Radiation induced dechlorination of 1,1,2-trichloroethane. Reactions of 1,2-dichloroethyl radicals

Abstract

The kinetics of the radiation induced free radical chain reactions in solutions of CHCl₂CH₂Cl in cyclohexane (RH) are studied in the temperature range of 120–250°C. 1,2-dichloroethyl, 1,1,2-trichloroethyl and 1,2,2-trichloroethyl radicals were produced by the reaction of radiolytically generated cyclohexyl (R) radicals with the solute. The reactions studied were: R + CHCl₂CH₂Cl → RCl + CHClCH₂Cl (2), R + CHCl₂CH₂Cl → RH + CCl₂CH₂Cl (3), R + CHCl₂CH₂Cl → RH + CHCl₂CHCl (4), CHClCH₂Cl + RH → CH₂ClCH₂Cl + R (5), CHClCH₂Cl → CHClCH₂+ Cl. (6)

The following rate expressions were obtained: log (k₂/k₃)= 0.752 ± 0.030 –(14 160 ± 250)/θ, log (k₂/k₄)= 0.467 ± 0.037 –(4 060 ± 310)/θ, log [(k₆/k₅)/mol dm^–3]= 5.74 ± 0.29 –(35 280 ± 2 260)/θ, where θ= 2.303 RT in J mol^–1, and the error limits are the standard deviation (1σ) from least mean squares Arrhenius parameters. The Arrhenius parameters for the Cl atom elimination reaction from chloroalkyl radicals derived from liquid and gas phase studies are compared.