Stereochemistry and orientation in alkene formation from gaseous halonium ions

A lecture. The nature and the isomeric distribution of neutral alkenes obtained from the gas-phase attack of CnH5+ (n = 1, 2) ions on stereoisomeric 2,3-dihalobutanes, in the presence of variable concns. of an added base (NMe3), provide the first direct information about the stereochem. and orientation of protonation-induced bimol. elimination reactions in the gas phase. A predominant trans-anti or anti-clinal stereochem. is invariably obsd. in these systems, whose extent depends significantly upon the configuration of the starting substrate, the nature of the halogen substituents, and the concn. of the added base.