Ab initio study of unimolecular pyrolysis mechanisms of dithioformic acid

Calculations at both the SCF and MP2 levels including electron correlation effects on both the geometries and energies of different stationary points encountered along the decomposition pathways for thioformic acids are reported. Four conformers of monothioformic acid and two conformers of dithioformic acids have been investigated using ab initio electronic structure calculations with a series of basis sets. Results show that the keto tautomer of monothioformic acid, HC(:O)SH, is the more stable form with respect to the thioketo tautomer, HC(:S)OH. Furthermore, all of the trans isomers of monothioformic and dithioformic acids are slightly more stable in energy than the corresponding cis isomers, which are in agreement with experimental results. Rice−Ramsperger−Kassel−Marcus (RRKM) calculations of the unimolecular rate constants for pyrolysis of these acids are carried out.

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“…e Experimentally from ref . f By Xie et al from ref at the MP4/6-31G**//HF/6-31G** level. g By So from ref at the MP2/3-21G*//HF/3-21G* level.…”

Section: Resultsmentioning

confidence: 99%

Unimolecular Pyrolysis Mechanisms of Monothioformic and Dithioformic Acids. An ab Initio Study and Evaluation of Rate Constant

et al. 1998

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“…Molecular H 2 dissociates upon adsorption on two neighboring sites, whereas CS 2 and H 2 S adsorb on a single site, steps (1)–(3) in Scheme (the nature of the sites is discussed below). Two subsequent hydrogen additions to adsorbed CS 2 lead to surface HSCS and dithioformic species (CS 2 H* and CS 2 H 2 *, respectively, steps (4)–(5)) 40. 41 The latter decomposes preferentially to H 2 S and a CS fragment40, 41 (step (6)), which hydrogenates until adsorbed methanethiol is formed (steps (7)–(10)).…”

Section: Discussionmentioning

confidence: 99%

Synthesis of Methanethiol from CS₂ on Ni‐, Co‐, and K‐Doped MoS₂/SiO₂ Catalysts

Gutiérrez¹,

Zhong²,

Zhu³

et al. 2013

ChemCatChem

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The synthesis of methanethiol from CS 2 catalyzed by Ni-, Co-, or K-modified MoS 2 /SiO 2 through the sequence CS 2 !CH 3 SH! CH 3 SCH 3 (DMS) has been studied. CS 2 is readily hydrogenated to CH 3 SH, whereas CH 3 SH and DMS decompose to CH 4 at high CS 2 conversions and temperatures. Thus, very high yields of CH 3 SH can be obtained on all the catalysts. The addition of Co or Ni accelerates all reaction steps to allow the formation of CH 3 SH under relatively mild conditions. On the contrary, K suppresses the formation of byproducts but also lowers the activi-ty. The surface reaction proceeds through a series of hydrogen-addition steps, the rate-controlling step of which is the addition of the first H atom. H 2 adsorbs dissociatively, whereas CS 2 adsorbs strongly in a single active site prior to hydrogenation. The addition of Ni has a stronger enhancing effect on hydrogenation and accelerates the CÀS bond cleavage to a smaller extent than Co. Therefore, Ni leads to optimum CH 3 SH yields and holds the best promise as promoter for the MoS 2 phase in the synthesis of methanethiol from CS 2 .

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“…On the other hand, the various styles of molecular dipole moment lead to the diverse rotational spectrum. Thus the geometry structures, total energies, dipole moments, vibrational and rotational spectra of CH2S2 isomers were investigated [9,10,[12][13][14][15][16][17][18][19][20][21][22][23][24] .…”

Section: Introductionmentioning

confidence: 99%

“…In 1979, the optimized geometries, relative energies, and dipole moment components of DTFA were calculated using LCAO-MO-SCF theory [22] . The theoretical calculations of molecular structure parameters of DTFA have been reported [9,10,[13][14][15][16][17][18] . The main methods used by them were SCF, SCF-MO, and CCSD(T); and the main basis sets were 3-21G*, 6-31G*, 6-31G**, and CBS+CV.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic constants and anharmonic force field of dithioformic acid and its isomers: a theoretical study

Pang

Song

Sun

et al. 2021

Preprint

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The potential astronomical interest dithioformic acid (trans-HC(=S)SH) exists five isomers and has received considerable attention of astronomical observation in recent years. The different positions of H atoms of five isomers lead to diverse point groups, dipole moments, and spectroscopic constants. The anharmonic force field and spectroscopic constants of them are calculated using CCSD(T) and B3LYP employing correlation consistent basis sets. Molecular structures, dipole moments, rotational constants, and fundamental frequencies of trans-HC(=S)SH are compared with the available experimental data. The B3LYP/Gen=5 and CCSD(T)/Gen=Q results can reproduce them well. Molecular structures, dipole moments, relative energies, spectroscopic constants of cis-HC(=S)SH and dithiohydroxy carbene (DTHC) are also calculated. The new data obtained in this study are expected to guide the future high resolution experimental work and to assist astronomical search for CH2S2.

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Ab initio study of unimolecular pyrolysis mechanisms of dithioformic acid

Cited by 11 publications

References 13 publications

Unimolecular Pyrolysis Mechanisms of Monothioformic and Dithioformic Acids. An ab Initio Study and Evaluation of Rate Constant

Unimolecular Pyrolysis Mechanisms of Monothioformic and Dithioformic Acids. An ab Initio Study and Evaluation of Rate Constant

Synthesis of Methanethiol from CS₂ on Ni‐, Co‐, and K‐Doped MoS₂/SiO₂ Catalysts

Spectroscopic constants and anharmonic force field of dithioformic acid and its isomers: a theoretical study

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Ab initio study of unimolecular pyrolysis mechanisms of dithioformic acid

Cited by 11 publications

References 13 publications

Unimolecular Pyrolysis Mechanisms of Monothioformic and Dithioformic Acids. An ab Initio Study and Evaluation of Rate Constant

Unimolecular Pyrolysis Mechanisms of Monothioformic and Dithioformic Acids. An ab Initio Study and Evaluation of Rate Constant

Synthesis of Methanethiol from CS2 on Ni‐, Co‐, and K‐Doped MoS2/SiO2 Catalysts

Spectroscopic constants and anharmonic force field of dithioformic acid and its isomers: a theoretical study

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Synthesis of Methanethiol from CS₂ on Ni‐, Co‐, and K‐Doped MoS₂/SiO₂ Catalysts