Kinetics of the Reaction of Ethyl Radicals with Molecular Oxygen from 294 to 1002 K

Article abstract of DOI:10.1021/j150660a054

The kinetics and mechanism of the reaction of ethyl radicals with molecular oxygen have been studied between 294 and 1002 K.The radicals were produced by the rapid Cl + C2H6 reaction following the pulsed production of chlorinr atoms from the infrared multiple-photon-induced decomposition of CFCl3.Reactant and product concentrations were monitored in real-time experiments using photoionization mass spectrometry.Overall rate constants of the C2H5 + O2 reaction were measured near seven temperatures between 294 and 1002 K.In addition, C2H4 product yields were determined at 302, 593, and 688 K.Special emphasis was given to obtaining the density dependence of the overall rate constant at four temperatures: 296, 467, 640, and 904 K.The results obtained below 500 K are consistent with a reaction mechanism that proceeds primarily by addition to form C2H5O2.The C2H5-C2H5O2 equilibrium was never observed at elevated temperatures, indicating that a second reactive route (that which produces C2H4 + HO2) is of major importance above 600 K.The pressure and temperature dependencies of the measured rate constants, the C2H4 product yields, and the results of prior studies of this reaction are discussed in terms of two mechanisms: one which proceeds by parallel uncoupled routes to C2H5O2 and C2H4 formation and another which proceeds by coupled routes via a common C2H5O2^* intermediate.The experimental findings appear to be more consistent with the coupled-path mechanism.