MCPBA epoxidation of alkenes: Reinvestigation of correlation between rate and ionization potential

A kinetic equation provides relative rate constants from product analysis under competition conditions. This has been applied to the epoxidation of a large number of alkenes with m-chloroperbenzoic acid in methylene chloride. The rate constants are well correlated with ionization potentials, but there are separate linear correlations for aliphatic and aromatic alkenes. However, the extent of electron transfer to the peracid is minimal. These results can be interpreted in terms of transition-state imbalance ('nonperfect synchronization'), frontier-orbital theory, and a transition state (1) that has little charge development at carbon.