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PRYDE, ANDERS, TEETER, AND COFVAN [ C O N T R I B U T I O N FROM TEE
25
NORTHERN R E G I O N A L RESEARCH LABORATORY']
The Ozonization of Methyl Oleate' E. H. PRYDE,
1). E.
AKDERS, H. >I. TEETER,
AND
J. C. COLTAS
Received July 13, l M 9 The effect of solvent on the ozonization of methyl oleate and on the reductive decomposition of the ozonolysis products has been studied. The use of a reactive solvent such as methanol or acetic acid resulted in isolated product yields of 87%. Carbonyl yields before isolation of product were on the order of 90-92%. The use of a nonreactive solvent such as ethyl acetate or heptane resulted in low vield and impure products. The results are explained on the basis of the Criegee zwitterion mechanism fbr ozonization.
The ozonide of oleic acid and the cleavage products obtained by treatment with water azelaic semialdehyde, azelaic acid, pelargonaldehyde, and pelargonic acid were first described by Harries and Thieme.3 This original work was carried out without the use of solvent. Subsequently, hexane14chl~roform,~ carbon tetrachloride16glacial acetic ethyl ~ h l o r i d e , ethyl ~ acetatello and ethyl alcohol" have been used as solvents. The highest yields of isolated product (607, of pure or 75% of crude methyl azelaaldehydate) were obtained by ozonization in glacial acetic acid followed by reduction with zinc.8 Azelaic semialdehyde has been isolated in SOTo yield as the semicarbazone by ozonization in ethyl chloride followed by catalytic hydrogenation in methan01.~Sodium oleate has also been ozonized in aqueous solution, but the apparent yield of product, isolated as the oxime, was only 53%.12 Recent studies on the ozonization of various unsaturated compounds have shown not only m e t h a n ~ l ' ~ -but ' ~ also ethanol17 to be a superior (1) This is a laboratory of the Xorthern Utilization Research and Development Division, Agricultural Research Service, U. S. Departmrnt of Agriculture. ( 2 ) Presented in part before the Division of Organic Chemistry a t the 136th meeting of the American Chemical Society a t Atlantic City, Tu'. J., September 16, 1959. (3) C. Harries and C. Thieme, Ann., 343, 318 (1905). (4)E. hfolinari and E. Soncini, Ber., 39, 2735 (1906). (5) C. Harries and C. Thieme, Rer., 38, 2844 (1906). (6) C. Harries, Ber., 39, 3728 (1906). (7) B. Helferich and IT. Schafer, Ber., 57B, 1911 (1924). (8) C. R. Noller and R. Adams, J . Am. Chem. Sac., 48, 1074 (1926). (9) F. G. Fischer, H. Dull, and L. Ertel, Ber., 65B, 1467 (1932). (10) M. Stoll and A. RouvB, He6. Chim. Acta, 27, 950 (1944). (11) A. S. Carpenter and F. Reeder, Brit. Patent 743,491 (to Courtaulds, Ltd.) Jan. 18, 1956. (1%)H. Ohtsuki and H. Funahashi, Japan Patent 8417, Dee. 21, 1954; U. S.Patent 2,862,940, Dec. 2, 1958. (13) P. S. Bailey, J . Org. Chem., 22, 1548 (1957). (14) P. 8.Bailey and B. M. Shashikant, J . Org. Chem., 23, 1089 (1958). (15) E. Briner and D. Frank, Helv. Chim. Acta, 21, 1297 (1938). (16) S. A. Milas, J. T. Nolan, Jr., and P. Ph. H. L. Otto, J . Org. Chem., 23,624 (1958). (17) J. L. Warnell and R. L. Shriner, J . -4m.Chem. Sac., 79, 3165 (1957).
reaction medium. Methanol reacts to a considerable extent with ozone at -15",18 but in the presence of an unsaturated compound little reaction occurs between the ozone and methanol, and the products of such a reaction do not interfere in the analysis or isolation of carbonyl compounds. l6 Application of methanol to the ozonization of methyl oleate in the present work resulted in a significant improvement in the yield of isolated carbonyl compounds. Thus, when chemical reduction with zinc and acetic acid was used, the total carbonyl yield as determined by the hydroxylamine hydrochloride method was 92%. The isolated yield of methyl azelaaldehydate with a two degree boiling range and purity of 92% was 88%. Redistillation gave a product of 96yo purity. The hydroxylamine analyses were confirmed by gas chromatography. Because methanol is not a satisfactory solvent for glycerides a t ozonization temperatures, other solvents and solvent combinations were investigated. Furthermore, a solvent system was sought which would obviate the washing step required to remove the dissolved zinc salts. Methylene chloride and propionic acid were tried (Table I). Methylene chloride precipitated the zinc salts as they mere formed, but an unsatisfactory yield was obtained. Reduction in propionic acid could not be carried out with zinc in the absence of water. Catalytic hydrogenation was then inrestigated. Hydrogeiiatioii with 5% palladium on calcium carbonate to give an 80% yield of azelaic semialdehyde isolated as the semicarbazone has been rep~rted.~ Hydrogenation was carried out in methanol after removal of the ethyl chloride used for the ozonolysis. Ethyl oleate ozonized and hydrogenated in ethyl acetate gave a 57% yield of the desired aldehydic products. lo X British patent describes the use of ethanol in the ozonization of oleic acid ivith subsequent hydrogeiiatioii in the same solvent, the product being isolated as t8he aldoxime.ll No yield is stated. The use of methanol as a common solvent for both ozonization and hydrogenation has beeii described in the preparation of adipaldehyde from (18) F. L. Greenwood, J . Org. C l ~ e m . 10, , 414 (1945)
APRIL
1960
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T H E OZONIZATION OF METHYL OLEATE
TABLE I OZONIZATION OF METHYL OLEATE Ozone, Solvent (Volume, yo) Methanol Xethylene chloride Methylene chloride Propionic arid
yo of
Consumed
Yield, Theory Not Consumed
Temperature of Reduction
A. Chemical Reduction (Zinc 101 1 6 105 1 7 132 1 0 124 2 1
Total Carbony1
+
+
MethylazelaPelargon- aldealdehyde hydat,e
Methyl Azelaaldehydate Purity"
+ Acetic Acid) 30 to 35 30 to 35 30 to 35 -
ii
88 75 76 72 6Gb (KOreduction occurred in absence of water)
92 72 -
B. Catalytic Hydrogenation ( 10% Palladium on Charcoal) lfethanolc 115 3 -10 to 0 78 n-Butanol 98 4 8
