Conclusive determination of ethynyl radical hydrogen abstraction energetics and kinetics*

Bowman, Michael C.; Burke, Alexandra D.; Turney, Justin M.; Schaefer, Henry F.

doi:10.1080/00268976.2020.1769214

Cited by 10 publications

(9 citation statements)

References 60 publications

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“…As far as the reaction mechanism is concerned, hydrogen abstraction could be competitive with addition/elimination (Bowman et al 2020), but test computations showed that the former reaction channel is at least one order of magnitude slower than the latter one. As a consequence, only the addition/elimination reaction channel is analyzed in detail in the following.…”

Section: Reactivity and Energeticsmentioning

confidence: 99%

“…Based on these premises, we decided to perform a state-of-the-art quantum-chemical (QC) characterization of the stationary points on the doublet reactive C 2 H + CH 2 NH potential energy surface (PES) followed by kinetic computations in the framework of a master equation model rooted in generalized transition state estimates of the elementary reaction rates. From a theoretical point of view, the reactions between the ethynyl radical and several substrates have been recently investigated by state-of-the-art QC approaches (Bowman et al 2020), but addition/elimination reactions with unsaturated substrates have not yet been explored.…”

Section: Introductionmentioning

confidence: 99%

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Methanimine as a key precursor of imines in the interstellar medium: the case of propargylimine

Lupi,

Puzzarini,

Barone

2020

Preprint

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A gas-phase formation route is proposed for the recently detected propargylimine molecule. In analogy to other imines, such as cyanomethanimine, the addition of a reactive radical (C 2 H in the present case) to methanimine (CH 2 NH) leads to reaction channels open also in the harsh conditions of the interstellar medium. Three possible isomers can be formed in the CH 2 NH + C 2 H reaction: Z-and E-propargylimine (Z-,E-PGIM) as well as N-ethynyl-methanimine (N-EMIM). For both PGIM species, the computed global rate coefficient is nearly constant in the 20-300 K temperature range, and of the order of 2-3 × 10 −10 cm 3 molecule −1 s −1 , while that for N-EMIM is about two orders of magnitude smaller. Assuming equal destruction rates for the two isomers, these results imply an abundance ratio for PGIM of [Z]/[E] ∼ 1.5, which is only slightly underestimated with respect to the observational datum.

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Section: Reactivity and Energeticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Methanimine as a key precursor of imines in the interstellar medium: the case of propargylimine

Lupi,

Puzzarini,

Barone

2020

Preprint

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“…A recent study by Bowman et al investigated numerous C 2 H hydrogen abstraction reactions with highly accurate ab initio methods . In the present study, a similar computational approach will be utilized to investigate the C 2 H + HX → C 2 H 2 + X reactions, where HX = HNCO, trans -HONO, cis -HONO, C 2 H 4 , and CH 3 OH.…”

Section: Introductionmentioning

confidence: 99%

“…Large rate constants have been calculated by kinetic studies for the reaction of C 2 H with different saturated hydrocarbons over a broad range of temperatures, implying moderately low barriers for abstraction. ,,− Theoretical results corroborate this claim with moderate to low reported barrier heights for several hydrogen atom donors. , At this time, most experimental and theoretical studies involving ethynyl radical hydrogen abstractions have focused on hydrocarbon hydrogen atom donors. Over the years, numerous studies have been done on these types of reactions with a wide variety of small molecules or radicals. ,,,,− However, little work has been done on larger molecules.…”

Section: Introductionmentioning

confidence: 99%

Ethynyl Radical Hydrogen Abstraction Energetics and Kinetics Utilizing High-Level Theory

Olive,

Heide,

Turney

et al. 2024

ACS Earth Space Chem.

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The ethynyl radical, C 2 H, is found in a variety of different environments ranging from interstellar space and planetary atmospheres to playing an important role in the combustion of various alkynes under fuel-rich conditions. Hydrogen-atom abstraction reactions are common for the ethynyl radical in these contrasting environments. In this study, the C 2 H + HX → C 2 H 2 + X, where HX = HNCO, trans-HONO, cis-HONO, C 2 H 4 , and CH 3 OH, reactions have been investigated at rigorously high levels of theory, including CCSD(T)-F12a/cc-pVTZ-F12. For the stationary points thus located, much higher levels of theory have been used, with basis sets as large as aug-cc-pV5Z and methods up to CCSDT(Q), and core correlation was also included. These molecules were chosen because they can be found in either interstellar or combustion environments. Various additive energy corrections have been included to converge the relative enthalpies of the stationary points to subchemical accuracy (≤0.5 kcal mol −1 ). Barriers predicted here (2.19 kcal mol −1 for the HNCO reaction and 0.47 kcal mol −1 for C 2 H 4 ) are significantly lower than previous predictions. Reliable kinetics were acquired over a wide range of temperatures (50−5000 K), which may be useful for future experimental studies of these reactions.

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“…Meanwhile, the SFX2C theory in its one‐electron variant (the SFX2C‐1e scheme) 124,158 together with its analytic derivative formulation 159–163 and recontracted basis sets 164–167 offer a promising framework for scalar‐relativistic CC calculations (see Refs. 168–174 for recent example applications). Perturbative treatment of spin‐orbit coupling using SFX2C‐1e EOM‐CC wave functions as the zeroth‐order approximation 132,175 has been shown to provide accurate results, even for molecules containing heavy elements because scalar‐relativistic effects on both the unperturbed wave function and the spin‐orbit integrals are accurately taken into account.…”

Section: Introductionmentioning

confidence: 99%

Relativistic coupled‐cluster and equation‐of‐motion coupled‐cluster methods

Liu

Cheng

2021

WIREs Comput Mol Sci

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The development of relativistic coupled‐cluster (CC) and equation‐of‐motion coupled‐cluster (EOM‐CC) methods is reviewed. An emphasis is placed on recent efforts to improve the computational efficiency of CC and EOM‐CC calculations with non‐perturbative treatments of spin‐orbit coupling (SO‐CC and EOM‐CC) by partially recovering spin symmetry in the formulations. Example calculations of electronic ground state as well as valence‐excited and core‐excited states for molecules containing heavy elements are presented to demonstrate the applicability and usefulness of the SO‐CC and EOM‐CC methods. Future directions for the development of the SO‐CC and EOM‐CC methods are also discussed. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods

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Conclusive determination of ethynyl radical hydrogen abstraction energetics and kinetics*

Cited by 10 publications

References 60 publications

Methanimine as a key precursor of imines in the interstellar medium: the case of propargylimine

Methanimine as a key precursor of imines in the interstellar medium: the case of propargylimine

Ethynyl Radical Hydrogen Abstraction Energetics and Kinetics Utilizing High-Level Theory

Relativistic coupled‐cluster and equation‐of‐motion coupled‐cluster methods

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