Kinetic model of ethylene oxidation by p-benzoquinone in solutions of cationic palladium(II) complexes in a binary acetonitrile—water solvent

A kinetic model was developed for the reaction of ethylene oxidation to acetaldehyde by p-benzoquinone (Q) at 30 ℃ catalyzed by the cationic palladium(II) complexes in a binary acetonitrile—water solvent at a molar fraction of water of 0.67. The three-route mechanism was proposed that adequately describes all experimental dependences of the concentrations of consumed ethylene on time at various partial ethylene pressures and concentrations of palladium, perchloric acid, and Q. The time-dependent (a) palladium distribution between the intermediates and (b) ratio of the rates of steps of acetaldehyde oxidation via different routes were analyzed. The role of the Pd^II, Pd^I, and Pd⁰ complexes in the catalytic formation of olefins was discussed. The quantum chemical estimates of the composition of the coordination sphere for several intermediates and probabilities of some elementary steps in the reaction mechanism were obtained.