Theoretical study of the reaction mechanism of the uncatalyzed epoxidation of alkenes by iodosylbenzene

The origin of the barrier for the uncatalyzed epoxidation of alkenes by iodosylbenzene is examined from a computational point of view. The reaction of a monomeric unit with ethylene presents a very low barrier, in disagreement with experimental data indicating the requirement of a catalyst. The polymeric structure of iodosylbenzene was then analyzed and the importance of the presence of a terminal hydration water in its linear structure confirmed. The reaction of a model dimer with ethylene is shown to have a high barrier, in good agreement with experiment. Implications of this result with respect to the nature of the catalytic mechanism are briefly discussed.