretical and practical studies. Because of this pioneering work, Prof. Criegee can justly be called the father of modern ozone-organic chemistry. During the past seven or eight years some excellent and novel studies have cast doubt upon the Criegee mechanism as the sole mechanism of ozonolysis. A l l of the newer mechanisms proposed, however, have acx



knowledged that the Criegee mechanism plays an essential, though perhaps sometimes minor, role i n ozonolysis. Thus, the genius of Criegee is unblemished. In the view of this writer, time is showing that the Criegee zwitterion mechanism, with necessary refinements to account for recent stereochemical observations, is the major route to the various peroxidic ozonolysis products. The other mechanisms may compete and even become predominant under specialized conditions but are minor or nonexistent under normal ozonolysis conditions. I agreed to arrange this symposium only if Prof. Criegee could be brought over as an honored participant. This was arranged through the help of the Petroleum Research F u n d of the American Chemical Society, for which I am grateful. Because of the overwhelming contribution of Prof. Criegee to modern ozone-organic chemistry and of his great influence on my own professional life, especially during my 1953-54 stay in Karlsruhe, I am pleased to dedicate this volume to him, a true gentleman, scientist, and personal friend. PHILIP

S.

Austin, Tex. March 1972

xi


BAILEY

1 Complexes and Radicals Produced during Ozonation of Olefins PHILIP S. BAILEY, JAMES W . W A R D , R E X E . HORNISH, and F R E D E . POTTS, III

Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch001

The University of Texas at Austin, Austin, Tex. 78712

Ozonation of certain hindered olefins at —78°C or higher is known to give epoxides or rearrangement products. Some new examples are given. It has been proposed that a pi complex is formed initially during ozonation of olefins and that this either proceeds into 1,3-dipolar cycloaddition and ozonolysis products or forms a sigma complex which loses oxygen to give an epoxide. The greater the steric hindrance, the more that epoxide formation is favored. Chemical, NMR, and visible spectral evidence are presented for the formation of complexes between ozone on the one hand and 1-mesityl-1-phenylethylene, 1,2,2-trimesityl-1-methoxyethylene and similar compounds on the other, at —150°C. Ozonation of 1,2,2-trimesitylvinyl alcohol at temperatures ranging from —20° to —150°C gives the corresponding oxy radical. An ozone-olefin complex precursor to this is suggested.

T n previous work it has been shown that a competition exists during ozonation of olefins between ozonolysis and epoxide formation ( I ) . As steric hindrance increases around the double bond, the yield of epoxide or subsequent rearrangement products increases. This is illustrated with both old (1) and new examples in Table I for purely aliphatic olefins and in Table II for aryl substituted ethylenes. It was suggested that the initial attack of ozone on an olefinic double bond involves TT ( p i ) complex formation for which there were two fates: (a) entrance into 1,3-dipolar cycloaddition (to a 1,2,3-trioxolane adduct), resulting i n ozonolysis products; (b) conversion to a o- (sigma) complex followed by loss of molecular oxygen and epoxide formation (Scheme 1). As the bulk 1 In Ozone Reactions with Organic Compounds; Bailey, P.; Advances in Chemistry; American Chemical Society: Washington, DC, 1972.

2

OZONE REACTIONS W I T H ORGANIC COMPOUNDS

Table I.

Percentage Epoxide from Ozonation of Aliphatic Olefins Percentage Epoxide

0

Olefins

10

tert-Bu-C=CH.

2

U)

CH

3

(ter^Bu) C=CH 2

2


2

15

2

(neopent) C = C H (tert-Bu) C

2

C=CHo

I

I

CH3 C H

U)

81

present present

2

b

29

3

(neopent) C = C H - £ e r £ - B u 0

Reference

b

present

91

Yield of epoxide based on unrecovered olefin, usually determined by V P C . Yield of molecular oxygen accompanying epoxide formation.

Table II. Percentage Epoxide from Ozonation of Aryl Substituted Ethylenes Percentage Epoxide

Olefins (C6H5) C = C H 2

CeH5C=CH

0

Reference V)

2

30

2

6

a)

o-tolyl C6H5C=CH

40

2

c

U)

o-carboxyphenyl 82

CeH5C=CH9

d

I

(1)

Mesityl (Mesityl) C=CH 2

95 2

(Mesityl) C = C (Mesityl) 2

c

present present

2

" Y i e l d of epoxide or rearrangement product(s) thereof based on unrecovered olefin. Molecular oxygen yield accompanying epoxide formation. Isolated yield of epoxide rearrangement product (s). V P C yield of epoxide rearrangement products. N o products from attack on double bond found. b 0

d e



1.

BAILEY E T A L .

A I

3

Ozonation of Olefins

,

c—c i

ozonolysis products

0

products such as III (see Scheme 2)

Scheme 1 of the groups around the double bond increases, the rate of 1,3-dipolar cycloaddition would be expected to decrease, and epoxide formation would be increasingly favored. In the case of tetramesitylethylene (Table II), steric hindrance is so great that there was no evidence for attack on the olefinic double bond to produce either ozonolysis products or an epoxide (or rearrangement products). It appeared that attack occurred only at the mesityl groups. Additional evidence for the above picture of ozone—olefin interaction arose from ozonation of 1,2,2-trimesitylvinyl alcohol (I). Ozonation of a methylene chloride-methanol solution of the vinyl alcohol (I) with 1 mole equivalent of ozone at — 78 °C gave a yield of the corresponding oxy radical (III) of approximately 50% (2). Since ozone itself has no radical character, the most reasonable explanation appeared to be a third fate of a complex (e.g., II, Scheme 2), which, because of excessive steric hindrance, undergoes neither 1,3-dipolar cycloaddition nor sigma complex formation but instead dissociates to a cation radical ( I V ) and the ozonate anion radical ( V ) . The anion radical then abstracts a proton from I V to give III (2). This third fate is also illustrated in Scheme I. Supporting this mechanism are new data indicating that the yield of III is greater in polar than in nonpolar solvents (only 10-20% i n pentane



4


and 5-10% in carbon disulfide). This is reasonable on the basis that solvent polarity should increase the ease of dissociation of complex II (or some similar complex) through solvation of the resulting moieties. Another possibility is that proton abstraction occurs intramolecularly in complex II, after which dissociation to III and - O O O H occurs. To test these hypotheses further, 1-mesityl-l-phenylethylene ( V i a ) and 1,2,2-trimesityrvinyl alcohol (I) were ozonized at temperatures ranging from the usual - 7 8 ° C (I, 2) to - 1 5 0 ° C , and the acetate ( V l l b ) and methyl ether ( V i l a ) of the vinyl alcohol were ozonized at temperatures ranging from 0° to —120°C. Ozonation of 1-mesityl-l-phenylethylene at —120 °C gave the same results as ozonation at — 78°C ( I ) : evolution of molecular oxygen throughout the ozonation and the production of the corresponding epoxide or the subsequent rearrangement products. However, when the ozonation was carried out in Freon 12 at —150 °C, ozone was rapidly absorbed, as at higher temperatures, but no molecular oxygen was evolved. As the ozone reacted, the reaction mixture changed from colorless to greenish to Burgundy red. N o ozone passed into the iodide trap, and no precipitate formed in the reaction mixture. When the temperature of the reaction mixture was raised to about —140°C, the color disappeared, a gas was evolved, and a precipitate of the epoxide appeared.

H

:0:

O

O-H

;0-H Mes C 2

^ - ' C — M e s 0

2

etc.

Scheme 2


1.

BAILEY E T A L . Table III.


Olefin (-150°C)

a

5

Ozonation of Olefins NMR Absorption Peaks of 1-Mesityl-1-phenylethylene and Ozonation Products" -150°C Complex

-135°C Reaction Mixture Containing Epoxide

7.69

7.52

7.09

6.96

6.99

6.74

6.58

6.68

5.92

5.79

5.03

4.90

2.29

2.15

2.17

2.06

1.97

2.04

Assignment phenyl protons mesityl ring protons vinyl protons

2.97

former vinyl protons mesityl methyl protons

The values shown are 8 values expressed in ppm, relative to T M S .

In another experiment the gas evolved was shown to be molecular oxygen (Beckman oxygen analyzer) (3). Additional experiments showed that the evolved oxygen contained singlet oxygen, through its decoloration of rubrene and tetraphenylcyclopentadienone (4) and through mass spectral characterization of the rubrene—singlet oxygen product. Further characterization of the ozone-mesitylphenylethylene complex produced at —150°C was done by N M R and visible spectral studies. The low temperature N M R spectra of the starting olefin, the red complex (ozonized olefin at —150°C) and the dilute reaction mixture at —135°C containing the epoxide of 1-mesityl-1-phenylethylene are described in Table III. The —150°C solutions of the olefin and the complex contain the same bands, the only difference being that the peaks were shifted slightly upfield in the formation of the complex. Such is typical of ir complexes with very little charge transfer, such as iodine and tetracyanoethylene complexes of various aromatic molecules (5, 6). When the temperature of the ozonized reaction mixture was allowed to rise above about —145 °C, the N M R spectrum changed, giving rise to the characteristic peaks of the epoxide of 1-mesityl- 1-phenylethylene. The two phenyl proton peaks in the olefin and the complex spectra must be conformational in origin since the olefin at room temperature has only one phenyl proton peak, at 8 = 7.18 ppm. A LaPine molecular model of the molecule indicates that the phenyl group can rotate freely, but the mesityl group is firmly held out of the plane of the olefinic double bond. A t room temperature there is only one phenyl proton peak


6


as a result of free rotation, but at —150 °C there are two as a result of the molecule's being "frozen" into one particular conformation. Visible spectra of frozen solutions of ozone and of the ozonemesitylphenylethylene complex in isopentane at —195°C (liquid N ) showed clearly the production of a new band (at 450 m/x) i n the formation of the complex. Only a trace of the characteristic (7) ozone band (at 575-625 m/x) was present in the spectrum of the complex. 2

Mes—C=CH,

Mes C=CMes 2

R

OR


VI (a) R = (b) R =

VII phenyl mesityl

(b) R =

CCH || 0

S

Ozonation of 1,1-dimesitylethylene ( V I b ) at —150°C also gave a color indicative of a complex, but because of the low solubility of the solvent, an N M R study was not possible. Ozonation of 1,2,2-trimesitylvinyl alcohol (I.) at —150°C gave radical III strongly, just as at — 78°C. Apparently, if a complex is formed first, the reaction over to the radical is so fast that the complex can not be detected. Ozonation of the acetate ( V l l b ) and the methyl ether ( V i l a ) of vinyl alcohol I in Freon 11, Freon 12, carbon disulfide or methylene chloride at temperatures ranging from —50° to —145°C gave no E S R signal for a radical. Only in pentane or isopentane at —110°C or below was an E S R signal observed, and this proved to have been caused by the action of ozone on the solvent. In Freon 11 or 12 at —120°C, a greenish gray color indicative of a complex was obtained during ozonation of both the ether and the acetate. A n N M R spectrum of the ozonemethyl ether (of trimesitylvinyl alcohol) complex was almost identical with that of the methyl ether itself at —120 °C, with any apparent shifts being slightly upfield, as with the ozone-mesitylphenylethylene complex. The visible spectrum of the complex was similar to that of the complex of mesitylphenylethylene, except that the pure ozone absorption was slightly stronger. The formation of these complexes is reversible, as one would expect. When a cold ( — 1 5 0 ° C ) solution of the reactive olefin cis-3-hexene was added to the mesitylphenylethylene complex, the complex was destroyed with about one-fifth of the ozone reacting with the olefin to give cis- and trans 3-hexene ozonides and the other four-fifths producing the epoxide of mesitylphenylethylene, as determined by V P C and N M R spectral monitoring of the reaction. Similar treatment of the complex of 1-meth-


1.

BAILEY E T A L .

7

Ozonation of Olefins


oxy-l,2,2,-trimesitylethylene ( V i l a ) with cis-3-hexene at —120°C robbed the complex of all of the ozone, producing the 3-hexene ozonides. P i complexes have frequently been proposed in initial ozone—olefin interactions ( I , 8, 9, 10). To our knowledge, however, the ones reported here are the first ever observed and characterized. The fact that complexes but no radicals were observed during ozonation of the ether and ester of trimesitylvinyl alcohol indicates that the hydroxy proton was essential to dissociation of the complexes to radicals. Further discussion of the significance of these complexes to ozonation of olefins, as well as a discussion of the ir systems involved, will be given elsewhere.

Experimental Materials. 3-te^Butyl-2,3,4,4-tetramethyl-l-pentene and 1,1-dineopentyl-2-ter£-butylethylene were prepared as described by Bartlett and Tidwell ( I I ) ; 1,1-dimesitylethylene was prepared by the method of Snyder and Roeske (12); tetramesitylethylene was prepared by the method of Zimmerman and Paskovitch (13); trimesitylvinyl alcohol and its acetate were prepared by the methods of Fuson et al. (14). The methyl ether ( V i l a ) of the vinyl alcohol was prepared by using sodium hydride and methyl iodide in tetrahydrofuran; recrystallized from pentane, m.p. 161°-162°C. Anal. Calcd. for C 3 o H 0 : C , 87.33; H , 8.79. F o u n d : C , 87.27; H , 8.70. Ozonolyses. Ozonolyses and product determinations at ordinary temperatures were carried out as described in previous publications (1,2). Complex between Ozone and 1-Mesityl-l-phenylethylene. A small ozonolysis vessel containing 1.0-2.0 mmole of 1-mesityl-l-phenylethylene was purged with nitrogen and cooled to —150 °C in an isopentane-liquid nitrogen bath, after which 1 m l of cyclopropane and 10-15 m l of Freon 12 were condensed in the vessel. The solution was purged with nitrogen, and an ozone—nitrogen stream (3) containing one equivalent of ozone was introduced into the reaction mixture. Some of the ozone condensed in the inlet tube but was slowly pushed into the reaction mixture by the nitrogen stream. As the ozone reacted, the color of the complex appeared and deepened. In some experiments cis and/or £rans-3-hexene was added dropwise to the —150 °C solution of the complex under a dry nitrogen atmosphere. Similar techniques were used with the other olefins which produced complexes. NMR Spectra. The instrument used was a Varian Associates HA-100 N M R spectrometer equipped for taking spectra at low temperatures. The ozonation of 1-mesityl-l-phenylethylene was carried out as described above, except in the N M R tube itself using a syringe needle as the inlet. In some of the solutions studied cyclopropane was used as the standard. However, in all cases the 8 values are relative to T M S . Visible Spectra. These were taken on frozen isopentane solutions in a rectangular quartz cell cooled in liquid nitrogen i n a quartz Dewar flask, using a Cary ultraviolet spectrophotometer. 3 6


8


ESR Spectra. These were recorded with a Varian Associates V-4502 spectrometer provided by N S F Grant GP-2090 to the Department of Chemistry. The techniques used are described i n earlier papers (2, 15). Singlet Oxygen Determinations. These were carried out as described by Murray et at. (4).


Acknowledgment The support of this work by the Robert A . Welch Foundation (Grant F-042) and the Petroleum Research F u n d of the American Chemical Society is gratefully acknowledged. T h e authors also thank Ben A . Shoulders for his patient help with the low temperature N M R determinations and Clifford Becker for the use of his low temperature quartz Dewar flask for visible and ultraviolet spectra. Literature Cited

1. Bailey, P. S., Lane, A. G., J. Amer. Chem. Soc. (1967) 89, 4473. 2. Bailey, P. S., Potts, F. E., III, Ward, J. W., J. Amer. Chem. Soc. (1970) 92 230. 3. Bailey, P. S., Reader, A. M., Chem. Ind. (1961) 1063. 4. Murray, R. W., Lumma, W. C., Jr., Lin, J. W. P., J. Amer. Chem. Soc. (1970) 92, 3205. 5. Foster, R., "Organic Charge—Transfer Complexes," Chaps. 1-4, Academic, New York, 1969. 6. Foster, R., Fyfe, C., "Progress in Nuclear Magnetic Resonance Spectros copy," Vol. 4, J. W. Emsley, J. Feenex, L. H. Sutcliffe, Eds., Chap. 1, Pergamon, New York. 7. Kirshenbaum, A. D., Streng, A. G., /. Chem. Phys. (1961) 35, 1440. 8. Bailey, P. S., Chem. Rev. (1958) 58, 925. 9. Murray, R. W., Youssefyeh, R. D., Story, P. R., J. Amer. Chem. Soc. (1967) 89, 2429. 10. Williamson, D. G., Cvetanovic, R. J.,J.Amer. Chem. Soc. (1968) 90, 4248. 11. Bartlett, P. D., Tidwell, T. T.,J.Amer. Chem. Soc. (1968) 90, 4421. 12. Snyder, H. R., Roeske, R. W., J. Amer. Chem. Soc. (1952) 74, 5820. 13. Zimmerman, H. E., Paskovitch, D. H., J. Amer. Chem. Soc. (1964) 86, 2149. 14. Fuson, R. C., Chadwick, D. H., Ward, M. L., J. Amer. Chem. Soc. (1946) 68, 389. 15. Bailey, P. S., Keller, J. E., Carter, T. P., Jr., J. Org. Chem. (1970) 35, 2777. R E C E I V E D May 20,

1971.


2 Ozonolysis: Formation of Cross Diperoxides ROBERT W. MURRAY, J O H N W.-P. L I N , and D A N I E L A. G R U M K E


University of Missouri, St. Louis, Mo. 63121

Parent and cross diperoxides are produced when tetra-substituted olefins containing suitable substituents are ozonized. Cross diperoxides are also produced when pairs of tetra -substituted olefins are ozonized together. Comparison samples of diperoxides are conveniently synthesized by treating the appropriate ketone with peracetic acid at low temperature. Peracetic acid oxidation of ketone pairs can also be used to prepare cross diperoxides. Low temperature NMR is used to study diperoxide stereochemistry as well as barriers to conformational isomerization.

*TT

v°"°y + v°^V^ +

R

Ri

R i ^ O — O ^ R i R: RaÔ—O^NR

R

R ^ o —

0^R

2

2



2.

MURRAY ET AL.

11

Cross Diperoxides

expected to give both normal and cross diperoxides. By choosing suitably substituted olefins we would ultimately want to examine diperoxide stereoisomer ratios and look for a dependence on olefin stereochemistry. In carrying out this approach there were at least four different variations to be considered. Ozonolysis of olefins type 1 could give both normal and cross diperoxides. Here one of the cross diperoxides is capable of existing as stereoisomers. Ozonolysis of stereoisomers of type 2 could give a single pair of stereoisomeric diperoxides. Ozonolysis of more complex tetrasubstituted olefins of type 3 could give both normal and cross diperoxides, each of which could exist in stereoisomeric forms. Finally, ozonolysis of pairs of symmetrically substituted olefins of types 4 and 5 could permit formation of both normal and cross diperoxides. In some of these cases more than one trans isomer of a diperoxide could be formed, depending upon axial-equatorial preferences of the substituents.

Experimental Microanalyses were done by Schwarzkopf Microanalytical Laboratory, Inc., 56-19 37th Ave., Woodside, N . Y. 11377. General Ozonolysis. A Welsbach T-23 ozonator was used as the ozone source. Its sample stream output was 0.5 mmole 0 /minute. NMR Analyses. N M R spectra were recorded on a Hitachi-Perkin Elmer R-20 high resolution N M R spectrometer equipped with an R-202VT variable temperature accessory. Temperatures were determined by measuring peak separations i n a methanol sample. Deuteriochloroform was used as solvent. GPC Analyses. G P C analyses were carried out using a Varian-Aerograph M o d e l A-700 gas chromatograph. Columns used were 3-10-ft columns containing 5-10% XF-1150 on chromosorb G . Ozonolysis of Tetramethylene and c*s-3,4-Dimethyl-S-hexene. A solution of tetramethylethylene (0.503 gram, 5.98 mmoles) and cis-3,4dimethyl-3-hexene (0.692 gram, 6.17 mmoles) in 20 m l pentane was ozonized to 63% theoretical yield at —40°C. The product mixture was analyzed by G P C using an 8-ft 10% XF^1150 column at 85 °C and a flow rate of 150 ml/minute. The mixture contained 25 mg acetone diperoxide, 36.7 mg l,l,4-trimethyl-4-ethyl-2,3,5,6-tetraoxacyclohexane, and 23.2 mg methyl ethyl ketone diperoxide as determined by G P C using an internal standard. Total yield of diperoxides was 14%. The diperoxides were identified by comparing mp, infrared, N M R , and G P C data with those of authentic samples. Ozonolysis of 2,3-Dimethyl-2-pentene. A solution of 2,3-dimethyl2-pentene (1.04 grams, 10.6 mmoles) in 20 m l pentane was ozonized to 60% theoretical yield at — 40 °C. The product mixture was analyzed by G P C using an 8-ft, 10% XF-1150 column of temperature 85°C and flow rate 150 ml/minute. The mixture contained 0.503 mmole acetone diperoxide, 0.210 mmole l,l,4-trimethyl-4-ethyl-2,3,5,6-tetraoxacyclohexane, and 0.12 mmole of methyl ethyl ketone diperoxide. Total yield of diper3


12

OZONE

REACTIONS

ORGANIC C O M P O U N D S

oxides was 31.1%. Anal Calcd. for C H 0 : C , 51.84; H , 8.70. F o u n d : C, 51.68; H , 8.51. Ozonolysis of cis-3,4-Dimethyl-3-hexene. A solution of cis-3,4-dimethyl-3-hexene (98% pure, Chemical Samples Co.) (1.12 grams, 10 mmoles) i n 50 m l pentane was ozonized at — 62°C until the blue color of excess ozone was evident. A nitrogen stream was used to purge the solution of excess ozone. Pentane was then carefully distilled off at atmospheric pressure. A water aspirator (20 m m H g ) was then used to remove the ketone product. Treatment of this material with 10 m l of an 0.1M solution of 2,4-dinitrophenylhydrazine gave 2.33 grams of crude 2,4dinitrophenylhydrazone. The crude product was recrystallized and identified as the 2,4-dinitrophenylhydrazone of methyl ethyl ketone, mp 115-116°C. Yield of the ketone was 92% based on olefin used. The remainder of the ozonolysis mixture was distilled from 22 °C (0.4 mm) to 55°C (0.03 mm) to give 0.549 gram of product. The crude product was distilled at 27°C (0.25 mm) to give 0.376 gram of a liquid. Analysis of this material by G P C showed that 70% of it was methyl ethyl ketone diperoxide (30% yield) identified by comparison with authentic material. The diperoxide had m.p. 7 ° - 8 ° C . The remainder of the product was not identified. Ozonolysis of tvans-3,4-Dimethyl-3 -hexene. A solution of trans-3,4dimethyl-3-hexene (83% pure, Chemical Samples Co.) (1.325 grams, 10 mmoles) in 50 m l pentane was ozonized at — 65°C until the blue color of excess ozone was evident. A nitrogen stream was used to purge the solution of excess ozone. Most of the pentane was carefully distilled off at atmospheric pressure, and methyl ethyl ketone was distilled off using the water aspirator. The ketone was identified through its 2,4-dinitrophenylhydrazone. The remaining reaction mixture was distilled at 25 °C (2 mm) to give 0.396 gram of product. Analysis of this material by G P C showed it to be 95% pure (42.7% yield), and it was identified as methyl ethyl ketone diperoxide by comparing its infrared and N M R spectra and melting points with those of an authentic sample. Ozonolysis of 2-Methyl-3-ethyl-2-pentene. A solution of 2-methyl-2ethyl-2-pentene (99% pure, Chemical Samples Co.) (4.48 grams, 40 mmoles) in 60 m l of methylene chloride was ozonized at — 65°C until excess ozone was present. After removal of excess ozone with nitrogen purging, methylene chloride and acetone were distilled off at atmospheric pressure. Diethyl ketone was removed under water aspirator pressure. The remaining reaction mixture was subject to short path distillation at 1 9 ° - 2 3 ° C (0.05-0.02 mm) to give 2.774 grams of liquid (fraction A ) . Further distillation at 30°C (0.02 mm) gave 0.504 gram of liquid (fraction B ) . Analysis of fraction A by G P C showed that it contained acetone, diethyl ketone, and three diperoxides. The diperoxides were identified as acetone diperoxide, l,l-dimethyl-4,4-diethyl-2,3,4,5-tetraoxocyclohexane, and diethyl ketone diperoxide by comparing infrared and N M R spectra and G P C retention times with those of authentic materials. G P C analysis of fraction B showed that it contained diethyl ketone diperoxide and another unidentified material. Yields as determined by G P C were: 4.26 mmoles acetone diperoxide, 5.19 mmoles l,l-dimethyl-4,4-diethyl-2,3,5,6tetraoxacyclohexane, and 3.34 mmoles of diethyl ketone diperoxide. Total yield of diperoxides was 32%. 7


WITH

1 4

4



2.

13

Cross Diperoxides

MURRAY ET AL.

Ozonolysis of Tetramethylethylene and Tetraphenylethylene. A solution of 0.259 gram (3.1 mmoles) of tetramethylethylene and 1.0 gram (3.1 mmoles) of tetraphenylethylene in 40 m l chloroform was ozonized to completion at room temperature. Chloroform was used as the solvent since tetraphenylethylene is fairly insoluble in pentane. Analysis of the reaction mixture by T L C and G P C showed only acetone diperoxide and benzophenone diperoxide to be present. Preparation of Diethyl Ketone Diperoxide. To a solution of 0.37 mole peracetic acid (54 grams, 52% solution in glacial acetic acid) and 32 grams of 70% sulfuric acid we added, dropwise, 22 grams (0.25 mole) of diethyl ketone. The reaction mixture was kept at 2 ° - 1 0 ° C for 80 minutes and then at 1 5 ° - 1 7 ° C for 130 minutes. The organic layer was separated immediately and washed twice with 25-ml portion of 2 M potassium bicarbonate solution. The total weight of the organic product was 21.48 grams. This material was distilled at 39°C (0.01 mm) to give 12.398 grams (46.2% ) of diethyl ketone diperoxide. Redistillation of this material at 45°C (0.035 mm) gave pure diethyl ketone diperoxide, m.p. 8 ° - 9 ° C . The room temperature N M R spectrum in C D C 1 of the diperoxide had a multiplet at 1.8 ( 8 H ) and a triplet at 0.98 (12H, / = 7.6 H z ) . Anal Calcd. for C H O : C, 58.80; H , 9.86. F o u n d : C , 58.62, H , 9.95. Preparation of Methyl Ethyl Ketone Diperoxide. To a solution of 0.37 mole peracetic acid (54 grams, 52% solution in glacial acetic acid) we added, dropwise, 1.8 grams (0.25 mole) of methyl ethyl ketone. The reaction mixture was maintained at 8 ° - 1 0 ° C during ketone addition. After addition was complete, the reaction mixture was stirred for 3.5 hours at 1 0 ° - 1 8 ° C . Stirring was ended when the organic layer had reached maximum volume. The organic layer was separated and washed twice with 2 M potassium bicarbonate solution. The crude diperoxide weighed 18.30 grams. The crude material was distilled at 4 4 ° - 4 5 ° C (1.95 mm) to give 16.2 grams (73% ) of pure methyl ethyl ketone diperoxide with mp 6 . 5 ° - 8 ° C . The G P C analysis of the diperoxide on a 10-ft X Vi-inch XF-1150 column at 82°C and with a flow rate of 80 ml/minute, showing that it had a retention time of 48 minutes. Anal. Calcd. for C H 0 : C , 54.43; H , 9.14. F o u n d : C , 54.39, H , 9.20. Preparation of 1,1 -Dimethyl-4,4-diethyl-2,3,4,5 -tetraoxacyclohexane. To a cold mixture of 65.8 grams (0.45 mole) of 52% peracetic acid and 55 grams of 70% sulfuric acid we added, dropwise, over a one-hour period a mixture of 11.6 grams (0.2 mole) of acetone and 17.2 grams (0.2 mole) of diethyl ketone. During this addition the reaction mixture was maintained at 3 ° - 6 ° C . The reaction mixture was then stirred vigorously at 6 ° - 1 0 ° C for 3.5 hours. The solid reaction product was filtered off and washed with water. The organic layer of the filtrate was separated and washed twice with a 2 M potassium bicarbonate solution. The total weight of the crude product obtained was 18.38 grams. Analysis of this material by G P C ( 5 % XF-1150, 3-ft X y4-inch, column temp - 8 1 ° C ) showed that the solid fraction contained 98.5% acetone diperoxide and 1.5% l,l-dimethyl-4,4-diethyl-2,3,5,6-tetraoxacyclohexane. The liquid fraction (12.23 grams) contained 3.28% acetone diperoxide, 60.5% 1,1-dimethyl4,4-diethyl-2,3,5,6-tetraoxacyclohexane and 3 1 % diethyl ketone diperoxide. The pure l,l-dimethyl-4,4-diethyl-2,3,5,6-tetraoxacyclohexane had m.p. 7 ° - 8 ° C and b.p. 2 7 . 5 ° - 3 0 ° C (0.02 m m ) . The N M R spectrum (room 3

1 0

8

1 6

2 0

4

4


14


temperature, C D C 1 ) of this material had a triplet at 0.975 ( 6 H , / = 7.6 H z ) , a singlet at 1.59, and a broad peak centered at 1.89. Anal. Calcd. for C H 0 : C , 54.53; H , 9.14. F o u n d : C , 54.50; H , 9.03. Preparation of 1,4,4-Trimethyl-1 -ethyl-2,3,5,6-tetraoxacyclohexane. To a cooled solution of 5.11 grams (0.035 mole) of peracetic acid and 4.9 grams (0.035 mole) of 70% sulfuric acid we added, dropwise, with stirring 1.015 grams (0.0175 mole) of acetone and 1.34 grams (0.186 mole) of methyl ethyl ketone. The reaction mixture was maintained at 5 ° - 1 0 ° C during this addition. After addition was completed, stirring at 10°C was continued for 3 hours. After addition of 20 m l of ice water the organic layer was separated and washed twice with 15-ml portion of 5 % sodium bicarbonate. The organic layer was diluted to 50 m l with chloroform and analyzed by G P C using an 8-ft, 10% XF-1150 column at 85 °C. The reaction mixture contained three diperoxides whose yields were determined by G P C using an internal standard. The products were acetone diperoxide (0.259 gram, 32.5%), l,4,4-trimethyl-l-ethyl-2,3,5,6tetraoxacyclohexane (0.41 gram, 47% ), and methyl ethyl ketone diperoxide (0.16 gram, 20.5%). The room temperature N M R spectrum of l,4,4-trimethyl-l-ethyl-2,3,5,6-tetraoxacyclohexane consisted of a triplet at 0.98 ( 3 H , / = 7.6 H z ) , and a broad singlet at 1.50 ( 1 1 H ) . Its m.p. was 31°C. 3


8

1 6

4

Results and

Discussion

One of our earlier attempts to form a cross diperoxide used a variation of olefin types 4 and 5. In this case equimolar amounts of tetraphenylethylene, 6, and tetramethylethylene, 7, were ozonized together. While ultimately both acetone diperoxide and benzophenone diperoxide could be isolated from the reaction mixture, it became apparent that these olefins have such different reactivities toward ozone that the tetramethylethylene was selectively ozonized. Only after most of the tetramethylethylene had been ozonized was the tetraphenylethylene attacked. The opportunity for cross diperoxide formation in this case is thus minimal. By choosing olefins of comparable reactivity towards ozone this difficulty can be avoided. W h e n approximately equimolar amounts of 7 and cis-3,4-dimethyl-3-hexene, 8, were ozonized together all three predicted diperoxides were obtained—i.e., acetone diperoxide, 9, the cross diperoxide, l,l,4-trimethyl-4-ethyl-2,3,5,6-tetraoxacyclohexane, 10, and methyl ethyl ketone diperoxide, 11. A l l of the diperoxides obtained in this study are capable of undergoing conformational isomerization of the type described earlier (22) for acetone diperoxide. By using variable temperature N M R studies the barriers to such isomerizations can be obtained. W e have measured these barriers for all of the diperoxides obtained in this study and w i l l report the results elsewhere.


2.

C H ^

^ C H

3

CH ^

V

3

C H

C H

3

3

^

^CHs

C H / / CH

3

^ C H \ CH 2

3

CH

0-0.

3


CH/

CH

3

0—O'XDHs 9

CH

/ CH

CH

X_X 0

2

CH

3

CH

3

0—0,

3

,CH

3

0—O^CHa—CH

3

10

0—O

3

15

Cross Dipewxides

M U R R A Y ET A L .

n

°

U

3

11

CH

CH

3

2

\

CH

3

L o w temperature N M R measurements are required in the present study, however, to attempt to determine the stereochemical makeup of diperoxides such as 11. These results are described later i n this paper. The total yield of diperoxides obtained is usually low. Presumably most of the available zwitterions end up as polymeric peroxides. In the ozonolysis of 7 and 8, for example, the total yield of diperoxides is 17.4%. The diperoxides were obtained in the ratio of 1:1.35:0.78 for 9:10:11 as compared with the statistically predicted ratio of 1:2:1. W e have found it useful to prepare authentic samples of the various diperoxides encountered by using a variation of the Baeyer-Villiger oxidation conditions. Oxidation of ketones at low temperatures using peracetic acid has been reported (23) to give diperoxides instead of the esters produced under Baeyer-Villiger conditions. Authentic samples of 10 and 11, can be prepared, respectively, by the peracetic oxidation of acetone and methyl ethyl ketone jointly or methyl ethyl ketone alone. W e are studying the mechanism of this interesting oxidation reaction. A n example of the ozonolysis of an olefin of type 1 is provided by the ozonolysis of 2,3-dimethyl-2-pentene, 12. In this case the diperoxides 9, 10, and 11 are produced from a single olefin. A nomenclature consistent with that used for ozonides would describe 10 as the parent diperoxide and 9 and 11 as cross diperoxides.


