A kinetic study of the copper-catalysed oxidative coupling of 2,6-dimethylphenol. The role of copper, base and phenol concentrations

The influence of varying concentrations and ratios of phenol, base and copper on the copper/N-methylimidazole catalysed oxidative coupling of 2,6-dimethylphenol (DMP) has been studied. The reaction obeys simple Michaelis-Menten kinetics with respect to the phenol. The amount of DPQ formed during the reaction increases linearly with the increasing initial amount of DMP. At higher base-to-copper ratios an oxidative coupling experiment takes longer to complete, despite higher initial rates, which is probably due to the formation of inactive copper hydroxide species in the later stages of the reaction. The phenol oxidation step is most likely the rate-determining step, and the fractional reaction orders in copper are determined by the position of the equilibrium between mono- and dinuclear copper species, the latter being the active one. (C) 1998 Elsevier Science B.V. All rights reserved.