Arene—onium cations—VI Electrode kinetics of the anodic formation of arene—sulphonium cations from bisarenesulphides

Electrode kinetic investigations (voltammetry at stationary electrodes, rotating ring—disc electrodes and rotating rod electrodes) of the anodic oxidation of bisanisole-, bismesitylene-, bisxylene-, bistoluene- and bisbenzenesulphide were performed in acetonitrile. Observed anodic half wave potentials increase in the given order. The S-radical cations of the bisarenesulphides form in a reversible one-electron oxidation step. The radical cations of bisanisole- and bismesitylenesulphide are unable to react, even with relatively strong bases like water, and they disproportionate to form the more reactive dications which react readily with different nucleophiles. The more reactive radical cations of bisxylene-, bistoluene- and bisbenzenesulphide react directly with nucleophiles, for instance with aromatic bases and with the more basic hydrocarbons (anisole, styrene). Participation of dications in their consecutive reactions cannot be detected. The anodic dimerization of these three bisarenesulphides is a relatively fast reaction and is due to the addition of the respective bisarenesulphide radical cation to bisarenesulphide molecules. The reason for the striking mechanistic difference for the two groups of radical cations is very likely an unfavourable disproportionation equilibrium for the more reaction bisarenesulphide radical cations.