Rate Coefficients and Products of Ethyl and Vinyl Cross-Radical Reactions
Askar Fahr, D C. Tardy
Rate constant and products of vinyl (H2C=CH) and ethyl (C2H5) cross-radical reactions have been determined at ambient temperature and 93 kPa (700 Torr) pressure. Vinyl and ethyl radicals were produced simultaneously through the 193-nm excimer laser photolysis of dilute mixtures of C2H5COC2H3/He. Time-resolved UV absorption spectroscopy and gas chromatographic/ mass spectrometric (GC/MS) product analysis methods were employed for kinetics and product studies. Analysis of the temporal absorptions at 230 nm and 235 nm through kinetic modeling of the reaction system resulted in an over-all rate constant of (9.6 1.3)x10-11 cm3molecule-1s-1 for the C2H5+C2H3 cross-radical reaction. The major reaction products, identified and quantified using GC/MS analysis, consisted of butane, 1-butene, 1,3-butadiene which are formed through the combination reactions: C2H5+C2H5 --> n- butane (1c), C2H3+C2H3 -->1,3-butadiene (2c) and C2H5+C2H3 -->1-butene (3c) and ethane, ethylene and acetylene, products of the disproportionation reactions. Using a comparative method and the yields of the combination products for the reactions (1c), (2c) (3c) and k1C = 2.0 x10-11 cm3 molecule-1s-1, k2C =9.3x10-11 a rate constant value of k3C = (6.5 1)10-11 cm3 molecule-1s-1 for the combination channel of the reaction C2H5+C2H3 has been determined.