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

Abstract

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. The thermochemical properties were improved using single point coupled-cluster (CCSD(T)) calculations on the BB1K geometries followed by extrapolation to the complete basis set (CBS) limit. This methodology was previously applied and has given accurate values of thermochemical and kinetics properties when compared to benchmark calculations and experimental data. For each reaction, the thermal rate constants were calculated using the improved canonical variational theory (ICVT) including the zero-curvature (ICVT/ZCT) and small-curvature (ICVT/SCT) tunneling corrections. For comparison, the overall ICVT/SCT reaction rate constant at 300 K obtained with single-point CCSD(T)/CBS calculations for the CH(3)SH+S reaction is approximately 1400 times lower than the isovalent CH(3)SH+O reaction, obtained with CVT/SCT. The reaction path involving the hydrogen abstraction from the thiol group is the most important reactive path in all temperatures.

Theoretical study on the atmospheric reaction of CH3SH with O2

“…As a kind of highly reactive sulfur compound, CH 3 SH (methanethiol or methyl mercaptan) has been drawing long‐term attention because of its critical role in the atmospheric sulfur cycle . Significant amount of recent studies have focused on the reactions of CH 3 SH with series of species, such as H, O( 3 P), S( 3 P), OH, NO x (x = 1, 2, 3), X(X = F, Cl, Br), CN, XO(X = Br, I), O 3 , HOCl, CH 3 SLi, H 2 O 2 , HOO, and so on.…”

Thermochemical and Kinetics of CH3SH + H Reactions: The Sensitivity of Coupling the Low and High-Level Methodologies

“…The methanethiol (CH 3 SH) molecule is a potential candidate as an atmospheric pollutant due to its release into the biosphere through both natural and anthropogenic actions. 3,4 Our research group has previously studied its reaction with oxygen 5 and sulfur 6 atoms, while this work focuses on reaction with a hydrogen atom.…”

“…In previous works, we have employed the dual-level methodology to calculate accurately the properties of several chemical reactions. ,,− In this work, with the experience gained from previous research, a rigorous analysis was carried out regarding the coupling of the low and high-level methods, in particular when calculating the thermochemical properties, and subsequent rate constant calculations. We have analyzed in which conditions this coupling can generate artificial tunneling and variational effects in the calculated rate constants.…”

“…In recent years, studies have shown that sulfur organic compounds significantly contribute to climate change by exacerbating acid rain and the greenhouse effect. , Knowledge of how the elementary reactions occur can help to reduce these effects. The methanethiol (CH 3 SH) molecule is a potential candidate as an atmospheric pollutant due to its release into the biosphere through both natural and anthropogenic actions. , Our research group has previously studied its reaction with oxygen and sulfur atoms, while this work focuses on reaction with a hydrogen atom.…”

A reaction kinetics study and model development to predict the formation and destruction of organosulfur species (carbonyl sulfide and mercaptans) in Claus furnace

“…Theoretical calculations have also been conducted on the reactions of COS with H, OH, and O radicals and on the reactions of mercaptans with H, OH, O, and S . Saheb et al .…”