16


CH CH

'CH

3

CH —CH

3

o

3

2

9 + 10 +

3

11

3


12 In this case the total yield of diperoxides was 27.6%. W e are still trying to improve the yield of diperoxide products from these reactions; hence these yields should not be regarded as optimum values. A t any rate, we have established that cross diperoxides can be formed so that we have an additional probe with which to examine the mechanism of ozonolysis problem. It was now important to examine the question of a possible stereochemical influence on diperoxide formation. W e have approached this problem initially by ozonizing olefins of type 2. W h e n either cis- or trans3,4-dimethyl-3-hexene are ozonized, presumably a single stereoisomeric pair of diperoxides can be formed. In fact, this case is complicated by the possibility of two trans-diperoxide conformers being produced. The cis-diperoxide conformers are identical. Ozonolysis of cis-3,4-dimethyl-3hexene, 8, for example, could give the diperoxides, cis-l,3-dimethy 1-1,3diethyl-2,3,5,6-tetraoxacyclohexane, 11a, and £rans-l,3-dimethyl-l,3-diethyl-2,3,5,6-tetraoxacyclohexane, l i b , with the latter capable of existing as conformers l i b and l i b ' with trans-diaxial methyl and trans-diaxial ethyl substituents, respectively.

CH

3

CH CH

lib

2

3

lib'



2.

MURRAY E T A L .

1.90

6

Figure 1.

17

Cross Diperoxides

1.49

0.96

Room temperature NMR spectrum of methyl ethyl ketone diperoxide

Similar stereochemical possibilities are present when 11 is obtained from £rans-l,3-dimethyl-3-hexene, 13, as a cross diperoxide from the ozonolysis of 12 or from the peracetic acid oxidation of methyl ethyl ketone. In fact, i n all of these cases 11 appears as a single G P C peak under various analytical conditions. The room temperature N M R spectrum of 11 obtained from all of the sources described is also identical (Figure 1) , consisting of a triplet at 0.96 ( 6 H , / = 7.6 H z ) , a broad singlet at 1.49 ( 6 H ) , and a broad peak at 1.90 ( 4 H ) (chemical shift values given are 8 values relative to internal T M S ) . The low temperature (ca. — 40 ° C ) N M R spectrum of 11 i n each case is also identical and consists of (Figure 2) a triplet at 1.0 (/ = 7.6 H z ) , a singlet at 1.31, a singlet at 1.8, a quartet centered at 1.73 (/ — 7.6 H z ) , and a quartet centered at 2.28 (/ = 7.6 H z ) . These N M R results can be interpreted as follows. A t room temperature rapid conformational isomerization is occurring i n 11. This leads to a single broad peak at 1.49 for the axial and equatorial methyl groups and a single broad peak at 1.90 for the axial and equatorial methylene groups. The triplet at 0.96 is then assigned to the methyl protons of the ethyl groups which are not affected by the conformational isomeriza-



18


tion. A t low temperature the isomerization process is slowed to the point where the chemical shifts of the protons i n the individual conformers can be detected. The triplet at 1.0 is still assigned to the methyl protons of the ethyl group. The two quartets at 1.73 and 2.28 are then assigned to the axial and equatorial methylene groups, respectively. The two singlets at 1.31 and 1.8 are assigned to the axial and equatorial methyl groups, respectively. The equatorial methylene and methyl groups are assigned the low field absorptions on the basis of ring current effects (24). The axial and equatorial methyl and methylene absorptions have essentially equal peak areas. This spectrum is therefore consistent with the product's being the cis isomer, 11a. F o r the trans isomer one might expect a preference for the conformer with the diequatorial ethyl groups, l i b . In this case the axial and equatorial absorptions should not have equal intensities. Such a preference is expected to be small, however, and the N M R spectrum must be regarded as consistent with the trans

i

s Figure 2.

Low temperature (—40°C) NMR spectrum of methyl ethyl ketone diperoxide


2.

C H ^

^CH CH

CH

+

9

0—0

y

X C H ,

3

/

N

CH CH 2

X O - 0 ^ C H

14

1

3

C H .

+

15

CH CH 3

CH CH 3


y

K

X 2

0

_

° —

2

CH CH

X'

Q

y

2

3

^CH CH

0

2

3

16

0 |j

3

2

H S0 2

CH —CH —C—CH —CH 2

4

>

3

X 6

CH —C—0—0—H II 0 3

0

0

II 2

2

4

II

CH —CH —C—CH —CH 3

H S0

2

3

+

CH —C—CH 3

> 3

CH -C-0-0-H 3

0

9 + 15 +

16

product also. Although the chemical shifts of the ring substituents in the cis and trans isomers can be different, the structures are so similar that any differences would probably not be detectable. The N M R results, therefore, are consistent with 11 as the cis or trans isomer or a mixture of both. Since the same product or mixture of products was obtained from both cis and trans olefins (8 and 13), it is not possible to determine whether there is any influence of olefin stereochemistry on diperoxide stereochemistry i n this case. W e hope to work with a stereoisomeric pair of olefins of type 2 where the substituent sizes are sufficiently different to permit an evaluation of the influence of olefin stereochemistry on the reaction. Similar considerations w i l l have to be kept in mind when choosing a more complex olefin of type 3.



20


W e also have examined one final type of olefin. This type of olefin, represented by 2-methyl-3-ethyl-2-pentene, 14, is also capable of giving cross diperoxides although i n this case the diperoxide products are not capable of existing as stereoisomers. Ozonolysis of 14 gave three diperoxides, 9, l,l-dimethyl-4,4-diethyl-2,3,5,6-tetraoxacyclohexane, 15, and 3-pentanone diperoxide, 16. Here again the peracetic oxidation method was used to prepare comparison samples of diperoxides. Oxidation of 3-pentanone, for example, gave a 46% yield of 16. This method can also be used to prepare diperoxides such as 15. W h e n equimolar amounts of acetone and 3-pentanone are oxidized by the peracetic acid method, diperoxide 15 is obtained along with 9 and 16. Similarly, oxidation of equimolar amounts of acetone and 2-butanone gave 9, 10, and 11. W e have shown that cross diperoxides can be formed by various ozonolysis procedures. W e now hope to parallel the work done where cross ozonides were produced—i.e., to examine the influence of olefin stereochemistry and other reaction variables.

Literature Cited

1. Criegee, R., Rec. Chem. Progr. (1957) 18, 111. 2. Riezebos, G., Grimmelikhuysen, J. C., Van Dorp, D. A., Rec. Trav. Chim. (1963) 82, 1234. 3. Lorenz, O., Parks, C. R., J. Org. Chem. (1965) 30, 1976. 4. Loan, L. D., Murray, R. W., Story, P. R., J. Amer. Chem. Soc. (1965) 87, 737. 5. Privett, O. S., Nickell, E. C., J. Amer. Oil Chemists' Soc. (1964) 41, 72. 6. Murray, R. W., Youssefyeh, R. D., Story, P. R., J. Amer. Chem. Soc. (1967) 89, 2429. 7. Murray, R. W., Youssefyeh, R. D., Story, P. R., J. Amer. Chem. Soc. (1966) 88, 3143. 8. Greenwood, F. L., J. Amer. Chem. Soc. (1966) 88, 3146. 9. Bauld, N. L., Thompson, J. A., Hudson, C. E., Bailey, P. S., J. Amer. Chem. Soc. (1968) 90, 1822. 10. Schröder, G., Chem. Ber. (1962) 95, 733. 11. Kolsaker, P., Acta. Chem. Scand. (1965) 19, 223. 12. Greenwood, F. L., Haske, B. J., Tetrahedron Letters (1965) 631. 13. Story, P. R., Murray, R. W., Youssefyeh, R. D., J. Amer. Chem. Soc. (1966) 88, 3144. 14. Fliszar, S., Carles, J., Canad. J. Chem. (1969) 47, 3921. 15. Criegee, R., Lohaus, G., Ann. (1953) 583, 6. 16. Marvel, C. S., Nichols, V., J. Org. Chem. (1941) 6, 296. 17. Pummerer, R., Schmidutz, G., Seifert, H., Chem. Ber. (1952) 85, 535. 18. Criegee, R., Bath, S. S., Bornhaupt, B. V., Chem. Ber. (1960) 93, 2891. 19. Criegee, R., Lohaus, G., Chem. Ber. (1953) 86, 1. 20. Murray, R. W., Story, P. R., Loan, L. D., J. Amer. Chem. Soc. (1965) 87, 3025. 21. Criegee, R., Korber, H., Chem. Ber. (1971) 104, 1812.


2.

MURRAY ET AL.

Cross Diperoxides

21

22. Murray, R. W., Story, P. R., Kaplan, M. L., J. Amer. Chem. Soc. (1966) 88, 526. 23. Lohringer, W., Sixt, J., U. S. Patent 3,076,852 (Feb. 5, 1963). 24. Jackman, L. M., "Applications of Nuclear Magnetic Resonance in Organic Chemistry," Section 7.2, Pergamon, New York, 1959.


RECEIVED May 20, 1971. Supported by the National Science Foundation grant No. GP-10895.


3 Fragmentation of Ozonides by Solvents R U D O L F C R I E G E E and H E L M U T KORBER


Institut für Organische Chemie, Universität Karlsruhe, Germany

Ozonides, bearing at least one H atom at the trioxolane ring, decompose quantitatively in some solvents into one molecule of acid and one molecule of aldehyde or ketone. Alcohols show the highest rate while solutions in hydrocarbons are stable. In methanol the reaction rates were measured at constant pH and salt concentration by automatic titration of the acid formed. The rates differ by a factor of 10 , depending upon the constitution and the configuration of the ozonides. The abstraction of an H atom from the trioxolane ring occurs in the rate-determining step. A mechanism similar to that of Kornblum-DeLaMare is proposed. Several new ozonides were prepared. In three cases their configuration was established by resolution into optically active forms by chromatography on cellulose acetate. 3

Solutions of stilbene ozonides i n methanol slowly decompose at room ^ temperature with the formation of benzoic acid and benzaldehyde. Other ozonides show similar behavior. However, the reaction rates differ from solvent to solvent and depend on the constitution and configuration of the ozonide. Therefore, we decided to investigate these reactions more carefully. Many new ozonides—especially those with one or more aromatic substituents—had to be prepared, and their configurations had to be established. Preparation

of the Ozonides

Ozonides having one or two substituents at the trioxolane ring—in the latter case symmetrically or unsymmetrically—were prepared from the corresponding olefins by ozonization i n pentane, usually at —78°C. The 3,5-disubstituted trioxolanes were separated into cis- and transisomers by crystallization or by column chromatography. 22 In Ozone Reactions with Organic Compounds; Bailey, P.; Advances in Chemistry; American Chemical Society: Washington, DC, 1972.

3.

CRIEGEE A N D KORBER

Table I.

C H —CH=CH—C H 6

5

6

5

New Trioxolanes

o -»• 3

S

acetone

r>

/O-O C H — C H ^ ^ C ( C H ) 44% 8

5

3

/ O - O CH C H —CHC^

o -»

C«H-—CHC

3

butanone

0

6

5

6

5

acetophenone 0 -» acetone 3


(06^)20=0(00^);,

(C H5) C=C(C«H ) 6

2

5

0 -* 3

2

butanone

o (C H ) C=C(C H ) C

5

2

6

3

0

X)—a

CH

3

6

3

62%

5 2

0

59% 74%

2

0

>0—CL CH (C H ) CL >C

29%

3

CeHs

3 2

C2H5

^ , 0 - 0

(C«H ) C^ ^ C ( C H ) 5

benzophenone

C2H5

/O—o "X(CH )

(CoH ) cC

3

2

3

3

3

C H —CH=CH—C H

2

0

-»

0

C H —CH=CH—C«H 6

23

Fragmentation of Ozonides

2

6

5

0

2

25%

Some trisubstituted ozonides could be obtained only b y the method of Murray, Story, and L o a n (1)—namely, the ozonization of disubstituted olefins i n ketones as solvents. Ozonization of tetraphenylethylene i n acetone, methyl ethyl ketone, or benzophenone gave the hitherto unknown trioxolanes with four hydrocarbon residues ( 2 ) . Table I shows some examples. Other new ozonides include those of acenaphthylene and 3,4-dichloro-3,4-dimethyl-cyclobut-l-ene. They are the cyclic analogs of cisstilbene ozonide and l,4-dichloro-but-2-ene ozonide, respectively. Altogether, more than 45 ozonides were investigated. Experimental Ozone was prepared with an ozone generator (type O Z II of the Fischer Labortechnik, B a d Godesberg, Germany). D r y oxygen containing about 10% ozone was introduced at a speed of 10-20 liters/hour in the olefin solution at — 78 °C. D r y and olefin-free n-pentane was used as solvent. After ozonation, the solvent usually was removed at 30°C under rotation. T h e residue was either distilled in vacuo or crystallized or purified by column chromatography on silica gel. n-Pentane, with i n creasing amounts of ether (up to 1.5% ), served for the elution. Those mixtures of stereoisomeric ozonides which could not be separated preparatively were analyzed by their N M R spectra using a Varian A 60 spectrometer. The results are summarized i n Tables I I - V . More details can be found i n Ref. 3.


24



Table II.

Preparation and Properties Yield,

Starting Olefin

l$,4-Trioxolane

Formula

Styrene

3-phenyl

G H 03

71*

p-Methoxystyrene

3-p-methoxyphenyl

C9H10O4

41

p-Methylstyrene

3-p-tolyl

C9H10O3

70

p-Chlorostyrene

3-p-chlorophenyl

C H C10

p-Nitrostyrene

3-p-nitrophenyl

C H N0

A l l y l chloride

3-chloromethyl

C3H5C10

5-Chloropentene

3- (3-chloropropyl)

C H C10

Calculated values in parentheses. Plus 9% stilbene ozonide (cis/trans

a b

8

8

8

B

%

8

7

7

9

8

70" 44

5

3

80

3

50

4/6).

Table III.

Preparation and Properties Yield, %

Starting Olefin

1,8,4-Trioxolane

Formula

1,1-Diphenylethylene

3,3-diphenyl

C14H12O3

57

2-Pheny 1-but-1-ene

3-ethyl-3-phenyl

C10H12O3

62

2-Phenyl-propene

3-methyl-3-phenyl

C9H10O3

74

2-Methyl-propene

3,3-dimethyl

C H 03

45

2,3-Dimethyl-but-l-ene

3-methyl-3-isopropyl

C6H1.2O3

45

a b

4

8

Calculated values in parentheses. P l u s 7% dimeric acetophenone peroxide.


6

c

3.


25


of Monosubstituted Trioxolanes Mp (Bp), °C/torr

Analysis' C

Spectrum" in CCl

t

4.90 (s), 4.85 (s), 4.10 (s), 2.70 (m) 1:1:1:5

(37-38/.01) 59.57 5.77 (59.37) (5.53)

6.24 (s), 4.73 (s), 4.63 (s), 4.06 (s), 2.83 (AB system, J = 9 H z ) ; 3:1:1:1:4

(55/0.01)

66.21 6.12 (66.05) (6.07)

7.75 (s), 4.81 (s), 4.73 (s), 4.08 (s), 2.79 (AB system, «/= 9 H z ) ; 3:1:1:1:4

(62/0.03)

51.23 3.73 (51.49) (3.38)

4.73(s), 4.67 (s), 4.04(s), 2.60 (s) 1:1:1:4

77

48.86 3.62 (48.74) (3.58)

4.65 (s), 4.61 (s), 3.82 (s), 2.02 (AB system, J = 9 H z ) ; 1:1:1:4

(51/18)

28.99 4.05 (28.94) (4.05)

6.50(d, J — 5 H z ) , 5.05(s), 4.77(s), 4.60(t, J = 5 H z ) ; 2:1:1:1

(36/0.04)

39.20 5.99 (39.36) (5.95)

8.11 (m), 6.45(m), 5.02(s), 4.90(s) 4:2:1:2

61-62


NMR

H

P l u s 13% p,p'-dichlorostilbene ozonide (cis/trans Values of T ; T M S as internal standard.

c d

4/6).

of 3,3-Disubstituted Trioxolanes Analysis

a

°C/torr n

NMR

H

Spectrum* in CCl

k

74.19 5.44 (73.67) (5.30)

4.85(s),2.75(m);2:10

46/0.05

66.15 6.79 (66.65) (6.71)

9.12 (t, J — 7Hz), 8.02 (q, J = 4.99 (s), 4.93 (s), 2.67 (m) ;

35/0.03

64.88 6.20 (65.05) (6.07)

3:2:1:1:5 8.33(s),4.94(s), 2.57(m); 3:2:5

44/143

45.62 7.61 (46.15) (7.75)

8.60(B), 5.00(s); 6:2

48/37

54.31 9.23 (54.53) (9.15)

9.06 (d, J — 7Hz), 8.70 (s), 8.06 (septet) 5.06(s), 4.95(s); 6:3:1:1:1

20

D

c d

1.5760

C

Plus 4% dimeric acetone peroxide. Values of r ; T M S as internal standard.


7Hz),

26

OZONE

REACTIONS W I T H ORGANIC

Table IV.

Preparation and Properties Yield;

%

Starting Olefin

1$^Trioxolane

trans- 1-Phenylpropene

3-methyl-5-phenyl

C9H10O3

3-methyl-5-bromomethyl

C H Br0

3,5-bis (bromomethyl)

CêBraOa

55 (36:64)

CftHftCloOa

61

CgHiaCkOs

43

C12H8O3

25

trans-Crotyl


COMPOUNDS

bromide

l,4-T)ibromo-but-2-ene (cis or trans) £rans-3,4-Dichloro3,4-dimethyl-cyclobutene £rans-3,4-Dichloro1,2,3,4-tetramethy 1cyclobutene Acenaphthylene

Formula

4

7

54 (37/63) c

3

74 (24:76)

• Cis-trans ratio in parentheses. Calculated values in parentheses. 6

Results and Discussion Configuration of cis-trans Isomeric Ozonides. In symmetrically disubstituted trioxolanes, the cis isomer is a meso and the trans isomer is a racemic form. Therefore, resolution into antipodes makes it possible to determine the configuration. In 1966, Loan, Murray, and Story (4) were able to obtain an optically active form of one of the diisopropyltrioxolanes, proving it to be the trans isomer. Their method—partial decomposition of the ozonide by brucine—could not be applied to the stilbene ozonides. Chromatography of a benzene solution of the low melting stilbene ozonide (mp 9 2 ° C ) on finely divided cellulose-2 1/2-acetate, however, yielded fractions of the ozonide with specific rotation at 360 nm of + 8 . 9 4 ° and —20.45°, respectively (5). This isomer, therefore, is the trans compound. Under the same conditions, the higher melting ozonide (mp 1 0 0 ° C ) gave no fraction with optical activity, in agreement with its cis configuration.


3.


27


of 3,5-Disubstituted Trioxolanes


Mp, °C

Analysis

b

C

H

NMR

Spectrum* in CCl

h

91

36.24 4.13 (36.21) (4.05)

cis: 8.57 (d, J — 5 H z ) , 4.52 (q, J — 5Hz), 3.97(s), 2.60(m); 3:1:1:5 trans: 8.60(d, J = 5 H z ) , 4.49 (q, J = 5Hz), 4.00(s), 2.60(m); 3:1:1:5 cis: 8.55 (d, J — 5 H z ) , 6.71 (d, J = 5Hz), 4.80 (q, J = 5 H z ) , 4.52(q, J —5Hz);3:2:l:l trans: 8.57 (d, J = 5Hz (, 6.64(d, J — 4.5Hz), 4.60 (q, J — 5 H z ) , 4.65 (q, J = 4 . 5 H z ) ; 3:2:1:1 cis: 6.55 (d, J = 4.5Hz), 4.56(t, J = 4.5Hz);4:2 trans: 6.64 (d, J — 5 H z ) , 4.43 (t, J = 5Hz) •• 4:2 8.24(s) ,8.21 (s), 4.43(s), 4.29(s); 3:3:1:1

75

42.38 5.34 (42.33) (5.29)

8.40(B), 8.29(s), 8.27 (s), 8.20 (s); 3:3:3:3

106

71.68 3.96 (72.00) (4.03)

3.63(s), 2.60(m); 2:6

trans: 54 cis: liquid

65.08 6.24 (65.06) (6.07)

trans: liquid cis: liquid

26.60 3.89 (26.25) (3.86)

trans: liquid cis: liquid

18.02 2.39 (18.34) (2.31)

Plus 15% stilbene ozonide; but-2-ene ozonide was also found by gas chromatography. Values of r; T M S as internal standard. c

d

In the same way, the l,4-dichloro-but-2-ene ozonide with the shorter retention time on silica gel yielded fractions with [a] oo = —2.66° and + 4 . 2 ° ; the ozonide of l,4-dibromo-2,3-dimethyl-but-2-ene, which only could be made i n one form with a melting point of 42 °C, yielded fractions with M330 — + 5 0 . 7 ° and —39.2°. Both, therefore, have the trans configuration. It is remarkable that the trans ozonide i n this case is the only product, even when pure cis-l,4-dibromo-2,3-dimethyl-but-2-ene is ozonized. The configurations of the other ozonides are based on the assumption that the trans isomers have the lower dipole moments i n comparison with the cis compounds. As a measure of the dipole moment the retention time i n liquid phase or gas chromatography was used. The isomer with the lower retention time should be the trans compound. Except for the trioxolanes with halo alkyl groups, the trans compounds always reacted more slowly with triphenylphosphine than d i d the cis isomers. The N M R values generally cannot be used to estimate the 4


28

OZONE

REACTIONS

Table V.

Starting Olefin £rans-Stilbene

£rans-Stilbene


cis-Stilbene

Solvent, Temperature, °C acetone —78 acetophenone 0 butanone -78

WITH

ORGANIC

COMPOUNDS

Preparation and Properties

1,8,4-Trioxolane 3,3-dimethyl5-phenyl 3-methyl-3,5diphenyl

Formula

3-methyl-3-ethyl5-phenyl

C11H14O3

C10H12O3 C15H14O3

1,1-Diphenylpropene

pentane -78

3-methy 1-5,5diphenyl

C15H14O3

2-Phenyl-but-2-ene

pentane -78

3,5-dimethyl3-phenyl

C10H12O3

a b c d

Calculated values in parentheses. Cis-trans ratio in parentheses. Plus 19% stilbene ozonide + 4% dimeric benzaldehyde peroxide. Phenyl and methyl in the cis position.

configuration because they are influenced by substituents in different ways. They can be of value, however, in series of homologous ozonides. As shown later, the rate of fragmentation is always higher for the trans ozonides, at least in the series of disubstituted trioxolanes. Fragmentation Products. A l l ozonides except for the tetrasubstituted ones are cleaved quantitatively by many solvents. While symmetrically disubstituted ozonides give one mole of acid and one mole of aldehyde as products, and trisubstituted ozonides yield one mole acid and one mole of a ketone, in the case of monosubstituted or unsymmetrically 3,5-disubstituted trioxolanes, two kinds of acids and two kinds of aldehydes are possible. The fragmentation products in these cases were treated with diazomethane, and the mixture of the methyl esters was analyzed by gas chromatography. The results are shown in Table V I . In all of these examples, the reactions go predominantly in one direction. When R and R ' are more similar, however, both kinds of reaction products would be expected in more nearly equal amounts.


3.

CRIEGEE AND KORBER

29


of Trisubstituted Trioxolanes


Yield,"

Analysis'

%

Bp, °C/torr

44

39/0.04

29 ° (43:57)

trans :m.p. 54 cis: liquid

59 (27:73)

70/0.02

68.34 7.31 (68.02) (5.82)

30'

94/0.02

74.18 5.82 (74.36) (5.82)

27' (42:58)

43/0.04

66.41 6.62 (66.65) (6.71)

H

C

67.35 6.62 (66.65) (6.71) 74.28 5.80 (74.36) (5.82)

Ν MR Spectrum' in CCl

k

8.49 (s), 8.45 (s), 3.96 (s), 2.60(m) ; 3:3:1:5 cis: 8.18(s),4.05(s), 2.65 (m);3:l:10 trans: 8.28(s), 3.98(s), 2.75(m); 3:1:10 cis:" 9.00 (t, J = 7 H z ) , 8.50(s),8.28(q,y = 7 H z ) , 4.08 (s), 2.70 ( m ) ; 3:3:2:1:5 trans: 9.04(t, J = 7 H z ) , 8.55 (s), 8.16 (q, J = 7 H z ) , 4.04(s), 2.70(m); 3:3:2:1:5 8 . 7 4 ( d , j = 5Hz),4.52(q, J = 5Hz),2.76(m); 3:1:10 cis: 8.74(d, J = = 5 H z ) , 8.37(s),4.63(q,J = 5 H z ) , 2.67(m); 3:3:1:5 trans: 8.62(d, J = 5 H z ) , 8.31 (s), 4.70 (q, J = 5 H z ) , 2.67(m); 3:3:1:5

' Plus 32% benzophenone + 5% dimeric benzophenone peroxide. ' Plus 5% dimeric acetophenone peroxide. 'Values of τ; T M S as internal standard.

Table VI.

Direction of Fragmentation of Unsymmetrical Ozonides .0—CL

R—CH^

^CH—R' 0

R n-C H 3

7

CICH2CH2CH2—

C1CH 2

CeHe— Cells—

Products, % RC0 H

R'

2

Η Η Η Η

CH 3

R'CO.H

97 98 100 99 95

3 2 0 1 5

Rates of Fragmentation. The solvent dependence was studied first (Table I V ) . Solutions of styrene ozonide were stored at 5 0 ° C . A t vari ous intervals, samples were quenched with ice water, and the acid formed was titrated with 0.05N K O H , using phenolphthalein indicator. W h i l e the ozonide was stable i n benzene, carbon tetrachloride, and chloroform


30

OZONE REACTIONS W I T H ORGANIC

COMPOUNDS

solution, the rates of cleavage increased in oxygen- and nitrogen-contain ing solvents, methanol being the fastest solvent. As shown in Table V I I , there is no clear connection between the rates of reaction and the polari ties of the solvents, as expressed by the E values of Dimroth (6). T

Table VII.

Fragmentation of Styrene Ozonide at 5 0 ° C in Different Solvents


Solvent

Χ 10 (sec' ) 4

k

50

Benzene Diisopropylether Acetonitril Butanone Dioxane Tetrahydrofuran Benzyl alcohol Methanol

E T (Réf. Q)

1

0 0.017 0.038 0.070 0.097 0.47 1.83 5.33

34.5 34.0 46.0 41.3 36 37.4 50.8 55.5

To study the dependence of the reaction rates on the constitution and configuration of the ozonides, an automatic method was worked out. Ozonides, dissolved in absolute methanol which was saturated with the barium salt of the acid produced in the reaction (mainly barium acetate or barium benzoate), were heated in a thermostat to 50°C. In a Combititrator (Methrom Co.) a methanol solution of barium methylate (O.IN) was added automatically at such speed that the p H of the solution remained unchanged. The variation in the volume of added methylate solution with reaction time was registered on chart paper. The reactions were carried out under pure nitrogen, and the curves always showed first-order kinetics. From the kinetic results some rules can be established. Rule 1: abstraction of a proton from the trioxolane ring occurs in the rate-determining step. This follows from the comparison of the rates Table VIII.

Isotope Effect k

1

50

X 10* (sec- )

H Ozonide

D Ozonide

k /k

0.21

0.073

2.9

4.5

1.17

3.9

7.15

1.48

H

0-0^ C H CHCT 6

X(CH )

5

3

2

O-O^

C H CHC e

C

6

^CH—C H

5

H

5

e

C H C

^ C H

2

5

"(Τ


4.8

D


3.


31

of protonated and deuterated ozonides (Table V I I I ) . The isotope effect was found to be between 3 and 5. The deuterated ozonides had the deuterium labels i n all positions of the trioxolane rings. They were prepared by ozonization of stilbene-d i n acetone or i n pentane and of styrene-ds i n pentane. Rule 2: aromatic residues at the trioxolane ring render the removal of a hydrogen atom from the same carbon atom easier than does an aliphatic substituent. The fragmentation rates are 7 to 30 times higher in the first case (Table I X ) . 2

Table IX.

Comparison of Aliphatic and Aromatic Substituents k


50

X 10 (sec- ) 4

1

aromatic/ R = X>—(1 H

2

C ^

—C H 3

3

—C H 6

5

aliphatic

R

" X

CT

0.107

0.71

6.6

0.019

0.31

16

0.021

0.59

28

0.083

10

H

R

X>——CT

Inductive Effect

J2H 2

X 10 (sec- )

k

4

50

1.07

CH3CH2CH2-

C1CH CH CH C1CH 2

2

1.50 5.7

2

2


1

Rule 5: the release of strain by the fragmentation of the ozonide is very important to the rate of fragmentation. Table X I I gives three pairs of ozonides. Each pair is chemically similar but differs i n the Baeyer strain. The strained ozonides are cleaved up to more than 100 times faster than the unstrained ozonides. Table XII.

~^C. H C 7

^ C T

3

J^CC

X H 3

Influence of Strain

0.19 T

I I H C\ ^ C H CH 2

0.96 2

2

H C "^ 5

6

X T

O—CI CICHf

X T

^ C H 6

3.1

/H XJH,C1

1.70

66.0

CtT V O '

5

Ek

/ O — / H

>

C. \ CT / H C—C C—CI I I CI CH

250

3

3

Rule 6: among stereoisomeric ozonides, the trans isomers (or the compounds which should be trans from the lower retention time) are always fragmentated faster than the cis isomers (Table X I I I ) . The trans/cis factor, however, usually is not large. Only with halogen containing substituents does it exceed 10.


3.

CRIEGEE

AND

Table XIII. R—CH:

R =

Reaction Rates of cis-trans Isomeric Ozonides

O—O,

:CH—R

CH n-C H £er£-C H 3

3

7

4


33


KORBER

9

k

50

X W

4

(sec ) 1

CIS

trans

0.123 0.193 0.202 3.13 1.70

0.131 0.213 0.333 5.90 19.5

trans/

&cis

1.07 1.15 1.65 1.88 11.5

Unfortunately, the dependence of the rates on p H cannot be measured by our method since acidimetric titrations are not possible in buffered solutions. However, in weakly acidic and neutral solutions, there cannot be much influence because otherwise no rate constants could have been obtained. In alkaline solution, on the other hand, a base induced fragmentation occurs, which is faster by some powers of 10 than the solvent fragmentation. Thus, in 0.025N methanolic N a O H at 0°C, the half lifetime of stilbene ozonide is only 2 minutes. Mechanism of the Solvent Fragmentation of Ozonides. The driving force for the fragmentation, in any case, is the cleavage of the energy rich O — O bond of the ozonide and the release of conformational strain present in the trioxolane ring. However, the strongly exothermic fragmentation into stable products can occur only if there is an acceptor for the trioxolane proton. It is surprising that this acceptor need not be a strong base but can be a solvent with a heteroatom's possessing lone pairs of electrons. The exceptional role of alcohols as solvents may arise from the fact that they are not only "bases" but simultaneously are "acids." Therefore, unlike the reaction with strong bases, free acids are formed instead of carboxylate anions.

H C 3

From our experiments we cannot say whether one or more molecules of methanol participates in the rate-determining step. The first possibility implies that one methanol molecule is simultaneously acceptor and



34


donator of a proton, while i n the second case these functions are carried out b y different molecules. The fragmentation seems to be concerted because according to rules 1 and 5 both the abstraction of the proton and the release of strain are rate determining. Thus, we formulate a mechanism which is similar to the well known Kornblum-DeLaMare mechanism for the base induced decomposition of dialkyl peroxides ( 7 ) . While this mechanism is not in disagreement with the various kinetic results, it can explain only with difficulty all details of the reaction rates. The higher rates in the case of ozonides with electron-attracting substituents show that i n the transition state there must be a partial negative charge at that C atom which loses the proton. Since, however, the rates are also influenced by steric factors (steric hindrance as well as steric effects upon the ring conformation), the whole situation is complicated. No effort has been made, therefore, to explain a l l rate differences, even small ones. F r o m a practical standpoint the solvent fragmentation seems to offer a very mild method to cleave ozonides into acids and carbonyl compounds. In a recent paper (8) which describes the fragmentation of stilbene ozonides with dimethyl sulfoxide and dimethyl formamide the authors propose a similar mechanism. Literature Cited 1. Murray, R. W., Story, R. P., Loan, L. D., J. Amer. Chem. Soc. (1965) 87, 3025. 2. Criegee, R., Korber, H., Chem. Ber. (1971) 104, 1812. 3. Korber, H., Ph.D. thesis, Universitat Karlsruhe, 1970. 4. Loan, L. D., Murray, R. W., Story, P. R., J. Amer. Chem. Soc. (1965) 87, 737. 5. Criegee, R., Korber, H., Chem. Ber. (1971) 104, 1807. 6. Dimroth, K., Reichardt, C., Siepmann, T., Bohlmann, F., Ann. Chem. (1963) 661, 1. 7. Kornblum, N., DeLaMare, H. E., J. Amer. Chem. Soc. (1951) 73, 880. 8. Ellam, R. M., Padbury, J. M., Chem. Commun. (1971) 1094. R E C E I V E D May 20, 1971.


