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.

Thermochemical and kinetics studies of the CH3SH+S (3P) hydrogen abstraction and insertion reactions.

Sulfur-containing molecules have a significant impact on atmosphere and biosphere. In this work we studied, from the point of view of electronic structure and chemical kinetics methods, the elementary reactions between a methanethiol molecule and a sulfur atom leading to hydrogen abstraction C-S bond cleavage (CH(3)SH+S; R1:→ CH(3)S+SH; R2: → CH(2)SH+SH; R3:→ CH(3)+HS(2)). The geometrical structures of the reactants, products, and saddle points for the three reaction paths were optimized using the BB1K method with the aug-cc-pV(T+d)Z basis set.