Mechanism and rate of the reaction CH3+ O—revisited
| Autor: | M. Hold, Karlheinz Hoyermann, Jens Wehmeyer, Thomas Zeuch, W. Hack |
|---|---|
| Rok vydání: | 2005 |
| Předmět: |
010304 chemical physics
Chemistry Radical Analytical chemistry General Physics and Astronomy 010402 general chemistry Mass spectrometry 7. Clean energy 01 natural sciences 0104 chemical sciences Reaction rate Deuterium Ionization 0103 physical sciences Kinetic isotope effect Flash photolysis Physical and Theoretical Chemistry Electron ionization |
| Zdroj: | Phys. Chem. Chem. Phys.. 7:1977-1984 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/b419137d |
| Popis: | The primary products and the rate of the reaction of methyl radicals with oxygen atoms in the gas phase at room temperature have been studied using three different experimental arrangements: (A) laser flash photolysis to produce CH3 and O from the precursors CH3I and SO2 (the educts and the products were detected by quantitative FTIR spectroscopy); (B) the coupling of a conventional discharge flow reactor via a molecular sampling system to a mass spectrometer with electron impact ionization, which allowed the determination of labile and stable species; (C) laser induced multiphoton ionization combined with a TOF mass spectrometer–molecular beam sampling–flow reactor, which was used for the specific and sensitive detection of the CH3, CD3, C2H5 and C2D5 radicals and the determination of rate coefficients. The branching ratio of the reaction channels was determined by the experimental arrangements (A) and (B) leading to CH3 + O → HCHO + H (55 ± 5)% → CO + H2 + H (45 ± 5)%. The rate coefficients of the normal and deuterated methyl and ethyl radicals with atomic oxygen showed no isotope effect: k(CD3 + O)/k(CH3 + O) = 0.99 ± 0.12, k(C2D5 + O)/k(C2H5 + O) = 1.01 ± 0.07 (statistical error, 95% confidence level). The absolute rate coefficient of the reaction CH3 + O was derived with reference to the reaction C2H5 + O (k = 1.04 × 1014 cm3 mol−1 s−1) leading to k(CH3 + O) = (7.6 ± 1.4) × 1013 cm3 mol−1 s−1. |
| Databáze: | OpenAIRE |
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