Experimental and theoretical study of the low-temperature kinetics of the reaction of CN with CH2O and implications for interstellar environments

Niclas A. West; Lok Hin Desmond Li; Tom J. Millar; Marie Van de Sande; Edward Rutter; Mark A. Blitz; Julia H. Lehman; Leen Decin; Dwayne E. Heard

doi:10.1039/d2cp05043a

Experimental and theoretical study of the low-temperature kinetics of the reaction of CN with CH₂O and implications for interstellar environments

Niclas A. West, Lok Hin Desmond Li, Tom J. Millar, Marie Van de Sande, Edward Rutter, Mark A. Blitz, Julia H. Lehman, Leen Decin, Dwayne E. Heard^*

^*Corresponding author for this work

Chemistry

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Abstract

Rate coefficients for the reaction of CN with CH₂O were measured for the first time below room temperature in the range 32-103 K using a pulsed Laval nozzle apparatus together with the Pulsed Laser Photolysis-Laser-Induced Fluorescence technique. The rate coefficients exhibited a strong negative temperature dependence, reaching (4.62 ± 0.84) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ at 32 K, and no pressure dependence was observed at 70 K. The potential energy surface (PES) of the CN + CH₂O reaction was calculated at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory, with the lowest energy channel to reaction characterized by the formation of a weakly-bound van der Waals complex, bound by 13.3 kJ mol⁻¹, prior to two transition states with energies of −0.62 and 3.97 kJ mol⁻¹, leading to the products HCN + HCO or HNC + HCO, respectively. For the formation of formyl cyanide, HCOCN, a large activation barrier of 32.9 kJ mol⁻¹ was calculated. Reaction rate theory calculations were performed with the MESMER (Master Equation Solver for Multi Energy well Reactions) package on this PES to calculate rate coefficients. While this ab initio description provided good agreement with the low-temperature rate coefficients, it was not capable of describing the high-temperature experimental rate coefficients from the literature. However, increasing the energies and imaginary frequencies of both transition states allowed MESMER simulations of the rate coefficients to be in good agreement with data spanning 32-769 K. The mechanism for the reaction is the formation of a weakly-bound complex followed by quantum mechanical tunnelling through the small barrier to form HCN + HCO products. MESMER calculations showed that channel generating HNC is not important. MESMER simulated the rate coefficients from 4-1000 K which were used to recommend best-fit modified Arrhenius expressions for use in astrochemical modelling. The UMIST Rate12 (UDfa) model yielded no significant changes in the abundances of HCN, HNC, and HCO for a variety of environments upon inclusion of rate coefficients reported here. The main implication from this study is that the title reaction is not a primary formation route to the interstellar molecule formyl cyanide, HCOCN, as currently implemented in the KIDA astrochemical model.

Original language	English
Pages (from-to)	7719-7733
Number of pages	15
Journal	Physical Chemistry Chemical Physics
Volume	25
Issue number	11
Early online date	24 Feb 2023
DOIs	https://doi.org/10.1039/d2cp05043a
Publication status	Published - 21 Mar 2023

Bibliographical note

Funding Information:
This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreements no. 646758 and 948525). TJM acknowledges the receipt of a Leverhulme Emeritus Fellowship and is grateful to the STFC for support through grant ST/T000198/1. MVdS acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 882991. We would like to thank the mechanical and electronics workshop in the School of Chemistry at the University of Leeds for support. The ab initio and MESMER work was undertaken on ARC3, part of the High-Performance Computing facilities at the University of Leeds, UK. We would like to thank Professor John Plane for helpful discussions on classical capture theory. The authors would like to thank Dr Tom Speak for valuable input on ab initio and MESMER calculations. The authors would like to thank the two reviewers, whose extensive reports and very constructive suggestions have led to a considerable improvement in the paper.

Publisher Copyright:
© 2023 The Royal Society of Chemistry.

