Effect of Methyl Group Substitution on the Kinetics of Vinyl Radical + O2 Reaction
| Autor: | Satya P. Joshi, Arkke J. Eskola, Timo T. Pekkanen, Raimo S. Timonen |
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| Přispěvatelé: | Department of Chemistry |
| Rok vydání: | 2019 |
| Předmět: |
MECHANISM
010304 chemical physics 116 Chemical sciences Kinetics chemistry.chemical_element 010402 general chemistry 01 natural sciences 7. Clean energy Oxygen Medicinal chemistry OXYGEN CH3CO THERMOCHEMISTRY O-2 0104 chemical sciences Laminar flow reactor BIODIESEL chemistry.chemical_compound chemistry 13. Climate action Torr 0103 physical sciences Thermochemistry Physical and Theoretical Chemistry Methyl group |
| Zdroj: | The Journal of Physical Chemistry A. 123:10514-10519 |
| ISSN: | 1520-5215 1089-5639 |
| Popis: | The kinetics of (CH3)(2)CCH + O-2 (1) and (CH3)(2)CCCH3 + O-2 (2) reactions have been measured as a function of temperature (223-600 K) at low pressures (0.4-2 Torr) using a tubular laminar flow reactor coupled to a photoionization mass spectrometer (PIMS). These reactions are important for accurate modeling of unsaturated hydrocarbon combustion. Photolysis of a brominated precursor by a pulsed excimer laser radiation at 248 nm wavelength along the flow reactor axis was used for the production of radicals. The measured bimolecular rate coefficient of reaction 1 shows a negative temperature dependence over the temperature range 223-384 K and becomes temperature independent at higher temperatures. The bimolecular rate coefficient of reaction 2 exhibits a negative temperature dependence throughout the experimental temperature range. The bimolecular rate coefficients of reactions 1 and 2 are expected to be at the high-pressure limit under the current experimental conditions, and the following values are obtained at 298 K: k(1)(298 K) = (4.5 +/- 0.5) x 10(-12) cm(3) s(-1) and k(2)(298 = (8.9 +/- 1.0) x 10(-12) cm(3) s(-1). The observed products for reactions 1 and 2 were CH3COCH3 and CH3 + CH3COCH3, respectively. Substituting both beta-hydrogens in the vinyl radical (CH2CH) with methyl groups decreases the rate coefficient of the CH2CH + O-2 reaction by about 50%. However, the rate coefficient of the triply substituted (CH3)(2)CCCH3 radical reaction with O-2 is almost identical to the CH2CH + O-2 rate coefficient under the covered temperature range. |
| Databáze: | OpenAIRE |
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