4 Quantitative Investigation of the Ozonolysis Reaction XVI.

Substituent Effects i n the Ozonization Rates of Ethylenes


JACQUES C A R L E S and SÁNDOR FLISZÁR University of Montreal, Montreal, Québec, Canada

The effects contributed by alkyl groups to the relative rate constants, k , for the reaction of ozone with cis- and trans1,2-disubstituted ethylenes are adequately described by Taft's equation k = k° + ρΣσ , where Σσ is the sum of Taft's polar substituent constants. The positive ρ values (3.75 for trans- and 2.60 for cis-1,2-disubstituted ethylenes) indicate that for these olefins the rate-determining step is a nucleophilic process. The results are interpreted by assuming that the electrophilic attack of ozone on the carbon-carbon double bond can result either in a 1,3-dipolar cycloaddition (in which case the over-all process appears to be electrophilic) or in the reversible formation of a complex (for which the ring closure to give the 1,2,3-trioxolane is the nucleophilic rate-determining step). rel

*

rel

*

rel

*

A T o s t of the experimental studies concerning the mode of attack of ozone on carbon-carbon double bonds have been done with aromatic compounds. F r o m the ozonolysis of polycyclic aromatic compounds, Badger ( I ) and Brown (2, 3) concluded that the ozone makes a one-step attack on the unsaturated system at the bond with the lowest bond localization energy, rather than an attack involving first the atom with the lowest atom localization energy. This is supported by the high yield ( 7 1 % ) of 4-formyl-5-phenanthrene carboxylic acid which is produced i n the ozone attack on the 1:2 bond of pyrene (J)—the bond with the lowest bond localization energy. O n the other hand, studies on the ozonolysis of substituted benzenes by van Dijk (4) and Wibaut (5,6) seem to indicate that the ozone attack 35 In Ozone Reactions with Organic Compounds; Bailey, P.; Advances in Chemistry; American Chemical Society: Washington, DC, 1972.

36

OZONE

ORGANIC COMPOUNDS

is electrophilic i n nature; the results presume an attack at the position with the lowest atom localization energy. This is confirmed by Bailey's finding (7) that anthracene is attacked by ozone at the positions with the lowest atom localization energy—i.e., 9 and 10 to give anthraquinone in 70% yield. More recent studies by Nakagawa, et al. (8) confirm the interpretation of the ozone attack on carbon-carbon double bonds i n terms of an electrophilic attack. Their investigations on the kinetics of ozonization of polyalkylbenzenes, i n C C 1 and C H C O O H solution, indicate that the logarithms of the rate constants for the ozonolysis of polymethylbenzenes increase linearly with the number of methyl substituents on the aromatic nucleus. Similar conclusions are drawn by Cvetanovic et al. from their results of ozonization of alkenes i n the gas phase (9) and i n C C 1 solution (10). The rate constants for the ozonolysis of chloroethylenes and allyl chloride, in C C 1 solution, indicate (11) that the rate of ozone attack decreases rapidly as the number of chlorine atoms in the olefin molecules is i n creased. However, to explain the departures from simple correlations, in some cases steric effects and the dipolar character of ozone had to be invoked (10). The relevance of the dipolar character of ozone i n its reactions has also been stressed by Huisgen (12), who provided evidence that the ozone—olefin reaction is usually a 1,3-dipolar cycloaddition. Finally (13), the relative rate constants for the reaction of ozone with selected ring-substituted styrenes i n C C 1 solution indicate that the second-order rate constants obey Hammett's equation: log k = log k + pa. The negative value of p (—0.91 db 0.03) confirms that for these olefins the ozone attack is electrophilic i n nature. The trends i n the ozonolysis rates of simple olefins require further examination. The object of the present work was to obtain kinetic data on the reaction of ozone with simple alkyl-substituted ethylenes. The results w i l l allow a discussion of the substituent effects on the reaction rates and of the mode of ozone attack on the carbon-carbon double bond. 4


REACTIONS W I T H

3

4

4

4

0

Relative Rate Constants O n the basis of the evidence (10) that, i n solution, the ozone-olefin reaction takes place with a 1:1 stoichiometry, the consumption of olefin i may be written — dXi/dt = ki[Oz]Xi

(1)

where ac« is the concentration of olefin i at time t = t, and ki the rate constant for its reaction with ozone. As indicated by the results obtained in a previous study (10), the integral rate law,


4.

CARLES AND FLISZAR

37

The Ozonolysis Reaction

log(z[03]o/[0 K) =

fa(*o-[0,]o)/2.3

3

(2)

which is derived from Equation 1, satisfactorily describes the kinetics of a variety of olefins with ozone i n C C 1 solution. In Equation 2, [ 0 ] and x are the ozone and olefin initial concentrations and it is assumed that [ 0 ] ^ x . The agreement of Equation 2 with the experimental results thus confirms the order of reaction postulated i n Equation 1. Attempts to calculate the rate constants, made with the assumption of orders of reaction different from unity (referred to each reactant), failed in giving constant values for k. In the present work, ozone was continuously bubbled through the olefin solution at a constant flow rate. Assuming a steady ozone concentration [ 0 ] under these conditions, the integral rate law which is derived from Equation 1 is as follows: 4

3

0

0


3

0

0

3

]n(xi/xi, ) 0

(3)

= — ki[0 ]t 3

where x- is the concentration of olefin i at time t = 0. Hence, i n the conventional ozonolysis of a mixture of two olefins which are identified b y the subscripts 1 and 2, it is h0

log(ziM.o) =

-fci[0 ]*/2.3 8

(4) log(x /3 .o) 2

2

=

-k [O ]t/2.3 2

z

and, consequently, ki/k

2

= log(xi/x o)/log(x /x2.o) lt

2

(5)

This equation enables relative rate constants fcrel = ki/ko

(6)

(with respect to olefin 2) to be measured in a simple way, by conventional ozonolysis, from the analyses of the unreacted olefins. The fact that fc i is independent of the ozone concentration and of the reaction time t (as predicted by Equation 5) considerably facilitates the measurements of k \. The results i n Table I concern the progressive ozonolysis of a C C 1 solution of p-methylstyrene (1) and styrene ( 2 ) , at 0 ° C , where the initial concentrations are x = 0.05M and x , = 0.1M. The constancy of fc i which is observed clearly confirms that fc i is independent of reaction time. re

re

4

ljQ

re

2 0

re



38

OZONE

0.0

0.2

REACTIONS W I T H

0.4

ORGANIC COMPOUNDS

0.6 \nx /%l 2

Figure 1. Typical plot for calculating k : ip-methylstyrene (l)vs. styrene (2) rel

To improve the analysis of the experimental results, it appears adequate to plot l o g ( x i A i ) vs. log(x /x2, ), indicated in Figure 1, and to calculate the slope—i.e., k by a least-squares method. Table II presents a summary of the values of k which were obtained in the way just indicated, for p-methylstyrene, in C C 1 solution, with respect to styrene. These results indicate that k is invariant with respect to the ozone flow rate, the temperature of ozonolysis, and the olefin initial concentration. The fact that fc i is independent of temperature in this case is readily understood when it is considered that the experimental activation energies for the ozone-olefin reaction are likely to be very similar for p-methylstyrene and styrene. > 0

2

0

a

s

reh

rel

4

reX

re

Table I. Relative Rate Constants for the Ozonolysis of J-Methylstyrene (1) with Respect to Styrene (2) Olefin Concentration, mole/liter Ozonolysis, %

x

0 5 10 20 25 48 67

0.0500 0.0474 0.0450 0.0397 0.0375 0.0259 0.0164

a

x

x

2

0.1000 0.0966 0.0933 0.0856 0.0826 0.0648 0.0470

k i = ki/k re

— 1.54 1.52 1.48 1.50 1.52 1.48 A v . 1.506

a

2

With respect to x\ = 0.0500.


±0.025

4.

CARLES AND FLISZAR

The

39

Ozonolysis Reaction

Table II. Relative Reaction Rates for ^-Methylstyrene (1) with Respect to Styrene (2), in C C l Solution, under Various Conditions 4

0 Output, mmole/ min

Temperature, °C

x°i (M)

x° (M)

0.090 0.120 0.142 0.142 0.142 0.142 0.114

0 0 0 35 0 0 0

0.10 0.10 0.10 0.10 0.05 0.025 0.05

0.10 0.10 0.10 0.10 0.05 0.025 0.10

3

2

l

n

1.48 1.51 1.52 1.52 1.49 1.49 1.51

4 3 3 2 3 2 6

k

tt

re


A v . 1.503 ° Average values, from n independent determinations.

Experimental Materials. A sample of pure cis-di-ter£-butylethylene was prepared by R. Criegee (Karlsruhe). A l l other olefins are commercial products ( K & K Laboratories Inc. and Aldrich Chemical Co. Inc.); their purity was controlled by gas chromatographic analysis. Ozonolysis Procedure. Ten m l of olefin solution were ozonized at 0 ° C with an oxygen-ozone mixture. The ozone concentration was sufficiently high 4 % ) to make the ozonolyses possible with relatively low 0 — 0 flow rates ( « 0.15 mmole 0 / m i n ) in order to prevent olefin loss by evaporation. Control experiments, performed with pure 0 , indicated that no appreciable amount of olefin is lost by bubbling the gas in the olefin solution i n time intervals comparable with those required for the actual experiments. Gas Chromatographic Analyses. Were performed with a 5750 F & M gas chromatograph, using a flame detector. Six-foot columns of silicone rubber U C W 9 8 were used for styrene, the ring-substituted styrenes, 3- phenylpropene, cis- and trans-stilbene, and cis-di-feit-butylethylene. Six-foot columns of 10% Carbowax 20M were used for styrene, 3-iodopropene, 3-chloropropene, cis- and £rans-3-hexene, cis- and trans-4,4dimethyl-2-pentene, cis- and £rans-5,5-dimethyl-3-hexene, cis- and trans4- methyl-2-pentene, £rans-2-methyl-3-hexene, cis- and £rans-2,5-dimethyl3-hexene, trans-di-tert-butylethylene, and 3-ethoxypropene. A 20-foot column of 10% nitrilesilicone on Chromosorb P was used for cis- and trans-4-octene and 3-bromopropene. A 6-foot 20% propylene carbonate column was used for cis- and £rans-2-hexene, cis- and trans-2-pentene, and 1-pentene. A 20% diisopropyl phthalate 6-ft column was used for 3,3dimethyl-l-butene and 3-methyl-l-butene. A l l analyses were repeated at least three times. The areas under the peaks corresponding to the olefins were measured by a planimeter and compared with the areas which were obtained under the same conditions with adequate reference solutions. 2

3

3

2


40


Results and Discussion In the following discussion, the relative rate constants (with respect to styrene) are calculated by a least-squares analysis of the data, using Equation 5, from six to 10 experimental results. The standard deviations (s) from the regression line (k ) are also indicated. The results obtained for the cis- and trans-l,2-disubstituted ethylenes are indicated, for the symmetrical and the unsymmetrical olefins, respectively, i n Tables III and I V and i n Table V for the monosubstituted ethylenes. A comparison of the results obtained with alkyl-substituted ethylenes (Tables III and I V ) indicates that fc i decreases with increasing bulk of the substituents. This is also found to be true with the terminal olefins (Table V ) , as indicated by the lowering of k i from 1.11 to 0.407 when n-propyl is replaced by the tert-butyl group. The terminal olefins bearing an electron-withdrawing substituent also indicate a significant decrease of k as compared with 1-pentene, which is i n agreement with Cvetanovic's observations ( I I ) . From this superficial consideration of substituent effects it would thus appear that the ozone attack is electrophilic i n nature and that important steric effects contribute i n determining the rate constants. The influence of steric effects could be adequately illustrated by the rel


re

re

reh

Table III. Relative Rate Constants for the Ozonolysis of Symmetrical Olefins ( R C H ^ C H R ) in CCI4 cis krel

s

krel

s

2.13 1.150 0.471 0.197 0.233

0.14 0.044 0.014 0.029 0.016

2.98 2.05 0.613 0.088 3.13

0.15 0.32 0.026 0.004 0.495

R C H n-C H ;-C H ter£-C H C6H5 2

5

3

7

3

7

4

9

trans

Table IV. Relative Rate Constants for the Ozonolysis of Unsymmetrical Olefins ( R ! C H = C H R ) in C C l 2

4

cis R2

Ri CH CH CH CH C H C H 3

3

3

3

7

3

3

2

5

2

5

0

C2H5 n-C H ;-C H tert-GJl^ ;-C H ter£-C H 7

3

7

4

9

trans

krel

s

krel

s

3.44 2.33 1.87 0.932 .) 0.48

0.09 0.09 0.05 0.041 («) 0.02

4.99 4.25 2.59 0.927 1.26 0.45

0.06 0.16 0.08 0.051 0.02 0.02

(

Not determined.


4.

CARLES A N D FLISZAR

Table V .

Relative Rate Constants for the Ozonolysis of Monosubstituted Ethylenes in CCI4

Olefin 3

4

s

krel

n-C H -CH = CH t-C H -CH = CH terf-C H -CH = CH 7

3

41


2

9

2

C6H5CH2 — C H = C H 2 C2H5OCH2 — C H = CH2

ICH -CH = CH BrCH -CH = CH C1CH -CH = CH 2

2

2

2

2

2

0.05 0.014 0.016 0.008 0.006 0.006 0.004 0.006

1.11 0.680 0.407 0.113 0.177 0.174 0.148 0.205

2

7

results i n Table III, which indicate that fc i drops from 2.98 to 0.008, i n trans-1,2-disubstituted ethylenes when the ethyl groups are replaced by two tert-butyl groups. It appears, however, that such a simplified explanation, i n which the effects from the alkyl substituents are interpreted mainly on steric grounds, meets with difficulties. The relative rate constants of ozonation can, i n fact, differ considerably for ethylenes which have different substituents although their steric factors are similar. This is clearly indicated by comparing the results obtained for 1-pentene and iodo-3-propene. The n-propyl and C H I groups exhibit similar steric effects, as indicated by Taft's steric constants (E = —0.36 for n - C H ; E = —0.37 for C H I ) ; yet jfc i is about six times greater for 1-propene than for iodo-3propene. Thus, it appears that the polar effects contributed b y the groups to k need a closer examination.


re

2

3

s

2

7

s

re

rei

CD

O) O — 0.5

tranSypQy^

0.0

-0.5

^

>

-1.0 1

-0.3

1

1

-0.2

-0.1 _ *

Figure 2. Comparison of log k with Taft's polar a* constants for symmetrical 1,2-disubstituted ethylenes rel


42

OZONE

REACTIONS

WITH

ORGANIC COMPOUNDS

The participation of polar effects can be studied adequately by Taft's equation (14): log(*A°)

= p*a*

(7)

where k is the rate constant for an olefin RiCH=CHR, and k° is the rate constant when R = CH . In terms of relative rate constants (Equation 6), this equation becomes 3

log k

= log k°


nl

+ p*c*

Tel

(8)

The satisfactory agreement of Equation 8 with the experimental results given i n Tables I I I - V is shown i n Figures 2-5. The good

Figure 3. Verification of Equation 8 for trans1,2-disubstituted ethylenes: CH CH=CHR (1), C H CH=CHR (2), i-C H CH=CHR (3), and tertC H CH=CHR (4) 3

2

5

3

U

7

9

correlations which are observed seem to indicate an important contribution of polar effects and a minor (if any) influence of steric effects on fcrei. This point is supported by an evaluation of the relative importance of polar and steric effects by Taft's generalized equation (15): log(k/k°)

= p*a* + hE

(9)

s

which, in terms of relative rate constants is: l0gfc l re

=*l0gA; el O

r

+

P

*S*

+

%E.


(10)


4.

CARLES A N D FLISZAR

The

43

Ozonolysis Reaction

Figure 4. Verification of Equation 8 for cis1,2-disuhstituted ethylenes: CH CH=CHR (1), ( ) i-C H CH=CHR (3), and C~H,CH=CHR tert-C H CH=CHR(4) 3

2 9

2

It

3

7

9

The symmetrical cis- and trans-olefins R C H = C H R (Table III) are particularly suited to this evaluation by Equation 10 because the polar reaction constant p* and the steric correlation coefficient 8 reflect, i n this series of olefins, the effect of varying two substituents. Hence, the expected effects (both on p* and 8) are more pronounced than those expected for olefins in which only one substituent is varied. A least-squares calculation of p* and 8 by Equation 10, from the data i n Table III, gives the following results for cis- and trans-olefins, RCH=CHR. trans

p* = 7.58

8 =

0.019

cis

p* = 5.37

8 = 0.0027

When Equation 10 is applied to symmetrical olefins, the term A:° i refers to 2-butene (R = C H ) . The calculated fc° i values are: 17.5 for trans-2-butene and 6.13 for the cis-isomer. The above calculations show that the steric contributions are small compared with the important polar effects, both in trans- and cis-olefins. Hence, in the following discussion, attention is focused on the predominant polar effects contributed by substituents, although a minor steric effect can possibly influence the overall reaction scheme. Figure 3 indicates that for the trans-olefins C H C H = C H R , C H C H = C H R , i - C H C H = C H R , and tert-C H CH=CHR the slopes (Equation 8) are similar, within experimental error. The same observation also applies to the cis-olefins represented in Figure 4. This suggests re

3

re

3

2

5

3

7

4

9


44

OZONE

REACTIONS

WITH

ORGANIC

COMPOUNDS

that i n olefins RiCH=CHR , the substituent effects possibly obey a simple additive rule—i.e., 2

log(k/k°)

(11)

= p*a*(Ri) + p*a*(R ) 2

Hence, in terms of relative rate constants, the dependence of fc i on polar effects contributed by both substituents is adequately described by the following equation: re

log fcrel =

log

ft° l re

+

(12)

P*2 C =

C
c

3

k-

>c-

la

/ 0\

I c
c- Ib -c
c- Ic -c
fci (cis) andfc (trans) > k (cis). In the final analysis, the geometry of the olefin has opposite effects (a) on K and ( b ) on ki and k . Present results seem to indicate that for large substituents the effect on K predominates since k (cis) > k (trans). c

c

2

3

2

2

c

2

c


4.

CARLES AND FLISZAR


49

Finally, the activated complex i n path 1 and the TT (or a) complex in path 2 have similar charge separations, which are similar to that of the ozone molecule. A n y solvent effect is thus expected to be similar i n both mechanisms. This is confirmed by the results i n Table V I , which indicate that k i is nearly independent of the ozonolysis solvent. Te

Acknowledgment


W e thank R. Criegee for preparing and supplying ds-di-terf-butylethylene. The financial support given by the National Research Council of Canada is gratefully acknowledged. Literature Cited

1. Badger, G. M., Campbell, J. E., Cook, J. W., Raphael, R. A., Scott, A. J., J. Chem. Soc. (1950) 2326. 2. Brown, R. D., Quart. Rev. Chem. Soc. (1952) 6, 63. 3. Brown, R. D., J. Chem. Soc. (1950) 3249. 4. van Dijk, J., Rec. Trav. Chim. Pays-Bos (1948) 67, 945. 5. Wibaut, J. P., Sixma, F. L. J., Kampschmidt, L. W. F., Boer, H., Rec. Trav. Chim. Pays-Bos (1950) 69, 1355. 6. Wibaut, J. P., Sixma, F. L. J., Rec. Trav. Chim. Pays-Bos (1952) 71, 761. 7. Bailey, P. S., Ashton, J. B., J. Org. Chem. (1957) 22, 98. 8. Nakagawa, T. W., Andrews, L. J., Keefer, R. M., J. Amer. Chem. Soc. (1960) 82, 269. 9. Vrbaski, T., Cvetanović, R. J., Can. J. Chem. (1960) 38, 1053. 10. Williamson, D. G., Cvetanović, R. J., J. Amer. Chem. Soc. (1968) 90, 3668. 11. Ibid., p. 4248. 12. Huisgen, R., Angew. Chem., Intern. Ed. Engl (1963) 2, 565, 633. 13. Klutsch, G., Fliszar, S., Can. J. Chem., in press. 14. Taft, R. W., J. Amer. Chem. Soc. (1953) 75, 4231. 15. Taft, R. W., "Steric Effects in Organic Chemistry," M. S. Newman, Ed., Wiley, New York, 1956. 16. Pritzkow, W., Schoppe, G., J. Prakt. Chem. (1969) 311, 689. 17. Bailey, P. S., Chem. Ind. (1957) 1148. 18. Bailey, P. S., Chem. Rev. (1958) 58, 925. 19. Bailey, P. S., Lane, A. G., J. Amer. Chem. Soc. (1967) 89, 4473. 20. Murray, R. W., Youssefyeh, R. D., Story, P. R., J. Amer. Chem. Soc. (1967) 89, 2429. 21. Durham, L. J., Greenwood, F. L., Chem. Commun. (1967) 843. 22. Durham, L. J., Greenwood, F. L., J. Org. Chem. (1968) 33, 1629. 23. Bailey, P. S., Potts, F. E., Ward, J. W., J. Amer. Chem. Soc. (1970) 92, 230. 24. Ingold, C. K., in "Structure and Mechanisms," G. Bell, London, 1953. 25. Murray, R. W., Youssefyeh, R. D., Story, P. R., J. Amer. Chem. Soc. (1966) 88, 3143. R E C E I V E D May 20,

1971.


5 The Interaction of Ozone with Double Bonds Containing Vinyl Bromide Moieties K A R L G R I E S B A U M and J. BRÜGGEMANN


Engler-Bunte-Institut der Universität Karlsruhe, 75 Karlsruhe, Germany

The present contribution reports the first results of a systematic approach to a study of the reaction and the products obtained in the liquid-phase ozonolysis of unsaturated substrates containing halogenated double bonds. As a model case the ozonolysis of trans-2,3-dibromo-2-butene was studied. Ozonolysis occurs at a slower rate than that of pure hydrocarbon olefins and less than equimolar amounts of ozone are sufficient for the quantitative conversion of the substrate. Double bond cleavage is not the overriding reaction, but the original double bond is to a large extent converted into C—C single bonds which are fairly stable towards further ozone attack.

T p h e ozonolysis of pure hydrocarbon olefins has been studied b y generations of chemists ever since 1905 when Harries established the interaction of ozone with double bonds. During this continued research practically all aspects of the ozonolysis reaction have been extensively scrutinized, starting from the nature and products of the initial ozonedouble bond interaction, via the mechanistic and stereochemical course of the ozone cleavage, to the correlation between the nature of the starting material and the reaction products. Consequently, the ozonolysis of hydrocarbon olefins is rather well understood. In contrast to this, very little is known about the ozonolysis of olefins which bear halogen substituents at the double bond. This is somewhat surprising since compounds containing vinyl halide moieties are important technical products whose properties could be adversely affected by ozone degradation. A case i n point is neoprene rubber, whose performance as an elastomer could suffer considerably by ozone attack and concurrent crack formation (1). /

A

50 In Ozone Reactions with Organic Compounds; Bailey, P.; Advances in Chemistry; American Chemical Society: Washington, DC, 1972.

5.

51

Double Bonds

GRIESBAUM AND BRUGGEMANN

Background


W h e n this work was initiated, there were only a few scattered reports i n the literature concerned with the interaction of ozone and halogenated double bonds. The bulk of these reports dealt with the ozonolysis of substrates containing both halogenated and non-halogenated double bonds. In a l l of these cases the non-halogenated double bond was attacked preferentially by ozone, and only products derived from that kind of reaction were described. Ozonolysis of 1,2,3,4,7,7-hexachlorobicyclo [2.2.1] hepta-2,5-diene, 1, in participating and i n non-participating solvents was reported to yield the cleavage products, 2 and 3, respectively ( 2 ) :

Ozonolysis of l,6,7,8-tetrachloro-2,3,4,5-tetramethylbicyclo [4.2.0.0. (2,5) ] octadiene, 4, i n pentane was reported to form the monomeric ozonide, 5 ( 3 ) :

cu CI'

CI

CH

3

..CH

S

CI C H

CH

3

3

. CI.

CI'

3

CI C H

3

CI

3

CH

CH

3

CH

3

Ozonolysis of hexachlorodicyclopentadiene, 6, i n methanol-methylene chloride solution produced 7 as a major ozonolysis product (4): CI

OH


52

OZONE

REACTIONS W I T H ORGANIC COMPOUNDS

Ozonolysis of the monobromide 8 i n ethyl acetate occurred also preferably at the non-halogenated double bond to form the ozonide 9 (5): CH

3

CH,


CH,

These scattered observations indicate that ozonolysis of a halogenated double bond occurs at a much slower rate than that of a non-halogenated double bond, even if the former is part of the more strained ring system as i n 6 or if the double is monohalogenated as in 8. This qualitative picture was substantially confirmed by the results of a quantitative study of the rate of ozone attack at variously chlorinated ethylenes (6). As shown in Table I, the rates of ozone attack decrease dramatically as chlorine is successively substituted for hydrogen in ethylene. Table I. Second-Order Rate Constants (K) for the Reactions of Ozone with Olefins in C C l Solutions at Room Temperature (6) 4

K , liter/mole

Olefin

CC1 =CC1 CHC1=CC1 CH =CC1 2

2 2

2

2

as-CHCl=CHCl £rems-CHCl=CHCl

CH =CHC1 2

CH2=CH

2

sec

1.0 3.6 22.1 35.7 591 1118 25,000 (estimated)

This decreased reactivity of halogenated double bonds towards ozone has been ascribed by some workers to the inductive electron-withdrawing effect of the halogen substituents and to a concurrent decrease of the electron density at the double bond (6); others argued more on the basis of steric hindrance of the double bond by the bulky halogen substituents (4). In any event, the slow reaction is probably the major reason for the fact that little is known about the products and thus about the course of the ozonolysis of halogenated double bonds. In fact, to our knowledge the reaction products have only been thoroughly examined for the ozon-


5.

GRIESBAUM

Double Bonds

AND BRUGGEMANN

53


olysis of certain special substrates such as tetrafluoroethylene (7) and the 9,10-dihaloanthracenes (8). Ozonolysis of tetrafluoroethylene 10 in non-participating solvents was reported to produce carbonyl fluoride 11 and tetrafluoroethylene oxide 13 as the major compounds, along with minor amounts of perfluorocyclopropane 15 as well as trace amounts of a compound to which the authors assigned the structure of the monomeric ozonide 16 of tetrafluoroethylene (7). This result was rationalized by assuming a normal Criegeetype cleavage via the two fragments 11 and 12, followed by secondary reactions of the zwitterion 12 such as epoxidation of tetrafluoroethylene and deoxygenation of 12 to form the carbene 14.

CF =CF 2

+

2

0

-> C F

CF

2

13

10

CF =0 2

11

+

2

3

+

CF —0—02

-0

•> : C F

+ 10 2

CF =0 2

11

CF

CF

2

2

2

12

14 15 O—O

/

v

^ F C 2

\ CF

2

16

Ozonolysis of 9,10-dibromo- (17a) and 9,10-dichloroanthracene (17b) was reported to occur partly by attack at the non-halogenated double bonds to yield the d i - (18) and tetracarboxylic acids, 19, as well as by attack at the 9,10-positions to yield the dehalogenated product anthraquinone, 22 (8). This dual attack might at first seem to be i n contrast to what was said above about the relative rates of ozone attack at halogenated and non-halogenated double bonds. However, this is not the case if one considers that (in analogy to the ozonolysis of the unsubstituted anthracene) the reaction at the 9,10-positions has to be formulated as an atom- rather than a bond attack. In accordance with such a rationalization, the authors (8) formulated the intermediates 20 and 21 as precursors for anthraquinone.



54

OZONE

REACTIONS W I T H

ORGANIC COMPOUNDS

It is apparent from the foregoing that these special cases cannot be viewed as typical examples for the ozonolysis of halogenated double bonds i n general. In the ozonolysis of tetrafluoroethylene there was partial cleavage of the double bond and no loss of halogen substituents, while ozonolysis of the 9,10-dihaloanthracenes resulted i n the loss of the halogen substituents, however, not i n a cleavage of the halogenated double bonds. To obtain information of a more general nature, it appeared necessary to select model substrates which more closely resemble the structures of the commonly occurring mono- and dihalosubstituted olefins. A s the first model we chose 2,3-dibromo-2-butene, whose ozonolysis is described below. Experimental Ozonolysis of 2,3-Dibromo-2-butene. The ozone-oxygen stream that left the ozonizer passed through a trap which was kept at — 78 °C in order


5.

GRIESBAUM AND BRUGGEMANN

55

Double Bonds


to keep the gas free of moisture. The gas then passed through the reaction mixture and then to a condenser kept at — 78 °C to minimize losses of low boiling components. Before entering an aqueous sodium iodide solution, the exit gas again passed a cold trap to avoid condensation of moisture from the sodium iodide solution into the reaction mixture. Samples for N M R analysis were taken b y transferring the reaction mixture pneumatically into a previously attached N M R tube so that during this operation also admission of moisture was minimized. Ozonolysis of £r*MM-2,3-Dibromo-2-butene in Inert Solvents. STARTING M A T E R I A L . The title compound 23 was prepared b y adding bromine to 2-butyne at ca. —30° to — 40 °C. The reaction produced 23 i n more than 9 5 % yield, along with less than 5 % of the cis-isomer, 24, and trace amounts of as yet unidentified by-products. CH

Br

3

CH

c=c Br

3

c=c CH

23

CH

3

3

Br

Br 24

Results The stereochemical assignments of 23 and 24 are based on the infrared spectra of the isolated pure compounds (Figure 1). The spectrum of the cis-isomer, 24, shows a sharp, presumably C = C stretching band at 1640 c m which is absent i n the spectrum of the trans-isomer, 23. Stoichiometry of the Reaction. U p o n ozonolysis of 23 i n inert solvents (pentane, methylene chloride, 1,1,2,2-tetrachloroethane) or without solvents, the originally colorless solutions turned light brown within minutes after the ozonolysis began and gradually assumed the typical deep red color of dissolved bromine. Unreacted ozone began to pass the reactor a few minutes after the ozonolysis began, and at any time thereafter the amount of ozone produced surpassed the amount of ozone consumed (Figure 2 ) . This result was undoubtedly caused by the decreased reactivity of the dibrominated double bond in 23. To assess the quantitative correlations between ozone consumption, olefin consumption and product formation, experiments were carried out in the presence of 1,1,2,2-tetrachloroethane as an internal standard for N M R analyses. These experiments showed that only about half the equimolar amount of ozone was required to consume the olefin completely (Figure 3 ) . This stoichiometry was obviously not the 1:1-stoichiometry usually found i n the ozonolysis of hydrocarbon olefins and which is the basis for the quantitative assessment of the number of double bonds i n organic molecules by ozonolysis. Attempts to explain this unusual stoi- 1


56

OZONE REACTIONS

5000 4000

3000

2500

2000 1800

1600

1400

1200

1000 950

f\f Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch005

r•••••••

,• | |--

r

i | •'

i

WITH 900

850

800

750

700

r

3

i

i

•

'

650

:

CH -C=C—CH

I

1

ORGANIC COMPOUNDS

i

-

3

i

i

i

f] 2

3

4

Figure 1.

5

6

7

8

9

10

11

12

13

14

15

Infrared spectra of cis- and trains~2,3-dibromo-2-butene (neat)

chiometry had to await the qualitative and quantitative analysis of the reaction products. Ozonolysis Products. Preliminary experiments showed that the ozonolysis of 23 produced a number of highly reactive components such as bromine, acetyl bromide, and acetic acid. Therefore, a quantitative analysis of the crude reaction products by G L C was not feasible. N M R analysis, on the other hand, was easily possible since both the starting material and most of the products exhibited singlet signals that were well enough separated for quantitative analysis. Figure 4 shows the N M R spectrum of a crude ozonolysis product i n which the substrate 23 had been completely converted. Each structural assignment of signals 1-7 i n the spectrum of Figure 4 is based on the addition of the authentic compound to the crude ozonolysis mixture, and—aside from peak 1—is also based on additional analytical evidence: 2,2,3,3-tetrabromobutane (peak 2 ) , 3,3-dibromobutanone (peak 4 ) , and acetic acid were actually isolated while acetyl bromide (peak 3) as well as acetic anhydride (peak 5) were further identified by their sensitivity to solvolysis reactions, particularly hydrolysis and alcoholysis to form the corresponding esters. Diacetylperoxide (peak 6) was identified by the disappearance of peak 6 from the N M R spectrum as well as the disappearance of the typical infrared bands at 1810 and 1835 cm" when the reaction mixture was treated with sodium iodide. 1


5.

GRIESBAUM

Double Bonds

AND BRUGGEMANN

57

In addition to the seven organic products mentioned above, ozonolysis of 23 also produced considerable amounts of free bromine, which was qualitatively and quantitatively detected by its addition to 2,3-dimethyl2-butene and subsequent analysis of the resulting dibromide.


Discussion Rationalization of Ozonolysis Products. Obviously the ozonolysis of £rans-2,3-dibromo-2-butene leads to a greater variety of products than one might have expected if the reaction were strictly analogous to the ozonolysis of hydrocarbon olefins. In particular, there is no evidence for the formation of the trioxolane-type ozonide 27. Nevertheless, all the reaction products identified could be readily rationalized by a normal Criegee-type primary cleavage pattern if one assumes that, owing to their special structural features, the two fragments, acetyl bromide 25 and the zwitterion 26, undergo a number of subsequent reactions which are not open to the ozonolysis fragments derived from purely hydrocarbon olefins:

Br

I

CH3

C==C C H 3

23

I

Br 0

Products <
24 +

Br

C

B r ^

> CH COBr CH 3

2

^ C H ,

26

30

31

The formation of the completely debrominated product, diacetyl peroxide 33, from the zwitterion intermediate, 26, probably proceeds via the d i meric peroxide of structure 32 in the manner depicted below:

O—O 2 CH —C—00"

C

>

3

Br

CH

3

/

CH N

s

C

3

/

>

Ôô'^Br 32

CH —C—0—0—C—CH 3

II

II

0

3

+ Br

2

0

33 Although the intermediate dimeric peroxide, 32, could not be isolated and rigorously proved, there are two items of evidence which favor the postulated reaction course. The first evidence comes from independent experiments i n which tetracyanoethylene was used as a coreagent during the ozonolysis of 23. In these cases, the formation of diacetyl peroxide, 33, as well as that of 3,3-dibromobutanone, 31, was drastically reduced, and at the same time tetracyanoethylene epoxide was formed. Apparently, the reaction of tetracyanoethylene with the zwit-


3


5.

