Kinetics and thermochemistry of the addition of atomic chlorine to acetylene

Gao, Yide; Alecu, I. M.; Hsieh, P.-C.; McLeod, A.; McLeod, Chris; Jones, M.; Marshall, Paul

doi:10.1016/j.proci.2006.07.103

Cited by 4 publications

(12 citation statements)

References 29 publications

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“…S4. The stationary points are consistent with previous theoretically studies (36,37). To validate the DFM, we first optimized each stationary geometry using a given DFM; then we did single-point calculation with W3X-L for each DFM-optimized geometry.…”

Section: Resultssupporting

confidence: 73%

“…This compares well to the harmonic frequency of 677 cm -1 on our fitted bend. We may compare this aspect of our calculations to the work of Gao et al (36), who also computed the anharmonic vibrational levels of the C≡C-H bending for thermochemistry calculations; the C≡C-H bending frequency of the trans β-chlorovinyl in their study was 364 cm -1 as compared to 694 cm -1 here. Consequently we obtained quite different energy levels than Gao et al…”

Section: Resultsmentioning

confidence: 69%

“…where we carry out calculations for the condition where the pressure is high enough that the kinetics is in the pressureindependent second-order regime. The temperature and pressure dependence of reaction 1 have been studied both experimentally (28)(29)(30)(31)(32)(33)(34)(35)(36) and theoretically (36,37). Experimental measurements of association rate constants generally do not go to high enough pressure to measure the high-pressure equilibrium limit directly, and this limit is obtained by theory-guided extrapolation.…”

mentioning

confidence: 99%

“…1). This reaction is barrierless (36,42) and serves as a prototype for barrierless addition of a doublet radical to a π-bond of an alkene or alkyne. Some previous closely related applications of VTST are studies of the addition reaction of OH to ethylene (39), the abstraction reaction of CN with ethane (40), the reactions of oxygen atoms with alkenes (41), and the addition of singlet methylene to acetylene (43).…”

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confidence: 99%

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Association of Cl with C ₂ H ₂ by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Zhang

Truhlar

Sun

2020

Proc. Natl. Acad. Sci. U.S.A.

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Barrierless unimolecular association reactions are prominent in atmospheric and combustion mechanisms but are challenging for both experiment and kinetics theory. A key datum for understanding the pressure dependence of association and dissociation reactions is the high-pressure limit, but this is often available experimentally only by extrapolation. Here we calculate the high-pressure limit for the addition of a chlorine atom to acetylene molecule (Cl + C2H2→C2H2Cl). This reaction has outer and inner transition states in series; the outer transition state is barrierless, and it is necessary to use different theoretical frameworks to treat the two kinds of transition state. Here we study the reaction in the high-pressure limit using multifaceted variable-reaction-coordinate variational transition-state theory (VRC-VTST) at the outer transition state and reaction-path variational transition state theory (RP-VTST) at the inner turning point; then we combine the results with the canonical unified statistical (CUS) theory. The calculations are based on a density functional validated against the W3X-L method, which is based on coupled cluster theory with single, double, and triple excitations and a quasiperturbative treatment of connected quadruple excitations [CCSDT(Q)], and the computed rate constants are in good agreement with some of the experimental results. The chlorovinyl (C2H2Cl) adduct has two isomers that are equilibrium structures of a double-well C≡C–H bending potential. Two procedures are used to calculate the vibrational partition function of chlorovinyl; one treats the two isomers separately and the other solves the anharmonic energy levels of the double well. We use these results to calculate the standard-state free energy and equilibrium constant of the reaction.

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Section: Resultssupporting

confidence: 73%

Section: Resultsmentioning

confidence: 69%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Association of Cl with C ₂ H ₂ by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Zhang

Truhlar

Sun

2020

Proc. Natl. Acad. Sci. U.S.A.

