The electrochemical oxidation of N,N-dimethyl-p-toluidine

Summary The electrochemical oxidation of N,N-dimethyl- p -toluidine (DMPT) was investigated in acetonitrile at platinum and also in aqueous buffer solutions in the pH range 3.0–9.0 at carbon paste. It was found that one-electron oxidation to the cation radical was followed by loss of a proton from the ring methyl group to form a benzyl-type free radical. Two of these then coupled to form the corresponding bitoluidine. Studies of the system were complicated by the fact that both DMPT and the bitoluidine were undergoing protonation by the protons liberated in the coupling reaction; this rendered kinetic measurements meaningless in a quantitative sense. Formation of the bitoluidine was verified by cyclic voltammetry, visible absorption spectroscopy, thin-layer chromatography and isolation of products from macro-scale electrolyses. The above type of mechanism has recently been demonstrated to be operative in a wide variety of organic systems, the only requisite being a labile proton on a carbon alpha to an aromatic ring, so it would appear to be a general reaction pathway in anodic electrochemistry.