Voltammetric Generation and Kinetic Stability of Nitro Anion Radical from Nitrofurazone in Ionic Liquids

Luisa Chiavassa,Fernanda Camilo,Mauro La Scalea

doi:10.21577/0103-5053.20200240

Abstract

The nitrofurazone (NF) electrochemical reduction has been studied by cyclic voltammetry (CV) and square wave voltammetry (SWV) in non-aqueous medium using three different ionic liquids (IL): BMImTf2N, BMImBF4 and BMMImTf2N, having a carbon fiber microelectrode as working electrode. In all of them, two reversible cathodic peaks were recorded for NF. Under higher frequency values, only one reversible cathodic peak was registered. The systems reversibility could also be observed by CV, since a reversible redox couple was registered for this reduction. The systems reversibility with product and reagent adsorptions on the electrode surface was confirmed and the electrons number involved in this reduction indicated the nitro-anion radical formation followed by its respective dianion. For the first reduction, the EC mechanism (an electrochemical step followed by a chemical one) was considered for the systems in aprotic medium, in which there was a probable second-order chemical reaction after the charge transfer process, being the kinetic constants calculated following the Olmstead and Nicholson model.

Highlights

Nitrocompounds belong to a class of organic compounds widely used as solvents, pesticides, dyes, explosives and drugs.[1,2] The therapeutic use of nitrocompounds as drugs deserves to be highlighted due to their wide range of biological actions, being classified as antibacterial, antiprotozoal and anticancer agents.[3]
An irreversible chemical reaction can occur after the reversible charge transfer process, characterizing an EC mechanism, in which the R-NO2– decay is promoted by means of a disproportionation reaction or dimerization reaction, determining the kinetic stability of nitro-anion radical electrochemically generated.[11,12,13,14]
Considering the NF electrochemical reduction as an EC mechanism and complementing the results described above, a second-order chemical reaction was adopted, considering that the model for a dimerization reaction is the best fit to what occurred in the ionic liquids (IL), as already registered in aprotic media.[11,33]

Summary

Introduction

Nitrocompounds belong to a class of organic compounds widely used as solvents, pesticides, dyes, explosives and drugs.[1,2] The therapeutic use of nitrocompounds as drugs deserves to be highlighted due to their wide range of biological actions, being classified as antibacterial, antiprotozoal and anticancer agents.[3]. In acidic medium, two voltammetric waves are registered, being the hydroxylamine derivative formation detected at less negative potential values followed by the second reduction process due to the amine derivative formation.[11,12,13,14] Distinctly, in alkaline aqueous media or aprotic/non-aqueous media, the nitro-anion radical generation is facilitated in function of low concentration or absence of protons in solution.

Results

Conclusion