Extreme Kinetics of Chemiluminescence in the Initiated Oxidation of Vegetable Lipids

During the oxidation of sunflower oil initiated by 2,2'-azo-bis-isobutyronitrile, which was used in this study as the model lipid system of plant origin, the previously unobserved form of kinetic chemiluminescence curves has been discovered. At the end of the induction period, during which chemiluminescence was suppressed by the antioxidants present in sunflower oil, instead of the expected smooth S-shaped output of the luminescence intensity at a significantly higher stationary level, a sharp surge in intensity was observed with its subsequent decrease to the stationary level. The standard kinetic scheme, which is used in most works on the effect of antioxidants on chemiluminescence in the chain free-radical oxidation of hydrocarbons, cannot explain the shape of the obtained kinetic curves. To explain the discovered phenomenon, an extended kinetic scheme, which takes into account the reactions of the initiator isobutyronitrile-peroxide radicals and their conversion to methyl-peroxide radicals, is proposed. It is shown that the observed extreme kinetics is possible only in the case of quantum yields of the chemiluminescence from the reaction of the initiator isobutyronitrile-peroxide radicals with the substrate peroxide radicals, which are 1–2 orders of magnitude higher than the quantum yields of other chemiluminescent reactions.