KINETICS OF ADDITION OF ETHYL, ISOPROPYL, N-BUTYL, AND ISOPENTYL RADICALS TO ETHYLENE

Kinetic parameters for the addition of ethyl, isopropyl, n-butyl, and isopentyl radicals to ethylene have been determined. Azoethane and azoisopropane were irradiated in the presence of ethylene in the temperature range 68-140°. Products were identified and measured quantitatively by a detailed gas chromatographic analysis. The products were interpreted as arising from the addition of ethyl and isopropyl radicals to ethylene. Products resulting from the addition to ethylene of the n-butyl and isopentyl radicals produced in these systems were also identified. The rate constants found here are compared with previous results. An activated complex is proposed which fits the observed A factors for the addition of ethyl radical to ethylene and its reverse reaction, the decomposition of n-butyl radical. Published rate parameters for the decomposition of n-butyl radical are combined with the present results to estimate thermodynamic properties for the n-butyl radical: ΔHf° ≅ 16.8 kcal/mol; S° ≅ 79.1 eu (standard state, 1 atm); D(n-C4H9-H) ≅ 99.1 kcal/mol.