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(O2)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 π (C—C) and of the peroxide LUMO orbital σ*(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 pKa value of a percarboxylic acid. Copyright © 2001 John Wiley & Sons, Ltd.