Unusual behavior of modifier mixtures in heterogeneous enantioselective catalysis: beyond nonlinear phenomena

Theoretical analysis for the kinetics of heterogeneous enantioselective hydrogenation in the presence of binary modifier mixtures revealed conditions when not only nonlinear dependence of the enantiomeric excess on the composition of the modifier mixtures is observed, but maxima in ee are possible for mixtures compared with single modifiers. Experimental data on (E)-2,3-diphenylpropenoic acid hydrogenation over Pd were used to illustrate the applicability of the advanced model. The key features for a system to display such unusual behavior are associated with rate constants for steps involving one modifier being dependant on the concentration of the other one.