MOLECULAR ORBITAL DESCRIPTIONS OF REACTION PATHWAYS: THE ROLE OF THE THREE MOLECULAR ORBITAL FOUR-ELECTRON INTERACTION IN THE REACTIONS OF ALKENES.

摘要

The nucleophilic substitution, electrophilic addition, and pericyclic reactions of alkenes have been studied using standard molecular orbital methods as implemented in the Gaussian 80 and 82 series of programs.;The replacement of a halide leaving group by a nucleophile at a vinylic carbon proceeds with retention of configuration in a concerted reaction. The substitution of a leaving group in an allylic substrate by a nucleophile has no inherent stereoelectronic preference for a syn versus anti geometry. The stereochemistry of the ;The transfer of an oxygen atom to an alkene from an epoxidizing agent has no consistant stereoelectronic preference for a planar or spiro orientation at the level of theory utilized here. The relative reactivity of epoxidizing agents is directly related to the stabilization of the leaving heteroatom's lone pair at the transition state by an empty orbital on a neighboring metal atom, or as part of a forming ;An analysis of the molecular orbitals at the transition state of the Diels-Alder reaction could not be performed in substituted cases due to extensive intermingling of all of the ;For each reaction studied, the