GRIESBAUM

61

Double Bonds

AND BRUGGEMANN

terion, 26, is faster than the dimerization of the zwitterion to form 32—a phenomenon already observed during the ozonolysis of normal olefins ( 9 ) . The second piece of evidence for the intermediacy of the dimeric peroxide, 32, stems from the low temperature ozonolysis of trans-2,3dibromo-2-butene, 23. In contrast to the usual reactions which were carried out at ca. —35°C, the ozonolysis of 23 i n pentane at —78°C yielded a solid white precipitate which exploded violently when we tried to isolate it. W h e n the low temperature ozonolysis was carried out i n methylene chloride, on the other hand, no precipitate appeared. However, when the methylene chloride solution of the ozonolysis product was allowed to warm up gradually, an exothermic reaction set i n at around —50°C, and the originally colorless solution showed the typical color of dissolved bromine. It is assumed that the explosive material is the dimeric peroxide, 32, which undergoes spontaneous debromination to form d i acetyl peroxide, 33. The remaining two products from the ozonolysis of 23—viz., the tetrabromide, 34, and the tribromide, 3 5, are the result of addition and substitution reactions of the bromine that is liberated during the ozonolysis reaction. Both reactions are probably favored by the presence of peroxidic materials i n the solution since it could be shown that they progress much slower if bromine and £rans-2,3-dibromo-2-butene, 23, react i n the absence of initiators. This is particularly true for the substitution reaction leading to 35. During independent experiments, when the substrate, 23, was added to ozonized solutions of bromine in methylene chloride, the substitution was markedly favored. Br

I

Br

CH —C=C—CH 3

|

23

Br

8

2

-»

CH CBr CBr CH + BrCH CBr=CBrCH 3

2

2

3

2

3

Peroxides

34

35

The nature and the distribution (Table II) of the ozonolysis products i n conjunction with the probable modes of their formation allow also a qualitative rationalization of the observed ozone-olefin stoichiometry. Three reactions compete with ozone for the starting material, £rarw-2,3-dibromo-2-butene. These reactions are the formation of 3,3dibromobutanone, 31, and the formation of the brominated products, 34 and 35. O n the other hand, hydrogen bromide is oxidized to form bromine and water, which consumes ozone on top of the regular olefinozonolysis reaction. A n attempt to explain the observed stoichiometry quantitatively did, however, not lead to a satisfactory correlation between the actual ozone consumption and the observed material balance. This


62

OZONE

REACTIONS W I T H

Table II.

none Pentane


CH2CI2

Products of the Ozonolysis

Product Distribution,

Conversion,

Solvent

ORGANIC COMPOUNDS

mole %

%

AcBr

AcOH

AcOAc

50 85 95

26 44 23

15 19 24

—

8

14

AcOOAc 9 6 13

could be the result of a concurrently occurring, ozone-initiated autoxidation reaction such as ozone-initiated oxidation of hydrogen bromide. Ozonolysis of tvans-2,3-Dibromo-2-butene in Participating Solvents. In contrast to the great variety of products resulting from the ozonolysis of 23 in inert solvents, the ozonolysis i n methanol, ethanol, and 1-butanol produced mainly the corresponding acetates, 37, and bromine. In addition, the presence of an as yet unidentified peroxidic material was detected by the sodium iodide method. However, in each case the amount of ester produced was greater than one would have expected if the acetyl bromide fragment, 25, were the only precursor for it. This seems to indicate that the second, presumably zwitterion fragment, 26, can also lead to the formation of ester. Obviously, this would require the reduction of a peroxidic intermediate, possibly of the type 36. This may proceed i n a manner similar to that formulated for the debromination of the dimeric peroxide, 32. The hypobromite that is also formed during this step can subsequently oxidize the hydrogen bromide produced during the alcoholysis of acetyl bromide. Br

I CH3—C=C—CH3 Br

03

CH —C—0—0-

OR ROH

CH —C—O—OH 3

3

Br 26

+

CH —C—Br 0 25 3

I

36

Br ROH -HBr

CH

3

J,-HOBr -C—OR

37

O

Conclusions If one disregards the tribromide, 35, i n which the double bond of the substrate, 23, has not been touched at all, the ozonolysis of trans-


5.

GRIESBAUM

63

Double Bonds

AND BRUGGEMANN

of 2,3 -Dibromo-2 -butene Product Distribution, CH COCBr CH 3

2

CH CBr CBr CH

3

3

14 20 13


mole %

2

2

CH CBr=CBrCH Br

3

3

16 6 9

2

11 5 4

2,3-dibromo-2-butene, 23, in inert solvents leads essentially to three types of reaction products—the two actual cleavage products, 25 and 28, two products (29 and 33) i n which the carbon atoms of the original double bond are still held together by a labile anhydride and peroxide group, respectively, and two products (31 and 34) i n which the original double bond has been converted to single bonds that are stable towards further ozone attack: -» C H C O B r + CH3COOH 25 28 3

C H — C B r = C B r — C H + 0, -» C H 3 C O — 0 — C O C H 3 + 23 29 CH3CO—00—COCH3 33 3

3

CH C0CBr CH + CH CBr CBr CH 31 34 3

2

3

3

2

2

3

Although the distribution among these products varies, depending on the reaction conditions, particularly on the solvent used, it is evident from the data i n Table II that the latter type of products i n which the double bond has been immunized towards further ozone attack comprises in each case a significant part (between 22 and 30% ) of the total product mixture. This is perhaps the most remarkable result of the present investigation. In contrast to the ozonolysis of hydrocarbon olefins, the ozonolysis of this dibromosubstituted double bond cannot be viewed primarily as a double bond cleavage reaction. This result may also give a partial explanation for the known ozone stability of polymers containing vinyl halide moieties. Part of this inertness is undoubtedly the result of the slow ozone attack. However, this phenomenon can only impart a prolonged ozone resistance, while the conversion of the original double bond into single bonds could impart a permanent ozone resistance. W e are extending our research to further model compounds of such polymer microstructures to find out whether


64


this is a general phenomenon of the ozonolysis of halogenated double bonds. From a preparative standpoint, ozonolysis i n inert solvents does not represent a satisfactory method for the ozone cleavage of dibromo-substituted double bonds. If this is the desired reaction, it is preferable to use alcohols as participating solvents, which lead to a clean cleavage and to a high yield of the corresponding ester fragments. The latter reaction constitutes a convenient preparative method for the cleavage of acetylenes into the corresponding ester fragments via the intermediate dibromination products.


Literature Cited 1. 2. 3. 4. 5. 6. 7. 8.

Kondo, A., Raba Daijesuto (Japan) (1968) 20 (3), 42. Slagel, R. C., J. Org. Chem. (1966) 31, 593. Criegee, R., Huber, H., Angew. Chem. (1969) 81, 749. Franz, J. E., Knowles, W. S., Osuch, C. J., J. Org. Chem. (1965) 30, 4328. Criegee, R., Schweickhardt, C., Knoche, H., Chem. Ber. (1970) 103, 960. Williamson, D. G., Cvetanović, R. J., J. Amer. Chem. Soc. (1968) 90, 4248. Gozzo, F., Camaggi, G., Chim. Ind. (Milan) (1968) 50, 197. Kolsaker, P., Bailey, P . S., Dobinson, F., Kumar, B., J. Org. Chem. (1964) 29, 1409.

9. Criegee, R., Günther, P., Ber. (1963 ) 96, 1564. RECEIVED August 23, 1971.


6 The Ozone-Hydrosilane Reaction: A Mechanistic Study


LEONARD SPIALTER, LEROY PAZDERNIK, WILLIAM A. SWANSIGER, GLEN R. BUELL, FREEBURGER

STANLEY BERNSTEIN, and MICHAEL E.

Chemical Research Laboratory, Aerospace Research Laboratories, Wright-Patterson AFB, Ohio 45433

The reaction

of a hydrosilane

quantitative

conversion

moiety.

The

mechanism

elucidated.

It involves

ozone (acting

3

silanol.

·OΗ

radical

Extensive of

mono-,

di-,

bond

rapid,

the

Si-OH

has now

been

silicon

of

atom,

fol

attack by the

bound

and decomposition

into

recombine

concerning properties and

to

complexation

the

electrophilic hydrogen,

other structure-dependent number

with

pair which

data

Si-H

of this conversion

as a nucleophile)

ozone upon the hydridic R Si·

the

a fast, reversible

lowed by rate-determining a

with ozone results in the

of

the

to produce

relative

in the

trihydrosilanes

ozonation are

the

rates

and of a

presented.

* T p h e use of o z o n e as a n o x i d a n t f o r o r g a n i c substrates has b e e n k n o w n A

f o r s e v e r a l decades, a n d the s c o p e a n d m e c h a n i s m ( s ) of these o x i d a

tions h a v e e x p e r i e n c e d c o n s i d e r a b l e i n v e s t i g a t i o n (1,

2).

H o w e v e r , it

was n o t u n t i l 1962 t h a t the i n i t i a l r e p o r t of the o z o n e o x i d a t i o n t i o n ) of organosilanes a p p e a r e d

(3).

(ozona

I n 1965, i t w a s d i s c o v e r e d t h a t

ozone w o u l d rapidly, cleanly, a n d quantitatively convert an S i - Η moiety to the c o r r e s p o n d i n g s i l a n o l ( S i - O H ) (4).

S u b s e q u e n t i n v e s t i g a t i o n s of

this r e a c t i o n e l u c i d a t e d its s c o p e a n d r e s u l t e d i n suggested m e c h a n i s t i c p a t h w a y s (5-11).

A l t h o u g h the o z o n a t i o n of the C - H b o n d is r e l a t i v e l y

s l o w a n d y i e l d s , i n g e n e r a l , a m i x t u r e of p r o d u c t s ( I , 12-15),

that of the

S i — H b o n d is r a p i d a n d affords o n l y s i l a n o l . T h e p r e s e n t p a p e r describes a r a t i o n a l m e c h a n i s m f o r t h e o z o n a t i o n of the S i — H b o n d .

D u r i n g the

i n v e s t i g a t i o n , c o n s i d e r a b l e d a t a c o n c e r n i n g s u b s t i t u e n t e l e c t r o n i c effects o n s i l i c o n w e r e a c c u m u l a t e d a n d are d e s c r i b e d .

Their implications i n

o r g a n o s i l i c o n c h e m i s t r y are also d i s c u s s e d . 65


66



Experimental Materials. Solvents u s e d i n c l u d e d hexane, c a r b o n t e t r a c h l o r i d e , a n d m e t h y l e n e c h l o r i d e , a l l of s p e c t r o q u a l i t y a n d f u r t h e r p u r i f i e d b y s a t u r a tion w i t h ozone followed b y nitrogen p u r g i n g a n d distillation. F o r ozone g e n e r a t i o n , o x y g e n gas, d r i e d b y passage t h r o u g h a d r y ice-acetone c o l d t r a p , was i n t r o d u c e d i n t o a W e l s b a c h m o d e l T - 2 3 l a b o r a t o r y ozonator o p e r a t e d at 10 volts a n d 7 p s i g . T h e effluent gas, a b o u t 4 % ozone i n o x y g e n , w a s passed t h r o u g h a n adjustable s t r e a m splitter for flow c o n t r o l a n d t h e n b u b b l e d t h r o u g h a saturator c o n t a i n i n g the solvent also b e i n g u s e d i n the r e a c t i o n system. ( F o r the experiments w i t h oxygen-free ozone, the o z o n e was first s e l e c t i v e l y a d s o r b e d f r o m the ozonator effluent s t r e a m o n t o s i l i c a g e l at — 77 ° C a n d t h e n d e s o r b e d b y w a r m i n g a n d e l u t i o n b y a d r y a r g o n stream. ) T h e h y d r o s i l a n e reagents u s e d , w h e r e a v a i l a b l e , w e r e o b t a i n e d f r o m c o m m e r c i a l s u p p l i e r s s u c h as P i e r c e C h e m i c a l ( R o c k f o r d , 111.), P e n i n s u l a r C h e m Research (Gainesville, F l a . ) , and Matheson, Coleman and Bell ( N o r w o o d , O h i o ) . O t h e r s w e r e s y n t h e s i z e d b y the l i t h i u m a l u m i n u m h y d r i d e or d e u t e r i d e ( A l f a C h e m i c a l , B e v e r l y , M a s s . ) r e d u c t i o n of a p p r o p r i a t e o r g a n i c c h l o r o - or fluorosilane, either p u r c h a s e d f r o m the a b o v e - m e n t i o n e d sources or s y n t h e s i z e d b y c o n v e n t i o n a l routes i n v o l v i n g o r g a n o m a g n e s i u m or - l i t h i u m condensations w i t h halosilanes. A l l s u c h c o m p o u n d s w e r e at least 9 8 % p u r e as d e t e r m i n e d b y v a p o r - p h a s e c h r o m a t o g r a p h y ( V P C ) . S t r u c t u r a l i d e n t i t y was e s t a b l i s h e d b y m o l e c u l a r analysis, i n f r a r e d , a n d N M R s p e c t r o s c o p y w h e r e necessary. A new compound synthesized was 2,2'-biphenylenylsilane, b y L i A l H r e d u c t i o n of 2 , 2 - b i p h e n y l e n y l d i f l u o r o s i l a n e ( p r o v i d e d b y A n d e r son C h e m i c a l D i v i s i o n , Stauffer C h e m i c a l C o . , A d r i a n , M i c h . ) w i t h m.p. 3 6 . 6 ° C , b . p . 8 6 ° C (0.31 m m . ) . Anal C a l c d for S i C H : S i , 15.41; C , 79.06; H , 5.53. F o u n d ( G a l b r a i t h M i c r o a n a l y t i c a l L a b , K n o x v i l l e , T e n n . ) : S i 15.12; C , 78.92; H , 5.61. Ozone Competition Reaction Procedures. I n t h e r e l a t i v e rate studies, t h e s o l v e n t - s a t u r a t e d ozone—oxygen s t r e a m was passed into a glass b u b b l e r r e a c t o r vessel c h a r g e d w i t h 4 m l of a b o u t 4 X 1 0 " M c o n c e n t r a t i o n of e a c h of the t w o silanes to b e c o m p e t i t i v e l y o z o n i z e d as w e l l as of a n inert s a t u r a t e d a l i p h a t i c h y d r o c a r b o n to f u n c t i o n as i n t e r n a l s t a n d a r d . ( F o r e x a m p l e , n - u n d e c a n e w a s u s e d for the t r i b u t y l s i l a n e / t r i h e x y l s i l a n e s t u d y . ) T h e effluent f r o m the r e a c t o r passed t h r o u g h a s o l v e n t - f i l l e d b u b b l e c o u n t e r to v i s u a l i z e t h e flow. T h e i n l e t s t r e a m splitter m e n t i o n e d e a r l i e r w a s a d j u s t e d to a l l o w 2 - 4 h o u r s for e a c h run's c o m p l e t i o n , as d e t e r m i n e d b y experience. T h e t e m p e r a t u r e w a s c o n t r o l l e d at 0 ° C i n b o t h the saturator a n d the reactor b y a h ice b a t h . T o f o l l o w the course of the r e a c t i o n , s m a l l (0.1 m l ) a l i q u o t s w e r e p e r i o d i c a l l y r e m o v e d a n d a n a l y z e d b y gas c h r o m a t o g r a p h y o n a 150-ft 0.1 i n c h i d c a p i l l a r y c o l u m n c o a t e d w i t h D o w - C o r n i n g D C - 5 5 0 silicone. P e a k areas w e r e d e t e r m i n e d a n d c o n v e r t e d to c o n c e n t r a t i o n values b y reference to the area of the i n t e r n a l s t a n d a r d p e a k . F r o m the u n r e a c t e d f r a c t i o n ( S i ) ^/ ( S i ) , of e a c h p a i r e d c o m p e t i n g silane S i at s a m p l i n g t i m e t was c o m p u t e d the r e l a t i v e r a t e constant fc i, the r a t i o of the c o r r e s p o n d i n g first o r d e r ( i n s i l a n e ) rate constants, b y the e a r l i e r r e p o r t e d ( 5 , 11) equation: 4

1 2

1 0

2

0

re


6.

spiALTER E T A L .

The

Table I.

Ozone-Ηydrosilane

Relative R a t e / S a *

Silane

&rel

T r i s ( p e r h y d r o - l - n a p h t h y 1) s i l a n e Tricyclohexylsilane tert-Butyldicyclohexylsilane Trihexylsilane Tributylsilane Triethylsilane 3 , 3 , 3 - T r i f l u o r o p r o p y l d i m e t h y lsilane D i c h l o r o m e t h y l d i m e t h y lsilane Tris(3,3,3-trifluoropropyl)silane Phenyldimethylsilane Diisopropylsilane Chloromethyldimethylsilane Diphenylmethylsilane Triphenylsilane Dibutylsilane Triethoxysilane Phenylmethylsilane 2 , 2 - D i p h e n y l e n y lsilane Diphenylsilane Cyclohexylsilane Dibenzylsilane H e x y lsilane Phenylsilane


c

Correlation 4

Σσ*

l0g fc l

Λ

re

378 236 226 115 100 84 51.7 41.7 35.6 30.7 28.5 23.6 23.0 23.0 21.7 19.0 12.0 9.6 7.9 3.65 3.31 3.04 2.10

67

Reaction

4

Σσ*
d)U

b a c k d o n a t i o n f r o m the substituent i n t o the v a c a n t 3d o r b i t a l s of s i l i c o n (21,

r e s u l t i n g i n p a r t i a l c a n c e l l a t i o n of the i n d u c t i v e e l e c t r o n - w i t h

22),

d r a w i n g p o w e r of the g r o u p . I n this research, since the silanes i n c l u d e d m o n o - , d i - , a n d t r i h y d r o


species, the s u m of all four σ* values w a s t a k e n as i n d i c a t i v e of the t o t a l e l e c t r o n i c e n v i r o n m e n t of s i l i c o n . W h e n t h e l o g a r i t h m s of t h e r e l a t i v e 4

rates ( l o g excellent

fc i) re

w e r e p l o t t e d against 2 σ *

(Table

I and Figure 1),

c o r r e l a t i o n was o b s e r v e d for m o s t substituents

(vide

an

infra).

L e a s t - s q u a r e s analysis of the d a t a afforded E q u a t i o n 1. log A w =

-1.2513 Σα* +

Substituents w h o s e s t a n d a r d T a f t removed

o| -4

2.2166

σ*

(1)

values p r o d u c e d

points

far

f r o m the p l o t of F i g u r e 1 i n c l u d e d p h e n y l , c h l o r o m e t h y l , d i -

I

I

0

.4

I 4

.8

I

1.2

Σσ* Figure

1.

Hydrosilane-ozone

rate/Σσ*

correlation


I

1.6

6.

The Ozone-Ηydrosïlane

SPIALTER E T A L .

Table II.

N e w asi* Values

β l-C

-.26 -.01 -.01 .01 .05 .09 .18

H -»

1 0

i r

F3C—CH2—CH2—

C1 CH2,2'-Biphenylenyl Phenyl C H 0C1CH 2

2

5

2

69

Reaction

σ*'

σ* —as»*

0.32 1.94

0.33 1.95

0.60 1.35 1.05

0.55 1.26 .87

e

d e

T h i s paper. M i x t u r e of 1-decalinyl isomers o b t a i n e d b y c a t a l y t i c hydrogénation of 1 - n a p h t h y l on silcon (δ). T h i s value is p r o b a b l y well b e h a v e d a n d equal to σ*. I n exact agreement w i t h value of A t t r i d g e . S u b s t a n t i a l l y different from calculated value of 0.75 for C H 0 - , whose standard σ* is 1.35 (see text). ' S t a n d a r d T a f t values (20, 29). α

6


c

d

e

3

chloromethyl,

ethoxy,

a n d 3,3,-trifluoropropyl.

These

points

may

be

b r o u g h t i n t o c o r r e l a t i o n b y r e d e f i n i n g the substituent constant as a i * , S

w h o s e v a l u e m a y b e d e d u c e d f r o m fc i. T a b l e I I lists the v a l u e s of re

σ$*

thus d e r i v e d . T h e factor w h i c h these substituents h a v e i n c o m m o n is the presence of u n s h a r e d e l e c t r o n p a i r s or Π-electrons close to the s i l i c o n atom. T h e v a l u e of σ ΐ* for p h e n y l , 0.05, δ

agrees w i t h t h a t c a l c u l a t e d f o r

p h e n y l f r o m the S i - Η s t r e t c h i n g f r e q u e n c y t w e e n the latter a n d 0.60, a t t r i b u t e d to (p —> d)li

This discrepany

(21).

be

the " n o r m a l " σ* for p h e n y l , has also b e e n

b a c k b o n d i n g (21, 23-25).

H o w e v e r , the h e r e -

o b s e r v e d a i * for ethoxy, —0.09, does n o t agree w i t h the v a l u e of S

0.75

d e r i v e d f r o m V Î-H stretch for m e t h o x y a l t h o u g h t h e i r σ* values are q u i t e S

similar—1.35

a n d 1.45,

respectively.

I n d e e d , a l l of the " e l e c t r o n - r i c h "

substituents i n d i c a t e a n e a r c a n c e l l a t i o n of i n d u c t i v e a n d

mesomeric

effects. H o w e v e r , alternate explanations of the s o - c a l l e d (p - » d)U d o n a t i o n exist (26, Improved

back

27).

u n d e r s t a n d i n g a n d treatment of

the p h e n y l case

was

d e v e l o p e d f r o m the r e c o g n i t i o n that the d e r i v e d a i * ( C H - ) is almost 6

S

5

identical w i t h the "standard" H a m m e t t σ value, a parameter containing both mesomeric

and inductive contributions.

Since p u b l i s h e d data on

the fc ei of o z o n a t i o n of s u b s t i t u t e d p h e n y l d i m e t h y l s i l a n e s w e r e a v a i l a b l e r

(11),

a n d i n c l u d e d the

common

point, phenyldimethylsilane,

simple

m a t h e m a t i c a l m a n i p u l a t i o n c o u l d b r i n g these a n d the present d a t a o n to t h e same scale. W h e n the H a m m e t t σ f o r t h e s u b s t i t u t e d p h e n y l s was 4

u s e d i n the 2σ* c a l c u l a t i o n , a l l of the c o m p o u n d s c o r r e l a t e d w e l l w i t h E q u a t i o n 1. A c o m p a r i s o n of the f o u n d a * ( X - C H - ) a n d t h e i r H a m m e t t σ values ( 2 9 ) appears i n T a b l e I I I . S i

6

4


70

OZONE REACTIONS W I T H

ORGANIC

COMPOUNDS

I n essence, t h e n , t h e e l e c t r o n i c e n v i r o n m e n t of the s i l i c o n c a n d e s c r i b e d b y a substituent v a l u e ,

w h i c h is ( a )

σ* i f the substituent is a n a l k y l g r o u p , ( b )

be

e q u a l to the T a f t

e q u a l to the H a m m e t t σ i f

t h e substituent is p h e n y l or s u b s t i t u t e d p h e n y l , a n d ( c )

for substituents

b e a r i n g u n s h a r e d e l e c t r o n p a i r s close t o the s i l i c o n , e a c h σ * m u s t b e 81

individually determined. T h e σ * 8

v a l u e s c o m p u t e d i n this s t u d y a p p e a r

in Table II. Reaction Mechanism. T h e p r o p o s e d m e c h a n i s m for t h e o z o n e - h y d r o silane r e a c t i o n ( 7 )

s h o w n i n E q u a t i o n 2, as d e d u c e d b y a n a l y z i n g a n d

c o r r e l a t i n g d a t a o n r e l a t i v e rates, substituent effects, d e u t e r i u m isotope effects, l o w t e m p e r a t u r e N M R , a n d u l t r a v i o l e t spectroscopy for a r a n g e Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch006

of h y d r o s i l a n e s , is a m u l t i s t e p one as f o l l o w s : 0

R Si—H

+

3

p r i m a r y ) exactly

A l t h o u g h this e x p l a n a t i o n s h o u l d n o t

fortuitous

coincidence

required

makes

be it

unattractive. A s e c o n d p o s s i b i l i t y is t h a t the o z o n e forms some k i n d of

complex

w i t h the silane before attack o n the h y d r o g e n . F r o m this c o m p l e x , a l l h y d r o g e n s are e q u a l l y accessible, a n d the d e c o m p o s i t i o n is first o r d e r i n complex.

I n t h e h o p e of o b s e r v i n g s u c h a c o m p l e x a t i o n , the u l t r a v i o l e t

s p e c t r a of o z o n e / s i l a n e m i x t u r e s i n c a r b o n t e t r a c h l o r i d e w e r e e x a m i n e d (33).

A l t h o u g h n o s p e c t r a l b a n d s a t t r i b u t a b l e to a s i l i c o n - o z o n e

complex

w e r e f o u n d , i t w a s o b s e r v e d t h a t any s i l i c o n - c o n t a i n i n g species c a t a l y z e d the d e c o m p o s i t i o n

of ozone.

T h a t is, n o t o n l y t r i e t h y l s i l a n e , b u t t r i -

e t h y l s i l a n o l a n d t e t r a m e t h y l s i l a n e as w e l l , destroy o z o n e i n c a r b o n t e t r a c h l o r i d e . T h i s r e s u l t i n d i c a t e s a n association of the o z o n e w i t h the s i l i c o n a t o m , regardless of t h e f u n c t i o n a l i t y of the s i l i c o n species types e x a m i n e d )

3

( w i t h i n the

a n d c o m p l e t e l y i n d e p e n d e n t of the s i l i c o n substrate's

4


6.

spiALTER E T A L .

The Ozone-Η y drosilane

73

Reaction

a b i l i t y to enter i n t o a subsequent t r a n s f o r m a t i o n r e a c t i o n . I n v i e w of the electropositive n a t u r e of s i l i c o n , the n u c l e o p h i l i c association of ozone w i t h t h e s i l i c o n is the l i k e l y c a n d i d a t e for a s u i t a b l e i n t e r m e d i a t e .

Possible

models for this t y p e of i n t e r a c t i o n r a n g e f r o m one of w e a k electrostatic a t t r a c t i o n , 3, to a f u l l y p e n t a c o o r d i n a t e s i l i c o n species, 4. I n a n a t t e m p t to observe

the c o m p l e x ,

a l o w temperature N M R

i n v e s t i g a t i o n of mixtures of o z o n e w i t h t r i e t h y l s i l a n o l a n d w i t h t e t r a methylsilane were conducted.

A t — 57 ° C i n m e t h y l e n e c h l o r i d e , there

was no d i s c e r n i b l e change i n the p r o t o n N M R of either t r i e t h y l s i l a n o l or t e t r a m e t h y l s i l a n e as the o z o n e c o n c e n t r a t i o n of the r e s u l t i n g b l u e solutions was i n c r e a s e d to the p o i n t of s a t u r a t i o n . T w o possible e x p l a n a Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch006

tions for these results a r e : ( a ) the c o m p l e x exists i n e q u i b r i u m w i t h the silane a n d ozone, a n d the a c t u a l c o n c e n t r a t i o n of c o m p l e x is too to be d e t e c t e d b y N M R (less t h a n 5%

small

i n this e x p e r i m e n t ) , or ( b )

c h e m i c a l shifts of the silane protons are not a l t e r e d b y

the

complexation.

O f the t w o explanations, the first seems the m o r e reasonable, p a r t i c u l a r l y if the c o m p l e x has m o r e of the character of 4 t h a n of 3. T h e exact n a t u r e of the c o m p l e x is i m p o s s i b l e to d e t e r m i n e at this t i m e , b u t one significant o b s e r v a t i o n is that o p t i c a l l y a c t i v e p e r h y d r o - l - n a p h t h y l p h e n y l m e t h y l s i l a n o l undergoes s l o w r a c e m i z a t i o n u p o n s t a n d i n g at r o o m t e m p e r a t u r e i n a pentane—ozone s o l u t i o n . T h i s is consistent w i t h r e v e r s i b l e c o m p l e x a t i o n to a species h a v i n g some p e n t a c o o r d i n a t e character f r o m w h i c h r a c e m i z a t i o n m a y o c c u r via p s e u d o r o t a t i o n

(34).

T h e s e d a t a suggest that the i n i t i a l step i n t h e r e a c t i o n of w i t h the S i - Η b o n d is the r e v e r s i b l e f o r m a t i o n of a s i l i c o n - o z o n e plex.

ozone com

T h i s cannot be the rate step since ρ w o u l d h a v e to b e p o s i t i v e

( n u c l e o p h i l i c a t t a c k ) a n d no p r i m a r y isotope effect w o u l d b e p r e d i c t e d . T o e l i m i n a t e the s t a t i s t i c a l factor for the d i - a n d t r i h y d r o s i l a n e s , attack b y o z o n e o n the h y d r i d i c p r o t o n f r o m w i t h i n the c o m p l e x m u s t be m u c h m o r e f a v o r a b l e t h a n d i r e c t encounter a n d r e a c t i o n w i t h

uncomplexed

ozone and S i - H . Step(s) B i and B — H y d r o g e n Abstraction. H o w t h e o z o n a t i o n p r o 2

ceeds f r o m t h e c o m p l e x is n o w c o n s i d e r e d . I f d i r e c t σ-bond i n s e r t i o n ( 1 ) is e l i m i n a t e d o n the basis of isotope effects as discussed above, t h e n 5 a n d 6 are the v i a b l e alternatives. T h e t r a n s i t i o n state 5 c o u l d collapse to f o r m the s i l i c o n h y d r o p e r o x i d e 7, w h i l e t r a n s i t i o n state 6 c o u l d collapse to f o r m the s i l i c o n h y d r o t r i o x i d e 8 ( p a t h B i ) ; a l t e r n a t i v e l y , 6 c o u l d collapse d i r e c t l y to i o n o r r a d i c a l p a i r s ( p a t h B ) . 2

T h e transformation

5 - » 7 is n o t m e a n t to suggest that a t o m i c o x y g e n is the other p r o d u c t . S i n c e the r e a c t i o n o r d e r i n o z o n e has n o t b e e n d e t e r m i n e d , the fate of the other o x y g e n a t o m ( s ) is m o o t .


74


R Si

H

3

^

0

3

0—0 7

5

•0-0 RsSic' Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch006

R si00H

\0

R3S1OOOH

R Si(+or«) 8

I f t h e r e a c t i o n is f o u r - c e n t e r e d should be formed.

(5 - »

7),

0

2

(-or-)OH

a silicon hydroperoxide

T h e r e a c t i o n of t r i e t h y l s i l a n e w i t h o z o n e w a s m o n i -

t o r e d b y N M R at — 5 7 ° C .

T h e o n l y species o b s e r v e d u n d e r these c o n d i -

tions w e r e t h e silane a n d the s i l a n o l ; n o e v i d e n c e f o r a h y d r o p e r o x i d e i n t e r m e d i a t e w h i c h m i g h t h a v e b e e n stable at t h a t t e m p e r a t u r e

(35)

w a s detected, a n d c h e m i c a l tests for peroxides p r o v e d n e g a t i v e ( 5 , 6 ) . A s the c o n c e n t r a t i o n of o z o n e w a s i n c r e a s e d f r o m z e r o to s a t u r a t i o n , the s p e c t r u m of the silane c o m p l e t e l y d i s a p p e a r e d w i t h the c o n c u r r e n t a p p e a r a n c e of the s i l a n o l N M R s p e c t r u m . I f the r e a c t i o n is be formed.

five-centered

( 6 - » 8 ) , a silicon hydrotrioxide may

S i n c e there has b e e n n o p r e v i o u s r e p o r t of a s i l i c o n h y d r o -

t r i o x i d e , the s t a b i l i t y of a species s u c h as 8 u n d e r these c o n d i t i o n s c a n o n l y b e e s t i m a t e d . A m o n g c a r b o n analogs, the r e p o r t e d d i a l k y l t r i o x i d e s h a v e o n l y m a r g i n a l s t a b i l i t y at l o w temperatures hydrotrioxides, proposed a n d ethers

(38),

(36, 3 7 ) ,

and alkyl

as i n t e r m e d i a t e s i n the o z o n a t i o n of

d e c o m p o s e at ca.

— 10°C.

alcohols

A d m i t t e d l y , speculative

e x t r a p o l a t i o n b a s e d o n t h e c o m p a r a t i v e stabilities of other types of s i l i c o n a n d c a r b o n analogs suggests t h a t a s i l i c o n h y d r o t r i o x i d e 8, s h o u l d have b e e n o b s e r v a b l e i f i t h a d b e e n present, b u t this r e q u i r e m e n t is d e b a t a b l e . Steps C and D — T h e N a t u r e of the Recombining Fragments. a s s u m p t i o n of the i n t e r m e d i a c y of a

five-center

Upon

t r a n s i t i o n state, the q u e s -

t i o n t h e n arises as to h o w 6 ( o r 8 ) d e c o m p o s e s to the s i l a n o l . T h e b r e a k d o w n c o u l d b e via r a d i c a l or i o n p a i r s . T h e l a r g e p r i m a r y isotope effect suggests a r a d i c a l p a t h w a y ( 1 2 ) . ozonation

of

optically

active

F u r t h e r i n s i g h t w a s g a i n e d f r o m the

perhydro-l-naphthylphenylmethylsilane,

w h i c h y i e l d s the s i l a n o l 1 0 w i t h r e t e n t i o n of c o n f i g u r a t i o n ( E q u a t i o n 3 ) . P r o l o n g e d exposure of 1 0 to o z o n e causes r a c e m i z a t i o n , b u t t h e p r o d u c t


6.

spiALTER E T A L .

The Ozone-Ηydrosilane

75

Reaction

10

i n i t i a l l y has r e t a i n e d its c o n f i g u r a t i o n . P r e s u m a b l y , the silane 9 is also r a c e m i z e d b y o z o n e (via Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch006

faster.

