Pressure dependent low temperature kinetics for CN + CH3CN: competition between chemical reaction and van der Waals complex formation
| Autor: | Chantal Sleiman, André Canosa, Gisèle El Dib, Sergio González, Stephen J. Klippenstein, Dahbia Talbi |
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| Přispěvatelé: | Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Universidad de Castilla-La Mancha (UCLM), Chemical Sciences and Engineering Division [Argonne], Argonne National Laboratory [Lemont] (ANL), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), PhD fellowship, Conseil Régional de Bretagne, Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Universidad de Castilla-La Mancha = University of Castilla-La Mancha (UCLM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2) |
| Rok vydání: | 2016 |
| Předmět: |
Work (thermodynamics)
Interstellar cloud Ab initio General Physics and Astronomy Thermodynamics 010402 general chemistry 7. Clean energy 01 natural sciences Chemical reaction symbols.namesake Transition state theory 0103 physical sciences Physical and Theoretical Chemistry 010303 astronomy & astrophysics [PHYS]Physics [physics] Chemistry Anharmonicity CRESU 0104 chemical sciences Theorem of corresponding states [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry 13. Climate action symbols Physical chemistry van der Waals force Molecular physics |
| Zdroj: | Physical Chemistry Chemical Physics Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2016, PCCP, 18 (22), pp.15118-15132. ⟨10.1039/C6CP01982J⟩ Physical Chemistry Chemical Physics, 2016, PCCP, 18 (22), pp.15118-15132. ⟨10.1039/C6CP01982J⟩ |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/c6cp01982j |
| Popis: | International audience; The gas phase reaction between the CN radical and acetonitrile CH3CN was investigated experimentally, at low temperatures, with the CRESU apparatus and a slow flow reactor to explore the temperature dependence of its rate coefficient from 354 K down to 23 K. Whereas a standard Arrhenius behavior was found at T > 200 K, indicating the presence of an activation barrier, a dramatic increase in the rate coefficient by a factor of 130 was observed when the temperature was decreased from 168 to 123 K. The reaction was found to be pressure independent at 297 K unlike the experiments carried out at 52 and 132 K. The work was complemented by ab initio transition state theory based master equation calculations using reaction pathways investigated with highly accurate thermochemical protocols. The role of collisional stabilization of a CN⋯CH3CN van der Waals complex and of tunneling induced H atom abstractions were also considered. The experimental pressure dependence at 52 and 132 K is well reproduced by the theoretical calculations provided that an anharmonic state density is considered for the van der Waals complex CH3CN⋯CN and its Lennard-Jones radius is adjusted. Furthermore, these calculations indicate that the experimental observations correspond to the fall-off regime and that tunneling remains small in the low-pressure regime. Hence, the studied reaction is essentially an association process at very low temperature. Implications for the chemistry of interstellar clouds and Titan are discussed. |
| Databáze: | OpenAIRE |
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