The kinetics of the thermal bromination of CF 3 I. Determination of the bond dissociation energy D (CF 3 −I)

The kinetics of the thermal bromination reaction\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Br + CF}_{\rm 3} {\rm I} \to {\rm IBr + CF}_{\rm 3} {\rm Br} $$\end{document}have been studied in the range of 173–321°C. For the stepwe obtain\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\,k_{11} \,({\rm cm}^{\rm 3} /{\rm mole} \cdot {\rm sec) = (13}{\rm .19) - (10840} \pm {\rm 460)/}\theta $$\end{document}where θ=2.303 RT cal/mole. From the activation energy for reaction (11), we calculate that\documentclass{article}\pagestyle{empty}\begin{document}$$ D({\rm CF}_{{\rm 3}^{\rm - } } {\rm I) = 52}{\rm .6} \pm {\rm 1}{\rm .1}\,{\rm kcal/mole}\,{\rm at 25}{}^{\rm 0}{\rm C} $$\end{document}This is compared with previously published values of D (CF 3 −I). The relevance of the result to published work on k c for a combination of CF 3 radicals is discussed.