Electro-oxidation of o-phenylenediamine at platinum electrodes in acetonitrile solutions

The study of o-phenylenediamine electro-oxidation at platinum electrodes in acetonitrile solutions under different experimental conditions is presented. Cyclic voltammograms show 4 oxidation peaks, which are assigned to o-phenylenediamine, o,o′-diamineazobenzene and protonated o-phenylenediamine anodic oxidation. An additional prepeak system is apparent at potentials less anodic than the first peak in successive scans. This prepeak system evidences the presence of two redox systems diphenylamine and H⁺, derived from the initial oxidation product o-phenylenediamine cation radical. The effect of base and acid addition is also studied. o,o′-Diamineazobenzene was identified as one of the principal soluble products in preparative scale electrolysis and a general mechanism for o-phenylenediamine oxidation is proposed.