Autoxidation of linoleic acid methyl ester studied by spin trapping

Abstract

2-Methyl-2-nitrosopropane (MNP) dimer has been used both to initiate autoxidation of linoleic acid methyl ester (LAME) and to trap pentadienyl radicals formed during autoxidation. The EPR spectrum of trapped pentadienyl radical is a triplet of doublets. The growth of spin-trapped pentadienyl radicals was linear with time and the growth rate was studied as a function of concentrations of MNP and LAME using cyclohexane as the solvent. A mechanism is put forward to explain the experimental results, and by comparing the proposed reactions with experiments, rate constants for self-trapping (identical with that of thermal decomposition of the spin trap) and initiation of pentadienyl radicals were found to be: 2 × 10^–8 s^–1 and 6.5 × 10⁵ dm³ mol^–1 s^–1, respectively, and the peroxidation rate was: 1.3 × 10⁵ s^–1 under laboratory conditions.