The oxidative coupling of phenols catalyzed by soluble copper—polymer complexes. The active role of the polymer chain during activation of the substrate—catalyst complexes

Abstract

Abstract The kinetics of the oxidative coupling of 2,6-dimethylphenol and 2,6-diphenylphenol was studied using a catalyst consisting of copper(II) chloride and polystyrene partially substituted with dimethylaminomethyl ligand groups. The polymers were not covalently crosslinked and were completely soluble in the reaction mixture. At an amino-nitrogen to copper ratio of 1 the reaction rate depended on the degree of substitution, α, of the polystyrenes. This effect was explained in terms of activation parameters obtained from the temperature dependence of the rate constant for the electron transfer step. It appeared that the polymer chain plays an active role in the activation process merely by increasing the entropy of activation with α. The formation of diphenoquinone appeared to be dependent on the reaction temperature and was almost independent of α.