The electrochemical oxidation of 4-chloro-, 2,4-dichloro-, 2,4,6-trichloro-anilines and 4-bromo-, 2,4-dibromo-, 2,4,6-tribromo-anilines and 4-iodo-aniline were investigated in unbuffered acetonitrile solution. The main reaction at the electrooxidation of these compounds is the dimerization which is accompanied by release of the p-substituent halide and formation of protons. To complete the so far achieved results by the apparent electron exchange number (n app ) determination in the voltammetric time scale have been attempted. These measurements were carried out with the aim, to have a clearer picture on the n app influencing role of the following complicating factors: The rejected halogenides in MeCN solvent at lower potential values as the substrates can be oxidized to the corresponding halogens, and these halogens except the iodine substitute the substrate which takes place even in the voltammetric time scale by increasing the n app value characteristic for the dimerization only. The measurable n app values are influenced by the protons produced at the oxidation as well, in the opposite direction. The explanation for the latter is, that the solvent is aprotic, therefore the differently basic primary amino groups of the diffusing substrate molecules binding partly the protons and in this way voltammetrically inactive substrate species are formed. This reaction is a typical equilibrium type and this inactivation effect decrease the measurable n app value. This effect depends on the quality and number of halogene substituent at a given substrate because these affect the protonation constant of the substrate. Therefore the protonation constants of the substrates had to be determined. In the knowledge of these quantitative data the explanation of the trends in the n app values measured in the voltammetric time scale is attempted. The mechanistic study of the dimerization reaction of these substrates is in progress in our laboratory.

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