Electrochemical reduction of 2-nitroimidazole in aprotic medium: Influence of its dissociation equilibrium on the reduction mechanism

The electrochemical reduction of 2-nitroimidazole in a non-aqueous medium using cyclic voltammetry (CV) at a mercury electrode was carried out.The 2-nitroimidazole derivative in DMF + 0.1 M tetra(n-butyl)ammonium hexafluorophosphate (TBAHFP6) resulted in the following dissociation equilibrium:HNRNO2 ⇆ −NRNO2 + H+The neutral species (HNRNO2) and the corresponding conjugate base (−NRNO2) are characterized by UV absorption bands at 328 and 370 nm, respectively.The voltammograms of 2-nitroimidazole produced two well-defined signals, which were determined by the above dissociation equilibrium. The first reduction peak was caused by the reduction of the neutral species according to the following overall mechanism:5HNRNO2 + 4e− → 4−NRNO2 + HNRNHOH + H2OThe second quasi-reversible couple was caused by the reduction of the conjugate base according to the following equation:−NRNO2 + e− → NRNO2−