Structure and Mechanism for Alkane Oxidation and Alkene Epoxidation with Hydroperoxides, α-Hydroxy Hydroperoxides, and Peroxyacids: A Theoretical Study.

DFT calculations (B3LYP/6-311+G(d,p)) have been employed to reexamine the mechanism of the oxidation of saturated hydrocarbons and the epoxidation of alkenes with a series of hydroperoxides, α-hydroxy perhydrates, and peroxyacids. Hydrocarbon oxidation and alkene epoxidation with the hydroperoxide group involve a diradicaloid process initiated by a homolytic O-O bond cleavage involving a somersault rearrangement (1,2-hydrogen shift) induced abstraction of a hydrogen atom followed by a final product forming an "oxygen rebound" step. The epoxidation of alkenes and the oxidation of saturated hydrocarbons with peroxyacids is a concerted process involving a 1,4-hydrogen shift in the transition state. Accurate (G4) O-O bond dissociation energies (BDEs) for the series of peroxides are included. Although the O-O BDEs for the series of peroxides examined differ by only 3 kcal/mol, the activation energies reported differ by more than an order of magnitude. Both SCRF-PCM and natural bond order (NBO) analyses have been included.