Theoretical study of the complex reaction of O(3P) with trans-2-butene

Abstract

The complex triplet potential energy surface for the reaction of the triplet oxygen atom O(3P) with cis-2-butene is investigated at the CBS-QB3 level of theory. The different possible isomerization and dissociation pathways, including both O-additions and H-abstractions, are thoroughly studied. Our calculations show that as found for the trans-2-butene reaction, in the high-pressure limit, the major product is CH3CHC(O)H + CH3 (P1), whereas in the low-pressure limit the most thermodynamically stable product forms CH3CO + CH3CH2 (P4). The experimental negative activation energy reported for the addition step is very well reproduced at the CBS-QB3 level of theory. Various thermodynamic and kinetic values of interest for these reactions are predicted for the first time. A discussion on the negative activation energy for the addition step of the trans- and cis-2-butene reactions with O(3P) focussing on the addition reactant complexes is presented.