The Competitive dehydrohalogenation of 1,1,1‐trifluoro‐2‐chloroethane in reflected shock waves

The thermal decomposition of 1,1,1‐trifluoro‐2‐chloroethane has been investigated in the single‐pulse shock tube between 1120° and 1300deg;K at total reflected shock pressures from ∼2610 to 3350 torr. Under these conditions, the major reaction is the α,α‐elimination of hydrogen chloride,\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CF}_{\rm 3} {\rm CH}_{\rm 2} {\rm Cl}\mathop {{\rm \rightarrow}}\limits^{k_1 } {\rm CF}_{\rm 2} {\rm CHF} + {\rm HCl}$$\end{document} with\documentclass{article}\pagestyle{empty}\begin{document}$${\rm log(}k_1^\infty {\rm, sec}^{ - {\rm 1}} {\rm) = 13}{\rm .3} \pm {\rm 0}{\rm .4} - (65.5 \pm 2.2{\rm kcal})/2.303RT$$\end{document} The decomposition also involves the slower α,β‐elimination of hydrogen fluoride,\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CF}_{\rm 3} {\rm CH}_{\rm 2} {\rm Cl}\mathop {{\rm \rightarrow}}\limits^{k_2 } {\rm CF}_{\rm 2} {\rm CHCl} + {\rm HF}$$\end{document} with the first‐order rate constant given by\documentclass{article}\pagestyle{empty}\begin{document}$${\rm log(}k_2^\infty {\rm, sec}^{ - {\rm 1}} {\rm) = 12}{\rm .7} \pm {\rm 0}{\rm .5} - (67.6 \pm 2.7{\rm kcal})/2.303RT$$\end{document} At temperatures above 1270°K, two additional minor products were observed. These were identified as CF 2 CFCl and CF 3 CHCl 2 and suggest CCl rupture as a third reaction channel leading to complicated kinetics.