Mechanism of the catalytic effect of the Pd(PPh3)2Cl2-PPh3-p-toluenesulfonic acid system on cyclohexene hydrocarbalkoxylation in cyclohexanol

Kinetic relations for cyclohexene hydrocarbalkoxylation with cyclohexanol in the presence of the Pd(PPh3)(2)Cl-2-PPh3-p-toluenesulfonic acid (TSA) catalyst system were revealed. It was shown that the reaction is first-order in cyclohexene and fractional-order in Pd(PPh3)(2)Cl-2 and that the dependences of the reaction rate on p(CO) and C6H11OH and PPh3 concentrations are nonmonotonic, passing through maxima at p(CO) = 3 MPa, [C6H11OH] = 0.15 mol/l, and [PPh3] = 8 x 10(-3) mol/l. The plot of the reaction rate versus the TSA concentration is S-shaped in character. The results were interpreted in terms of the mechanism that suggests the formation of cationic hydride complexes as intermediates. A rate equation fitting the experimental data was obtained on the basis of the concept of quasi-equilibrium states for this reaction.