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

Abstract

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 reversible arrow -NRNO, + 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: 5HNRNO(2) + 4e(-) -> 4(-)NRNO(2) + HNRNHOH + H2O The second quasi-reversible couple was caused by the reduction of the conjugate base according to the following equation: -NRNO2 + e(-) -> NRNO2 center dot-