The reaction between C₂H₅ and O₂ at 295 K has been studied with a flow reactor sampled by a mass spectrometer. With helium as the carrier gas the rate coefficient was found to increase from (1.2 ± 0.3) × 10⁻¹² to (3.6 ± 0.9) × 10⁻¹² cm³/s as [He] was increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm⁻³. The importance of equation image has been determined from a knowledge of the initial C₂H₅ concentration together with a measurement of the C₂H₄ produced in reaction (5). F, the fraction of the C₂H₅ radicals removed by path (5), was found to decrease from 0.15 to 0.06 as [He] increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm⁻³. The rate coefficient for reaction (5) was found to be independent of [He] and to have a value of (2.1 ± 0.5) × 10⁻¹³ cm³/s. The variation in F reflects the fact that k_1b increases as [He] increases. These observations are taken as evidence for a direct mechanism for C₂H₄ production and a collision‐stabilized route for C₂H₅O₂ formation. Calculations indicate that the high‐pressure limit for reaction (1b) is ∼4.4 × 10⁻¹² cm³/s and that in the polluted troposphere the branching ratio for reactions (1b) and (5) will be ∼l20.

Publications with shared reference:

0 publications found