Kinetics of the reaction: 2C2H4→ C2H5+ C2H3· heat of formation of the vinyl radical

The initial rates of formation of the major products in the thermal reactions of ethylene at temperatures in the neighborhood of 800 K have been measured in the presence and absence of the additives neopentane and ethane. It has been shown that in the absence of the additive the main initiation process is (1) while in the presence of neopentane and ethane the following additional initiation processes occur: (2) From the ratios of the rates of formation of the major products in the presence and absence of the additive the ratios kN/k1 and kE/k1 were measured over the temperature range of 750–820 K. Taking values from the literature for kN and kE, the following value was obtained for k1: Previous results using butene-1 as additive were rexamined and shown to be consistent with this measurement. From this measurement the following values were derived: ΔHf(C2H3) = 63.4 ± 2 kcal/mol and D(C2H3H) = 103 kcal/mol.