Oxidation of 4-chlorophenol catalyzed by Cu(II) complexes under mild conditions: Kinetics and mechanism

Abstract

Three synthetic copper(II) complexes exhibited remarkable catalytic activity for 4-chlorophenol (4-CP) oxidation by H 2O 2 in neutral and weak alkaline solution at 25 °C. The decomposition of H 2O 2 catalyzed by copper(II) complexes was investigated. The studies by fluorescence and UV–vis measurements proved that free hydroxyl radical was not the primary reactive species for the oxidation of 4-CP. “Associative radical” LCu I- OOH was suggested as the possible predominant reactive species in this work. The reaction kinetics of 4-CP oxidation catalyzed by copper(II) complexes was studied in detail. The pH effect was explicated by the catalytic kinetics model proposed in this paper. The catalysis involved not only the activation of H 2O 2 by copper(II) complex to yield more reactive species LCu I- OOH, but also the formation of 4-chlorophenolate anion. A possible catalytic reaction mechanism of 4-CP oxidation was proposed.