Spectroscopic Analysis on Elementary Reactions of Oxidative Polymerization of 2, 6-Xylenol Catalyzed by Copper Complex

Abstract

The catalytic cycle of the polymerization of 2, 6-xylenol catalyzed by the copper-pyridine complex is divided into four elementary processes, the coordination of the substrate(1), the electrontransfer from the substrate te the cupric ion (k), the dissociation of the aetivated substrate (kd) and the reoxidation of the catalyst (ke). The rate constant of each elementary reaction was determined by means of the stoppedfiow spectrophotometric study of the copper complex, and the detailed mechanism of the catalysis was discussed. From the comparison of rate constants (Table 1), the process involning, either k. or kd was considered to be the ratedetermining step but the latter could not be measured in the present procedure. It was found that the oxygen molecule was involved in the cupric substrate omplex, promoting the k. process. The rate constants were affected by the components of the solvent. Except for a few cases where solvents having coordinating ability are used, k and ke increased and ke decreased with the increasing solvent polarity.