The Unimolecular Reactions of CF3CHF2 Studied by Chemical Activation: Assignment of Rate Constants and Threshold Energies to the 1,2-H Atom Transfer, 1,1-HF and 1,2-HF Elimination Reactions, and the Dependence of Threshold Energies on the Number of F-Atom Substituents in the Fluoroethane Molecules
| Autor: | Blanton R. Gillespie, Caleb A Smith, Donald W. Setser, George L. Heard, Bert E. Holmes |
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| Rok vydání: | 2017 |
| Předmět: |
010304 chemical physics
Chemistry Radical 010402 general chemistry Photochemistry 01 natural sciences 0104 chemical sciences chemistry.chemical_compound Elimination reaction Reaction rate constant Pentafluoroethane Excited state 0103 physical sciences Atom Physical chemistry Singlet state Physical and Theoretical Chemistry Carbene |
| Zdroj: | The Journal of Physical Chemistry A. 121:8746-8756 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/acs.jpca.7b06769 |
| Popis: | The recombination of CF3 and CHF2 radicals in a room-temperature bath gas was used to prepare vibrationally excited CF3CHF2* molecules with 101 kcal mol–1 of vibrational energy. The subsequent 1,2-H atom transfer and 1,1-HF and 1,2-HF elimination reactions were observed as a function of bath gas pressure by following the CHF3, CF3(F)C: and C2F4 product concentrations by gas chromatography using a mass spectrometer as the detector. The singlet CF3(F)C: concentration was measured by trapping the carbene with trans-2-butene. The experimental rate constants are 3.6 × 104, 4.7 × 104, and 1.1 × 104 s–1 for the 1,2-H atom transfer and 1,1-HF and 1,2-HF elimination reactions, respectively. These experimental rate constants were matched to statistical RRKM calculated rate constants to assign threshold energies (E0) of 88 ± 2, 88 ± 2, and 87 ± 2 kcal mol–1 to the three reactions. Pentafluoroethane is the only fluoroethane that has a competitive H atom transfer decomposition reaction, and it is the only example with... |
| Databáze: | OpenAIRE |
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