R e t e n t i o n of

t r a t e d (39)

c o m p l e x a t i o n ) , b u t t h e rate of o z o n i z a t i o n is

configuration b y

s i l y l r a d i c a l s has b e e n

whereas the o p t i c a l p r o p e r t i e s ( i n d e e d , the v e r y

of t r i v a l e n t s i l i c o n i u m ions h a v e n o t b e e n established.

demon-

existence)

F o r this reason,

d e c o m p o s i t i o n of 6 ( o r 8 ) t h r o u g h a r a d i c a l p a i r w i t h subsequent, r a p i d r e c o m b i n a t i o n is the m e c h a n i s m w h i c h appears most c o m p a t i b l e

with

the e x p e r i m e n t a l observations. Conclusions W h e n a l l the m e c h a n i s t i c e v i d e n c e is t a k e n i n t o c o n s i d e r a t i o n , the f o l l o w i n g r e a c t i o n sequence appears to best satisfy the d a t a . T h e silane undergoes

reversible complexation

(A)

w i t h the ozone, the

b e i n g present i n o n l y s m a l l concentrations.

complex

T h e rate step t h e n i n v o l v e s

e l e c t r o p h i l i c attack o n the h y d r i d i c h y d r o g e n , p a s s i n g t h r o u g h a

five-

center t r a n s i t i o n state. T h i s m a y d e c o m p o s e to either a s i l y l h y d r o t r i o x i d e ( B i ) or d i r e c t l y to the r a d i c a l p a i r ( B ) . 2

T h e silyl hydrotrioxide, if pres

ent, m u s t d e c o m p o s e r a p i d l y to the r a d i c a l p a i r ( C ) . then r e c o m b i n e s

This radical pair

w i t h r e t e n t i o n of c o n f i g u r a t i o n to afford t h e u l t i m a t e

p r o d u c t , the s i l a n o l ( D ) . W i t h r e g a r d to the

five-center

t r a n s i t i o n state, K e n n e t h W i b e r g ( Y a l e

U n i v e r s i t y ) has k i n d l y p o i n t e d out to us t h a t the m a g n i t u d e of the isotope effect supports the

five-centered

activated complex w h i c h w e have postu

l a t e d . I n the s m a l l e r r i n g complexes, the v i b r a t i o n a l m o d e c o n v e r t e d to the r e a c t i o n c o o r d i n a t e is a b e n d i n g m o d e , w h i c h w o u l d n o t p r o d u c e a l a r g e isotope

effect.

s t r e t c h i n g m o d e s are

I n the

five-centered

converted,

complex,

both bending

a n d the l a r g e isotope

and

effect is

not

F i n a l l y , a referee has suggested t h a t 8 c o u l d d e c a y to p r o d u c t

via

unexpected. a concerted pathway (i)

[p. 7 6 ] .

A l t h o u g h s u c h a p a t h w a y cannot

be

r u l e d out, w e f e e l that t h e l a r g e isotope effect suggests the r a d i c a l p a i r , probably from B . 2

B o t h i a n d the r a d i c a l m e c h a n i s m w o u l d p r o c e e d w i t h

r e t e n t i o n of c o n f i g u r a t i o n .


76

OZONE REACTIONS W I T H ORGANIC

R Si—Ο—0 3

R SiOH + 0 3

COMPOUNDS

2

(i)

Η—0


Literature Cited 1. Long, L.Jr.,Chem. Rev. (1940) 27, 437. 2. Bailey, P. S., Chem. Rev. (1958) 58, 925. 3. Barry, A. J., Beck, H. N., "Inorganic Polymers," pp. 221, 236, 256, 296, Academic, New York, 1962. 4. Spialter, L., Austin, J. D., J. Amer. Chem. Soc. (1965) 87, 4406. 5. Austin, J. D., Spialter, L., ADVAN. CHEM. SER. (1968) 77, 26-31. 6. Spialter, L., Austin, J. D., Inorg. Chem. (1966) 5, 1975. 7. Spialter, L., Pazdernik, L., Bernstein, S., Swansiger, W. Α., Buell, G. R., Freeburger, M. E., J. Amer. Chem. Soc. (1971) 93, 5682. 8. Spialter, L., Swansiger, W. Α., J. Amer. Chem. Soc. (1968) 90, 2187. 9. Spialter, L., Swansiger, W. Α., "Resumes of Communications," Second Inter national Symposium on Organosilicon Chemistry, Bordeaux, pp. 183-184, 1968. 10. Spialter, L., Swansiger, W. Α., Pazdernik, L., Freeburger, M. E., J. Organometal. Chem. (1971) 27, C25. 11. Ouellette, R. J., Marks, D. L.,J.Organometal. Chem. (1968) 11, 407. 12. Batterbee, J. E., Bailey, P. S.,J.Org. Chem. (1967) 32, 3899. 13. Erickson, R. E., Hanson, R. T., Harkins, J., J. Amer. Chem. Soc. (1968) 90, 6777. 14. Erickson, R. E., Bakalik, D., Richards, C., Scanlon, M., Huddleston, G., J. Org. Chem. (1966) 31, 461. 15. White, H. M., Bailey, P. S., J. Amer. Chem. Soc. (1965) 30, 3037. 16. Becsey, J., Berke, L., Callan, J. R., J. Chem. Ed. (1968) 45, 728. 17. Ponomarenko, V. Α., Egorov, Yu P., Izvest. Akad. Nauk S.S.S.R., Otdel. Khim. Nauk (1960) 1133. 18. Smith, A. L., Angelotti, N.C.,Spectrochim. Acta (1959) 15, 412. 19. Thompson, H. W., Spectrochim. Acta (1960) 16, 238. 20. Newman, M. S., Ed., "Steric Effects in Organic Chemistry," p. 619, Wiley, New York, 1956. 21. Attridge, C. J., J. Organometal. Chem. (1958) 13, 259. 22. Egorochkin, A. N., Vyazankin, N. S., Dokl. Akad. Nauk S.S.S.R., (1970) 193, 590. 23. Alt, H., Bock, H., Tetrahedron (1969) 25, 4825. 24. Bock, H., Alt, H., Chem. Ber. (1970) 103, 1784. 25. Bock, H., Alt, H., J. Amer. Chem. Soc. (1970) 92, 1569. 26. Pitt, C. G., J. Organometal Chem. (1970) 24, C35. 27. Ramsey, B. G., "Electronic Transitions in Organometalloids," pp. 76ff, Aca demic, New York, 1969. 28. McDaniel, D. H., Brown, H. C., J. Org. Chem. (1958) 23, 420; see also Ref. 29, p. 87. 29. Hine, J., "Physical Organic Chemistry," 2nd ed., p. 97, McGraw-Hill, New York, 1962. 30. Westheimer, F. H., Chem. Rev. (1961) 61, 265. 31. Melander, L., "Isotope Effects on Reaction Rates," p. 20, Ronald Press, New York, 1960. 32. Seyferth, D., Damrauer, R., Mui, J. Y.-P., Jula, T. F., J. Amer. Chem. Soc. (1968) 90, 2944.


6.

SPIALTER

E T AL.

The Ozone-Hydrosilane

Reaction

77

33. Nakagawa, T . W., Andrews, L . J., Keefer, R. M., J. Amer. Chem. Soc. (1960) 82, 269. 34. Muetterties, E. L., Accounts Chem. Res. (1970) 3, 266. 35. Dannley, R. L., Jalics, G.,J.Org. Chem. (1965) 30, 2417. 36. Bartlett, P. D., Guaraldi, G.,J.Amer. Chem. Soc. (1967) 89, 4799. 37. Mill, T., Stringham, R. S., J. Amer. Chem. Soc. (1968) 90, 1064. 38. Murray, R. W., Lumma, W. C., Lin, J. W.-P., J. Amer. Chem. Soc. (1970) 92, 3205. 39. Brook, A. G., Duff, J. M.,J.Amer. Chem. Soc. (1969) 91, 2118. 1971.


R E C E I V E D May 20,


7 The Ozonolysis of Organomercurials WILLIAM

L. WATERS,

PAUL E. PIKE, and JOSEPH G. RIVERA

University of Montana, Missoula, Mont. 59801


The

reaction

curials

of ozone

with

and alkylmercuric

carboxylic ondary,

acids,

ketones,

and tertiary

carbon—mercury

conditions

was the

cleavage

four-center

processes.

from

primary,

respectively. chief

of sec

Although reaction,

did occur in varying

degrees.

course

under pseudo first-order of positive

step.

is depicted

dialkylmer-

good yields

of

a build-up

in the rate-determining -mercury cleavage ozonolysis

and alcohols

study of the reaction indicated

produced

alkylmercurials,

scission

some carbon—carbon A kinetic

over 20 different

halides

The

mechanism

as a mixture

Although

of organomercurials

charge

somewhat does promise

on

for

carbon

of pure limited

rate carbon

S2 E

in

synthetic

and

scope, utility.

Τ η t h e s e a r c h for n e w s y n t h e t i c uses of o r g a n o m e r c u r i a l s a n d t h e olefin A

m e r c u r a t i o n reactions i n g e n e r a l , a t t e n t i o n w a s d r a w n to o z o n e as a

p o s s i b l e reactant. O r g a n o m e r c u r i a l s r e a c t r a p i d l y w i t h a v a r i e t y of e l e c t r o p h i l i c spe cies, a n d a recent b o o k b y J e n s e n a n d R i c k b o r n f u l l y describes the scope of these reactions ( I ) .

F o r e m o s t a m o n g the e l e c t r o p h i l i c reagents are

the halogens w h i c h cleave the carbon—mercury b o n d to p r o d u c e a l k y l m e r c u r i c h a l i d e s a n d / o r a l k y l h a l i d e s , d e p e n d i n g o n the t y p e of o r g a n o mercurial involved. fast

R Hg + Br 2

• RBr + RHgBr

2

^

slower

RHgBr + Br

> RBr +

2

HgBr

2

I n a d d i t i o n , p r o t i c acids also cleave o r g a n o m e r c u r i a l s to y i e l d the p r o t o n s u b s t i t u t e d p r o d u c t s analogous to those for h a l o g e n a t i o n above.

Finally,

m e r c u r i c salts also act as e l e c t r o p h i l i c reagents t o w a r d s o r g a n o m e r c u r i a l s . 78 In Ozone Reactions with Organic Compounds; Bailey, P.; Advances in Chemistry; American Chemical Society: Washington, DC, 1972.

7.

Ozonolysis

WATERS E T A L .

R Hg + 2

RHgBr +

of

HgBr

*HgBr

2RHgBr

2

R*HgBr +

2

where * H g = Several mechanisms c l e a v a g e reactions.

have

79

Organomercurials

been

203

HgBr

(2)

2

Hg

proposed

for

these

electrophilic

I n g e n e r a l , these m e c h a n i s m s r a n g e f r o m p u r e

S 1 E

to p u r e S 2 processes a l t h o u g h these t w o extreme m e c h a n i s m s are u s u a l l y E

r e s e r v e d f o r s p e c i a l cases.

R Hg +

S l: Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch007

B

2

Y

R +

-» R — H g — R

RHgY

I

γ

(3)

X

RX R Hg +

Sd:

2

R—Hg—R

X — Y

•R

Χ—Y

Hg—R

X — Y

RX +

+

(4)

YHgR

R Four-Center

: R Hg + Χ—Y

>R

2

>R X + YHgR

H£

(5)

X S 2: E

R Hg + 2

R—X—Y

R—Hg—R

X — Y

X—Y

H g - R

RX +

(6)

YHgR

O z o n e has l o n g b e e n assigned the r o l e of e l e c t r o p h i l e i n a d d i t i o n a n d s u b s t i t u t i o n reactions

(2).

I n this respect the reagent has

r e p o r t e d to cleave v a r i o u s c a r b o n - m e t a l b o n d s

(Et) Sn 4

0

3

AcH +

been

(3-9).

( E t ) S n O + a peroxide 2


(7)

80

OZONE REACTIONS WITH ORGANIC COMPOUNDS

(Et) Pb

(Et) PbOH +

4

3

20°

+ AcH + Os

( E t ) «Si

AcOH + H 0 2

0

R Se

3

2

+ Et Si0 H + 3

2

0

3

2

RSeH +

2

(t-Pr) Hg

3

(8)

EtOH

R SeO

2


2

(Et) PbO + (Et) PbOEt

2(CH ) CO + 3

2

(Et Si) 0 3

2

aldehyde

HgO

(9)

(10)

(11)

A l t h o u g h reports of m e c h a n i s t i c studies are scarce f o r these reac tions, O u e l l e t t e a n d M a r k s d i d p r o p o s e a 1,3-dipolar attack b y ozone (10). T h e c o r r e s p o n d i n g i n t e r m e d i a t e w a s p r e d i c t e d to be a h y d r o t r i o x i d e of s i l i c o n .

-H R —Si 3

Ο-

-ο

/

Ο

->

[R —Si—Ο—Ο—OH] 3

(12)

T h e u n s t a b l e h y d r o t r i o x i d e c o u l d t h e n d e c o m p o s e via singlet or t r i p l e t o x y g e n ejection to f o r m the o b s e r v e d s i l a n o l p r o d u c t s The

(10).

Reaction

T h e cleavage of c a r b o n - m e t a l b o n d s b y o z o n e is i n t r i g u i n g . S t u d y was b e g u n to discover the scope of this r e a c t i o n u s i n g m e r c u r i a l s as the o r g a n o m e t a l l i c reagent. I t w a s h o p e d t h a t n o t o n l y w o u l d the cleavage m e c h a n i s m be c l a r i f i e d b u t also that a s y n t h e t i c a l l y u s e f u l m e t h o d of i n t r o d u c i n g o x y g e n f u n c t i o n a l i t y m i g h t be d e v e l o p e d . O z o n a t i o n of over 20 different o r g a n o m e r c u r i a l s r e s u l t e d i n a f a i r l y r a p i d d i s a p p e a r a n c e of o r g a n o m e t a l l i c s t a r t i n g m a t e r i a l , a c c o m p a n i e d b y a constant p r e c i p i t a t i o n of i n o r g a n i c m e r c u r y salts. A p r o d u c t s t u d y i n c h l o r o f o r m a n d m e t h y l e n e c h l o r i d e solvents at temperatures r a n g i n g f r o m —75° to + 2 5 ° C s h o w e d that m e r c u r y was r e p l a c e d b y a n o x y g e n c o n t a i n i n g m o i e t y i n a l l cases (11). A l t h o u g h these p r o d u c t s w e r e chiefly the analogous a l c o h o l , ketone, or a c i d f r o m the p a r e n t 3 ° , 2 ° , or 1° o r g a n o m e r c u r i a l r e s p e c t i v e l y , some c a r b o n - c a r b o n scission d i d occur.


7.

WATERS E T A L .

Ozonolysis

of

81

Organomercurials

T h i s was e s p e c i a l l y e v i d e n t at the h i g h e r temperatures a n d i n the case of the a l k y l m e r c u r i c h a l i d e s . A k i n e t i c s t u d y of the r e a c t i o n w a s also p e r f o r m e d i n w h i c h N M R o b t a i n e d rate d a t a w e r e c o r r e l a t e d w i t h m e r c u r i a l s t r u c t u r e changes

(12).

This study revealed a quite distinct reactivity order w h i c h , coupled w i t h a 1:1 reactant s t o i c h i o m e t r y , i n d i c a t e s a 1,3-dipolar e l e c t r o p h i l i c attack b y o z o n e via SL S 2 or four-center process. e

A l t h o u g h the exact m e c h a n i s m

was n o t c o n c l u s i v e l y p r o v e d , it is c e r t a i n that n e i t h e r the S 1 or S i E

E

processes w e r e o p e r a t i v e d u r i n g these reactions.


Experimental Materials. G e n e r a l l y t h e o r g a n o m e r c u r i c h a l i d e s w e r e p r e p a r e d u s i n g the G r i g n a r d m e t h o d as o u t l i n e d b y M a r v e l et al. (13). The dialkylm e r c u r i a l s w e r e also s y n t h e s i z e d b y the G r i g n a r d p r o c e d u r e as o u t l i n e d b y G i l m a n a n d B r o w n (14). E x a c t s t r u c t u r a l i d e n t i f i c a t i o n of the o r g a n o m e r c u r i a l s was f a c i l i t a t e d b y c o r r e l a t i o n of N M R - o b t a i n e d Hg- H s p i n - s p i n c o u p l i n g d a t a w i t h l i t e r a t u r e values for s i m i l a r systems ( 1 5 , 1 6 ) . P r e l i m i n a r y i d e n t i f i c a t i o n was p e r f o r m e d b y the u s u a l c o m p a r i s o n of p h y s i c a l properties w i t h those for k n o w n c o m p o u n d s . Apparatus. T h e a p p a r a t u s u s e d i n these studies consisted of a W e l s b a c h T - 4 0 8 e l e c t r i c d i s c h a r g e o z o n a t o r c o n n e c t e d to three 2 0 0 - m l gas w a s h i n g bottles i n series. T h e first bottle w a s the r e a c t i o n vessel, a n d its t e m p e r a t u r e was m a i n t a i n e d at — 7 6 ° , 0 ° , or + 1 0 ° C . T h e s e c o n d b o t t l e was a c o l d t r a p for t h e m o r e v o l a t i l e products—e.g., a c e t o n e — w h i c h w e r e g e n e r a l l y s w e p t out of the r e a c t i o n vessel b y the l a r g e v o l u m e of 0 . T h e t h i r d b o t t l e c o n t a i n e d a n aqueous K I s o l u t i o n for t r a p p i n g a n y u n r e a c t e d 0 . A f t e r c o m p l e t i o n of a r e a c t i o n this s o l u t i o n c o u l d b e t i t r a t e d w i t h t h i o s u l f a t e f o r l i b e r a t e d I a n d thus u n r e a c t e d 0 . B y u s i n g Ο as the f e e d gas, a n 0 - 0 m i x t u r e , 3 - 4 % 0 b y w e i g h t , was p r o d u c e d b y the ozonator. F l o w rates w e r e adjusted to p r o d u c e 1 8 - 3 0 m m o l e s of 0 p e r h o u r . F o r the rate studies the a b o v e - m e n t i o n e d r e a c t i o n vessel was m o d i f i e d to a l l o w for r a p i d a n d p e r i o d i c r e m o v a l of s o l u t i o n a l i q u o t s d u r i n g the progress of the r e a c t i o n . 1 9 9

1

2

3

2

2

3

3

2

3

3

Procedure. P R O D U C T - D E T E R M I N I N G STUDIES. I n a t y p i c a l p r o d u c t d e t e r m i n i n g r u n 10 m m o l e s of o r g a n o m e r c u r i a l w e r e d i s s o l v e d i n ca. 50 m l of C H C 1 a n d p l a c e d i n the r e a c t i o n vessel. A f t e r the vessel w a s c o o l e d to the p r o p e r t e m p e r a t u r e , the 0 - 0 flow w a s started. I n a l l cases a n i m m e d i a t e w h i t e p r e c i p i t a t e a p p e a r e d . T h i s p r e c i p i t a t i o n was constant t h r o u g h o u t the entire ozonolysis p r o c e d u r e a n d i n fact w a s u s e d as a n e n d p o i n t d e t e r m i n a n t i n c e r t a i n cases. O z o n a t i o n w a s g e n e r a l l y h a l t e d after a l l of the o r g a n o m e r c u r i a l h a d r e a c t e d . T h e r e s u l t a n t w h i t e s o l i d was t h e n c o l l e c t e d , w a s h e d w i t h C H C 1 , d r i e d , a n d subjected to analysis b y p o w d e r x - r a y d i f f r a c t i o n w i t h a N o r e l c o a n a l y t i c a l x - r a y diffractometer. T h e C H C 1 s o l u t i o n was a n a l y z e d b y v a p o r phase c h r o m a t o g r a p h y (VPC) m e t h o d s u s i n g 6 ft X % i n c h 3 0 % C a r b o w a x or 6 ft X % i n c h 2 0 % S E - 3 0 c o l u m n s . R e t e n t i o n times of the r e a c t i o n p r o d u c t s w e r e m a t c h e d o n b o t h c o l u m n s w i t h p r e c a l i b r a t e d c h r o m a t o g r a p h s of k n o w n 2

2

3

2

2

2

2

2


82


c o m p o u n d s . A n i n t e r n a l s t a n d a r d w a s a d d e d to the C H C 1 i n t e g r a t i o n purposes. 2

s o l u t i o n for

2

K I N E T I C STUDIES. I n a t y p i c a l k i n e t i c r u n 10 m m o l e s of o r g a n o m e r c u r i a l w e r e d i s s o l v e d i n 100 m l of C H C 1 a n d p l a c e d i n the r e a c t i o n vessel. T o this s o l u t i o n w e r e a d d e d 30 m m o l e s of C H N 0 as a n i n t e r n a l N M R s t a n d a r d . O z o n e flow rates w e r e d e t e r m i n e d a n d the m e r c u r i a l solution w a s t h e n o z o n i z e d at 0 ° C . A l i q u o t s w e r e p e r i o d i c a l l y w i t h d r a w n ( g e n e r a l l y , 8 - 1 0 samples t a k e n ) a n d s h a k e n w i t h a s o l i d m i x t u r e of ca. 0.1 g r a m K I a n d 0.1 g r a m N a S 0 . I n this m a n n e r excess 0 w a s i m m e d i a t e l y q u e n c h e d a n d the r e s u l t a n t I , w h i c h itself reacts w i t h o r g a n o m e r c u r i a l s at r o o m t e m p e r a t u r e , w a s q u i c k l y r e d u c e d . 3

3

2

2

2

3

3


2

E a c h a l i q u o t was a n a l y z e d w i t h o u t f u r t h e r w o r k - u p b y a n H A - 6 0 A n a l y t i c a l N M R S p e c t r o m e t e r , u s i n g the field s w e e p m e t h o d to e l i m i n a t e the u s u a l phase changes associated w i t h the f r e q u e n c y s w e e p m o d e . T h e r e l a t i v e integrals for C H N 0 a n d one set of resonance lines for the o r g a n o m e r c u r i a l w e r e r e p e a t e d 10 t i m e s a n d averaged. T h i s average v a l u e w a s c o m p a r e d w i t h the o r i g i n a l C H N 0 / o r g a n o m e r c u r i a l r a t i o to d e t e r m i n e the c o n c e n t r a t i o n of o r g a n o m e r c u r i a l at that t i m e . T h e s e a c t u a l concentrations, a l o n g w i t h the respective t i m e intervals f r o m f , w e r e s u b m i t t e d to a least-squares c o m p u t e r p r o g r a m . U s i n g a n I B M 1620 c o m p u t e r , the n a t u r a l l o g a r i t h m of t h e c o n c e n t r a t i o n w a s p l o t t e d vs. t i m e (ca. 10 p o i n t s ) to g i v e the best-fitting l i n e a r r e l a t i o n s h i p b e t w e e n the t w o v a r i a b l e s . F r o m this p l o t the least-squares slope, (/-intercept, absolute rate constant, a n d c o r r e l a t i o n coefficient of the l i n e w e r e determined. 3

2

3

2

0

O T H E R STUDIES. C e r t a i n ozonations w e r e c a r r i e d out u s i n g N as the c a r r i e r gas i n s t e a d of 0 . F o r these reactions the u s u a l s i l i c a g e l p r o c e d u r e (17) was u s e d . S i l i c a gel, 1 0 0 - 1 5 0 grams, 6 - 1 2 m e s h , w a s p l a c e d i n a 2 0 0 - m l s i d e - a r m c o l d t r a p a n d c o o l e d to — 76 ° C . O z o n e was i n t r o d u c e d i n t o this t r a p as the u s u a l 0 - 0 m i x t u r e . A f t e r the d e s i r e d a m o u n t of 0 h a d b e e n a d s o r b e d b y the s i l i c a g e l , the ozonator was d i s c o n n e c t e d a n d the c o l d t r a p flushed w i t h a m b i e n t t e m p e r a t u r e N for 5 m i n u t e s to r e m o v e a n y 0 . O z o n e was t h e n flushed s l o w l y f r o m the s i l i c a g e l b y g r a d u a l l y m o v i n g the t r a p v e r y short distances out of the d r y i c e — acetone b a t h w h i l e c o n t i n u i n g to flush w i t h N [ h a s t e n i n g this w a r m i n g procedure resulted i n a violent explosion]. 2

2

3

2

3

2

2

2

N e x t , a s t o i c h i o m e t r i c s t u d y was u n d e r t a k e n to d e t e r m i n e the n u m b e r of moles of 0 w h i c h r e a c t e d w i t h e a c h m o l e of o r g a n o m e r c u r i a l . T o a c c o m p l i s h this task the 0 flow rate was a c c u r a t e l y d e t e r m i n e d b y the K I - N a S 0 p r o c e d u r e . O z o n a t i o n of a m e r c u r i a l i n C H C 1 or C H C 1 w a s t h e n b e g u n . I n c l u d e d i n the r e a c t i o n m i x t u r e was a s m a l l a m o u n t of C H N 0 as a n N M R i n t e g r a t i o n s t a n d a r d . T h e r e a c t i o n w a s s t o p p e d s e v e r a l times to c h e c k the o r g a n o m e r c u r i a l c o n c e n t r a t i o n b y N M R spectroscopy. T h e a m o u n t of u n r e a c t e d o z o n e also h a d to b e c a l c u l a t e d at e a c h s a m p l i n g p e r i o d for the p r i m a r y a n d s e c o n d a r y a l k y l m e r c u r i c h a l i d e s . T h e 0 flow rate w a s also r e c h e c k e d at e a c h s a m p l i n g i n t e r v a l to ensure t h a t the d i s p e r s i o n tubes h a d not c l o g g e d . T h e n u m b e r of moles of r e a c t e d 0 w a s t h e n c o m p a r e d w i t h the n u m b e r of moles of reacted organomercurial. 3

3

2

3

2

3

2

2

2

3

3


3

7.

WATERS E T A L .

Ozonolysis

of

83

Organomercurials

Results Product Studies. T a b l e I outlines t h e o r g a n i c a n d i n o r g a n i c p r o d u c t s of the ozonolysis reactions. T h e ozonolysis p r o d u c t s of n - a l k y l m e r c u r i c h a l i d e s a n d d i - n - a l k y l m e r c u r i a l s w e r e a m i x t u r e of c a r b o x y l i c acids w h i c h h a d a c a r b o n c h a i n e q u a l to or shorter t h a n the a l k y l g r o u p of the p a r e n t organomercurial. O z o n o l y s i s of the s - a l k y l m e r c u r i c h a l i d e s a n d the d i - s - a l k y l m e r c u r i a l s p r o d u c e d the c o r e s p o n d i n g ketone. A l t h o u g h some c a r b o n - c a r b o n c l e a v age o c c u r r e d , i t was g e n e r a l l y less t h a n w i t h the r e a c t i o n of the p r i m a r y o r g a n o m e r c u r i a l s (see

R e a c t i o n s 13 a n d 14, T a b l e I ) .

I n p a r t i a l contrast


to the results of B o c k e m u l l e r a n d Pfeuffer ( R e a c t i o n 11),

the ozonation

of d i i s o p r o p y l m e r c u r y y i e l d e d acetic a c i d i n a d d i t i o n to acetone ( R e a c t i o n 14, T a b l e I ) . T e r t i a r y a l k y l m e r c u r i c h a l i d e s y i e l d e d a c o n s i d e r a b l e a m o u n t of the corresponding alcohol upon ozonation

( R e a c t i o n 17, T a b l e I ) .

Some

c a r b o n - c a r b o n cleavage a c c o m p a n i e d the m a i n r e a c t i o n i n this case as well. T h e i n o r g a n i c p r o d u c t s of the ozonolysis reactions w e r e d e t e r m i n e d for three different o r g a n o m e r c u r i a l s .

O z o n o l y s i s of

two

dialykylmer-

c u r i a l s p r o d u c e d a m i x t u r e of m e r c u r i c c h l o r i d e , m e r c u r o u s c h l o r i d e , a n d m e r c u r i c o x i d e ( R e a c t i o n s 3 a n d 14, T a b l e I ) w h i l e one a l k y l m e r c u r i c h a l i d e gave o n l y m e r c u r i c a n d m e r c u r o u s c h l o r i d e s ( R e a c t i o n 13, T a b l e I ) . A k n o w n m i x t u r e of the three salts w a s tested f o r its s t a b i l i t y to the r e a c t i o n c o n d i t i o n s . T h e salts w e r e o z o n i z e d as a s o l u t i o n / m i x t u r e w i t h m e t h y l e n e c h l o r i d e . P o w d e r x - r a y d i f f r a c t i o n s h o w e d n o difference i n the m e r c u r y salt m i x t u r e after a 2-hour o z o n a t i o n at 1 0 ° C . Carbon—Carbon

Cleavage.

As

mentioned

above,

carbon—carbon

cleavage

u s u a l l y a c c o m p a n i e d the " n o r m a l " carbon—mercury

reaction.

W h i l e this c h a i n - s h o r t e n i n g process was most p r o m i n e n t for

the n - a l k y l m e r c u r i c h a l i d e s w h i c h w e r e o z o n a t e d at 1 0 ° C

cleavage

(Reactions 1

a n d 6, T a b l e I ) , i t w a s r e d u c e d to a m u c h l o w e r l e v e l w h e n the d i - n a l k y l m e r c u r i a l s w e r e o z o n a t e d at — 7 6 ° C ( R e a c t i o n s 5 a n d 10, T a b l e I ) . A c t u a l l y e v e n less carbon—carbon scission o c c u r r e d d u r i n g the o z o n a t i o n of the d i - s - a l k y l m e r c u r i a l s h a l i d e s ( R e a c t i o n 14, T a b l e I ) a n d d u r i n g the p a r t i a l o z o n a t i o n of t h e f e r f - a l k y l m e r c u r i c h a l i d e s ( n o t l i s t e d ) . B y c o m p a r i s o n of the n - a l k y l m e r c u r i a l results alone, i t is possible to g e n e r a l i z e that b o t h h i g h e r o z o n a t i o n temperatures a n d the presence of a h a l o g e n l i g a n d o n m e r c u r y p r o m o t e carbon—carbon cleavage

during

the o z o n o l y s i s of the c a r b o n - m e r c u r y b o n d . A s a c h e c k of a possible r e a c t i o n p a t h w a y for the f o r m a t i o n of the shorter a c i d s d u r i n g o z o n a t i o n of n - a l k y l m e r c u r i a l s , p e n t a n o i c a c i d w a s o z o n i z e d for 4 hours at 10 ° C . T h e o z o n a t i o n w a s c a r r i e d out i n d i c h l o r o -


84


m e t h a n e w h i c h c o n t a i n e d s m a l l amounts of m e r c u r i c c h l o r i d e a n d m e r curous

chloride.

O n l y starting material could

be

detected

by

VPC

analysis of the p r o d u c t m i x t u r e . I n another test of the r e a c t i o n p a t h w a y for c a r b o n - c a r b o n

cleavage,

the exit gas f r o m the r e a c t i o n vessel d u r i n g a 10 ° C o z o n a t i o n of p r o p y l m e r c u r i c b r o m i d e w a s passed t h r o u g h a B a ( O H )

n-

solution. This

2

s o l u t i o n s h o w e d a n almost i m m e d i a t e a n d constant p r e c i p i t a t i o n of B a C 0

3

d u r i n g ozonation. H o w e v e r , further investigation revealed that methylene chloride yielded C 0

2

at a b o u t the same rate at 10 ° C .

Hence,

after

d e t e r m i n i n g that F r e o n 114 d i d n o t react w i t h o z o n e at —76°C., the test was r e p e a t e d o n d i - n - p r o p y l m e r c u r y at the r e d u c e d t e m p e r a t u r e a n d i n Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch007

the i n e r t solvent.

U n d e r these c o n d i t i o n s C 0

w a s s t i l l p r o d u c e d at a n

2

a p p r e c i a b l e rate. O n e final e x p e r i m e n t , h o w e v e r , p l a c e d the o r i g i n of the C0

2

b a c k i n t o a n u n d e c i d e d l i g h t . F o r m i c a c i d w a s o x i d i z e d s l o w l y to

C0

2

w h e n o z o n i z e d i n F r e o n 114 at — 76 ° C . T o define p r o p e r l y t h e role w h i c h 0

The Role of Oxygen.

2

played

i n these ozonolysis reactions, n i t r o g e n was o c c a s i o n a l l y u s e d as the c a r r i e r gas for ozone.

A f t e r o z o n i z i n g n - h e x y l m e r c u r i c b r o m i d e at 1 0 ° C

the u s u a l 0 - 0

2

3

Experimental).

m i x t u r e , the r e a c t i o n w a s r e p e a t e d w i t h 0 - N 3

with

2

(see

B y c o m p a r i n g the r e a c t i o n p r o d u c t s f r o m runs 6 a n d 7

( T a b l e I ) , it c a n b e r e a d i l y seen t h a t n o p r o d u c t differences exist w h e n N

2

is s u b s t i t u t e d for 0 . 2

I n a s i g n i f i c a n t l y different a p p r o a c h to the p r o b l e m , i s o p r o p y l m e r curic chloride was oxygenated i n C H C 1 of 0

2

at 10 ° C for 2 hours at 24 liters

3

p e r h o u r . A n a l y s i s ( V P C ) s h o w e d t h a t 4 % of the o r g a n o m e r c u r i a l

h a d r e a c t e d to g i v e acetone. Stoichiometry of Ozone Uptake.. T h e results of the s t o i c h i o m e t r y s t u d y are o u t l i n e d i n T a b l e I. Intermediate Products from Ozonolysis

of Organomercurials.

b o n u s of the N M R m e t h o d for k i n e t i c analysis of the

A

0 -organomer3

c u r i a l r e a c t i o n was the fact t h a t c e r t a i n 0 - r e a c t i v e i n t e r m e d i a t e s w e r e 3

o b s e r v e d d u r i n g ozonolysis of some of the o r g a n o m e r c u r i a l s . Diisopropylmercury

yielded

isopropylmercuric

chloride

and

iso-

p r o p y l a l c o h o l as w e l l as acetone. T h e first t w o p r o d u c t s gave acetone upon

further reaction w i t h

0 .

The

3

following

equation

appears

to

d e s c r i b e this s y s t e m :

0

[(CH ) CH] Hg—— 3

2

2

CHCl-

—•

(CH ) CO
(CH ) CH—OH 8

2

(CH ) CHOH 3

2


(13)

7.

WATERS E T A L .

