Premium
Thermal dimerization of fatty ester hypdroperoxides
Author(s) -
Frankel E. N.,
Evans C. D.,
Cowan J. C.
Publication year - 1960
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02631198
Subject(s) - chemistry , double bond , dimer , medicinal chemistry , linolenate , fatty acid , peroxide , polyunsaturated fatty acid , intramolecular force , organic chemistry , stereochemistry , photochemistry
Summary When autoxidized fatty esters and purified fatty hydroperoxides were decomposed in the absence of oxygen at 210°C., the principal reaction was dimerization of the fatty acid chains with elimination of the hydroperoxide groups. Dimers isolated by molecular distillation (60 to 90% of the polymer) have approximately 1 mole hydroxyl, 0.5 mole carbonyl, and two double bonds per mole of dimer. Diene conjugation in the dimers from polyunsaturated fat hydroperoxides varied from 10 to 23%. The infrared spectra of the dimers were similar to those of the original fatty esters except for one striking band at 2.9 μ, which is attributed to the secondary hydroxyl group. The cis‐trans diene in the polyunsaturated hydroperoxides was isomerized to the trans‐trans configuration on dimerization. The methyl oleate hydroperoxide dimer showed only absorption for isolated trans double bond. The dimer was not split either by catalytic hydrogenation or by hydrogen iodide, indicating a carbon‐carbon bond between the monomer units. On oxidation with permanganate and periodate, the dimeric acids behaved like a monounsaturated mixture containing double bonds in the C 6 , C 7 , C 8 , C 9 , and C 10 positions in the oleate dimer and in the C 8 , C 9 , and C 10 positions in the safflower ester dimer. Although the dimers showed no peroxidic oxygen iodometrically with potassium iodide, a reduction occurred with hydriodic acid that may indicate the presence of intramolecular peroxide groups and/or allylic alcohol or carbonyl groups. Bromination with N‐bromosuc‐cinimide and dehydrobromination with N,N‐dimethyl aniline produced no aromatization. Subsequent oxidation of the dehydrobrominated dimer yielded 2.6% residue, which was not aromatic. This evidence indicates that the dimer does not have a six‐membered cyclic structure. Dimerization of the hydroperoxides is suggested as occurring through alkyl or alkoxy hydroperoxide radicals to give carbon‐carbon linked fatty acid dimers and some higher polymeric units.