Olefin epoxidation by dioxiranes and percarboxylic acids:: an analysis of activation energies calculated by a density functional method

The activity of dioxiranes, R2CO2, and percarboxylic acids, RCO(O-2)H, in olefin epoxidation reactions can be rationalized by a frontier orbital interaction. Barrier heights of these oxygen transfer reactions, as calculated by a density functional method, depend linearly on the energy of the olefin HOMO orbital pi (C-C) and of the peroxide LUMO orbital sigma*(O-O). Activation barriers can be predicted from linear relationships with the proton affinity of a dioxirane (as measured by the hydrogen fluoride association energy) or the pK(n) value of a percarboxylic acid. Copyright (C) 2001 John Wiley & Sons, Ltd.