Concurrent oxidation of accumulated hydroperoxides in the autoxidation of methyl linoleate

Abstract

Summary Kinetic studies showed that concurrent oxidation of preformed hydroperoxides may be expected to take place at all stages of the autoxidation of methyl linoleate. The rate of oxidation relative to the rate of autoxidation of unoxidized ester is determined chiefly by the extent of the accumulation of hydroperoxides. Infrared spectral analysis of hydroperoxides oxidized to various degrees indicated thattrans, trans diene conjugation and isolatedtrans double bonds produced in the autoxidation of methyl linoleate are related to the concurrent oxidation of the accumulated hydroperoxides. The low absorptivity observed for diene conjugation, compared to that which may be expected for the exclusive production ofcis, trans diene conjugated hydroperoxide isomers during the autoxidation of methyl linoleate is attributed to the concurrent oxidation of accumulated hydroperoxides. The effect of antioxidants in giving a well‐defined induction period in the oxidation of hydroperoxides isolated from autoxidized methyl linoleate indicated that the oxidation proceeds by a chain reaction. The primary reaction products of the oxidation of hydroperoxides isolated from autoxidized methyl linoleate were found to be polymers formed in a sequence of reaction involving the diene conjugation. Studies on the autoxidation of methylcis‐9,trans‐11‐linoleate showed thatcis, trans isomerization of the conjugated diene took place with the concurrent production of isolatedtrans double bonds and loss of diene conjugation.