Ozonolysis

of

85

Organomercurials

T h e b e l i e f that acetone w a s one of t h e i n i t i a l p r o d u c t s of t h e r e a c t i o n is s u p p o r t e d b y its e x t r e m e l y fast rate of f o r m a t i o n c o m p a r e d w i t h t h e rate of o x i d a t i o n of i s o p r o p y l a l c o h o l to acetone b y 0 - 0 . 3

2

A s t u d y of t h e i n t e r m e d i a t e p r o d u c t s f r o m t h e ozonolysis of i s o p r o p l y m e r c u r i c c h l o r i d e shows alcohol adequately

accounts

that t h e r a t e of b u i l d - u p of i s o p r o p y l

f o r t h e rate of acetone f o r m a t i o n .

The

r e a c t i o n sequence therefore appears to b e o n e of c a r b o n - m e r c u r y c l e a v age, f o l l o w e d b y o x i d a t i o n b y ozone. T h e tertiary alkylmercuric halide, ierf-butylmercuric chloride y i e l d e d o n l y tert-butyl

a l c o h o l as t h e p r i m a r y p r o d u c t .

It was not until a l l the

o r g a n o m e r c u r i a l h a d r e a c t e d that acetone a p p e a r e d as a r e a c t i o n p r o d Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch007

u c t (see R e a c t i o n 17, T a b l e I ) . T h u s i t a g a i n is suggested that a n a l c o h o l is the i m m e d i a t e p r o d u c t of C - H g cleavage b y ozone, at least i n t h e case of a l k y l m e r c u r i c h a l i d e s . Results Kinetic Studies. T h e o z o n a t i o n rates of 10 a l k y l m e r c u r i c h a l i d e s w e r e d e t e r m i n e d i n c h l o r o f o r m at 0 ° C . T h e rate of o z o n e o x i d a t i o n of i s o p r o p y l a l c o h o l to acetone u n d e r i d e n t i c a l c o n d i t i o n s w a s also m e a s u r e d . A n a t t e m p t to measure t h e o z o n a t i o n rate of six d i a l k y l m e r c u r i a l s f a i l e d , h o w e v e r , because t h e r e a c t i o n w i t h R H g w a s m u c h too fast u n d e r these 2

conditions. T h e p r e v i o u s l y d e s c r i b e d m e t h o d u s e d to o b t a i n rate constants f o r these reactions i n v o l v e d the c o n t i n u o u s passage of a s t r e a m of 0 — 0 3

2

t h r o u g h t h e r e a c t i o n vessel. F o r t h e k i n e t i c s t u d y of t h e s l o w e r - r e a c t i n g alkylmercuric halides the 0

3

concentration remained saturated a n d there-

fore constant. T h i s w a s n o t true f o r t h e d i a l k y l m e r c u r i a l s , h o w e v e r , since t h e y r e a c t e d so fast w i t h ozone that a n 0

3

concentration approaching the

s a t u r a t i o n v a l u e c o u l d never b e r e a c h e d .

T h i s s i t u a t i o n w a s also b o r n e

o u t b y t h e consistent o b s e r v a t i o n t h a t t h e K I t r a p ( of t h e r e a c t i o n a p p a r a t u s ) b e c a m e c o l o r e d d u r i n g t h e d i a l k y l m e r c u r y ozonations o n l y after a l l of t h e m e r c u r i a l h a d r e a c t e d .

B y c o m p a r i s o n , t h e reactions of t h e

a l k y l m e r c u r i c h a l i d e s w e r e s l o w e n o u g h so t h a t i o d i n e w a s f o r m e d i n the K I t r a p s h o r t l y after s t a r t i n g t h e 0 - 0 3

flow.

2

I n t h e case of t h e a l k y l m e r c u r i c h a l i d e s , t h e rate e q u a t i o n appears as,

~

d [ R

(ti

g X ]

=

k

[

R

H

g

X

]

[

°

3 ]

(

1

4

)

S i n c e w e m a y c o n s i d e r / c [ 0 ] to b e constant after i n i t i a l s a t u r a t i o n is 3

a c h i e v e d , t h e i n t e g r a t e d rate expression is that i n E q u a t i o n 15.


OZONE REACTIONS

COMPOUNDS

Table I.

Products

Reaction Temperature,

Organomercurial 1. C H C H C H H g B r

10

2. C H C H C H H g B r

0

3. ( C H C H C H ) H g

10

4. ( C H C H C H ) H g

0

5. ( C H C H C H ) H g

-76

3

2

3

2

2

2

3


W I T H ORGANIC

2

3

2

2

3

2

2

2

2

2

2

6. C H ( C H ) H g B r

10

7. C H ( C H ) H g B r

10

8. [ C H ( C H ) ] H g

10

9. [ C H ( C H ) ] H g

0

10. [ C H ( C H ) ] H g

-76

3

2

3

5

2

3

5

2

3

2

3

2

5

5

6

2

2

2

11. ( C H ) C C H H g C l

10

12.

10

3

13.

3

2

(CH ) CH(CH ) HgBr 3

2

2

(CH ) CHHgCl 3

2

2

10


°C

7.

Ozonolysis

WATERS E T A L .

of

Organomercurials

of Ozonolysis"

Inorganic

Organic

Products

Products

44% C H C H C O O H 54% C H C O O H 3

2

3

48% C H C H C O O H 50% C H C O O H 3

2

3

45% HgCl 35% Hg Cl 20% HgO

64% C H C H C O O H 20% CH COOH 15% H C O O H 3

2

2

2

3

2

67% C H C H C O O H 19% C H C O O H 14% H C O O H


3

2

3

72% C H C H C O O H 16% C H C O O H 12% H C O O H 3

2

3

30% CH 40% CH 10% C H 5% C H

3 3 3 3

30% CH 40% CH 10% CH 5% C H 50% CH 25% CH 10% C H 10% C H 5% C H 70% CH 10% C H 5% CH

R H g B r , etc.)

( 2 ) m a y b e e x p l a i n e d b y a s s u m i n g that a less


94


energetic t r a n s i t i o n state exists w h e n the d e v e l o p i n g p o s i t i v e c h a r g e o n m e r c u r y is m o r e f u l l y d i s p e r s e d .

H e n c e , b a s e d o n i n d u c t i v e a n d reso

n a n c e effects, one w o u l d expect the t r a n s i t i o n state for C - H g R or C - H g l c l e a v a g e to b e at a l o w e r e n e r g y l e v e l t h a n t h a t for C - H g C l

cleavage.

T h e a b o v e d i s c u s s i o n assumes the u s u a l i n d u c t i v e effect w h i c h h a l o gens h a v e o n c a r b o n i u m ions, b u t , of course, necessitates a r e v e r s a l of the u s u a l o r d e r for resonance effects. fluorine

I t is i m p o r t a n t to note t h a t w h i l e

c a n q u i t e effectively f o r m a p i b o n d w i t h c a r b o n , i t c a n n o t do so

w i t h the l a r g e m e r c u r y a t o m . T h u s , structures s u c h as 24 s h o u l d be i m


p o r t a n t o n l y f o r the l a r g e r halogens.

+ - ^ C -

Hg-_^J=X

(24)

I n this same r e g a r d , the t r a n s i t i o n state for cleavage of the d i a l k y l m e r curials m u s t b e of r e l a t i v e l y l o w e r energy, solely as a result of the i n d u c t i v e effect of the a l k y l g r o u p since h y p e r c o n j u g a t i o n effects s h o u l d b e nonexistent here. F i n a l l y , i n this s t u d y , as w e l l as most others

( 2 ) , s u b s t i t u t i o n of

c a r b o n for h a l o g e n as t h e m e r c u r y l i g a n d p r o d u c e d a h u g e rate increase f o r e l e c t r o p h i l i c cleavage.

A l t h o u g h the P a u l i n g e l e c t r o n e g a t i v i t y values

for i o d i n e a n d c a r b o n are i d e n t i c a l , the b o n d s of these t w o atoms to m e r c u r y are t o t a l l y d i s s i m i l a r . H e n c e , comparisons of these t w o systems s h o u l d i n v o l v e a c o m p l e t e t r e a t m e n t of o r b i t a l t h e o r y before o n e arrives at a n y conclusions c o n c e r n i n g r e l a t i v e r e a c t i v i t i e s . T u r n i n g to the other h a l f of the k i n e t i c s t u d y — t h a t of r a t e effects f r o m changes of the R g r o u p i n R H g X — i n c r e a s e d s u b s t i t u t i o n o n the c a r b o n b o u n d to m e r c u r y c a u s e d a n a p p r e c i a b l e r e a c t i o n rate increase ( T a b l e I I I a n d sequence 17).

T h e s e results c e r t a i n l y i n d i c a t e t h e g e n

e r a t i o n of p a r t i a l p o s i t i v e c h a r g e o n c a r b o n i n the t r a n s i t i o n state of the carbon-mercury cleavage reaction. W h i l e such a positive charge b u i l d - u p m i g h t a p p e a r i m p o s s i b l e at first c o n s i d e r a t i o n of the f o u r g e n e r a l m e c h a nisms for e l e c t r o p h i l i c cleavage

( R e a c t i o n s 3 - 6 ) , m i n o r m o d i f i c a t i o n of

t w o of t h e m a d e q u a t e l y p r e d i c t s i t . Jensen a n d R i c k b o r n ( 2 ) d i s c u s s e d the p o s s i b i l i t y of t r a n s i t i o n states i n w h i c h the e l e c t r o p h i l i c species w a s p a r t i a l l y b o u n d to the σ o r b i t a l of carbon—mercury

bonds.

T h u s the f o u r t h " c e n t e r " of

the

four-center

b r o m i n a t i o n m e c h a n i s m w a s p i c t u r e d as t h e carbon—mercury b o n d itself, o r m o r e specifically, the c a r b o n sp

s

orbital (2).


7.

WATERS E T A L .

Ozonolysis

of

95

Organomercurials

+ δ /

Br

+

Hg

Br^ ^Br "


8

(25)

T h e c a r b o n sp

a t o m i c o r b i t a l w a s d e p i c t e d as a s o l i d l i n e " i n d i c a t i n g

3

that its c h a r g e d e n s i t y is c h a n g e d p r i m a r i l y b y e l e c t r o n i c factors r a t h e r t h a n the a c t u a l m a k i n g a n d b r e a k i n g of the b o n d " (2).

I n a similar

f a s h i o n the same authors i l l u s t r a t e d the S 2 cleavage of a d i a l k y l m e r E

curial by X H g . +

7°^

8 •Hg—R +

(26)

Hg

8

+

\

X

T h e authors stated t h a t the p o s i t i v e c h a r g e w o u l d p r o b a b l y b e d i v i d e d b e t w e e n the three a t o m i c centers a n d t h a t e l e c t r o n - d o n a t i n g groups o n c a r b o n s h o u l d increase t h e cleavage rate. Mechanism. I n c o n s i d e r a t i o n of a possible m e c h a n i s m for

cleavage

of t h e c a r b o n - m e r c u r y b o n d b y o z o n e , i t s h o u l d b e possible to r u l e o u t the S 1 m e c h a n i s m ( R e a c t i o n 3 ) E

demands

altogether.

This mechanism clearly

t h e f o r m a t i o n of a c a r b a n i o n i n the r a t e - d e t e r m i n i n g step.

L i k e w i s e , the S i m e c h a n i s m for e l e c t r o p h i l i c cleavage seems i m p r o b a b l e E


96


since the b i m o l e c u l a r r a t e - d e t e r m i n i n g step i n v o l v e s a s i m i l a r n e g a t i v e c h a r g e b u i l d - u p o n c a r b o n (4).

T h e t r a n s i t i o n state to s u c h i n t e r m e d i a t e s

w o u l d o b v i o u s l y p r o d u c e i n v e r t e d r e l a t i v e - r a t e orders f r o m t h a t s h o w n i n s e q u e n c e 17. O f the t w o r e m a i n i n g m e c h a n i s m s , the four-center a n d S 2 processes, E

no selection is possible b a s e d o n the d a t a c o l l e c t e d i n this s t u d y .

More

over, since t h e S 2 a n d S i m e c h a n i s m s are m e r e l y t h e t w o possible ex E

E

t r e m e versions of the four-center m e c h a n i s m , t h e exact " p u r i t y " of a n S 2 or f o u r - c e n t e r process c a n often not b e d e t e r m i n e d . O n e test w h i c h E

has b e e n u s e d to d e t e r m i n e the p a r t i c u l a r i n v o l v e m e n t of t h e n u c l e o p h i l i c p a r t of the a t t a c k i n g X - Y m o l e c u l e d u r i n g o r g a n o m e r c u r i a l c l e a v Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch007

age reactions is to change the n a t u r e of Y s u c h t h a t it b e c o m e s a better or p o o r e r n u c l e o p h i l e ( 2 1 ) .

I f the r e a c t i o n rate r e m a i n s u n c h a n g e d , the

process is p u r e l y S 2—i.e., no i n t e r a c t i o n occurs b e t w e e n the Y

group

and mercury.

course

E

T h i s p r o c e d u r e of m e c h a n i s t i c d e t e r m i n a t i o n is of

i m p o s s i b l e f o r cleavage reagents s u c h as ozone. A t this p o i n t i n o u r studies w e f a v o r a

five-membered

cyclic transi

t i o n state, q u i t e analogous to the four-center t r a n s i t i o n state

(Reaction

5 ) , except t h a t n o σ b o n d s of the a t t a c k i n g e l e c t r o p h i l e are b r o k e n . f o u r t h b o n d i n g " c e n t e r " is the c a r b o n sp

B

The

o r b i t a l as i n structures 25

a n d 26.

\

—

8

+

c

8 -Hg-Cl +

/

(27)

I I

A l t h o u g h no

kinetic evidence

exists at this t i m e to i n c l u d e

n u c l e o p h i l i c o x y g e n i n s u c h a b o n d i n g process (i.e., S 2 vs. E

the

four-center),

i t is difficult to b e l i e v e that a n e g a t i v e l y c h a r g e d o x y g e n w o u l d n o t p a r t i c i p a t e i n the n e a r b y f o r m a t i o n of a p o s i t i v e l y c h a r g e d m e r c u r y a t o m . Such a

five-membered

c y c l i c t r a n s i t i o n state has b e e n p r o p o s e d f o r the

t r i i o d i d e cleavage of c a r b o n - m e r c u r y b o n d s ( 2 ) .

W h i l e s u c h a structure

is u n l i k e l y for the l i n e a r I ~ i o n , i t s h o u l d easily a c c o m m o d a t e the o z o n e 3

m o l e c u l e w h o s e b o n d i n g a n g l e is 116° p l a u s i b i l i t y of S t r u c t u r e 27 d e p e n d s

(12).

O f course the g e o m e t r i c a l

o n t h e degree of

carbon-mercury


7.

WATERS E T A L .

Ozonolysis

of

b o n d b r e a k i n g i n the t r a n s i t i o n state.

97

Organomercurials

M o d e l s s h o w that the e x t r e m e l y

l o n g c a r b o n - m e r c u r y b o n d ( 2 . 0 6 - 2 . 2 0 A ) (22)

n e e d not b e stretched too

m u c h i n o r d e r to p e r m i t a 1,3-dipolar attack b y o z o n e as p i c t u r e d . T h e exact c h r o n o l o g y of b o n d b r e a k i n g a n d b o n d m a k i n g is i m p o r tant i n c o n s i d e r i n g S t r u c t u r e 27 as the t r a n s i t i o n state f o r carbon—mercury cleavage.

T h e i n i t i a l attack b y o z o n e m u s t l i e o n the S 2 side of the E

c o n c e r t e d , four-center process i n o r d e r to a l l o w for the b u i l d - u p of some positive charge on carbon.

T h u s , the e l e c t r o p h i l i c o x y g e n s h o u l d h a v e

a c h i e v e d a greater degree of b o n d m a k i n g w i t h the c a r b o n sp

orbital

3

t h a n t h a t of the n u c l e o p h i l i c o x y g e n w i t h t h e m e r c u r y a t o m b y the t i m e S t r u c t u r e 27 is r e a c h e d . A t t e n t i o n is p a i d to this b o n d m a k i n g order b y Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch007

the different lengths of p a r t i a l b o n d s i n S t r u c t u r e 27

(2).

T h e o v e r a l l i m p o r t a n c e of t r a n s i t i o n state 27 is that rate sequences 16 a n d 17 are a d e q u a t e l y e x p l a i n e d . It is o n l y this t y p e of energy m a x i m u m w h i c h p r e d i c t s p a r t i a l p o s i t i v e charge o n b o t h c a r b o n and m e r c u r y . As

a n alternate t r a n s i t i o n state, one m i g h t e n v i s i o n the r e s u l t of

i n i t i a l attack b y the 1,2-dipolar resonance

f o r m of o z o n e via

a four-

m e m b e r e d c y c l i c t r a n s i t i o n state.

Since this t r a n s i t i o n state c o u l d y i e l d a n i n t e r m e d i a t e w h i c h i n t u r n c o u l d c o n c e i v a b l y p r o d u c e the p r o d u c t s o b s e r v e d , i t cannot b e r u l e d out at this p o i n t . P e r h a p s after m o r e d a t a h a v e b e e n c o l l e c t e d c o n c e r n i n g the existence

of the analogous

Staudinger intermediates

(23)

from

olefin

reactions, i t w i l l b e possible to choose b e t w e e n the t w o r e a c t i o n p a t h w a y s . F o l l o w i n g the p r o p o s e d

t r a n s i t i o n state 27, a l i k e l y i n t e r m e d i a t e

w o u l d b e a t r i o x i d e s i m i l a r to that p r o p o s e d h y d r o g e n cleavage

(Reaction

b y O u e l l e t t e for s i l i c o n -

12).


98


(29)

[—C—0—0—0—HgX]

/

A l t h o u g h this i n t e r m e d i a t e was n o t i s o l a t e d or e v e n d e t e c t e d b y N M R spectroscopy

( a t 31 ° C ) , its existence is i n f e r r e d f r o m the t y p e of o r g a n i c

a n d i n o r g a n i c p r o d u c t s f o r m e d i n the r e a c t i o n . F u t u r e l o w t e m p e r a t u r e N M R studies of the ozonolysis solutions w i l l b e d o n e to v e r i f y S t r u c t u r e 29. The

trioxide

intermediate

may

decompose

by

many

pathways.

Results o b t a i n e d i n this p a p e r suggest that these d e c o m p o s i t i o n p a t h w a y s


m i g h t e x p l a i n the t w o classes of m e r c u r y salts p r o d u c e d ( H g

2 +

and H g ) +

as w e l l as the t w o d i v i s i o n s of o r g a n i c p r o d u c t s f o r m e d ( w i t h a n d w i t h o u t carbon-carbon

scission).

T h i s p o s s i b i l i t y looks p a r t i c u l a r l y a t t r a c t i v e

w h e n the a c e t o n e / f o r m i c a c i d a n d H g C l / H g C l 2 ratios are c o m p a r e d i n 2

R e a c t i o n 13, T a b l e I.

2

H o w e v e r , b e f o r e e x t e n d i n g s p e c u l a t i o n o n this

matter, s e v e r a l f u t u r e experiments a n d t h e o r e t i c a l c a l c u l a t i o n s m u s t b e pursued.

A m o n g these w i l l b e a n effort to m e a s u r e q u a n t i t a t i v e l y t h e

a m o u n t a n d t y p e ( s i n g l e t or t r i p l e t ) of oxygen generated b y a n 0 / N 3

ozonolysis.

2

A l s o , t h e o r e t i c a l c o n s i d e r a t i o n w i l l b e g i v e n to the m e t a l o -

t r i o x y a l k a n e s i n l i g h t of p u b l i s h e d d a t a o n the k n o w n d i a l k y l t r i o x i d e systems (24,

25).

Synthetic U t i l i t y . O n e g o a l of this research w a s to investigate n e w s y n t h e t i c uses of o r g a n o m e r c u r i a l s . A l t h o u g h the s y n t h e t i c u t i l i t y of this r e a c t i o n has n o t b e e n

extensively i n v e s t i g a t e d , p r o d u c t s

s u c h as that

f r o m R e a c t i o n 16 i n T a b l e I d o suggest a possible u t i l i t y to

organic

chemists. T h u s , the p r e p a r a t i o n of α-alkoxyketones s h o u l d b e possible b y consecutive a l k o x y m e r c u r a t i o n a n d o z o n a t i o n reactions. OR' HgX

2

R2C = C H — R R'OH

R2C—CH—R HgX

OR

(30)

0; R 2—C—C—R Ο A n a t t e m p t to p r e p a r e α-diketones via consecutive

hydroxymercuration

a n d o z o n a t i o n f a i l e d , p r e s u m a b l y because of the p r o d u c t ' s extreme r e a c t i v i t y t o w a r d s ozone.


7.

WATERS E T A L .

Ozonolysis

of

Organomercurials

99

COOH COOH


90% A s t u d y is n o w u n d e r w a y to e v a l u a t e c o m p l e t e l y t h e f u t u r e synthetic r o l e o f t h e o x y m e r c u r a t i o n - o z o n o l y s i s sequence. Literature

Cited

1. Jensen, F. R., Rickborn, B., "Electrophilic Substitution of Organomercu rials," McGraw-Hill, New York, 1968. 2. Belew, J. S., "Oxidation," Vol. I, R. L. Augustine, Ed., p. 259, Marcel Dekkar, New York, 1969. 3. Aleksandrov, Yu. Α., Sheyanov, N. G., Shushunov, V. Α., Zh. Obshch. Khim. (1968) 38, 1352-6; CA (1968) 69, 77388q. 4. Aleksandrov, Yu. Α., Sheyanov, N. G., Zh. Obshch. Khim. (1966) 36, 953; CA (1966) 65, 8955e. 5. Emel'yanov, Β. V., Shemyakina, Ζ. N., Shvarov, V. N., Khim.Prom.(1968) 44, 498-500; CA (1968) 69, 7964y. 6. Aleksandrov, Yu. Α., Sheyanov, N. G., Zh. Obshch. Khim. (1969) 39, 141-3; CA (1969) 70, 96847a. 7. Spialter, L., Austin, J. D., Inorg. Chem. (1966) 5, 1975-8. 8. Ayrey, G., Barnard, D., Woodbridge, D. T.,J.Chem. Soc. (1962) 2089-99. 9. Bockemuller, W., Pfeuffer, L., Ann. (1939) 537, 178. 10. Ouellette, R. J., Marks, D. L.,J.Organometal. Chem. (1968) 11, 407-13. 11. Pike, P. E., Marsh, P. G., Erickson, R. E . , Waters, W. L . , Tetrahedron Letters (1970) 2679; Pike, P. E., MS Thesis, University of Montana (1970). 12. Rivera, J. T., MS Thesis, University of Montana (1971). 13. Marvel, C. S., Gauerke, C. G., Hill, E. L., J. Amer. Chem. Soc. (1925) 47, 3009-11. 14. Gilman, H., Brown, R. E., J. Amer. Chem. Soc. (1929) 51, 928. 15. Hatton, J. V., Schneider, W. G., Siebrand, W.,J.Chem. Phys. (1963) 39, 1330-6. 16. Kiefer, E. F., Waters, W. L., J. Amer. Chem. Soc. (1965) 87, 4401. 17. Bailey, P. S., Reader, A. M., Chem. Ind. (London) (1961) 1063. 18. Ref. 2, p. 98. 19. Brilkina, T. G., Shushunov, V. Α., "Reactions of Organometallic Compounds with Oxygen and Peroxides," Chemical Rubber Co. Press, Cleveland, 1966. 20. Hughes, E. D., Ingold, C. K., Roberts, R. M. G., J. Chem. Soc. (1964) 3900.


100


ORGANIC

COMPOUNDS

21. Charmen, Η. Β., Hughes, E. D., Ingold, C. K., J. Chem. Soc. (1959) 2530. 22. Grdenic, D., Quart. Rev. (1965) 19, 303-28. 23. Story, P. R., Alford, J. Α., Ray, W.C.,Burgess, J. R., "Abstracts of Papers," 161st National Meeting, ACS, March 1971, PETR A13. 24. Bartlett, P. D., Günther, P.,J.Amer. Chem. Soc. (1966) 88, 3288. 25. Bensen, S. W., J. Amer. Chem. Soc. (1964) 86, 3922.


RECEIVED June 21, 1971. Supported by the National Science Foundation Grant No. GP-18317.


8 Ozonation of p-Nitro-N,N-Dimethylaniline PER

KOLSAKER

Universitetets Kjemiske Institutt, Blindern/Oslo BRITA

3, Norway

TEIGE


Odontologisk Institutt for Fysiologi og Biokjemi, Blindern/Oslo

The reaction studied.

of p - n i t r o - N , N - d i m e t h y l a n i l i n e with ozone

Only

side-chain

oxidation

oxide,

No N-oxide

could

be

dimeric per-

obtained.

2-carboxy-4-nitro-N,N-dimethylaniline,

- N , N - d i m e t h y l a n i l i n e , and ized.

a

di-[(N-methyl-N-p-nitrophenyl)aminomethyl]

were formed.

comparison

was

p-nitro-N-

products,

- m e t h y l a n i l i n e , p - n i t r o - N - m e t h y l f o r m a n i l i d e , and peroxide,

3, Norway

A mechanism

is

N,N-dimethylaniline

For

p-chlorowere

ozon-

proposed.

^ V z o n a t i o n of t e r t i a r y a l i p h a t i c amines has r e c e i v e d some a t t e n t i o n i n recent years. A m i n e oxide f o r m a t i o n was e s t a b l i s h e d l o n g ago ( 1 ). O x i d a t i o n of a l k y l groups w a s r e p o r t e d b y H e n b e s t a n d S t r a t f o r d S h u l m a n ( 3 ) , a n d B a i l e y et al. (4, 5 ) .

(2),

F o r m a t i o n of a m i n e h y d r o c h l o -

rides w a s e s t a b l i s h e d w h e n c h l o r i n a t e d solvents w e r e u s e d ( 2 - 5 ) .

De-

a l k y l a t e d p r o d u c t s w e r e f o r m e d (2, 4, 5 ) , a n d amides w e r e f o u n d b y the same authors (2-^5). I n a p r e v i o u s p a p e r ( 6 ) w e r e p o r t e d o n the o z o n a t i o n of 2-carboxy4-nitro-N,N-dimethylaniline (I)

and p-nitro-N,N-dimethylaniline

(IVc).

N - o x i d e s w e r e n o t f o u n d i n these cases, a n d the p r o d u c t s f o r m e d i n d i c a t e d o n l y s i d e - c h a i n o x i d a t i o n . T h e i n t e r m e d i a c y of a c a r b i n o l a m i n e I I is i n d i c a t e d b y t h e f o r m a t i o n of the lactone I I I . C H

3\

^

C H

3

C

H

3 \

M

/

C

H

2

O

H

C H

3\

K I

/ «ÎÎ2 C

C

H

3\

M

/

C

H

3

a:X = H b:X = Cl c:X=N0 N0

2

II

III

IV


2

102


Table I.

Ozonation of 2-Carboxy-4-nitro-2V,N-dimethylaniline Demethylated Starting Material,

Solvent CH C1 EtOAc MeOH 2

%

Lactone (III),

81 71 64

2

(I) %

18 28 32

D e m e t h y l a t e d s t a r t i n g m a t e r i a l was also a p r o d u c t of the

ozonation.

P r o d u c t c o m p o s i t i o n v a r i e d w i t h solvent as s h o w n i n T a b l e I. W h e n p-nitro-N,N-dimethylaniline (IVc)

w a s o z o n i z e d at 0 ° C i n

e t h y l acetate, m e t h y l e n e c h l o r i d e , or m e t h a n o l , a m i x t u r e of Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch008

resulted.

products

I n a d d i t i o n to the e x p e c t e d s i d e - c h a i n o x i d a t i o n p r o d u c t s —

p-nitro-N-methylaniline

( V c ),

p-nitro-N-methyl formanilide

peroxide compound was formed.

(Vic ) —a

T h i s p e r o x i d e , w h i c h is n o t

u n t i l the solvents are r e m o v e d , w a s s h o w n b y a series of

formed

experiments

( d e s c r i b e d b e l o w ) to b e i d e n t i c a l w i t h d i - [ ( N - m e t h y l - p - n i t r o p h e n y l ) aminomethyl] peroxide ( V I I ) .

D e o x y g e n a t i o n of V I I w i t h t r i e t h y l p h o s

p h i t e ( 7 ) y i e l d e d the ether V I I I , w h i c h i n t u r n d e c o m p o s e d at its m e l t i n g p o i n t to t h e a m i n e I X .

Χ

X

V

VI

N0

N0

2

VIII

2

VII

α:Χ = Η , b:X = CI , c : X = N 0

N0

N0

2

2

2

N0

N0

2

2

IX

W e n o w r e p o r t o u r results w h e n the e x p e r i m e n t a l c o n d i t i o n s are s y s t e m a t i c a l l y v a r i e d . O z o n a t i o n s of some other Ν,Ν-dimethylanilines are also i n c l u d e d . T h e results are g i v e n i n T a b l e I I . Experimental General. T h e o z o n a t i o n p r o c e d u r e s are those d e s c r i b e d i n t h e l i t e r a ture, b o t h u s i n g ozone—oxygen a n d o z o n e - n i t r o g e n . O x y g e n analyses



8.

KOLSAKER AND T E i G E

Ozonation

of p-Nitro-N,Ν-Dimethy

laniline

103

w e r e p e r f o r m e d u s i n g a B e c k m a n F 3 o x y g e n a n a l y z e r as d e s c r i b e d p r e v i ously ( 8 ) . Gas l i q u i d chromatographic ( G L C ) determinations were c a r r i e d out w i t h a n A e r o g r a p h m o d e l A 700, u s i n g a n 8.5-ft X 0.25-inch c o l u m n of p o l y e t h y l e n e g l y c o l 2 0 M ( 3 0 % o n C h r o m o s o r b W H M D S , 6 0 / 8 0 m e s h ) f o r E x p e r i m e n t s 1 a n d 2. P r o t o n m a g n e t i c resonance ( P M R ) s p e c t r a w e r e r e c o r d e d o n a V a r i a n A 6 0 A spectrometer u s i n g o r d i n a r y c h l o r o f o r m as solvent a n d t e t r a m e t h y l s i l a n e as i n t e r n a l reference. M e l t i n g points w e r e not c o r r e c t e d . Materials. 2 - C a r b o x y - 4 - n i t r o - N , N - d i m e t h y l a n i l i n e ( I ) w a s s y n t h e s i z e d f r o m its c h l o r o a n a l o g w i t h d i m e t h y l a m i n e ( a q u e o u s s o l u t i o n ) , mp 164°-166°C. p-Chloro-N,IV-dimethylaniline ( I V b ) and N,N-dim e t h y l a n i l i n e ( I V a ) w e r e c o m m e r c i a l l y a v a i l a b l e i n the p u r e state a n d w e r e u s e d as s u p p l i e d . p - N i t r o - N , N - d i m e t h y l a n i l i n e ( I V c ) w a s p r e p a r e d from p-nitrochlorobenzene a n d dimethylamine ( 9 ) ; m p 166°C. Ozonation of 2-Carboxy-4-nitro-N,N-dimethylaniline (I)· The a m i n e (2.10 grams, 10 m m o l e s ) was d i s s o l v e d i n the a p p r o p r i a t e solvents ( 200 m l m e t h a n o l , e t h y l acetate, or m e t h y l e n e c h l o r i d e ) a n d o z o n i z e d at 0 ° C w i t h e q u i m o l a r amounts of o z o n e ; q u a n t i t a t i v e a b s o r p t i o n o c c u r r e d . N e a r the e n d of t h e o z o n a t i o n t i m e , a p r e c i p i t a t e f o r m e d . I n ozonations i n m e t h a n o l this substance was i d e n t i c a l w i t h l a c t o n e I I I ; m p 1 7 6 ° - 1 7 7 ° C . , p r e p a r e d a c c o r d i n g to V i l l i g e r (10). I n the other solvents the i n s o l u b l e p r o d u c t w a s the d e m e t h y l a t e d s t a r t i n g m a t e r i a l , m p 2 6 5 ° - 2 6 8 ° C ( d e c ) ; r e p o r t e d m p 2 6 3 ° - 2 6 4 ° C (11). T h e m o t h e r l i q u o r was e v a p o r a t e d , a n d the t w o c o m p o u n d s w e r e s e p a r a t e d b y f r a c t i o n a l c r y s t a l l i z a t i o n . T h e results are s h o w n i n T a b l e I. Ozonation of N,N-dimethylaniline (IVa). T h e amine (10 mmoles) was d i s s o l v e d i n m e t h y l e n e c h l o r i d e (150 m l ) a n d o z o n i z e d at — 7 8 ° C w i t h 10 m m o l e s of o z o n e ( n i t r o g e n as c a r r i e r gas) (12); q u a n t i t a t i v e a b s o r p t i o n o c c u r r e d . T h e s o l u t i o n b e c a m e d a r k b r o w n , a n d finally a t a r r y substance s e p a r a t e d out. T h i s substance, w h i c h a d h e r e d to the w a l l s of the o z o n a t i o n vessel, w a s r e p e a t e d l y d i g e s t e d w i t h m e t h y l e n e c h l o r i d e . T h e c o m b i n e d m e t h y l e n e c h l o r i d e extracts, after w a s h i n g w i t h w a t e r , w e r e c o n c e n t r a t e d a n d a n a l y z e d b y G L C . T h e results are s h o w n in Table II. Ozonation of £-Chloro-N,N-dimethylaniline ( I V b ) . T h e a m i n e ( 1 0 m m o l e s ) w a s d i s s o l v e d i n m e t h y l e n e c h l o r i d e (100 m l ) a n d o z o n i z e d at —78 ° C w i t h 10 m m o l e s of ozone. Q u a n t i t a t i v e a b s o r p t i o n o c c u r r e d . T h e solution was carefully washed w i t h water a n d then analyzed b y G L C . F o r the results see T a b l e I I . Ozonation of ^-Nitro-2V,2V-dimethylaniline ( I V c ) . C o n c e n t r a t i o n , t e m p e r a t u r e , a n d solvents w e r e v a r i e d as s h o w n i n T a b l e I I . I n a t y p i c a l r u n , 5 m m o l e s of a m i n e w e r e d i s s o l v e d i n 200 m l of e t h y l acetate a n d o z o n i z e d at 0 ° C w i t h 5 m m o l e s ozone, u s i n g n i t r o g e n as c a r r i e r gas; q u a n t i t a t i v e a b s o r p t i o n o c c u r r e d . T h e exit gas w a s a n a l y z e d for m o l e c u l a r o x y g e n . A f t e r the s o l u t i o n h a d c o m e to r o o m t e m p e r a t u r e , i t was still clear a n d h o m o g e n e o u s . T h e solvent was e v a p o r a t e d , a n d the r e s i d u e was d r i e d a n d w e i g h e d . E t h y l acetate (200 m l ) was a d d e d . A y e l l o w c o m p o u n d ( V I I ) was n o w i n s o l u b l e a n d was r e m o v e d b y filtration. T h e filtrate was e v a p o r a t e d , a n d the r e s i d u e was e x a m i n e d b y P M R . T h e amounts of p - n i t r o - I V , N - d i m e t h y l a n i l i n e ( I V c , s t a r t i n g m a t e r i a l ) , p - n i t r o N - m e t h y l a n i l i n e ( V ) , a n d p - n i t r o - N - m e t h y l f o r m a n i l i d e ( V I ) w e r e esti-


104


Table II.


