The mechanism of the catalytic hydrogenation of α,β unsaturated carbonyl compounds—V : Tritium isotope effects

Abstract

The isotope effects of the hydrogenation of some α,β-unsaturated carbonyl compounds with H 2/HT in the presence of different catalysts have been determined. The isotope effects depend on both catalyst and substrate. In general the size decreases in the order Pt > Pd > Rh > tris(triphenylphosphine) rhodium chloride. For the hydrogenation of dimethyl acrylate the isotope effects shown by Pt, Pd and Rh agree reasonably well with maximum calculated values assuming a reversible hydrogen addition to the β carbon and an irreversible addition to the α position. For the hydrogenation of fumarate another mechanism seems to be valid.