Role of glassy carbon material and water on the competitive processes during the electro-oxidation of aryl sulfides in acetonitrile

The effect of electron donating and withdrawing substituents, electrode material and water. addition on the electrochemical oxidation of aryl sulfides in acetonitrile has been investigated using cyclic voltammetry, coulometry and constant current electrolysis. The cation radical formed in all the cases are found to undergo faster dimerization on relatively hydrophobic glassy carbon electrode surface when compared to Pt electrodes. In the case of phenyl methyl sulfide and methyl p-tolyl sulfide three distinct oxidation peaks corresponding to formation of cation radical, oxidation of sulfonium salt and further oxidation of cation radical or sulfoxide are observed. Water does not have significant effect on the first anodic peak. In the case of nitro substituted aryl sulfides the first oxidation, leading to the formation of cation radical occurs at more positive potentials. The cation radical formed in this case, however, reacts with water and undergoes further oxidation in the same potential region leading to the formation of sulfoxide.