An electron spin resonance study of the reactions of hydrogen atoms with halocarbons

Jones, W. E.; Joseph, Lynnette

doi:10.1139/v86-360

Cited by 33 publications

(29 citation statements)

References 21 publications

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“…Also shown in Fig. 3 are the lower T measurements of Lede and Villermaux 46, Jones and Ma 47, and Azatyan and Filippov 48 that do not agree with the present theoretical predictions for k 1 . As discussed by Bryukov et al 44, these measurements all required stoichiometric corrections and were not free from secondary reaction perturbations and this may be the reason for their departure from the present theoretical predictions.…”

Section: Resultscontrasting

confidence: 60%

“…—: theory, present work, H + C 2 H 6 , (300—2000 K); —: theory, present work, D + C 2 H 6 , (300–2000 K); —: three parameter evaluation, present work, Eq. (E2), (385–1228 K); *: Bryukov et al 44, (467–826 K); ˆ: Jones et al 45, (385–544 K); +: Jones and Ma 47, (298 K); □: Lede and Villermaux 46, (281–347 K); Δ—Δ: Azatyan and Filippov 48, (290–579 K); •: present work, C 2 D 5 I/C 2 H 6 mixtures (Table IV), (1128–1228 K). A figure in the inset depicts an expanded version of the Arrhenius plot over the T range 1000–2000 K for clarity.…”

Section: Resultsmentioning

confidence: 99%

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High‐temperature rate constants for H/D + C₂H₆ and C₃H₈

Sivaramakrishnan

Michael

Ruščić

2012

Int J of Chemical Kinetics

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The title reactions have been studied at the CCSD(T)/aug-cc-pv∞z level of theory using saddle point geometries at B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) levels of theory. The reaction endothermicities are in good agreement with current Active Thermochemical Tables values. Theoretical rate constants were estimated using transition state theory. The theoretical rate constants are in good agreement with the present experiments and lower temperature literature data. Over the T range of the present experiments, the theoretically predicted isotope effects are close to unity.

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Section: Resultscontrasting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

High‐temperature rate constants for H/D + C₂H₆ and C₃H₈

Sivaramakrishnan

Michael

Ruščić

2012

Int J of Chemical Kinetics

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“…The CH 4 + H − −→ CH 3 + H 2 abstraction reaction has been thoroughly studied both experimentally and theoretically 42,62,70,71,[132][133][134][135][136][137][138][139][140]142 . A pair of experiments at 298 K place its rate coefficient between 1.7-3.5×10 −17 C2H5 − −→ C2H4 + H…”

Section: Previous Theoretical Datamentioning

confidence: 99%

A Consistent Reduced Network for HCN Chemistry in Early Earth and Titan Atmospheres: Quantum Calculations of Reaction Rate Coefficients