ASJC Scopus subject areas

General Physics and Astronomy
Physical and Theoretical Chemistry

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Cite this

West, N. A., Li, L. H. D., Millar, T. J., Van de Sande, M., Rutter, E., Blitz, M. A., Lehman, J. H., Decin, L., & Heard, D. E. (2023). Experimental and theoretical study of the low-temperature kinetics of the reaction of CN with CH₂O and implications for interstellar environments. Physical Chemistry Chemical Physics, 25(11), 7719-7733. https://doi.org/10.1039/d2cp05043a

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title = "Experimental and theoretical study of the low-temperature kinetics of the reaction of CN with CH2O and implications for interstellar environments",

abstract = "Rate coefficients for the reaction of CN with CH2O were measured for the first time below room temperature in the range 32-103 K using a pulsed Laval nozzle apparatus together with the Pulsed Laser Photolysis-Laser-Induced Fluorescence technique. The rate coefficients exhibited a strong negative temperature dependence, reaching (4.62 ± 0.84) × 10−11 cm3 molecule−1 s−1 at 32 K, and no pressure dependence was observed at 70 K. The potential energy surface (PES) of the CN + CH2O reaction was calculated at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory, with the lowest energy channel to reaction characterized by the formation of a weakly-bound van der Waals complex, bound by 13.3 kJ mol−1, prior to two transition states with energies of −0.62 and 3.97 kJ mol−1, leading to the products HCN + HCO or HNC + HCO, respectively. For the formation of formyl cyanide, HCOCN, a large activation barrier of 32.9 kJ mol−1 was calculated. Reaction rate theory calculations were performed with the MESMER (Master Equation Solver for Multi Energy well Reactions) package on this PES to calculate rate coefficients. While this ab initio description provided good agreement with the low-temperature rate coefficients, it was not capable of describing the high-temperature experimental rate coefficients from the literature. However, increasing the energies and imaginary frequencies of both transition states allowed MESMER simulations of the rate coefficients to be in good agreement with data spanning 32-769 K. The mechanism for the reaction is the formation of a weakly-bound complex followed by quantum mechanical tunnelling through the small barrier to form HCN + HCO products. MESMER calculations showed that channel generating HNC is not important. MESMER simulated the rate coefficients from 4-1000 K which were used to recommend best-fit modified Arrhenius expressions for use in astrochemical modelling. The UMIST Rate12 (UDfa) model yielded no significant changes in the abundances of HCN, HNC, and HCO for a variety of environments upon inclusion of rate coefficients reported here. The main implication from this study is that the title reaction is not a primary formation route to the interstellar molecule formyl cyanide, HCOCN, as currently implemented in the KIDA astrochemical model.",

author = "West, {Niclas A.} and Li, {Lok Hin Desmond} and Millar, {Tom J.} and {Van de Sande}, Marie and Edward Rutter and Blitz, {Mark A.} and Lehman, {Julia H.} and Leen Decin and Heard, {Dwayne E.}",

note = "Funding Information: This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreements no. 646758 and 948525). TJM acknowledges the receipt of a Leverhulme Emeritus Fellowship and is grateful to the STFC for support through grant ST/T000198/1. MVdS acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Sk{\l}odowska-Curie grant agreement no. 882991. We would like to thank the mechanical and electronics workshop in the School of Chemistry at the University of Leeds for support. The ab initio and MESMER work was undertaken on ARC3, part of the High-Performance Computing facilities at the University of Leeds, UK. We would like to thank Professor John Plane for helpful discussions on classical capture theory. The authors would like to thank Dr Tom Speak for valuable input on ab initio and MESMER calculations. The authors would like to thank the two reviewers, whose extensive reports and very constructive suggestions have led to a considerable improvement in the paper. Publisher Copyright: {\textcopyright} 2023 The Royal Society of Chemistry.",

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month = mar,

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doi = "10.1039/d2cp05043a",

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T1 - Experimental and theoretical study of the low-temperature kinetics of the reaction of CN with CH2O and implications for interstellar environments

AU - West, Niclas A.

AU - Li, Lok Hin Desmond

AU - Millar, Tom J.

AU - Van de Sande, Marie

AU - Rutter, Edward

AU - Blitz, Mark A.

AU - Lehman, Julia H.

AU - Decin, Leen

AU - Heard, Dwayne E.

N1 - Funding Information: This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreements no. 646758 and 948525). TJM acknowledges the receipt of a Leverhulme Emeritus Fellowship and is grateful to the STFC for support through grant ST/T000198/1. MVdS acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 882991. We would like to thank the mechanical and electronics workshop in the School of Chemistry at the University of Leeds for support. The ab initio and MESMER work was undertaken on ARC3, part of the High-Performance Computing facilities at the University of Leeds, UK. We would like to thank Professor John Plane for helpful discussions on classical capture theory. The authors would like to thank Dr Tom Speak for valuable input on ab initio and MESMER calculations. The authors would like to thank the two reviewers, whose extensive reports and very constructive suggestions have led to a considerable improvement in the paper. Publisher Copyright: © 2023 The Royal Society of Chemistry.