Expt.

Compound

Amine, mmoles

O /0 mmoles s

2

Ozonation

O /N mmoles

Solvent (ml)

Temp., °C

10

CH C1 (150) CH C1 (100) EtOAC(200) EtOAc(200)

-78 -78 -78 -78

5 5 5 10

MeOAc(200) CH C1 (200) EtOAc(200) EtOAc(lOO) EtOAc(200) MeOAc(200) CH C1 (200) EtOAc(lOO) EtOAc(200) EtOAc(200) EtOAc(200) MeOAc(200) CH C1 (200) EtOAc(200) EtOAc(200) MeOAc(200) CH C1 (200) EtOAc(200)

-78 -78 -40 -40 -40 -40 -40 0 0 0 0 0 0 25 25 25 25 -78 -40

s

2

1 2 3 4

IV IV IV IV

a b c c

10 10 10 5

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

IV IV IV IV IV IV IV IV IV IV IV IV IV IV IV IV IV IV

c c c c c c c c c c c c c c c c c c

5 5 10 10 5 5 5 10 10 5 5 5 5 10 5 5 5 5

23

IV c

5

10

EtOAc(200)

24

IV c

5

10

EtOAc(200)

0

25

IV c

5

10

EtOAc(200)

25

26 27 28 29

IV IV IV IV

5 5 5 5

2.5 2.5 2.5 2.5

EtOAc(200) EtOAc(200) EtOAc(200) EtOAc(200)

-78 -40 0 25

c c c c

10 10 5 5 5 10 10 5 5 5 10 10 5 5 5 5 10

2

2

2

2

2

2

2

2

2

2

2

2

m a t e d b y m e a s u r i n g the i n t e g r a t e d areas for the N - m e t h y l protons. T h e l i m i t of error i n s u c h a d e t e r m i n a t i o n is p r o b a b l y a r o u n d 5 % . Insoluble Compound VII. T h i s c o m p o u n d m e l t e d at 1 7 6 ° - 1 7 7 ° C ( a c e t o n i t r i l e - w a t e r ) . It w a s i d e n t i c a l ( b y i n f r a r e d ) w i t h t h e p r o d u c t obtained when p-nitro-N-methylaniline, formaldehyde, and hydrogen peroxide were heated i n ethanol ( 7 ) . ACTIVE OXYGEN CONTENT.

A

t o t a l of

181.2

mg

(0.5

mmole)

of

VII

w e r e d i s s o l v e d i n 7 5 m l of a c e t o n i t r i l e ; 1 g r a m of s o d i u m i o d i d e i n 2 5 m l a c e t o n i t r i l e w a s a d d e d , a n d n i t r o g e n w a s p a s s e d t h r o u g h the s o l u t i o n . N o r e a c t i o n o c c u r r e d ; w h e n 2 m l p e r c h l o r i c a c i d ( 6 0 % ) w e r e a d d e d , the


8.


Ozonation

105

of p-Nitro-N,N-Dimethylaniline

Experiments


Products 02, mmoles

V, mmoles (%)

VI, mmoles (%)

VII, mmoles (%)

Rec. IV, mmoles (%)

7.9 — 6.5 4.0-4.7

1.0(10) 1.7(17) 0 0

0 0 0 0

4.4 4.5 6.9 — 4.1 4.1 3.9 n.c. 9.0 — 4.1 4.0 3.4 — 4.0 4.3 3.3 7.9

0 2.6(52) 1.7(17) 0.6(6) 0.7(14) 0.9(18) 2.1(42) 0.8(8) 1.1(11) 1.0(20) 0.8(16) 0.6(12) 1.5(30) 0.3(3) 0 traces 1.3(26) 0

2.0(20) 2.6(26) 1.3(13) 0.5-1.0 (10-20) 1.3(26) 1.2(24) 2.5(25) 2.7(27) 1.8(36) 1.7(34) 1.2(24) 2.7(27) 3.3(33) 1.4(28) 1.5(30) 1.6(32) 1.2(24) 3.5(35) 1.8(36) 1.2(24) 1.3(26) 2.3(46)

0.1(4) 0.6(24) 1.6(32) 1.5(30) 0.8(32) 0.7(28) 0.7(28) 1.9(38) 2.2(44) 0.9(36) 1.0(40) 0.9(36) 0.7(28) 2.2(44) 1.0(40) 0.7(28) 0.8(32) 0

2.4(24) 2.0(20) 8.7(87) 4.0^.5 (80-90) 3.5(70) 0 2.7(27) 4.4(44) 0.8(16) 0.9(18) 0.2(4) 2.7(27) 1.3(13) 0.8(16) 0.7(14) 0.9(18) 0.7(14) 1.6(16) 1.2(24) 2.2(44) 0.8(16) 2.5(50)

8.4

0

3.3(66)

0

traces

6.1

0

3.7(74)

0

0

6.9

0

4.3(86)

0

0

2.1 1.9 1.5 1.3

0 0 0 0

0 0.6(12) 0.6(12) 0.5(10)

0 0.4(16) 0.5(20) 0.3(12)

5.0(100) 3.6(72) 3.3(66) 3.9(78)

Remarks tar f o r m a t i o n tar f o r m a t i o n several r u n s

no o x y g e n a n a l y s i s

0.3 m m o l e s (12%) 0.9 m m o l e s (36%) 0.7 m m o l e s (28%) 0.4 m m o l e s (16%)

diperoxide diperoxide diperoxide diperoxide

b r o w n c o l o r of i o d i n e a p p e a r e d i m m e d i a t e l y . A f t e r 20 m i n u t e s at r o o m t e m p e r a t u r e t h e s o l u t i o n w a s t i t r a t e d w i t h 0 . 1 N s o d i u m thiosulfate. T h e e n d p o i n t w a s difficult to observe, b u t a p p r o x i m a t e l y 1 0 - 1 1 m l of titer s o l u t i o n w e r e u s e d , c o r r e s p o n d i n g to a b o u t 1 0 0 % a c t i v e oxygen. S o l i d sodium bicarbonate was then added, a n d the acetonitrile was evaporated. Y e l l o w crystals w e r e filtered off, m e l t i n g at 1 5 0 ° - 1 5 2 ° C . I n f r a r e d s p e c t r a ( K B r p e l l e t ) c o n f i r m e d the i d e n t i t y of t h e substance as p - n i t r o - N - m e t h y l a n i l i n e ( V ) ; the y i e l d w a s 133 m g ( 8 7 . 5 % ). T H E R M A L D E C O M P O S I T I O N : C o m p o u n d V I I (101.7 m g ) w a s h e a t e d neat at 1 5 5 ° C ( b o i l i n g a n i s o l e ) . A n i n f r a r e d s p e c t r u m ( K B r p e l l e t ) of


106


the r e s i d u e s h o w e d it to be i d e n t i c a l w i t h p - n i t r o - N - m e t h y l f o r m a n i l i d e ( V I ) ; the y i e l d w a s 96 m g ( 9 5 % ). REACTION WITH T R I E T H Y L PHOSPHITE (7).

Refluxing V I I

6

1 6


in

triethyl

p h o s p h i t e y i e l d e d a v e r y i n s o l u b l e c o m p o u n d ( V I I I ) m e l t i n g at 1 7 7 ° 1 7 8 ° C . ( F o u n d : C 55.4, H 5.3, Ν 26.4. C a l e . ( C i H N 0 ) : C 55.5, Η 5.2, Ν 16.2). D E C O M P O S I T I O N O F V I I I . H e a t i n g V I I I neat at its m e l t i n g p o i n t y i e l d e d I X ; m p 2 7 6 ° - 2 7 8 ° C ( F o u n d : C 56.9, Η 5.1, Ν 17.3. C a l e . ( C i 5 H N 0 ) : C 57.0, H 5.1, Ν 17.7). C o m p o u n d I X c o u l d also b e synthesized from p-nitro-N-methylaniline and formaldehyde. Ozonation of £-Nitro-N,N-dimethylaniline with T w o Mole E q u i v a lents of Ozone. T h e p r o d u c t s f r o m this o z o n a t i o n w e r e o b t a i n e d a n d a n a l y z e d b y the same p r o c e d u r e as for the e q u i m o l a r runs. T h e i n s o l u b l e c o m p o u n d ( X V I I I ) m e l t e d at 1 5 0 ° C . ( F o u n d : C 49.0, Η 4.4, Ν 14.3. C a l e . ( C i H N 0 ) : C 49.0, H 4.1, Ν 14.3). 4

6

1 8

4

5

4

1 6

4

8

Results ( 1 ) T h e r e seems to b e no significant difference i n p r o d u c t y i e l d s u s i n g either o z o n e - o x y g e n or ozone—nitrogen (e.g., E x p e r i m e n t s 14 a n d 1 5 ) . T h e s m a l l differences m a y b e the result of different rates of o z o n e delivery. ( 2 ) U s e of m e t h y l e n e c h l o r i d e as solvent consistently leads to h i g h e r y i e l d s of d e m e t h y l a t e d p r o d u c t ( V ) , a c c o m p a n i e d m o s t l y b y a decrease i n r e c o v e r e d s t a r t i n g m a t e r i a l . L o w e r o x y g e n y i e l d s are also o b s e r v e d at a l l temperatures except at — 7 8 ° C . ( 3 ) O z o n e appears to b e décomposée! b y p - n i t r o - N , N - d i m e t h y l a n i l i n e i n e t h y l a n d m e t h y l acetate at — 7 8 ° C (cf. E x p e r i m e n t s 3, 4, 5, a n d especially 26). ( 4 ) T h e o n l y t e m p e r a t u r e effect of a n y significance is o b s e r v e d i n e t h y l or m e t h y l acetate i n g o i n g f r o m — 4 0 ° to — 8 0 ° C ( E x p e r i m e n t s 4 and 9). ( 5 ) T h e h i g h e r y i e l d s of the f o r m a n i l i d e V I are a c c o m p a n i e d b y h i g h e r y i e l d s of the p e r o x i d e V I I . ( 6 ) S i n c e s t a r t i n g m a t e r i a l a l w a y s is r e c o v e r e d i n the e q u i m o l a r r u n s , the i n i t i a l attack of o z o n e m u s t b e s o m e w h a t s l o w e r t h a n one ( o r s e v e r a l ) of the subsequent steps i n v o l v i n g o z o n e a n d the p r i m a r y r e a c t i o n product(s). Discussion S e v e r a l authors ( I , 3, 4)

p r o p o s e t h a t o z o n e attacks amines electro-

p h i l i c a l l y at the n i t r o g e n lone p a i r . A d d i t i o n a l s u p p o r t for this comes f r o m the f o l l o w i n g o b s e r v a t i o n .

O z o n e passes u n c h a n g e d t h r o u g h s o l u -

t i o n of p - n i t r o - A ^ N - d i m e t h y l a n i l i n e ( I V c ) [or Ν,Ν-dimethylaniline ( I V a ) ] i n 7 0 % p e r c h l o r i c a c i d . D i l u t i n g the a c i d to about 2 0 - 2 5 % p r o d u c e s the y e l l o w color of u n p r o t o n a t e d a m i n e , a n d o z o n e is n o w a b s o r b e d q u a n t i tatively.

S i n c e the y e l l o w c o l o r of the free a m i n e ( I V c )

disappears i n


8.

K O L S A K E R AND T E i G E

Ozonation


107

c o n c e n t r a t e d a c i d s o l u t i o n , the a m i n e n i t r o g e n ( a n d not another p o i n t of the m o l e c u l e ) m u s t b e p r o t o n a t e d . NMR

studies s h o w that a m i d e s are p r o t o n a t e d at the o x y g e n a t o m ,

i n d i c a t i n g a l o w e r electron d e n s i t y at the n i t r o g e n a t o m i n a m i d e s t h a n e v e n i n p - n i t r o - N , N - d i m e t h y l a n i l i n e . A b o u t 5 0 % excess o z o n e h a d to be passed t h r o u g h a s o l u t i o n of Ν,Ν-dimethylbenzamide a n d as m u c h as 1 2 5 % excess t h r o u g h p - n i t r o - N , I V - d i m e t h y l b e n z a m i d e to ensure a c o m plete r e a c t i o n . S i n c e the p r o d u c t s of the o z o n a t i o n of I V o n l y i n d i c a t e s i d e - c h a i n o x i d a t i o n , i t is possible t h a t o z o n e i n s e r t i o n i n the

carbon—hydrogen

b o n d is the s t a r t i n g p o i n t of the m e c h a n i s m . A g a i n the a n s w e r m a y b e Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch008

f o u n d i n N M R spectroscopy, b e a r i n g i n m i n d that the v a r i o u s resonance positions reflect the e l e c t r o n d e n s i t y near the h y d r o g e n a t o m i n a c a r b o n h y d r o g e n b o n d ( i n the absence of s t r o n g a n i s o t r o p i c g r o u p i n g s ) . c h e m i c a l shift difference for the m e t h y l protons i n g o i n g f r o m

The

N,N-di-

m e t h y l a n i l i n e to its conjugate a c i d is 0.45 p p m , i n d i c a t i n g a s o m e w h a t l o w e r e l e c t r o n d e n s i t y i n the c a r b o n - h y d r o g e n b o n d . T h e c h e m i c a l shift difference for t h e m e t h y l e n e g r o u p protons g o i n g f r o m t r i e t h y l a m i n e to d i e t h y l ether is a b o u t 1 p p m (12).

F o r b o t h these c o m p o u n d s s i d e - c h a i n

o x i d a t i o n takes p l a c e a l t h o u g h a m u c h l a r g e r e l e c t r o n d e n s i t y than i n amine-conjugate

change

a c i d p a i r is i n d i c a t e d b y N M R . T h u s , the

i n a b i l i t y of o z o n e to react w i t h the conjugate a c i d m u s t b e l i n k e d to the absence of the lone p a i r o n the a m i n e n i t r o g e n . F r o m these considerations i t seems safe to c o n c l u d e t h a t the

initial

attack of ozone o n amines takes p l a c e at the n i t r o g e n atom. T h i s is also l o g i c a l since the e l e c t r o p h i l i c o z o n e m o l e c u l e m u s t i n t e r a c t w i t h

the

center of highest n u c l e o p h i l i c i t y i n the substrate—viz., the lone p a i r of the n i t r o g e n a t o m . T h e secondary reactions w i l l t h e n b e d e t e r m i n e d b y the rest of the molecule. W h e t h e r amine oxide formation w i l l be competitive w i t h sidec h a i n o x i d a t i o n or not d e p e n d s o n the s t r e n g t h of the nitrogen—oxygen b o n d i n the p r i m a r y a d d u c t .

T h i s a g a i n is d e t e r m i n e d m a i n l y b y the

electron d e n s i t y at the n i t r o g e n a t o m of the substrate—viz., the s t r e n g t h of the base.

A l i p h a t i c amines are stronger bases t h a n t h e a r o m a t i c ( t r i -

m e t h y l a m i n e , pK

h

are f o r m e d

=

4.2, Ν,Ν-dimethylaniline, p K = 6

9.6).

A m i n e oxides

f r o m a l i p h a t i c a m i n e s , i n d i c a t i n g that t h e b o n d

between

n i t r o g e n a n d o x y g e n i n the p r i m a r y a d d u c t is covalent a n d stronger t h a n the o x y g e n - o x y g e n

b o n d , w h i c h breaks d o w n to f o r m a m i n e oxide a n d

m o l e c u l a r oxygen.

I n the a r o m a t i c amines s t u d i e d here the n i t r o g e n -

o x y g e n b o n d is w e a k e r t h a n a n o r m a l c o v a l e n t b o n d a n d p r o b a b l y is m o r e l i k e a c h a r g e transfer b o n d , a n d s e c o n d a r y attack o n a c a r b o n h y d r o g e n b o n d of the side c h a i n takes p l a c e as i n d i c a t e d i n R e a c t i o n s 1 a n d 3.


108


Table III.

Expt. Solvent


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

CH2CI2 CH2CI2 EtOAc EtOAc MeOAc

CH2CI2 EtOAc EtOAc EtOAc MeOAc

CH2CI2 EtOAc EtOAc EtOAc EtOAc MeOAc

CH2CI2 EtOAc EtOAc MeOAc

CH2CI2 EtOAc EtOAc EtOAc EtOAc EtOAc EtOAc EtOAc EtOAc

Ozonation Experiments Consumed IV

Temp., °C -78 -78 -78 -78 -78 -78 -40 -40 -40 -40 -40 0 0 0 0 0 0 25 25 25 25 -78 -40 0 25 -78 -40 0 25

a

Consumed 03

a

Produced" 02

Calcd.

Found

Calcd.

Found

Calcd.

3.0 4.3 1.3 0.51.0 1.5 5.0 7.4 6.3 4.1 4.0 4.7 7.3 8.8 4.2 4.3 4.0 4.1 8.2 3.8 2.6 4.2 2.9 5.1 5.1 5.1 0 1.4 1.6 1.1

7.6 8.0 1.3 0.51.0 1.5 5.0 7.3 5.6 4.2 4.1 4.8 7.3 8.7 4.2 4.3 4.1 4.3 8.4 3.8 2.8 4.2 2.5 5.0 5.0 5.0 0 1.4 1.7 1.1

5.0 6.9 2.6 1.02.0 2.7 5.6 8.3 7.5 5.1 5.0 5.2 8.1 9.9 4.7 4.8 4.7 4.6 9.5 4.6 3.1 4.7 5.2 8.4 8.8 9.4 0 1.6 1.7 1.3

10.0 10.0 10.0

5.0 6.9 2.6 1.02.0 2.7 5.0 6.7 6.0 4.3 4.3 4.5 6.2 7.7 3.8 3.8 3.8 3.9 7.3 3.6 2.4 3.9 4.6 6.6 7.4 8.4 0 1.2 1.2 1.0

a

Y i e l d s are g i v e n i n mmoles.

b

N o entry i n c o l u m n means v a l u e not

5.0 5.0 5.0 10.0 10.0 5.0 5.0 5.0 10.0 10.0 5.0 5.0 5.0 5.0 10.0 5.0 5.0 5.0 10.0 10.0 10.0 10.0 2.5 2.5 2.5 2.5

>

b

Found 7.9 6.5 4.04.7 4.4 4.5 6.9 4.1 4.1 3.9 9.0 4.1 4.0 3.4 4.0 4.3 3.3 7.9 8.4 6.1 6.9 2.1 1.9 1.5 1.3

checked.

A t t a c k other t h a n o n the a m i n o g r o u p a p p a r e n t l y does represent a c o m p e t i t i v e r e a c t i o n course w h e n the substituents o n t h e a r o m a t i c r i n g are less electronegative t h a n the n i t r o g r o u p .

T h i s is d e m o n s t r a t e d b y

the s t r o n g c o l o r a t i o n a n d tar f o r m a t i o n o b s e r v e d w h e n

A/,N-dimethyl-

a n i l i n e a n d p - c h l o r o - N , A - d i m e t h y l a n i l i n e are o z o n i z e d a n d b y the fact 7

that m o r e o z o n e is c o n s u m e d b y these c o m p o u n d s t h a n c a n b e a c c o u n t e d for b y side c h a i n o x i d a t i o n ( T a b l e I I I , E x p e r i m e n t s 1 a n d 2 ) .


8.


CH

J

+

r u

of p-A/itro-N,Ν-Dimethy'foniline

Ar-N

J

109

CH,

CH,

3

δ / δ _ Ar-N—0-0-0] • +

Ozonation

Ar-N

+ 000H"

+ OH"

•

0 (1) 2

CH,

XH,

V ι i*

XI

XII

A t t a c k of a s e c o n d m o l e of o z o n e o n X I I I , s i m i l a r to R e a c t i o n 1, w i l l t h e n l e a d to t h e N - m e t h y l f o r m a n i l i d e s V I ( R e a c t i o n 3 ) :

+

/

CH


Ar-N

3

+ OH"

Ar-N

V

XII

/

/ Ν

V

(2)

XIII

/ 3

,

3

C H

δ /δ _ / N---0-0-07 — •— — •• Ar-N — • Ar-N---0-0-0j —• Ar-N +

XIII + 0

CH,

+

3 3

+ 0 •H0 2

2

(3)

\HO

I OH

XIV

VI

A c c o r d i n g to R i e c h e et al. ( 13 ) a l i p h a t i c c a r b i n o l a m i n e s m a y react w i t h h y d r o p e r o x i d e s to f o r m α - a m i n o a l k y l p e r o x i d e s . H o r n e r a n d K n a p p ( 7 ) prepared di-a-aminoalkylperoxides from N-alkylanilines,

formaldehyde,

a n d h y d r o g e n p e r o x i d e s . I f t h e r e a c t i o n sequences l e a d i n g to these p e r oxides are those o u t l i n e d b e l o w , a s i m i l a r α - a m i n o h y d r o p e r o x i d e ( X V ) p r o b a b l y also is t h e p r e c u r s o r i n t h e f o r m a t i o n of t h e d i - a - a m i n o a l k y l p e r o x i d e o b t a i n e d i n t h e o z o n a t i o n of p-nitro-IVjIV-dimethylaniline.

+ /

CH

3

Ar-N

• OH"

Η00Η

"CH,

Ar-N

/

CH

q

\CH 00H 2

XII

XII

/

Ar-N

C

H

\C H

XV

CH,

3

\ N-Ar Ν

2

(A)

/ - 00- CH, VII

T h e p r o b l e m t h e n is t h e r o u t e to h y d r o g e n p e r o x i d e i n t h e present case. I n s e r t i o n of o z o n e i n t o a c a r b o n - h y d r o g e n b o n d has b e e n p o s t u l a t e d b y W h i t e a n d B a i l e y (14)

to e x p l a i n t h e o z o n a t i o n of b e n z a l d e h y d e s , b y

P r i c e a n d T u m o l o (15) i n t h e o z o n a t i o n studies of ethers, a n d b y B a t t e r bee a n d B a i l e y (16)

i n t h e i r studies o n t h e o z o n a t i o n o f a n t h r o n e . W e

postulate a s i m i l a r i n t e r m e d i a t e to e x p l a i n t h e f o r m a t i o n o f h y d r o g e n peroxide a n d subsequently the diaminoperoxide V I I .


110


/ Ar-N

ChU

3

C H

+

V

67

Oo

/

3

C H

3

Ar-NΝ

Ar-N—0-0-0,

\H OOOH 2

XVI (5) /

H

3

/ H

Ar-N I

• C ρ Η

+ Η00Η CH0

0-0-0Η VI

XVI


3

Ar-N

A s seen a b o v e , N - m e t h y l f o r m a n i l i d e is also p r o d u c e d b y this route.

The

r e a c t i o n routes p e r t i n e n t to o u r studies a r e s u m m a r i z e d i n S c h e m e 1.

N = CH \

+ OH'

2

χ + 2y•(z-y)

N Ν - C H , • 0,

/ N—CH 000H 2

N=CH

2

N—CHO + 0 + Γ

• OH

\

\

N-CH 000H

Y

2

2

z-y

z-y

N=CH

H0

2

2

N-CHO + H 0

I

2

2

/

\l —CH 00CH -N^ + 2 /

• OH'

2

2

H0 2

2y N = C H * OH' 2

N —CH,0H

N-H

+

CH 0 2

Scheme 1

F r o m these sequences the f o l l o w i n g c a n b e o b t a i n e d : C o n s u m e d s t a r t i n g m a t e r i a l : a = χ -\- y -\- 2y -\- (z — y) = χ C o n s u m e d o z o n e : b = χ + 2y + ζ +

(ζ — y) = χ + y +

2ζ,


2y

z,

8.

KOLSAKER AND

Ozonation

TEiGE

of

111

p-Nitro-N,N-Dimethylaniline

P r o d u c t i o n of o x y g e n : c = χ + 2y + (z — y) + (z — y) = χ -\- 2z, H e r e χ is the y i e l d o f d e m t h y l a t e d s t a r t i n g m a t e r i a l ( V ), y is the y i e l d o f the d i a m i n o p e r o x i d e V I I , ζ is the y i e l d o f N - m e t h y l f o r m a n i l i d e s ( V I ) . A c o m p a r i s o n o f the c a l c u l a t e d values for a, b, a n d c w i t h those o b t a i n e d i n the experiments, as seen f r o m T a b l e I I , are s h o w n i n T a b l e I I I . W h e n 2 m o l e e q u i v a l e n t s o f ozone are u s e d , a c o m p o u n d w h i c h a p p a r e n t l y i s a d i p e r o x i d e is f o r m e d molecular

formula

(see T a b l e I I ) .

of C i 6 H i N 4 0 , 6

E l e m e n t a l analysis indicates a

and

8

amounts o f p - n i t r o - N - m e t h y l a n i l i n e ( V c ) .

acid

hydrolysis

gives

small

F o r m a t i o n o f this d i p e r o x i d e


c a n b e r a t i o n a l i z e d as f o l l o w s :

/

H

C H ,

3

•/ Ar-N

Ar-N

\C H (

2

OOH

3

OH' CHOOH XVII

XV

(6)

C Ηο

/ 2 XVII

Ar-N

\

CΗο

\

3

/ CH

η-0

3

N-Ar \ / C H

+

2 Η,Ο

XVIII

T h e e n t i t y X V I I o f q u e s t i o n a b l e s t a b i l i t y is t h o u g h t t o d i m e r i z e t o the diperoxide X V I I I .

A m o d i f i e d r e a c t i o n m u s t t h e n be a p p l i e d t o E x p e r i

ments 22-25 ( S c h e m e 2 ) ( p .

112).

F r o m Scheme 2: C o n s u m e d s t a r t i n g m a t e r i a l : a = ζ + 2y

f

C o n s u m e d o z o n e : b = (z + 2y') + (z — 2 i / ) + 2y' = 2z + 2y' r

P r o d u c t i o n of o x y g e n : c = ζ + (ζ — 2y') + 2y = 2z, f

T h e v a l u e o f y' is n o w the y i e l d of d i m e r i c d i p e r o x i d e X V I I I . T h e results are e n t e r e d i n T a b l e I I I , E x p e r i m e n t s 22-25. T a b l e I I I s h o w s that the s t a r t i n g m a t e r i a l is a c c o u n t e d for w e l l . I n E x p e r i m e n t s 1 a n d 2 c o n s i d e r a b l e attack o n the a r o m a t i c n u c l e u s m u s t have t a k e n p l a c e since m u c h tar is f o r m e d i n these ozonations.

When

p - c h l o r o - N , N - d i m e t h y l a n i l i n e ( I V b ) is o z o n i z e d , m o r e attack takes p l a c e


112


\+ N = C H + OH 2

Ν—CH, • 0 ,

(z - 2 y ' ) + 2y' 'N—CH 000H

\

Γ

2

/

V

\

N=CH,+ OH"

N-CHO + 0

V

z'-2y'

+H 0

2

2

ζ -2y' \

ί' N-CH 000H /

/

2y*

V.

N=CH + OH' 2

+

H 0 2

N-CH0 • H 0

I

2


2y'

2

2y*

N = CH,+ 00H"

2

2y'

2y' N=CH + 00H' 2

0

N = CH00H + OH' + 0?

3

2y'

2y* N = CH00H + OH"

2

0-0 \ / \ / N —CH CH-N

o-o

2y'

• 2 H.,0

Scheme 2

o n t h e a m i n e f u n c t i o n t h a n is t h e case w i t h t h e u n s u b s t i t u t e d

N,N-di-

m e t h y l a n i l i n e ( I V a ). T h i s is expected since t h e c h l o r i n e a t o m deactivates the r i n g f o r e l e c t r o p h i l i c attack. T h i s t r e n d is a c c e n t u a t e d i n g o i n g to t h e n i t r o s u b s t i t u t e d d i m e t h y l a n i l i n e ( I V c ) , w h e r e r i n g attack is n o t observed. T h e a m o u n t o f ozone u s e d f o r r i n g attack is n o t a c c o u n t e d f o r i n o u r expressions; therefore t h e values f o r b a n d c i n E x p e r i m e n t s 1 a n d 2 w i l l be erroneous. T h e large d i s c r e p a n c y i n c o n s u m e d o z o n e a n d o z y g e n y i e l d w h e n o z o n i z i n g i n e t h y l o r m e t h y l acetate at — 7 8 ° C ( E x p e r i m e n t s 3-5, 22, a n d 2 6 ) cannot b e a c c o u n t e d f o r b y a n y o f o u r schemes. b i l i t y o f ozone attack o n t h e solvents cannot b e e x c l u d e d .

T h e possi

However, we

h a v e n o t b e e n a b l e to d i s c o v e r a n y p r o d u c t a r i s i n g f r o m o x i d a t i o n o f t h e solvent. O z o n a t i o n of e t h y l acetate w a s s h o w n b y P r i c e a n d T u m o l o to b e n o n q u a n t i t a t i v e w h i l e o z o n e is q u a n t i t a t i v e l y a b s o r b e d at — 78 ° C w h e n p-nitro-N^N-dimethylaniline

( I V c ) is d i s s o l v e d i n e t h y l acetate.

p r o b l e m has to b e left o p e n at this stage o f o u r research.


This

8.

KOLSAKER AND TEIGE

Ozonation


113

Literature Cited 1. 2. 3. 4.

Bailey, P. S., Chem. Rev. (1958) 58, 925. Henbest, H. B., Stratford, J. W.,J.Chem. Soc. (1964) 711. Shulman, G. P., Can. J. Chem. (1965) 43, 3069. Bailey, P. S., Mitchard, D. Α., Khashab, A.-I. Y., J. Org. Chem. (1968) 33, 2675.

5. Bailey, P. S., Keller, J. E., Mitchard, D. Α., White, Η. M., ADVAN. C H E M .


6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

SER. (1968) 77, 58. Kolsaker, P., Meth-Cohn, O., Chem. Commun. (1965) 423. Horner, L., Knapp, Κ. H., Ann. (1959) 622, 79. Bailey, P. S., Reader, A . M., Chem. Ind. (1961) 1063. Shirley, D. Α., "Preparations of Organic Intermediates," p. 221, Wiley, New York, 1951. Villiger, V., Chem. Ber. (1909) 42, 3534. Morley, J. S., Simpson, J. C. E., J. Chem. Soc. (1948) 360. Spiesecke, H., Schneider, W. G., J. Chem. Phys. (1961) 35, 722. Rieche, Α., Schmitz, E., Beyer, E., Chem. Ber. (1959) 92, 1206. White, Η. M., Bailey, P. S., J. Org. Chem. (1965) 30, 3037. Price, C.C.,Tumolo, A . L., J Amer. Chem. Soc. (1964) 86, 4691. Batterbee, J. E., Bailey, P. S., J. Org. Chem. (1967) 32, 3899.

RECEIVED June 7, 1971. Work supported by a grant from Det Videnskapelige Forskningsfond av 1919.


9 Mechanism of Ozonation Reactions V . Feist's Ester RONALD

E. ERICKSON

and GARY D.

MERCER


University of Montana, Missoula, Mont. 59801

The

ozonation

of Feist's

ester yields

three

dicarbomethoxytetrahydrofuran-4-one thoxy-5-hydroxy-2-oxa-2,3-dihydropyran

NMR,

primarily

and infrared

is probably

through

and trapping

studies).

4,5-diwere

evidence

(mass,

compounds

product

A mechanism is

and

Structures

The last of these

ozonation

the initial step is formation stage, the breakdown

spectroscopic

spectra).

not a direct

(V).

2,3-

3,4-dicarbome-

(IV),

carbomethoxy-1-oxaspiro[2.2]pentane assigned

products:

(III),

(stoichiometry

is proposed

in

ozonide.

From

of a primary

which that

abnormal.

>Tphe structure of Feist's a c i d , l a , w a s d e t e r m i n e d w i t h c e r t a i n t y some 60 years after its p r e p a r a t i o n (1-6).

M o r e r e c e n t l y , the p r o p o s a l

that the o z o n a t i o n p r o d u c t of F e i s t ' s ester ( l b ) s h o w n to b e i n c o r r e c t ( 7 ) .

h a d s t r u c t u r e I I was

O u r i n i t i a l r e p o r t not o n l y s h o w e d t h a t no I I

w a s present i n a n y o z o n a t i o n of Feist's ester b u t offered c h e m i c a l a n d spectroscopic p r o o f for I I I as a m a j o r o z o n a t i o n p r o d u c t . RO—C^ Ο II RO-C

Η —

Ο II R O - C —

Ο CH

2

Ο

Ο

RO—C—C—C—C—CH

.

Ο.

HC \ HC-

I

I

COOR

I

Η la, R = H Ib, R = C H

Η

\

II

CH

2

/ -C Ο

RO

Ο

III

3


9.

