Ab initio molecular orbital study on reactivity of phenol, biphenyl, benzoate and p-hydroxybenzoate in the ˙OH addition reaction and stability of the corresponding ˙H and ˙OH cyclohexadienyl adducts

Abstract

The reactivity of phenol, biphenyl, benzoate and p-hydroxybenzoate towards ˙OH addition and the relative stability of the corresponding ˙H and ˙OH cyclohexadienyl adducts have been studied using ab initio molecular orbital calculations. The compounds studied were optimized at the R(O)HF/6-31G* level. The SCRF method has been used to model solvent effects. The HOMO orbital coefficients were found to explain the observed isomeric distributions in the earlier radiolytic hydroxylation studies. The stabilization energies of the cyclohexadienyl radicals as investigated using the isodesmic reaction were found to be qualitatively different at the ROHF/6-31G*//6-31G* and ROMP2/6-31G*//6-31G* levels. The ROMP2/6-31G*//6-31G* energies revealed that the OH group stabilized most ortho and phenyl group para isomers of the cyclohexadienyl radicals.