KINETIC COUPLING IN AND BETWEEN CATALYTIC CYCLES

Quasi-equilibrium between catalytic reactive intermediates and reactan t or product molecules is a common assumption. As process conditions v ary, this assumption may cease to be valid because of kinetic coupling between steps in the catalytic cycle. In the case of coupled catalyti c cycles, kinetic coupling manifests itself by substantial changes in selectivity. An elegant example of catalytic coupling in and between c atalytic cycles is the change in enantioselection with H2 pressure for the asymmetric hydrogenation of a prochiral alkene, as discovered in the Halpern laboratory.