A spin-coupled investigation of the electrophilic addition of hydrochloricacid to ethylene

The gas-phase reaction of hydrochloric acid and ethylene to give chloroetha ne is investigated in the framework of spin-coupled (SC) theory, with empha sis on the widely accepted bimolecular mechanism. The transition-state stru cture and intrinsic reaction coordinate path are studied in detail. Our res ults indicate that the driving force in the reaction is the electrophilic a ttack of the hydrogen atom in HCl on one of the ethylenic carbons. There is little evidence supporting the occurrence of a four-membered transition st ate; rather, the spin-coupled results suggest that the breaking of the H-Cl bond occurs before the C-Cl bond formation. These findings are supported b y the results from a topological analysis of the total electron density. (C ) 1999 John Wiley & Sons, Inc.