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

Author(s)

Cardoso, Daniely V. V. ; Cunha, Leonardo A. ; Spada, Rene F. K. ; Petty, Corey A. ; Ferrao, Luiz F. A. ; Roberto-Neto, Orlando ; Machado, Francisco B. C.

• Document type: Journal article
• Source: Journal of Physical Chemistry A; v. 121, n. 2, p. 419-428, JAN 19 2017.
• Web of Science Citations: 5

Abstract

The reaction system formed by the methanethiol molecule (CH3SH) and a hydrogen atom was studied via three elementary reactions, two hydrogen abstractions and the C-S bond cleavage (CH3SH + H -> CH3S + H-2 (R1); -> CH2SH + H-2 (R2) -> CH3 + H2S (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 improyed with coupled cluster theory with single, double, and connected triple excitations (CCSD(T)) calculations. The sensitivity of coupling the low and high-level methods to calculate the thermochemical and rate constants were analyzed. The thermal rate constants were obtained by means of the improved canonical variational theory (ICVT) and the tunneling corrections were included with the small curvature tunneling (S CT) approach. Our results are in agreement with the previous experimental measurements and the calculated branching ratio for R1:R2:R3 is equal to 0.96:0:0.04, with k(R1) = 9.64 x 10(-13) cm(3) molecule s(-1) at 298 K. (AU)

• FAPESP's process: 14/14470-1 - Exact quantum dynamics of small molecular systems using ScalIT program
• Grantee: Corey Alan Petty
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/25734-0 - MULTI-CONFIGURATIONAL STUDY OF DIAMINES (N2HX, X=1-4) REACTIONS WITH THE HYDROGEN, OXYGEN AND NITROGEN ATOMS
• Grantee: Rene Felipe Keidel Spada
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/24155-6 - Study of electronic states in polycyclic aromatic hydrocarbons and their properties as models of electronic graphene structures
• Grantee: Francisco Bolivar Correto Machado
• Support Opportunities: Regular Research Grants
• FAPESP's process: 12/11857-7 - Study of elementary reactions present in the decomposition mechanisms of sulfur containing organic materials
• Grantee: Daniely Verônica Viana Cardoso
• Support Opportunities: Scholarships in Brazil - Doctorate