Thermochemical and Kinetics of CHSH + H Reactions: The Sensitivity of Coupling the Low and High-Level Methodologies.

The reaction system formed by the methanethiol molecule (CHSH) and a hydrogen atom was studied via three elementary reactions, two hydrogen abstractions and the C-S bond cleavage (CHSH + H → CHS + H (R1); → CHSH + H (R2); → CH + HS (R3)). The stable structures were optimized with various methodologies of the density functional theory and the MP2 method. Two minimum energy paths for each elementary reaction were built using the BB1K and MP2 methodologies, and the electronic properties on the reactants, products, and saddle points were improved with coupled cluster theory with single, double, and connected triple excitations (CCSD(T)) calculations.