Reactivity of hydroxy-containing aromatic compounds towards electrogenerated hydroxyl radicals

A kinetic study on the oxidation of hydroxy-containing aromatic compounds by electrogenerated HO radical and simultaneous by direct electron transfer is presented. First order kinetics are used to describe consumption rates of hydroquinone, benzoic acid and hydroxybenzoic acid derivatives by galvanostatic electrolysis with simultaneous oxygen evolution at a Pt electrode. Linear correlations were established from the effect of electrolyses current density on kapp. The meaning of the intercept and slope is analyzed. A good agreement is found between intercept values and the apparent rate constants from potentiostatic electrolysis without O2 evolution. Simultaneously, the slopes magnitude corroborate the relative reactivity order of species that was established considering the occurrence of positive charge densities on carbon atoms of the aromatic ring. Therefore, the present analysis provides kinetic information concerning both, the direct electron-transfer and the reaction with HO radical.