ERICKSON A N D M E R C E R

Ozonation

115

Reactions

T h i s p a p e r is c o n c e r n e d w i t h t h e s t r u c t u r e p r o o f of e a c h of t h e major p r o d u c t s of the o z o n a t i o n of t h e m e t h y l ester of Feist's a c i d . O t h e r d a t a p e r t a i n i n g to t h e m e c h a n i s m of this u n u s u a l o z o n a t i o n are p r e s e n t e d , and

a m e c h a n i s m is h y p o t h e s i z e d .


Experimental Materials. Solvents w e r e t h e best c o m m e r c i a l grades a v a i l a b l e a n d w e r e n o t p u r i f i e d f u r t h e r . F e i s t s a c i d w a s p r e p a r e d b y t h e m e t h o d of Goss et al. ( 2 ) . T h e m e t h y l ester w a s p r e p a r e d i n t h e n o r m a l F i s h e r m a n n e r w i t h m e t h a n o l a n d s u l f u r i c a c i d . A d d i t i o n of w a t e r , ether ex t r a c t i o n , r e m o v a l of ether, a n d d i s t i l l a t i o n y i e l d e d a colorless l i q u i d ( b p 7 8 ° - 8 0 ° C at 1.5 m m H g ) w h i c h c r y s t a l l i z e d u p o n s t a n d i n g , m p 30 ° C (lit. v a l u e 3 0 ° C ) ( 8 ) . 2,3-DiCARBOMETHOXYMETHYLENECYCLOPROPANE-2,3d2.

The

methyl

ester of Feist's a c i d w a s specifically d e u t e r a t e d b y d i s s o l v i n g 5.0 grams of t h e ester i n 25 m l of d e u t e r o m e t h a n o l c o n t a i n i n g 0.5 g r a m s o d i u m m e t h o x i d e a n d a l l o w i n g t h e m i x t u r e to s t a n d f o r o n e d a y . A f t e r a d d i n g 40 m l of d i l u t e s u l f u r i c a c i d a n d e x t r a c t i n g w i t h t w o 2 0 - m l p o r t i o n s of m e t h y l e n e c h l o r i d e , a d i s t i l l a t i o n y i e l d e d 3.5 grams of t h e d i d e u t e r o c o m p o u n d . Its N M R s p e c t r u m s h o w e d o n l y t h e m e t h o x y protons ( singlet at δ = 3.63) a n d m e t h y l e n e protons ( s i n g l e t at δ = 5.53). Ozonations. T h e ozonations w e r e c a r r i e d o u t u s i n g a W e l s b a c h T - 2 3 ozonator at — 78 ° C i n m e t h a n o l , m e t h y l e n e c h l o r i d e , F r e o n 11, or acetone. N o changes i n p r o d u c t ratios o r o z o n e s t o i c h i o m e t r y w e r e n o t e d w h e n n i t r o g e n w a s u s e d as the o z o n e c a r r i e r . Isolation of Products. P r o d u c t i s o l a t i o n p r o v e d to b e e x t r e m e l y difficult. A t y p i c a l p r o c e d u r e i n v o l v e d t h e o z o n a t i o n of t h e ester (2.0 g r a m s ) i n 30 m l m e t h a n o l at — 7 8 ° C u n t i l t h e s o l u t i o n b e c a m e b l u e a n d a precipitate h a d formed. After flushing w i t h nitrogen, a n d a l l o w i n g the m i x t u r e to s t a n d o v e r n i g h t at —78°C., w e c o l l e c t e d 1.0 g r a m of p r e c i p i tate. T h i s w a s r e c r y s t a l l i z e d three times f r o m 15 m l of a n h y d r o u s ether to y i e l d I I I , m p 6 7 ° - 7 1 ° C ( l i t . 6 8 ° C ) . E v a p o r a t i o n of t h e first ether r e c r y s t a l l i z a t i o n r e s i d u e a n d s l o w c r y s t a l l i z a t i o n f r o m 1.5 m l of a n h y d r o u s ether y i e l d e d c o m p o u n d I V , m p 9 6 ° - 1 0 2 ° C [ c a l c u l a t e d f o r C H i O : C — 44.04, Η = 4.58, Ο — 51.8; f o u n d : C = 44.67, Η — 4.66]. C o m p o u n d V w a s i s o l a t e d b y o z o n a t i o n of t h e ester i n F r e o n 11 at — 78 ° C a n d a l l o w i n g t h e p r e c i p i t a t e w h i c h f o r m e d to s t a n d i n s o l u t i o n o v e r n i g h t . A f t e r the p r e c i p i t a t e w a s c o l l e c t e d i n a c o l d B u c h n e r f u n n e l ( t h e p r e c i p i t a t e melts b e l o w 0 ° C a n d w a s s h o w n to b e a m i x t u r e of I I I a n d I V b y N M R ) , t h e filtrate w a s e v a p o r a t e d a n d t h e l i q u i d r e s i d u e w a s d i s t i l l e d to y i e l d ( b p 9 5 ° - 1 0 0 ° C . , 1 m m ) a m i x t u r e r i c h i n V ( > 9 0 % a c c o r d i n g to N M R ) [ c a l c u l a t e d f o r C H O r > : C = 51.63, Η =* 5.34, Ο = 43.03; f o u n d : C = 50.24, 50.53, Η = 5.27, 5.29]. 8

8

0

7

1 0

Product Analysis. Q u a n t i t a t i v e analysis f o r e a c h of t h e p r o d u c t s of t h e o z o n a t i o n of F e i s t ' s ester w a s c a r r i e d o u t b y a n N M R m e t h o d ( V a r i a n H A 6 0 ) . T h e solvent f o r t h e o z o n a t i o n w a s e v a p o r a t e d in vacuo, a s u i t a b l e i n t e r n a l s t a n d a r d ( u s u a l l y tert-butyl benzoate), was added a n d t h e spectra w e r e d e t e r m i n e d a n d i n t e g r a t e d i n c h l o r o f o r m - d . A l l analyses w e r e r e p r o d u c i b l e to ± 1 0 % .


116


Table I.

Important Ions in the Mass Spectra of III and I l i a ///

ΙΠα m / e (%

Assignment Ρ P-H 0 P-OCH P-CH3OH 2

3

P-C2H3O2

and P-C H and P-C H 2


2

{OCH CO}H 0 , CH 0, {C H 0 CHO}H 0 , CH OH

202 184 171 170 143

(2) (3) (9) (53) (73)

2

3

2

2

2

3

2

3

Assignment Ρ P-HDO P-OCH P-CH OD 3

3

P-C2H3O2

P-{OCH CO}D P-C2H3O2, C H 0 P-{C H 0 CDO}H P - C H 0 , CH2OD 2

113 (100)

2

3

m / e (% rel. abundance)

rel.

abundance)

2

2

111

(53)

2

3

3

2

2

204 (1) 185 (3) 173 (4) 171 (60) 145 (21) 144 (75) 115 (33) 114(100) 112 (63)

Results T h e structure of I I I was reasonably w e l l established i n l i m i n a r y c o m m u n i c a t i o n of this w o r k . A c o m p a r i s o n of its mass ( T a b l e I ) w i t h that of its d i d e u t e r o a n a l o g I l i a confirms its a n d p r o v i d e s a mass s p e c t r a l m o d e l for c o m p a r i s o n w i t h compounds I V and V . D H s C O O C - C ^ 1 H3COOC-C D

our pre spectrum structure unknown

,0, X

C H I C

2

0

III a T h e h i g h mass peaks i n T a b l e I c a n b e r a t i o n a l i z e d q u i t e easily. H o w e v e r , the ions of highest a b u n d a n c e at 143 a n d 113 i n I I I w h i c h at first glance c a n be assigned to f r a g m e n t a t i o n of a c a r b o m e t h o x y g r o u p are, f r o m i n s p e c t i o n of the d a t a f r o m I l i a , of m o r e c o m p l e x o r i g i n . C o m p o u n d I l i a h a d a p e a k at 145 as expected for loss of c a r b o m e t h o x y , b u t it also shows a n intense p e a k at 144 w h i c h m u s t c o m e f r o m the loss of { — O C H C = 0 } D . T h e d e u t e r i u m t h e o r e t i c a l l y c o u l d be transferred f r o m either t h e a or β carbons to either the keto or ether functions. N o n e of these rearrangements are p a r t i c u l a r l y f a c i l e a c c o r d i n g to the l i t e r a ture. T h e base peaks i n the spectra of I I I a n d I l i a ( 113 a n d 114 respec t i v e l y ) are also of interest. L o s s of c a r b o m e t h o x y a n d C H 0 , w h i c h appears to b e a l i k e l y f r a g m e n t a t i o n p a t t e r n , does not seem to o c c u r to a m a j o r extent for I l i a w h e r e the c o r r e s p o n d i n g 115 p e a k is present i n 2

2


9.

Ozonation

ERICKSON A N D M E R C E R

only 3 3 %

relative abundance.

117

Reactions

T h u s , a n o t h e r h y d r o g e n transfer, this

t i m e f r o m the m e t h y l e n e g r o u p to one of the o x y g e n atoms, m u s t t a k e place. T h e i n f r a r e d s p e c t r u m of I V i n d i c a t e s a n e n o l (3200 a n d 1650 c m " ) , 1

a n α,β u n s a t u r a t e d ester (1675 c m " ) , a n d a n o r m a l c a r b o m e t h o x y c a r 1

b o n y l g r o u p (1725 c m " ) .

T h e N M R s p e c t r u m substantiates t h e e n o l i c

1

character of the m o l e c u l e w i t h a singlet (δ •= 11.3 p p m ) . t w o d o u b l e t s ( ^ 4 . 4 0 a n d 4.84 p p m , / =

It also shows

16.5 c p s ) w h i c h c a n b e assigned

to t w o m e t h y l e n e protons ( s i m i l a r c h e m i c a l shift to analogous

protons

i n I I I ) , a n d singlets at 3.78 p p m a n d 5.16 p p m . T h e r a t i o of protons w a s s h o w n to be 1 : 1 : 1 : 6 : 1 i n the o r d e r g i v e n . S u c h a s p e c t r u m is consistent Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ch009

w i t h either the e n o l f o r m of I I I ( I l l b s h o w n b e l o w ) or w i t h s t r u c t u r e I V .

H cooc-cif ° o

Hscooc^

N

3

?

H COOC— Cs.

P*

H

1 2

I

I

/C =

C

H COOC

2

^cr

I

OH

3

. C H

3

0

Illb

H

IV

C o m p o u n d I V gave a p o s i t i v e p e r o x i d e test w i t h p o t a s s i u m i o d i d e i n m e t h a n o l a n d a n a l y z e d r e a s o n a b l y w e l l for t h e s t r u c t u r e s h o w n .

How

ever, i t w a s difficult to p u r i f y a n d d e c o m p o s e d u p o n s t a n d i n g , a n d w e b e l i e v e d that mass s p e c t r a l e v i d e n c e w a s necessary for its final s t r u c t u r e proof.

W e e x p e r i e n c e d some difficulty i n o b t a i n i n g p u r e d i d e u t e r o I V

b u t w e r e a b l e to o b t a i n a satisfactory m o n o d e u t e r o

compound by

ex

c h a n g e of the e n o l i c p a t t e r n w i t h methanol-ci. T a b l e I I c o m p a r e s

the

mass s p e c t r u m of I V w i t h that of the m o n o d e u t e r o d e r i v a t i v e . H C O O C 8

^(V

N

CH

Ο

I

H C O O C ^

I

3

I OD

Although

IVa the p a r e n t , p a r e n t - O H ( D ) , a n d p a r e n t - H 0 2

(HDO)

peaks g i v e strong c o r r o b o r a t i v e e v i d e n c e for I V a n d I V a as the correct


118


Table II.

Important Ions in the Mass Spectra of IV and IVa IV

Ρ P-OH P-H 0 P-OCH3 P-COOCH P-C H 0 or C H 0

218 (4) 201 (1) 200 (3) 187 (1) 159 (100)

2

3

7

IVa

3

2

3

127

4

(44)

Ρ P-OD P-HDO P-OCH P-COOCH P-C H 0 P-C H 0 P-C H D0 or C H D 0

219 (4) 201 (2) 200 (3) 188 (1) 160 (100)

3

3

3

7

3

2

3

4

3

6

128

(17)

127

(25)

3

2



m / e (% rel. Assignment abundance)

Assignment

3


2

4

s t r u c t u r e for the h i g h m e l t i n g c o m p o u n d , i n t e r p r e t a t i o n of the c o m p l e t e mass s p e c t r u m is not s t r a i g h t f o r w a r d . F o r e x a m p l e , t h e base p e a k for b o t h I V a n d I V a is a c c o u n t e d for r e a d i l y b y a loss of c a r b o m e t h o x y , b u t t h e s e c o n d most intense m/e, pathways

127, m u s t arise f r o m at least t w o different

( n e i t h e r of w h i c h is o b v i o u s ) .

The accumulated

evidence

leaves l i t t l e d o u b t b u t t h a t I V is the correct s t r u c t u r e of the h i g h m e l t i n g product. T h e t h i r d c o m p o u n d to b e i s o l a t e d f r o m ozonations of Feist's ester w a s V . Its N M R s p e c t r u m w a s of p r i m e i m p o r t a n c e i n e s t a b l i s h i n g its structure. O t h e r t h a n t h e m e t h o x y s i g n a l at 3.67 p p m , the o u t s t a n d i n g feature of the s p e c t r u m w a s t h e presence of t w o sets of A B d o u b l e t s w i t h c h e m i c a l shifts f o r the f o u r protons at 3.33, 3.23, 2.90, a n d 2.72 p p m . T h e r a t i o of p e a k intensities w a s 6 : 1 : 1 : 1 : 1 for the five types of protons. I n t h e s p e c t r u m of the d i d e u t e r o d e r i v a t i v e , the A B p a t t e r n at h i g h field w a s n o t present, s h o w i n g t h a t these h i g h field protons w e r e those a to the c a r b o m e t h o x y Table III.

groups. Important Ions in the Mass Spectra of V and V a V m / e (% rel. abundance)

Assignment Ρ P-CH 0 P-OCH3 P-CH3OH P-C H 0 P-C H 0 , C H 2

2

3

2

3

2

2

Va

2

186 (0) 156 (2) 155 (11) 154 (12) 127 (100) 113 (40)


Assignment Ρ P-CH 0 P-OCH3 P-CH OD 2

3

P-C2H3O2

P-C H 0 , C H 2

3

2

2

188 (0) 158 (2) 157 (12) 155 (13) 129 (100) 115 (44)

T h e m a j o r features of the mass s p e c t r a of V a n d its d i d e u t e r o d e r i v a t i v e are p r e s e n t e d i n T a b l e I I I . A l t h o u g h w e w e r e u n a b l e to detect t h e p a r e n t p e a k for V , t h e r e a s o n a b l e assignments i n T a b l e I I , the s i m p l i c i t y


9.

ERiCKsoN AND M E R C E R

Ozonation

119

Reactions

of the N M R s p e c t r u m , a c o m p a r i s o n w i t h n o r m a l e p o x i d e c h e m i c a l shifts ( m e t h y l e n e signals at l o w e r field t h a n m e t h o x y s i g n a l s ) , a n d the a n a lytical

data

compound

argue

for

4 , 5 - d i c a r b o m e t h o x y - l - o x a s p i r o [2.2] p e n t a n e

as

V. Ο


II

T a b l e I V s u m m a r i z e s s o m e of the s p e c t r a l d a t a for the assignment of s t r u c t u r e to c o m p o u n d s I I I , I V , a n d V . T a b l e V shows the r e l a t i v e amounts of I I I , I V , a n d V f o u n d i n differ ent solvents u n d e r v a r i a b l e e x p e r i m e n t a l c o n d i t i o n s . K n o w l e d g e of the m a j o r p r o d u c t s of the o z o n a t i o n of F e i s t ' s ester does not l e a d i m m e d i a t e l y to a k n o w l e d g e of t h e m e c h a n i s m of the r e a c t i o n a l t h o u g h the n a t u r e of t h e p r o d u c t s m a k e s i t o b v i o u s

t h a t the

m e c h a n i s m is different f r o m t h a t of most ozonations. H o w e v e r , i n s p e c t i o n of T a b l e I V , i n w h i c h p r o d u c t ratios change w i t h changes i n c o n d i t i o n s a n d other types of e x p e r i m e n t s , a l l o w s us to r a t i o n a l i z e a reasonable m e c h a n i s t i c sequence. T h e m o s t i m p o r t a n t p o i n t s to n o t e a r e : ( 1 ) T h e e p o x i d e is not a p r i m a r y p r o d u c t ; b o t h the s t o i c h i o m e t r y a n d the t e t r a c y a n o e t h y l e n e experiments i n d i c a t e that i t is f o r m e d f r o m a t t a c k of a n i n t e r m e d i a t e o n u n r e a c t e d F e i s t ' s ester. F o r e x a m p l e , less t h a n 1 m o l e of o z o n e p e r m o l e of Feist's ester is r e q u i r e d for a l l o z o n a t i o n s — w i t h the less r e a c t i v e solvents, s u c h as m e t h y l e n e c h l o r i d e a n d F r e o n 11, the d e f i c i e n c y i n o z o n e r e q u i r e d is a p p r o x i m a t e l y e q u a l to the a m o u n t of e p o x i d e f o r m e d . A d d i t i o n of t e t r a c y a n o e t h y l e n e b e f o r e o z o n a t i o n results i n a n o z o n a t i o n of n o r m a l s t o i c h i o m e t r y w i t h n o e p o x i d e being formed. ( 2 ) I f the r e a c t i o n is s t o p p e d b e f o r e c o m p l e t i o n , t h e r e l a t i v e a m o u n t s of I V f o r m e d are g r e a t l y decreased. T h i s suggests to us t h a t the i n i t i a l o z o n a t i o n p r o d u c t has s e v e r a l m o d e s of d e c o m p o s i t i o n a v a i l a b l e , a n d that r e a c t i o n w i t h F e i s t ' s ester ( o r t e t r a c y a n o e t h y l e n e ) is m o r e r a p i d than unimolecular decomposition. ( 3 ) W e w e r e u n a b l e to mary ozonide ( 9 ) ] b y l o w a b o v e - m e n t i o n e d results a n d ester s t r o n g l y suggest t h a t a

detect a n i n t e r m e d i a t e [e.g., Criegee's p r i t e m p e r a t u r e N M R (to — 1 3 0 ° C ) ; y e t t h e t h e f a c t t h a t I V does n o t r e a c t w i t h F e i s t ' s h i g h l y r e a c t i v e i n t e r m e d i a t e does exist.


120

O Z O N E R E A C T I O N S W I T H ORGANIC

COMPOUNDS

Table I V . Compound

C-H

MW

°C

III

ΟδΗχοΟβ

67-71

202

IV

ΟδΗχοΟγ

96-102

218

V

CSHIOOÔ

liquid

186

° As reported i n Ref.


Mp,

Spectral

7.

W e h y p o t h e s i z e t h e f o l l o w i n g g e n e r a l r e a c t i o n scheme: H

C O O C .

3

C H

2

+

0

3

H3COOC la

N C

C N

P a t h a i n v o l v e s u n i m o l e c u l a r d e c o m p o s i t i o n of a n i n i t i a l (VI).

I t is i m p o r t a n t to n o t e that since o t h e r

ozonide

methylenecyclopropane

d e r i v a t i v e s , s u c h as 2 , 3 - d i m e t h y l m e t h y l e n e c y c l o p r o p a n e , d o not u n d e r g o r i n g o p e n i n g o f t h e c y c l o p r o p a n e r i n g , b o t h r i n g strain a n d t h e presence of t h e c a r b o m e t h o x y g r o u p s m u s t be necessary for s u c h a n u n u s u a l d e c o m p o s i t i o n of a n i n i t i a l o z o n i d e .

T h e f o l l o w i n g sequence r a t i o n a l i z e s


9.

ERICKSON AND

MERCER

Ozonation

121

Reactions

Data for III, I V , and V


Infrared,

NMR σ mult. (rel. intensity)

cm~i

1778, 1740, 1675, 1636

5.1d(l), 4.25d(l), 3.8e(6), 3.7d(l)

3200, 1725, 1675, 1600

1 1 . 3 8 ( 1 ) , 5.16e(l), 4 . 8 4 d ( l ) , 4 . 5 5 d ( l ) , 3.78s(6)

3080, 3030, 1720, 890, 865, 833

3.67sC6), 3 . 3 3 d ( l ) , 2.90d(l), 2.72d(l)

4.12d(l),

e

3.23d(l),

s u c h a n o c c u r r e n c e b y suggesting that a p a r t i a l n e g a t i v e charge is sta b i l i z e d b y the c a r b o m e t h o x y groups.

Just as the c o n v e r s i o n of V I to I V m a y b e a c o n c e r t e d r e a c t i o n w i t h o u t the i n t e r m e d i a r y a c t i o n of V I I , so p a t h w a y b m i g h t r e a s o n a b l y i n v o l v e either V I or V I I . C r i e g e e a n d G u n t h e r h a v e s h o w n that t e t r a c y a n o e t h y l e n e c a n c h a n g e the n o r m a l course of t h e o z o n a t i o n of alkenes b y r e a c t i o n w i t h e i t h e r a z w i t t e r i o n or t h e " p r i m a r y " o z o n i d e p r o d u c e d i n s u c h reactions (10).

W e h a v e no p r o o f as to w h e t h e r t e t r a c y a n o e t h y l e n e

reacts w i t h V I or V I I , a n d e i t h e r r e a c t i o n c a n b e e n v i s a g e d t o p r o d u c e I I I as i n p a t h w a y c.

W e are left w i t h t h e d i f f i c u l t y of e x p l a i n i n g t h e

r e l a t i v e l y h i g h y i e l d s of I I I i n some solvents l i s t e d i n T a b l e I V .

When

I I I , a t w o - o x y g e n p r o d u c t is f o r m e d , e i t h e r o x y g e n or some o t h e r o x i d i z e d


122


Table V .

CH2CI2 CH3OH CH OH« F r e o n 11 Freon 1 1 Acetone Acetone-CH Cl Acetone-CH Cl ' b

2

2

2

2

c

d

Relative III 40 64 57 35 62 38 33 71

0.67 0.76 0.86 0.74 0.71 0.75 0.65 1.03

3

Yields,

%

IV

V

21 23 13 33 0 30 32 29

39 13 30 30 37 32 35 0

Reaction stopped after 60% of I had reacted. Reaction stopped after 34% of I had reacted. 75% C H 2 C I 2 by volume. Tetracyanoethylene (equimolar with I) added before reaction began.

a


Relative Yields

Stoichiometry, moles Oz/moles I

Solvent


6 c d

product must be produced.

W i t h o x i d i z a b l e solvents, s u c h as m e t h a n o l

or acetone, t h e most reasonable a s s u m p t i o n m i g h t b e that V I o r V I I reacts w i t h solvent to y i e l d I I I ( p a t h d ) , b u t w e h a v e n o d i r e c t p r o o f for such a n assumption. S t o r y et al. h a v e suggested that V I I I m i g h t b e t h e i m p o r t a n t i n t e r m e d i a t e i n t h e o z o n a t i o n o f Feist's ester ( I I ) .

VIII

I f this is the i n t e r m e d i a t e , other m e t h y l e n e c y c l o p r o p a n e s s h o u l d g i v e o z o n a t i o n p r o d u c t s s i m i l a r t o those f o u n d i n t h e o z o n a t i o n o f Feist's ester.

Since they do not a n d because o u r evidence indicates that t h e

e p o x i d e is n o t a p r i m a r y p r o d u c t , t h e m e c h a n i s m o f Story et al. does n o t seem t o a p p l y t o this r e a c t i o n .

Literature Cited 1. Feist, F., Chem. Ber. (1893) 26, 747. 2. Goss, F. R., Ingold, C. T., Thorpe, J. F., J. Chem. Soc. (1923) 123, 327.


Ozonation Reactions

123

9.

ERICKSON AND M E R C E R

3. 4. 5. 6. 7. 8. 9. 10. 11.

Ettlinger, M . G . , J. Amer. Chem. Soc. (1952) 74, 5805. Ettlinger, M . G . , Kennedy, F . , Chim. Ind. (1956) 166. Kende, A. S., Chim. Ind. (1956) 437. Bottini, A. T., Roberts, J. D . , J. Org. Chem. (1956) 2 1 , 1169. Erickson, R. E., Tetrahedron Letters (1966) 1753. Schwan, U . , Ph.D. thesis, Technische Hochschule, Karlsruhe (1958). Criegee, R., Rec. Chem. Progr. (1957) 18, 111. Criegee, R., Günther, P., Chem. Ber. (1963) 96, 1564. Story, P. R., Alford, J. Α., Ray, W . L., Burgess, J. R., Preprints, Div. Petro leum Chemistry, ACS (1971) 16, A13.


R E C E I V E D May 20, 1971. Supported by the Petroleum Research Fund, admin istered by the American Chemical Society.


COMPOUNDS


O Z O N E R E A C T I O N S W I T H ORGANIC


Publication Date: June 1, 1972 | doi: 10.1021/ba-1972-0112.ix001

INDEX A Acetic acid 56, 83 Acetone 83 formation 85 A c e t y l bromide 56 hydrolysis of 59 Acetylenes, cleavage of 64 A c i d method, peracetic 20 Alcohol 83 formation 90 as solvent 64 A l k e n e s , ozonation of 36 A l k y l m e r c u r i c halides 78,83,85,90 A m i n e s , ozonation of tertiary aliphatic 101 α-Aminoalkylperoxides 109 Anthraquinone 53 A n throne, ozonation of 109 Antipodes 26 A t o m attack 53 A t t a c k on the aromatic nucleus . . . I l l

Β Back bonding B a c k donation B a e y e r - V i l l i g e r oxidation B a r i u m methylate Benzaldehydes, ozonation of Bromine f e r f - B u t y l m e r c u r i c chloride

69 68 15 30 109 56 85

C Carbon -carbon cleavage -carbon scission -hydrogen b o n d -mercury cleavage - m e t a l bonds sp o r b i t a l p-Chloro-N,N-dimethylaniline, ozonation of Complexes, p i Conjugation Criegee mechanism Cross diperoxides, formation of

83 80 107 89 79 95

3

..

103 7 48 9 9

D e m e t h y l a t e d product D i a c e t y l peroxide l , 4 - D i c h l o r o - b u t - 2 - e n e ozonide . . . Dichlorocarbene D i d e u t e r o derivative D i e t h y l ketone diperoxide 9,10-Dihaloanthracenes

106 60 27 71 118 13 53

D

Diisopropylmercury D i m e r i c peroxide Ν,Ν-Dimethylaniline, ozonation of £rans-3,4-Dimethyl-3-hexene 2,3-Dimethyl-2-pentene Dimerization 1,1 - D i m e t h y l - 4 , 4 - d i e t h y l 2,3,4,5-tetraoxacyclohexane .. Di-n-propylmercury 1,3-Dipolar c y c l o a d d i t i o n 3,5-Disubstituted trioxolanes Double bond, immunized D o u b l e b o n d , non-halogenated . . .

84 60 103 12 11 61 13 84 1,47 22 63 51

Ε E l e c t r o n density 107 E l e c t r o n i c environment of silicon . 70 E l e c t r o p h i l i c attack 44, 9 3 , 106 b y ozone 4 5 , 70 E l e c t r o p h i l i c cleavage 79 Enol 117 Epoxide 1,45 Epoxidation 60 Ethers, ozonation of 109 E t h y l acetate 112 E t h y l e n e s , ozonization rates of . . . 35

F Feist's a c i d 114 ozonation of the m e t h y l ester of 115 Feist's ester 114 intermediate i n the ozonation of 122 mass spectral data for the ozonation of 116,118 mechanism for the ozonation of 121 reaction scheme for the ozonation of 120 F i v e - m e m b e r e d c y c l i c transition state 96 Formanilide 106 Formic acid 84 Four-center process 104 Fragmentation of ozonides b y solvents 22 rates of 29 of u n s y m m e t r i c a l ozonides . . . . 29 F r e e radicals 45 H H a l o g e n atoms Hammett equation sigma H y d r o g e n abstraction


32 31,36 69 73

128


H y d r o l y s i s of acetyl b r o m i d e H y d r o s i l a n e reaction, ozone-

59 65, 75

I Inductive effect Infrared spectrum of 2,3-dibromo2-butene I m m u n i z e d double b o n d Inorganic products Interaction of ozone w i t h double bonds containing v i n y l b r o m i d e moieties Isomeric ozonides, reaction rates of cis-trans Isomerization, conformational . . . . Isotope effect, p r i m a r y deuterium .

94 56 63 87 50 33 17 71


Κ

Kinetics,

first-order

30

L

L a P i n e molecular m o d e l

5

M Mass spectral data for the ozonation of Feist's ester 116,118 Mechanism for the ozonation of Feist's ester 119 of ozonation reactions 114 of the solvent fragmentation of ozonides 33 M e r c u r i c chloride 83 M e r c u r i c oxide 83 M e r c u r o u s chloride 83 Methanol 30 M e t h y l e n e protons 117 M e t h y l e t h y l ketone diperoxide . . . 13 2- M e t h y l - 3 - e t h y l - 2 - p e n t e n e 12 N-Methylformanilides 109 p-Methylstyrene 38

Ν Neoprene rubber p-Nitro-N,N-dimethylaniline, ozonation of Nitrogen-oxygen b o n d N M R spectra, l o w temperature . . . Nucleophilic attack process

50 101 107 5 73 44

Ο

Olefin consumption, ozone consumption vs ozonation of ozonolysis of ozonolysis of h y d r o c a r b o n ozonolysis of u n s y m m e t r i c a l . . . reactions of ozone w i t h 36, stereochemistry 0 3 - reactive intermediates

58 58 1 11 50 40 52 9 84

ORGANIC

COMPOUNDS

O r g a n i c products 87 Organomercurials ozonolysis of 78 synthetic uses of 98 Organosilanes 65, 67 Oxy radical 3 O x y g e n insertion 71 Ozonation of an throne 109 of benzaldehydes 109 of 2-carboxy-4-nitro-N,2Vdimethylaniline 103 of p - c h l o r o - N , N - d i m e t h y l a n i l m e 103 of diisopropylmercury 83 of Ν,Ν-dimethylaniline 103 of ethers 109 of Feist's ester 116, 122 of 1-mesityl-l-phenylethylene . . 4 of the m e t h y l ester of Feist's a c i d 115 of p-nitro-IV,N-dimethylaniline 1 0 1 , 1 0 3 of olefins 1 of pentanoic a c i d 83 of p e r h y d r o - 1 naphthylphenylmethylsilane 74 rate constants of 89 reactions, mechanism of 114 of tertiary aliphatic amines 101 of 1,2,2-trimesitylvinyl alcohol . . 3 yields 122 Ozone attack on the solvents 112 cleavage of dibromo-substituted double bonds 64 consumption vs. olefin consumption 58 cycloaddition 46 decomposition of 72 w i t h double bonds containing v i n y l b r o m i d e moieties, interaction of 50 electrophilic attack b y 70 a n d halogenated double bonds, interaction of 51 hydrosilane reaction 65, 75 insertion 107 mesityl phenylethylene complex 5 nitrogen ' 106 olefin reaction 36, 52 olefin stoichiometry 61 oxidation (ozonation) of organosilanes 65 oxygen 106 reaction of triethylsilane w i t h . . 74 resistance 63 stability of polymers 63 uptake, stoichiometry of 91 Ozonides fragmentation of u n s y m m e t r i c a l . 29 mechanism of the solvent fragmentation of 33 reaction rates of cis-trans isomeric 33 b y solvents, fragmentation of . . 22 stilbene 22


129


INDEX

Ozonization of alkenes rates of ethylenes of tetraphenylethylene Ozonolysis of 2,3-dibromo-2-butene, products of the formation of cross diperoxides . . of h y d r o c a r b o n olefins of p-methylstyrene of olefins of organomercurials products of rates reaction stoichiometry of role of oxygen i n of symmetrical olefins of tetrafluoroethylene of u n s y m m e t r i c a l olefins

36 35 23 63 9 50 37 11 78 87 93 35 55 84 40 54 40

Ρ

Pentanoic a c i d , ozonation of 83 Peracetic a c i d m e t h o d 20 Perhydro-1 -naphthylphenylmethylmethylsilane, ozonation of . . . 74 Phenyl 69 P h e n y l groups, substituted 72 P i complexes 7 P o l a r effects 41,43 Polar reaction constant 43 Polymers, ozone stability of 63 Positive peroxide test 117 P r i m a r y d e u t e r i u m isotope 71 P r i m a r y ozonide 47 Products of ozonolysis 86 n-Propylmercuric bromide 84

R Racemization Rate constants of ozonation relative Rate data, relative Rates of cleavage Rates of fragmentation Reaction chain-shortening concerted of ozone w i t h olefins rates of cis-trans isomeric ozonides scheme for the ozonation of Feist's ester of triethylsilane w i t h ozone . . . . R e a c t i v i t y of organosilanes Reversible complexation Role of oxygen i n ozonolysis

74 89 36 71 30 29 89 121 52 33 120 74 67 75 84

S S 2 cleavage Si-H stretching frequency Si-OH E

95 65 68 65

Side c h a i n oxidation 102,107 Silanol 65,80 Silicon electronic environment of 70 hydrotrioxide 74 ozone complex 73 S i l y l hydrotrioxide 75 Solvent fragmentation of ozonides 33 Solvents alcohols as 64 fragmentation of ozonides b y . . 22 ozone attack on 112 Spectra, visible 6 Staudinger intermediates 97 Stereochemistry, olefin 9 Stereoisomers 11 Steric correlation coefficient 43 effects 40 hindrance 1,52 Stilbene ozonide 22,26 Stoichiometry of ozone uptake 91 ozone-olefin 61 of ozonolysis reaction 55 Styrene 38 Styrene ozonide 30 Substituent effects 35 Substituted p h e n y l groups 72 Τ

T a f t parameter

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