Oxidative coupling of 2,6‐dimethylphenol catalyzed by copper(II) complexes in aqueous solution

Abstract

AbstractThe oxidative coupling reaction of 2,6‐dimethylphenol (DMP) with H2O2 catalyzed by four copper(II) complexes was investigated in Tris‐HNO3 buffer solution at 25°C. The kinetics of formation of diphenoquinone (DPQ, 4‐(3,5‐dimethyl‐4‐oxo‐2,5‐cyclohexadienylidene)‐2,6‐dimethyl‐2,5‐cyclohexadienone) from DMP was studied in detail. The kinetic parameters k2 and Km were obtained in the pH range of 6.0–9.0. The copper(II) complexes exhibited the optimal catalytic activity at around pH 7.0. The pH effect was reasonably explicated by the catalytic kinetic model suggested in this work. The catalytic mechanism was discussed. The deprotonized associated radical LCuI(OH−)‐•OOH was suggested as the possible predominant species to oxidize DMP. The CC and CO coupling products were analyzed and the ratio of poly (2,6‐dimethyl‐1,4‐phenylene ether) (PPE) to DPQ was also evaluated. Both in weak acidic (pH < 6.5) and in alkaline aqueous solution (pH > 8) were suitable to the CO coupling reaction in our catalytic systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010