Relative reactivity and regioselectivity of halogen-substituted ethenes and propene toward addition of an OH radical or O (P-3) atom: An ab initio study

摘要

This paper describes the results of ab initio investigations on the reactions of OH radical/O (P-3) atom addition to halogen-substituted ethenes (CH2=CHX, CH2=CX2; X=F, Cl, Br) and propene. Two reaction pathways, addition to the substituted carbon atom (alpha-site) and addition to the non-substituted carbon atom (beta-site), have been examined. The energetic of each reaction coordinate has been evaluated at the computational level of PMP2/aug-cc-pVTZ//MP2/6-311+G(2d,p). Our calculations suggested that the reactions of OH radical addition should be more exothermic than those of the O(P-3) atom addition and that the alpha-addition products should be lower in energy than the corresponding beta-addition products. Relative stabilities of the transition states for the alpha- and beta-addition channels can be discussed in terms of the exothermicities of the reaction channels and the relative spin densities in the (3)pi pi* states of the reactant ethene molecules. For the reactions of the chloro- and bromo-substituted ethenes, the transition states for the alpha-addition were found to be higher in energy than those for the beta-addition, but for the reactions of the fluoro-substituted ethenes and propene, the differences in energy between the transition states for the alpha- and beta-addition channels were found to be rather small. (c) 2006 Elsevier B.V. All rights reserved.