Direct Observation of Equilibration in the System H + C2H4 C2H5: Standard Enthalpy of Formation of the Ethyl Radical

Article abstract of DOI:10.1021/j100106a011

The approach to equilibrium in the reaction H + C2H4 <*> C2H5 has been studied at 800 K in He.Exciplex laser flash photolysis at 193.3 nm of ethene-helium mixtures was used to generate H atoms, which were detected by time-resolved resonance fluorescence.Rate coefficients k_a and k_d for the forward and reverse reactions were deduced from measurements of the equilibrium constant and relaxation rate coefficient at nine pressures in the range 97 p, were combined with the entropy of reaction (calculated from literature data), ΔH⁰_f,298(H), and ΔH_0f,298(C2H4) to give a value of ΔH⁰_f,298(C2H5) = 120.2 +/- 0.9 kJ mol^-1.The Troe factorization technique was applied to values of k_a from this work and the literature to find Troe parameters for the forward reaction over the range 285 a returned agreed to better than 1percent.