Kinetic Study of the Heck Reaction by the Method of Competing Reactions

The method of competing reactions is used to measure the isotope effect in styrene phenylation by iodobenzene. The kinetics of styrene, methyl acrylate, and methyl methacrylate phenylation is studied. Experimental data suggest that the step of alkene insertion is relatively fast, while the subsequent step that involves C–H bond dissociation is rate-limiting. The kinetic parameters of the process point to the dependence of the rate-limiting step of the catalytic cycle on the concentrations of base and alkene. These results are consistent with the existing hypothesis that the step of -elimination of palladium hydride is present in the mechanism.