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Density functional theory was adopted in this work to reveal the reaction mechanism of CH2SH with HO2. Reaction rate constants were computed from 200 to 2000 K using the transition state theory combined with Wigner and Eckart tunneling correction. Moreover, localized orbital locator, atoms in molecules and Mayer bond order analyses were used to study the essence of chemical bonding evolution. Eleven singlet paths and three triplet ones are located on the potential surface (PES). The results show that the main products on the singlet PES are 1CH2S and H2O2, whereas on the triplet PES they are CH3SH + 3O2, which are coincident with the similar reaction of CH3S and HO2. This conclusion is also supported by rate constant calculation results. Interestingly, all the possible paths are involved in the hydrogen transfer. The results have provided underlying insights to the analogous reactions and further experimental studies. [ABSTRACT FROM AUTHOR]

The mechanism of imine hydrogenation catalyzed by thiolate complexes of Rh(III) bearing a hydrotris(3,5-dimethylpyrazolyl)borato ligand has been investigated via the density functional theory calculations. The overall catalytic cycle for heterolytic cleavage of H2 and hydrogenation of N-benzylidenemethylamine by the model catalyst [TpRh(bdt)MeCN)] is presented in detail. The results show that the reaction proceeds via an ionic mechanism through three steps: formation of dihydrogen complex, protonation of imine and the hydride transfer process. Protonation of imine occurs after the formation of Rh(H)-S(H) moiety. For the whole catalytic cycle, the heterolytic splitting of dihydrogen is the step with the highest free energy barrier. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Theoretical calculation has been carried out for the nucleophilic displacement reaction of 1,2-dichloroethane catalyzed by haloalkane dehalogenase. The results indicate that different hydrogen bond patterns of the oxyanion hole and the halide-stabilizing residues play an important role in the dehalogenation reaction. They cause concertedly an earlier transition state (TS) with the activation barrier of 16.60 kcal/mol. The stabilization effect of Trp125 and Trp175 on chlorine atom in the TS is larger than that of the reactant complex by 15.67 kcal/mol so that, they make contribution to the stabilization of the TS. Moreover, the reaction shows the enzymatic action can be attributed to a combination of reactant-state destabilization and transition-state electrostatic stabilization. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

The disproportionation of superoxide radical anions catalyzed by copper-zinc superoxide dismutase was investigated in detail using density functional theory. The structures of each stationary point and the transition states were located so that the reaction pathways were determined. The results indicate that the reactions proceed by two steps both for the oxidized process of superoxide radical anion and the reduced one. The rate for the determining step of the reaction (2) is in very good agreement with the experimental value. The solvation effect on the reaction was also discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

A detailed study on the reaction mechanism of CH3SH with O2 was carried out using quantum chemical methods. Eleven singlet pathways and four triplet pathways were found based on CCSD(T)//M06‐2x calculations. The nature of chemical bonding evolution was also studied using electron localization function and atoms in molecules analysis. Moreover, reaction rate constants were calculated between 200 and 800 K at the level of the transition state theory by Wigner tunneling correction. The results suggest that the main products should be CH2SO, H2O, CH3OH, SO, CH4, and SO2, respectively, basically coinciding with the experimental results. The corresponding feasible pathways are channels R7, R8, and R9, respectively, with an effective energy barrier of 56.21 kJ/mol. Obviously, given the low energy barrier similar to the main paths mentioned above, the products CH2SH and HO2 should assume a definite proportion in all possible products, although such species were not yet detected in experiment. Sulfur compounds have important influences on the atmospheric environment and living organisms. The mechanism of the reaction of CH3SH with O2 is explored by density functional theory calculations both on the singlet and triplet potential energy surfaces (PESs). This study suggests that the CH3SH + O2 reaction is more favorable for the singlet PES, and the corresponding feasible product species include CH3OH, SO, CH2SO, H2O, CH4, and SO2. [ABSTRACT FROM AUTHOR]

A detailed study on the reaction mechanism of CH3SH with O2 was carried out using quantum chemical methods. Eleven singlet pathways and four triplet pathways were found based on CCSD(T)//M06‐2x calculations. The nature of chemical bonding evolution was also studied using electron localization function and atoms in molecules analysis. Moreover, reaction rate constants were calculated between 200 and 800 K at the level of the transition state theory by Wigner tunneling correction. The results suggest that the main products should be CH2SO, H2O, CH3OH, SO, CH4, and SO2, respectively, basically coinciding with the experimental results. The corresponding feasible pathways are channels R7, R8, and R9, respectively, with an effective energy barrier of 56.21 kJ/mol. Obviously, given the low energy barrier similar to the main paths mentioned above, the products CH2SH and HO2 should assume a definite proportion in all possible products, although such species were not yet detected in experiment. Sulfur compounds have important influences on the atmospheric environment and living organisms. The mechanism of the reaction of CH3SH with O2 is explored by density functional theory calculations both on the singlet and triplet potential energy surfaces (PESs). This study suggests that the CH3SH + O2 reaction is more favorable for the singlet PES, and the corresponding feasible product species include CH3OH, SO, CH2SO, H2O, CH4, and SO2. [ABSTRACT FROM AUTHOR]