Electrochemical Reduction Characterizations of Aromatic Nitro-Compounds

In this paper, the electrochemical reduction characterizations of the aromatic nitro-compounds including nitrobenzene, α-nitronaphtahlene and l,5-dinitroanthraquinone in the sulfuric acid solution were investigated and the reaction mechanism was proposed as well. The electrochemical measurements such as cyclic voltammetry, quasi-steady-state polarization, fast linear potential sweep and chronoamperometry were carried out by using EG&G 273A electrochemical measurement system. The results showed that three compounds could be reduced electrochemically to the corresponding aminophenol confounds under the suitable reaction conditions on Cu-Hg cathode. The reduction peak potential was all in the range of -0.4 to -0.6 V (vs. SCE) for the above confounds. The corresponding specific surface activity energy tested was 21.5, 16.4 and 21.2 kJ/mol respectively, means the better electrochemical reduction activity on Cu-Hg electrode. Further investigation on the reaction mechanism disclosed that α-nitronaphtahiene and 1,5-dinitroanthraquinone have the similar reaction mechanism to that of nitrobenzene to para-aminophenol, i.e.,Bamberger rearrangement courses. With the increasing of the number of benzene number, the temperature and the concentration of needed for the electrochemical reduction increased correspondingly, i.e.,90℃ for nitrobenzene, 110℃ for α-nitronaphtahlene and 140℃ for l,5-dinitroanthraquinone respectively. The reaction rates are proportional to the concentration of the reactants the corresponding conditions.