The Role of Halogen Substituents in the Electrooxidation of 4‐Halogenoanilines in Neutral Acetonitrile

The specialities of the electrooxidation of 4-halogenoanilines, in neutral MeCN solvent is described. The CV behavior of 4-chloro-, bromo- and iodoanilines the corresponding 2,4-dihalogenoanilines, and the n-tetrabutylammonium-halogenides are shown. Using controlled potential coulometry, the products of the individual anilines were prepared. The products were isolated by extraction, which is followed by identification of the products, using electrospray MS measurements. This efficient analytical method proved equivocally, that besides the main oxidized forms of diphenylamine type dimers, the corresponding monomer 2,4-dihalogenoanilines are formed as well, except 4-iodoaniline. It has been proved by CV and CPC measurements that the formations of these dihalogeno-compounds take place by parallel oxidation of the rejected halogenides, on the course of the electrodimerization of cation radicals. The reason for this special behavior is that the halogenide ions can be oxidized at lower or coinciding positive potentials, compared to the 4-halogenoanilines thus by forming elementary halogens. These halogens in the presence of 4-Cl-, or 4-Br-anilines attack the parent compounds by formation of the corresponding 2,4-dichloro-, and 2,4-dibromoanilines. The actual redox potentials of Cl2/Cl–Br2/Br– and I2/I– systems were determined in neutral MeCN solvent by CV measurements.