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 iodoani lines the corresponding 2,4-dihalogenoanilines, and the n-tetrabutylammoniu m-halogenides are shown. Using controlled potential coulometry, the product s of the individual anilines were prepared. The products were isolated by e xtraction, which is followed by identification of the products, using elect rospray MS measurements. This efficient analytical method proved equivocall y, that besides the main oxidized forms of diphenylamine type dimers, the c orresponding monomer 2,4-dihalogenoanilines are formed as well, except 4-io doaniline. It has been proved by CV and CPC measurements that the formation s of these dihalogeno-compounds take place by parallel oxidation of the rej ected halogenides, on the course of the electrodimerization of cation radic als. The reason for this special behavior is that the halogenide ions can b e oxidized at lower or coinciding positive potentials, compared to the 4-ha logenoanilines thus by forming elementary halogens. These halogens in the p resence 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 re dox potentials of Cl-2/Cl-Br2/Br- and I-2/I- systems were determined in neu tral MeCN solvent by CV measurements.