Reaction Mechanism and Topological Analysis of Electronic Density for the Reaction of HNCS with Cl

The reaction mechanism of HNCS with Cl was investigated at the QCISD (T)/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels of theory. Reaction rate constants were calculated over a temperature range of 200-2500 K using classical transition state theory and canonical variational transition state theory combined with a small-curvature tunneling correction. Results show that there are three reaction channels for the HNCS+Cl reaction. At temperatures lower than 294 K, hydrogen abstraction reaction (a) is the major channel and HCl+NCS are the main products, while addition reaction (c) is the major reaction process and HNC(Cl)S is the dominant product at temperatures higher than 294 K. Reaction channel (b), where Cl atom attacks N atom, is a difficult process because of the higher energy barrier.