Chlorination Chemistry. 3. Ab Initio Study of the Reaction of Chlorine Atom with Allene

Abstract

Highly correlated ab initio molecular orbital calculations have been used to map out the potential energy surface of the Cl + allene reaction in the gas phase. Eight transition state structures governing the mechanism of the title reaction were computed at seven different levels of theory. The results show that UMP2 calculations are adversely affected by contamination from higher spin states. QCISD(T) calculations illustrate the importance of correlation including triple electron excitations in the quadratic configuration wave function for obtaining an accurate description of the potential energy surface. Results computed at the QCISD(T)/6-31+G(d,p)// QCISD/6-31+G(d,p) level indicate that chlorine atom addition at the center and end carbons of allene are barrierless processes and that the chemically activated C 3H4Cl complex may isomerize through chlorine atom transfer but not through hydrogen atom transfer. The metathesis transition state corresponding to hydrogen