Electrochemical Reduction of 2-Nitroimidazole in Aqueous Mixed Medium

A detailed investigation of the electrochemical reduction of 2-nitroimidazole (2-NIm) in a mixed aqueous medium was carried out by means of cyclic voltammetry (CV) at a mercury electrode. The voltammetric behavior of 2-NIm in 60% dimethylformamide (DMF) ( tetrabutyl ammonium perchlorate, TBAP)/40% aqueous buffer is pH-dependent, changing from one irreversible reduction peak at acid pHs to two reduction peaks at alkaline pHs. At pH 2.5 it is possible to obtain a voltammetric p K which is due to the protonation-deprotonation equilibrium produced by the hydroxylamine derivative formed from the reduction of 2-NIm. This indicates that 2-NIm is reduced to the unprotonated hydroxylamine derivative above pH 2.5 and to its protonated form below it. At it is possible to observe a cyclic voltammetric couple due to the one-electron reduction of 2-NIm to produce the corresponding nitro radical anion. Furthermore, the nitro radical anion disproportionates with a rate constant, , of and a half-life, , of for the first half-life. The voltammetric behavior of 2-NIm in aqueous mixed medium is substantially different from that described in nonaqueous medium; in fact, only in the aqueous medium is it possible to study in isolation the nitro radical anion.