A Molecular Orbital Study of the Electrophilicity of Hydroxyl Radical in Hydrogen Abstraction Reaction

The electrophilicity of the hydroxyl radical in hydrogen abstraction from methane was studied by the CNDO/2 method. The stabilization energy due to the delocalization of the electrons (SEDE) between methane and the radical at a close distance was calculated. The electrophilicity defined by the SEDE from methane to the hydroxyl radical was larger than the nucleophilicity defined by that from the hydroxyl radical to methane. This result is consistent with the electrophilicity observed in hydrogen abstraction by the hydroxyl radical from a series of substituted methanes. For sulfhydryl radical, the electrophilicity was also suggested by the calculation for hydrogen abstraction from methane. The calculations were also carried out for various radicals which have low electron affinity (hydrogen atom and methyl radical), and the SEDE from methane to the radical was found to be large compared with that from the converse case.