The electrochemical oxidation of 4-chloroaniline, 2,4-dichloroaniline and 2,4,6-trichloroaniline in acetonitrile solution

The electrochemical oxidation of 4-chloro-, 2,4-dichloro- and 2,4,trichloro anilines was investigated in acetonitrile solution. Based on the experiment al results, it can be stated that the mechanism introduced by J. Bacon and R.N. Adams (J. Am. Chem. Sec. 90 (1968) 6596) describing the voltammetric o xidation of 4-substituted aniline derivatives in acidic aqueous media is th e main electrochemical oxidation route in acetonitrile as well. It is shown , that in the cases of 4-chloro- and 2,4-dichloroanilines, the substituent in the para position is not only eliminated at the electrochemically initia ted dimerization step, but it was oxidized to chlorine, which substitutes t he free ortho position of the starting chloroaniline. As a consequence of t hat oxidized form of chlorinated 4-amino-diphenylamines is formed also besi des chlorinated anilines. 2-Amino-4',5-dichloro-diphenylamine has been foun d as a product of oxidation at the oxidation of 4-chloroaniline. This can b e explained by dimerization of 4-chloroaniline at the ortho position by the one electron oxidized substrate. In the case of both monomer compounds, th e role of 'head-to-head' coupling found negligible (azobenzene type compoun ds). Chlorination did not take place at the oxidation of 2,4,6-trichloroani line, because the rejected chloride ion can be oxidized only to chlorine. The oxidation products prepared by controlled potential electrolysis (CPC), were isolated and identified by different techniques (GC-ECD, GC-MS and ES -MS: gas chromatography, gas chromatograph-mass spectrometry and electrospr ay mass spectrometry). Cyclic voltammograms of the chloroaniline type subst rates and n-tetrabutylammonium chloride have been recorded before and after the CPC electrolysis, and were also used for product identification. (C) 2 001 Elsevier Science Ltd. All rights reserved.