Co-oxidation of 2,2,5,7,8-pentamethyl-6-chromanol and diphenyl disulfide with 3-chloroperoxybenzoic acid.

The aim of this study was to determine whether disulfides could serve as protective antioxidants for alpha-tocopherol or vice versa. The chosen reaction system was a co-oxidation of the model compound of alpha-tocopherol, 2,2,5,7,8-pentamethyl-6-chromanol (PMC), and diphenyl disulfide (1) by 3-chloroperoxybenzoic acid. The rate of oxidation of the disulfide was approximately twice as fast as that of PMC when each compound was oxidised separately. However, when they were co-oxidised, the rate of loss of PMC increased while that of the disulfide decreased. The reason appeared to be that the disulfide was preferentially oxidised to the thiosulfinate (2) and the thiosulfonate (3) which then reacted with unchanged PMC to form compound (4), the major product, and benzenethiol. Benzenethiol was then re-oxidised to the disulfide.