THEORETICAL STUDY OF THE REGIOSELECTIVITY OF THE ADDITION OF THE TRIPLET OXYGEN ATOM TO UNSYMMETRICAL SUBSTITUTED ALKENES

Abstract

A theoretical study of the reactivity and regioselectivity of the addition of the triplet oxygen atom O(3P) to a series of unsymmetrical substituted alkenes has been performed at the PMP2/6-311++G (d,p) level of theory. Two reaction pathways, namely, the addition to the substituted carbon atom (α-site) and addition to the non-substituted carbon atom (β-site), have been studied. Our calculations show that the β-addition products are kinetically more favored; whereas the α-addition products are found to be thermodynamically more stable. The regioselectivity (α vs. β) of the addition of the O(3P) to the carbon–carbon double bond is predicted by means of the relative energies of the localized transition states and also by the calculation of spin densities of the 3ππ* states of reactants and Fukui indices corresponding to the radical attack to alkenes. Our calculations are in good agreement with experimental outcomes.