Electrochemical nitration of catechols has been studied in the presence of nitrite ion as nucleophile in aqueous solution, by means of cyclic voltammetry and controlled-potential coulometry. The results indicate the participation of produced o-benzoquinones in Michael reaction with nitrite ion to form the corresponding nitrocatechols. Based on EC mechanism, the observed homogeneous rate constants of nitration reaction were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. (c) 2006 Elsevier B.V. All rights reserved.