SOME SPECIFIC FEATURES IN AUTOXIDATION OF METHYL LINOLEATE

Abstract

A scheme of manual counter-current extraction, ingeniously devised, has facilitated quantitative isolation of initial products from autoxidized methyl linoleate under controlled conditions. A sole product of monomeric monohydroperoxide with one spatial configuration has been shown to be the outcome of interactions of oxygen molecule with methyl linoleate. The physical and chemical analyses prove this product as conjugated cis,trans methyl linoleate hydroperoxide. The fractionations of its derivative, hydroxystearic acid, and its scission products go to establish the formation of two positional isomers (9- and 13-) exclusively for this cis,trans product. Such positional isomers leave no doubt about two possibilities of attack by oxygen on the two 3-C segments in the 5-C system of methyl linoleate containing mobile π electrons. A mechanism has been proposed relevant to the experimental findings. Such initiation processes offer the missing link between neutral methyl linoleate and formation of its hydroperoxide without decomposition. These investigations, thus, emphasize the fact that the initiation processes must be distinguished from the main autoxidation reactions.