Theoretical mechanistic study on the ion-molecule reaction of CHCl- with CS2

A detailed theoretical study for the poorly understood ion-molecule reaction of CHCl(-) with CS(2) is explored at the B3LYP/6-311++G(d,p) and CCSD(T)/6-311++G(3df,2p) (single-point) levels. Various possible reaction pathways are considered. On the doublet potential energy surface, five dissociation products are both thermodynamically and kinetically possible. Among these products, P(7) (SCHCl(-) + CS) may be the most favorable product with predominant abundances, whereas P(1) (Cl(-) + SCHCS) and P(2) (Cl(-) + HCCSS) may be the second and third feasible products followed by the almost negligible P(3) (Cl(-) + HSCCS), P(4) (CClS(-) + HCS), and P(6) (S-cCCS(-) + HCl). Because the isomers and transition states involved in the most feasible pathways all lie below the reactant, the title reaction is expected to be fast, which is consistent with the measured large rate constant in recent experiment. The present paper may provide a useful guide for understanding other analogous ion-molecule reactions such as CHF(-) and CHBr(-) with CS(2), COS, and CO(2).