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“…Having identified HSCS as the likely major product, the issue now is to deduce its entropy. A straightforward rigid rotor-harmonic oscillator treatment would miss any anharmonic effects such as those important in the entropy of chlorovinyl radicals [28] . The two HSCS isomers interconvert most easily via SCS bending.…”

Section: Computational Analysismentioning

confidence: 99%

Experimental and computational studies of the kinetics of the reaction of hydrogen atoms with carbon disulfide

Kerr

Gao

Marshall

2019

Proceedings of the Combustion Institute

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Pulsed laser photolysis at 193 nm of NH 3 /CS 2 mixtures in an Ar bath gas combined with resonance fluorescence detection of atomic H yielded the rate constant for H + CS 2 over 295-490 K. The reaction was found to be pressure dependent and in the fall-off region or near the low pressure limit. Fitting to the Troe formalism yielded k 0 = 7.5 × 10 −24 (T /300 K) −14.76 exp(−5180 K/ T) cm 6 molecule −2 s −1 over 295-490 K. At 490 K equilibration of adduct formation was observed which yielded a H-SCS bond dissociation enthalpy of 73 ± 10 kJ mol −1. These observations are consistent with W1 results for the potential energy surface and comparison suggests HSCS is the major addition product. Transition state theory yields an estimate for the high-pressure limit of addition over 290-300 K of 1.3 × 10 −9 exp(−7.2 kJ mol −1 /RT) cm 3 molecule −1 s −1. Uncertainties are discussed in the text.

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A theoretical kinetic model of the temperature and pH dependent dimerization of orthosilicic acid in aqueous solution

McIntosh

2012

Phys. Chem. Chem. Phys.

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The first steps in a pH- and temperature-dependent theoretical kinetic model of silicate polymerization and dissolution are examined in this work with a combined ab initio and transition state theory based study of the dimerization of H(4)SiO(4). The role of solvation has been of primary concern in this work, and its influence on theoretical activation energies and pre-exponential factors has been thoroughly benchmarked. Relatively inexpensive MP2/6-31+G(d)//HF/6-31+G(d) calculations of octahydrate clusters, with conductor-like polarizable continuum model corrections obtained in the MP2-level single-point calculations, have been shown to lead to a good description of the limited experimentally determined energetics of dimerization for most elementary reactions. Pre-exponential factors computed from this level of theory are found to be relatively insensitive to the level of theory utilized for geometry optimizations, the number of explicit waters, hindered rotor corrections, and variational effects arising from the minimization of rate constants. Within this framework, a kinetic model of the chemistry of H(4)SiO(4) and H(3)SiO(4)(-), forming H(6)Si(2)O(7) and H(5)Si(2)O(7)(-), has been compiled. Numerical simulations over pH = 3-12 show that a number of pH- and temperature dependent trends in reaction rates and positions of equilibrium are well described with this simple dimerization model. More specifically to the dimerization process, we obtain dimerization constants, log K(dim), of 1.85 and -7.15 for the formation of H(6)Si(2)O(7) and H(5)Si(2)O(7)(-) respectively, which compare well with experimentally determined values of 1.2 and -8.5, respectively.

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Kinetics and thermochemistry of the addition of atomic chlorine to acetylene

Cited by 4 publications

References 29 publications

Association of Cl with C ₂ H ₂ by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Association of Cl with C ₂ H ₂ by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Experimental and computational studies of the kinetics of the reaction of hydrogen atoms with carbon disulfide

A theoretical kinetic model of the temperature and pH dependent dimerization of orthosilicic acid in aqueous solution

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Kinetics and thermochemistry of the addition of atomic chlorine to acetylene

Cited by 4 publications

References 29 publications

Association of Cl with C 2 H 2 by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Association of Cl with C 2 H 2 by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Experimental and computational studies of the kinetics of the reaction of hydrogen atoms with carbon disulfide

A theoretical kinetic model of the temperature and pH dependent dimerization of orthosilicic acid in aqueous solution

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Product

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Association of Cl with C ₂ H ₂ by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Association of Cl with C ₂ H ₂ by unified variable-reaction-coordinate and reaction-path variational transition-state theory