Autoxidation of methyl linoleate initiated by the ozonide of allylbenzene

Abstract

Allylbenzene ozonide (ABO), a model for polyunsaturated fatty acid (PUFA) ozonides, initiates the autoxidation of methyl linoleate (18:2 ME) at 37 degrees C under 760 torr of oxygen. This process is inhibited by d-alpha-tocopherol (alpha-T) and 2,6-di-tert-butyl-4-methylphenol (BHT). The autoxidation was followed by the appearance of conjugated diene (CD), as well as by oxygen-uptake. The rates of autoxidation are proportional to the square root of ABO concentration, implying that the usual free radical autoxidation rate law is obeyed. Activation parameters for the thermal decomposition of ABO were determined under N2 in the presence of radical scavengers and found to be Ea = 28.2 +/- 0.3 kcal mol-1 and log A = 13.6 +/- 0.2; kd (37 degrees C) is calculated to be (5.1 +/- 0.3) X 10(-7) sec-1. Autoxidation data are also reported for ozonides of 18:2 ME and methyl oleate (18:1 ME).