The concentration effects of reactants and components in the Pd(OAc)2/p-toluenesulphonic acid/trans-2,3-bis(diphenylphosphinomethyl)-norbornane catalytic system on the rate of cyclohexene hydrocarbomethoxylation

Abstract

The reactants and components of a catalytic system were studied for their effects on the rate of Pd-catalysed cyclohexene hydrocarbomethoxylation. First-order reaction rate dependences were established for cyclohexene and Pd(OAc)2, while non-monotonic rate dependences were determined for the diphosphine and p-toluenesulphonic acid concentrations and the СО pressure. The reaction was shown to follow first-order kinetics when the methanol concentration was below 0.4mol/L; however, the reaction rate slowed upon a further increase in the methanol concentration. The obtained results were interpreted by considering a hydride mechanism supplemented with ligand exchange reactions, which decreased the activity of the catalyst, and with hydride complex annihilations by p-toluenesulphonic acid, resulting in complete loss of catalytic activity. Treatment of the proposed mechanism using the quasi-equilibrium concentration method gave a kinetic equation for the reaction that was consistent with the experimental data.