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Abstract
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Electrochemistry provides very versatile means for electrosynthesis, mechanistic, and kinetic studies. The main goal of the electrochemical studies is the elucidation of the sequence of electron transfer and chemical reactions that occur near the electrode surface and their applications to electrosynthesis of organic compounds[1-3]. Additionally, bis(4-aminophenyl) derivatives are usually used as the monomer, chain extender, or cross-linking agent in the field of polymers[4]. Therefore, detailed mechanistic information is important in the understanding of the stability and in identifying the intermediates structure resulting from the oxidative of these derivatives. In this work, the electrochemical oxidation of bis(4-aminophenyl) sulfide (TDA), bis(4-aminophenyl) ether (ODA) and bis(4-aminophenyl) methane (MDA), has been exhaustively studied in aqueous solutions with different pH values, using cyclic voltammetry, differential pulse voltammetry, chronocoulometry and chronoamperometry. The results showed that the Ep–pH diagram comprise three linear segments with different equations and slopes at pH values 4.3 and 10.1 for TDA, 5.2 and 8.7 for MDA and 5.6 and 8.6 for ODA derivatives. These diagrams indicate that in the aqueous solutions, all three derivatives are in different reduced and oxidized forms, that their relative amounts are dependent on the pH and electrode potential. In the first and third linear segments for all three molecule Ep value shifts by -60 mV/pH. However, at the second segment, the situation is a little complicated. The Ep value for ODA is independent of pH, for TDA and MDA shifts by -30 mV/pH. This study has provided new insights into the mechanistic details, pH dependence and intermediate structure of electrochemical oxidation of these compounds.
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