Chlorine‐photosensitized reactions in the Cl 2 + O 2 + 1,1,1,2‐C 2 H 2 Cl 4 system

The gas‐phase photochlorination (λ = 436 nm) of the 1,1,1,2‐C 2 H 2 Cl 4 has been studied in the absence and the presence of oxygen at temperatures between 360 and 420°K. Activation energies have been estimated for the following reaction steps:\documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {{\rm CCl}_3 {\rm CHCl}^{\rm .} + {\rm Cl}_2 \to {\rm CCl}_3 {\rm CHCl}_{\rm 2} + {\rm Cl}^{\rm .}} & {E_3 = (4.6 \pm 0.4){\rm kcal/mole}} \\ \end{array}$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {{\rm CCl}_3 {\rm CHCl}^{\rm .} \to {\rm CCl}_2 {\rm CHCl} + {\rm Cl}^{\rm .}} & {E_4 = (20.6 \pm 1.4){\rm kcal/mole}} \\ \end{array}$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {{\rm CCl}_3 {\rm CHClO}_{\rm 2} {\rm CHClCCl}_3 \to 2{\rm CCl}_3 {\rm CHClO}^{\rm .}} & {E_{15} = (33.5 \pm 3.0){\rm kcal/mole}} \\ \end{array}$$\end{document}The dissociation energy D (CCl 3 CHClO 2 ) ± (24.8 ± 1.5) kcal/mole has also been estimated from the difference in activation energy of the direct and reverse reactionsThe mechanism is discussed and the rate parameters are compared to those obtained for a series of other chlorinated ethanes.