Chlorine-catalysed pyrolysis of 1,2-dichloroethane. Part 2.—Unimolecular decomposition of the 1,2-dichloroethyl radical and its reverse reaction

Abstract

Fall-off curves for the unimolecular rate constant k₂ of the reaction Ċ₂H₃Cl₂ [graphic omitted] C₂H₃Cl +Ċl have been calculated by the Forst and RRKM methods and compared with the experimental results reported in Part 1 and by Huybrechts et al. The Forst calculations can be fitted to the Part 1 results, but then predict k^(∞)₂ values that lie below the experimental results of Huybrechts et al. which refer to lower temperatures and higher pressures. In contrast RRKM calculations using higher Arrhenius parameters give fall-off curves that are compatible with all available experimental data. The preferred RRKM models without allowance for the centrifugal effect have E^(∞)₂≈ 19.6 kcal mol^–1(82 kJ mol^–1) and A^(∞)₂≈ 10^14.0 s^–1. When a reasonable centrifugal effect is allowed for the early transition state (I⁺/I≈ 2) the preferred models have E₂≈ 20.0 kcal mol^–1(84 kJ mol^–1) and A^(∞)₂≈ 10^14.3 s^–1. Our experimental evaluations of k^(p)_–2 are used in conjunction with earlier experimental results and RRKM-based calculations for the reverse reaction Ċl + C₂H₃Cl [graphic omitted] Ċ₂H₃Cl₂ to evaluate A^(∞)_–2 and E^(∞)_–2.