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 pK_a value of a percarboxylic acid.