Pearce

Ayers

2019

J. Phys. Chem. A

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HCN is a key ingredient for synthesizing biomolecules such as nucleobases and amino acids. We calculate 42 reaction rate coefficients directly involved with or in competition with the production of HCN in the early Earth or Titan atmospheres. These reactions are driven by methane and nitrogen radicals produced via UV photodissociation or lightning. For every reaction in this network, we calculate rate coefficients at 298 K using canonical variational transition state theory (CVT) paired with computational quantum chemistry simulations at the BHandHLYP/augcc-pVDZ level of theory. We also calculate the temperature dependence of the rate coefficients for the reactions that have barriers from 50-400 K. We present 15 new reaction rate coefficients with no previous known value. 93% of our calculated coefficients are within an order of magnitude of the nearest experimental or recommended values. Above 320 K, the rate coefficient for the new reaction H2CN − −→ HCN + H dominates. Contrary to experiments, we find the HCN reaction pathway, N + CH3 − −→ HCN + H2, to be inefficient, and suggest the experimental rate coefficient actually corresponds to an indirect pathway, through the H2CN intermediate. We present CVT using energies computed with density functional theory as a feasible and accurate method for calculating a large network of rate coefficients of small-molecule reactions. * Corresponding author:pearcbe@mcmaster.ca these sources has errors associated with it, and there are often a range of experimental and theoretical values to choose from for a single reaction. As a result, atmospheric HCN compositions can vary by orders of magnitude from one simulation to the next. Therefore, it is perhaps unsurprising that, as of yet, no simulation has matched the HCN profile of Titan completely.There are also several reactions without past experimental, theoretical, or suggested values that are missing in these networks that may play important roles in HCN formation (e.g. 1 CH 2 + 2 N − −→ H 2 CN and H 2 CN − −→ HCN + H).The focus of this work is to create a theoretical reduced HCN chemical network, where all the rate coefficients are consistently calculated with the same theoretical and computational method. Using this strategy, all reactions can be theoretically validated before being employed in a chemical network, and key reaction pathways with previously unknown rate coefficients can be included. Furthermore, by constructing a model chemistry 19,20 the errors for consistently calculated rate coefficients are expected to be similar, thus employing such a network has a chance to improve accuracy.The limitation of calculating a consistent theoretical network is that one cannot feasibly include a large number of molecular species. For every additional species, there is a potential additional reaction with all the existing species in the network. Therefore in this work, we focus only on the small set of reactions involved in the production of HCN from methane and nitrogen dissociation radicals, as well as the direct competing ...

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“…Direct measurements for some of these reactions have been reported in the literature. [1][2][3][4][5][6][7][8][9][10][11] Table 1 summarizes the available experimental results together with the corresponding references. To our knowledge, there is no experimental kinetic data for the reaction CHFCl 2 + H f products.…”

Section: Introductionmentioning

confidence: 99%

Direct Combined ab Initio/Transition State Theory Study of the Kinetics of the Abstraction Reactions of Halogenated Methanes with Hydrogen Atoms

2004

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Theoretical calculations were carried out on the H-, Cl-, and F-atom abstraction reactions from a series of seven substituted halogenated methanes (CH 3 Cl, CH 2 Cl 2 , CHCl 3 , CCl 4 , CHF 3 , CHF 2 Cl, and CHFCl 2 ) by H atom attacks. Geometry optimizations and vibrational frequency calculations were performed using unrestricted Møller-Plesset second-order perturbation theory (UMP2) with the 6-311++G(d,p) basis set. Single-point energy calculations were performed with the highly correlated ab initio coupled cluster method in the space of single, double and triple (pertubatively) electron excitations CCSD(T) using the 6-311++G(3df,3pd) basis set. Canonical transition-state theory with a simple tunneling correction was used to predict the rate constants as a function of temperature (700-2500 K), and three-parameter Arrhenius expressions were obtained by fitting to the computed rate constants for elementary channels and overall reaction.

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An electron spin resonance study of the reactions of hydrogen atoms with halocarbons

Cited by 33 publications

References 21 publications

High‐temperature rate constants for H/D + C₂H₆ and C₃H₈

High‐temperature rate constants for H/D + C₂H₆ and C₃H₈

A Consistent Reduced Network for HCN Chemistry in Early Earth and Titan Atmospheres: Quantum Calculations of Reaction Rate Coefficients

Direct Combined ab Initio/Transition State Theory Study of the Kinetics of the Abstraction Reactions of Halogenated Methanes with Hydrogen Atoms

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An electron spin resonance study of the reactions of hydrogen atoms with halocarbons

Cited by 33 publications

References 21 publications

High‐temperature rate constants for H/D + C2H6 and C3H8

High‐temperature rate constants for H/D + C2H6 and C3H8

A Consistent Reduced Network for HCN Chemistry in Early Earth and Titan Atmospheres: Quantum Calculations of Reaction Rate Coefficients

Direct Combined ab Initio/Transition State Theory Study of the Kinetics of the Abstraction Reactions of Halogenated Methanes with Hydrogen Atoms

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High‐temperature rate constants for H/D + C₂H₆ and C₃H₈

High‐temperature rate constants for H/D + C₂H₆ and C₃H₈