Direct determination of the equilibrium constant and thermodynamic parameters in the reaction of pentadienyl radicals with O2 |
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| Institution: | 1. Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. CAS Center for Excellence in Regional Atmospheric Environment (CERAE), Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China;4. State Key Laboratory of NBC Protection for Civilian, Beijing 102205, China;1. College of Resources and Environment, Shaanxi University of Science and Technology, Xi’an, Shaanxi Province 710021, PR China;2. Shaanxi Research Institute of Agricultural Products Processing Technology, Xi’an, Shaanxi Province 710021, China;3. College of Foreign Languages and Communications, Shaanxi University of Science and Technology, Xi’an, Shaanxi Province 710021, PR China;1. Department of Physical Chemistry, Saarland University, 66123 Saarbrücken, Germany;2. Korean Institute of Science and Technology, Campus E 7.1, 66123 Saarbrücken, Germany;3. Department of Informatics and Microsystem Technology, University of Applied Sciences Kaiserslautern, 66482 Zweibrücken, Germany |
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| Abstract: | Reaction of pentadienyl radicals (C5H7) with O2 has been studied by a combination of pulsed laser photolysis and photoionization mass spectrometry. These radicals could be generated either by the photolysis of 1,3-pentadiene or by the two-step reaction of carbon tetrachloride photolysis followed by the H-atom abstraction reaction of Cl atom with 1,4-pentadiene. The equilibrium between pentadienyl radicals, O2 and pentadienylperoxy radicals could be observed over the range 268–308 K. An analysis of the temporal signal of pentadienyl radicals was used to evaluate the equilibrium constant. Third-law analysis was used to evaluate the enthalpy change for the reaction C5H7 + O2 ⇌ C5H7O2. The observed C O bond energy in the C5H7O2 adduct was found to be 56.0 ± 2.2 kJ·mol–1, which is lower than the values of peroxy radicals formed with allyl and cyclohexenyl radicals which have an allylic resonance structure. |
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