Kinetics of the bimolecular initiation process in the thermal reactions of ethylene

The initial rates of formation of the major products in the thermal reactions of ethylene at temperatures in the neighborhood of 750 K have been measured in the presence and absence of the additive butene-1. It has been shown that this ratio of rates is related to the ratio of rate constants for the two initiation processes: The ratio k′₁/k₁ has been measured over the temperature range of 700–773 K and may be expressed as (R = 1.987 cal/mol deg) log k′₁k₁(mol/L) = 2.8 ? 4400/2.3RT. Assuming a value for k′₁ of log k′₁ (s^?1) = 16 ? 71,500/2.3RT, the value of k₁ may be expressed as log k₁(L/mol) = 13.2 ? 67,000/2.3RT. The values for the frequency factor and activation energy for reaction (1) are discussed in relation to the heat of formation of the vinyl radical, and it is concluded that reaction (1) is the main initiation process in the thermal decomposition of ethylene under the present conditions.