Mechanisms of antioxidant action: Nature of transformation products of dithiophosphates. II. Antioxidant action of thiophosphoryl disulphides

The nature of transformation products of high-temperature reactions of thiophosphoryl disulphides with hydroperoxides in the absence and presence of oxidisable substrates and the role of the disulphide in the overall antioxidant mechanism was investigated using a range of techniques such as oxygen absorption, 31P nuclear magnetic resonance (NMR), gas-liquid chromatography (GLC), and peroxide determination. The major transformation products of the above oxidation reactions were found to be the thio and thiono-phosphoric acids, in addition to mono and polysulphides. At high molar ratios of peroxide to disulphide (>10), these oxidation products are the main catalysts for peroxide decomposition, while at lower ratios the disulphide itself was found to play a major role in the antioxidant mechanism.