Rate Coefficients and Products of Ethyl and Vinyl Cross-Radical Reactions

Abstract

Rate constants and products for cross-radical reactions of vinyl (C2H3) and ethyl (C2H5) radicals have been determined at T = 298 K and a total pressure (predominately helium) of 93.3 kPa (700 Torr). C2H3 and C2H5 were produced simultaneously through the 193-nm excimer laser photolysis of dilute mixtures of C2H5COC2H3 (EVK)/He. This is the first report of direct rate determination for the C2H5 + C2H5 reaction and using the photolysis of EVK as a precursor for producing a nearly 1:1 ratio of C2H5/C2H3. Time-resolved UV absorption spectroscopy and gas chromatographic/mass spectroscopic (GC/MS) product analysis methods were employed for kinetics and product studies. Major reaction products consisted of n-butane, 1,3-butadiene, and 1-butene which are formed, respectively, through the combination reactions: C2H5 + C2H5 → n-butane (1c), C2H3 + C2H3 → 1,3-butadiene (2c,) and C2H5 + C2H3 → 1-butene (3c). Minor products, ethane, ethylene, and acetylene, result from disproportionation reactions. Analysis of the te...