Kinetic studies of the reaction of C₂H₅ with O₂ at 295 K

Abstract

The reaction between CzH5 and 0 2 a t 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 f 0.3) X cm3/s as [He] was increased from 2 X 10I6 to 3.4 X 1017The importance of to (3.6 f 0.9) X (Ib) relative tohas been determined from a knowledge of the initial CzHs concentration together with a measurement of the CzH4 produced in reaction (5). F, the fraction of the C2Hs radicals removed by path (5), was found to decrease from 0.15 to 0.06 as [He] increased from 2 X 10I6 to 3.4 X 1017 The rate coefficient for reaction (5) was found to be independent of [He] and to have a value of (2.1 f 0.5) X cm3/s. The variation in F reflects the fact that k Ib increases as [He] increases. These observations are taken as evidence for a direct mechanism for C2H4 production and a collision-stabilized route for CzH5O2 formation. Calculations indicate that the high-pressure limit for reaction ( l b ) is -4.4 X cm3/s and that in the polluted troposphere the branching ratio for reactions ( l b ) and (5) will be -20.

Kinetics of the reaction of C2H5O2 with NO at 295 K

“…This dependence of k 11 on the reaction length can be considered to result from an increase in the reaction time over that computed from the reaction length and the flow velocity. This could be due to back diffusion of the NO or more probably the time taken to attain uniform distribution of the NO as noted earlier [9,17].…”

Measurements of the kinetics of the OH-initiated oxidation of isoprene: Radical propagation in the OH + isoprene + O2 + NO reaction system

“…Measurements of the C 2 H 4 produced from the reaction indicate that the branching ratio C H ϩ O 2 5 2 for the channel producing HO 2 produced is less than 20% at approximately 1 torr, and decreases as the pressure increases [19,20]. This implies that the branching ratio decreases as the stabilization of the excited RO 2 intermediate increases.…”

“…2 [19,20]. This would lead to an overestimation of the rate constant for the reaction, as radical RO ϩ NO 2 propagation could bypass this reaction (e.g., reactions (5 -7)): O 2 OH ϩ CH ϭ CHC(CH ) ϭ CH 9 9 : HOCH CH(O )C(CH ) ϭ CH * !…”

Kinetics of the reactions of CH3 with O(3P) and O2 at 295 K

“…From this measurement, and procedures described earlier [9], the pressure at any point in the flow tube could be calculated. Calibrated mass flow meters were used to determine the flow of each component gas.…”