PY - 2023/3/21

Y1 - 2023/3/21

N2 - Rate coefficients for the reaction of CN with CH2O were measured for the first time below room temperature in the range 32-103 K using a pulsed Laval nozzle apparatus together with the Pulsed Laser Photolysis-Laser-Induced Fluorescence technique. The rate coefficients exhibited a strong negative temperature dependence, reaching (4.62 ± 0.84) × 10−11 cm3 molecule−1 s−1 at 32 K, and no pressure dependence was observed at 70 K. The potential energy surface (PES) of the CN + CH2O reaction was calculated at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory, with the lowest energy channel to reaction characterized by the formation of a weakly-bound van der Waals complex, bound by 13.3 kJ mol−1, prior to two transition states with energies of −0.62 and 3.97 kJ mol−1, leading to the products HCN + HCO or HNC + HCO, respectively. For the formation of formyl cyanide, HCOCN, a large activation barrier of 32.9 kJ mol−1 was calculated. Reaction rate theory calculations were performed with the MESMER (Master Equation Solver for Multi Energy well Reactions) package on this PES to calculate rate coefficients. While this ab initio description provided good agreement with the low-temperature rate coefficients, it was not capable of describing the high-temperature experimental rate coefficients from the literature. However, increasing the energies and imaginary frequencies of both transition states allowed MESMER simulations of the rate coefficients to be in good agreement with data spanning 32-769 K. The mechanism for the reaction is the formation of a weakly-bound complex followed by quantum mechanical tunnelling through the small barrier to form HCN + HCO products. MESMER calculations showed that channel generating HNC is not important. MESMER simulated the rate coefficients from 4-1000 K which were used to recommend best-fit modified Arrhenius expressions for use in astrochemical modelling. The UMIST Rate12 (UDfa) model yielded no significant changes in the abundances of HCN, HNC, and HCO for a variety of environments upon inclusion of rate coefficients reported here. The main implication from this study is that the title reaction is not a primary formation route to the interstellar molecule formyl cyanide, HCOCN, as currently implemented in the KIDA astrochemical model.

AB - Rate coefficients for the reaction of CN with CH2O were measured for the first time below room temperature in the range 32-103 K using a pulsed Laval nozzle apparatus together with the Pulsed Laser Photolysis-Laser-Induced Fluorescence technique. The rate coefficients exhibited a strong negative temperature dependence, reaching (4.62 ± 0.84) × 10−11 cm3 molecule−1 s−1 at 32 K, and no pressure dependence was observed at 70 K. The potential energy surface (PES) of the CN + CH2O reaction was calculated at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory, with the lowest energy channel to reaction characterized by the formation of a weakly-bound van der Waals complex, bound by 13.3 kJ mol−1, prior to two transition states with energies of −0.62 and 3.97 kJ mol−1, leading to the products HCN + HCO or HNC + HCO, respectively. For the formation of formyl cyanide, HCOCN, a large activation barrier of 32.9 kJ mol−1 was calculated. Reaction rate theory calculations were performed with the MESMER (Master Equation Solver for Multi Energy well Reactions) package on this PES to calculate rate coefficients. While this ab initio description provided good agreement with the low-temperature rate coefficients, it was not capable of describing the high-temperature experimental rate coefficients from the literature. However, increasing the energies and imaginary frequencies of both transition states allowed MESMER simulations of the rate coefficients to be in good agreement with data spanning 32-769 K. The mechanism for the reaction is the formation of a weakly-bound complex followed by quantum mechanical tunnelling through the small barrier to form HCN + HCO products. MESMER calculations showed that channel generating HNC is not important. MESMER simulated the rate coefficients from 4-1000 K which were used to recommend best-fit modified Arrhenius expressions for use in astrochemical modelling. The UMIST Rate12 (UDfa) model yielded no significant changes in the abundances of HCN, HNC, and HCO for a variety of environments upon inclusion of rate coefficients reported here. The main implication from this study is that the title reaction is not a primary formation route to the interstellar molecule formyl cyanide, HCOCN, as currently implemented in the KIDA astrochemical model.

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