Theoretical studies of thermal syn elimination reaction of organic amine oxide, sulfoxide and phosphoxide by ab initio and density functional methods

The geometries of the reactants and transition structures for the Ei elimination of organic oxides (GO, PO, NO and SO) were generated with the RHF/6-31G(d), MP2/6-31G(d) ab initio, SVWN/6-31G(d) and BLYP/6-31G(d) density functional theory (DFT) models. The energies were evaluated at the same level of theory. The planarity of the transition structures was confirmed for all of the applied theory models. It was estimated that 2-7 kcal mol(-1) is the necessary energy to change the reactants into a conformer which is suitable for elimination. Aldehydes and phosphoxides are not suitable starting materials for the preparation of olefins. The most reactive species are the nitroxides. The order of reactivity is in general agreement with experimental knowledge. The local and non-local DFT methods predict very similar activation energies. These activation energies are closer to the expected values than the energies predicted with the MP2/6-31G(d) theoretical model.