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Molecular Physics
An International Journal at the Interface Between Chemistry and Physics
Volume 118, 2020 - Issue 19-20: Special Issue of Molecular Physics in Honour of Jürgen Gauss
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Research Articles

Conclusive determination of ethynyl radical hydrogen abstraction energetics and kinetics*

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Article: e1769214 | Received 31 Mar 2020, Accepted 11 May 2020, Published online: 24 Jun 2020
 

Abstract

The ethynyl radical (C2H) is ubiquitous, appearing in a variety of environments from interstellar space to oxy-acetylene flames. Under these diverse conditions, ethynyl has a high affinity to abstract hydrogen atoms from nearby molecules. In this study, C2H+HXC2H2+X, X=CH3, NH2, OH, F, PH2, SH, Cl, C2H, CN, and NC reactions have been examined at a rigorously high level of theory. Various additive corrections have been appended to the coupled-cluster framework to converge the relative enthalpy of stationary points on the C2H + HX surfaces to subchemical accuracy (≤0.5 kcal mol1). The barriers for the abstraction of a hydrogen from NH3, PH3, and H2S are submerged below the relative enthalpy of their reactant asymptotes by 2.75, 2.48, and 1.39 kcal mol1, respectively. Abstractions from H2, CH4, H2O, and HCl are predicted to have moderate barriers to the abstraction of 2.64, 0.77, 3.82, and 2.19 kcal mol1, respectively, suggesting these reactions will be significant to various systems at moderate to high temperatures. Accurate kinetics were obtained for the C2H+H2, CH4, NH3, and H2O reactions over a wide range of temperatures with excellent agreement to present experimental rate constants.

GRAPHICAL ABSTRACT

Acknowledgments

The authors are grateful for helpful comments and suggestions by Dr. Sarah N. Elliot.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors acknowledge support from the US Department of Energy (DOE), Office of Basic Energy Sciences (BES) under Grant No. DE-SC0018412.

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