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 be...