Theoretical analysis of the electrochemical oxidation of some pbenzoqoinone derivatives in aqueous solution

Electrochemical methods are widely applied to study of the reactions of electroactive compounds. They can be used to obtain both thermodynamic and kinetic information (1,2). Amongelectrochemical techniques, cyclic voltammetry has been used as a powerful independent routefor qualitative and quantitative characterization of complex electrode processes. In this work electrochemical oxidation of some p-benzoqoinone derivatives (1-5) in aqueous solution has been investigated theoretically to bring hints into the connection of thermodynamic and oxidationpotential. The effect of ΔGtot of the electrochemical oxidation was investigated with considering a general thermodynamic cycle (Born- Haber cycle). ΔGtot of the oxidation of p-benzoqoinone derivatives were calculated at DFT (B3LYP, BP86) levels of theory using 6-311+G (p,d) and 6-311G (p,d) basis sets. E1/2 of studied species in pH=6.0, obtained using cyclic voltammetry (3), were used as experimental data, and ΔGtot of the electrochemical oxidation of studied species (1- 5) have been calculated from computational method. The results show a good correlationbetween ΔGtot of electrochemical oxidation and E1/2. These data illustrate that thermodynamic indicates precedence of electrochemical oxidation of studied species. In other word it can be concluded that species with more positive oxidation potential have larger ΔGtot values.

Keywords:

p-benzoqoinone derivatives , electrochemical oxidation , Gibbs free energy , Cyclic voltammetry