Electrochemical and QSPR studies of several hydroxy- and amino-polysubstituted benzenes constituents of useful compounds

Abstract

The environmental impact of hydroxy- and amino-polysubstituted benzenes—constituents of natural and synthetic molecules of interest in food, pharmaceutical, and textile industries—demands new procedures for degradation of such pollutants, electrochemical oxidation being an important tool. Electrochemical studies have been performed to characterize these benzene derivatives by cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV), and rotating disk electrode voltammetry (RDE). Their oxidation potential (EOX) has been measured by CV, DPV, and SWV. Linear correlations EOX vs. pH were established for the nondissociated forms of these compounds and good fitting was noticed for EOX vs. Hammett constant for the meta and para-substituted compounds. Diffusion coefficients were also estimated. According to the reversibility of their electrochemical oxidation, studied by CV, the compounds were classified into two main groups: reversible-type I (benzene-1,2-diol, benzene-1,4-diol, and benzene-1,2,4-triol) and irreversible-type II (benzene-1,3-diol, benzene-1,2,3-triol, benzene-1,3,5-triol, 4-aminophenol, benzene-1,4-diamine, and 3,4,5-trihydroxybenzoic acid). A quantitative structure–property relationship (QSPR) study has revealed the characteristics that influence their EOX values. A very good agreement resulted between the calculated and experimental EOX values. The proposed descriptors may be used in the prediction of EOX value for other related compounds. Thus, the optimal conditions for the degradation by electrochemical procedures of environmental pollutants containing such structures can be easily estimated.