AbstractA mixture of Br2+ HBr + C2F5I was photolyzed in the vapor phase. The reaction\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Br + C}_{\rm 2} {\rm F}_{\rm 5} {\rm I} \to {\rm IBr + C}_{\rm 2} {\rm F}_{\rm 5} $$\end{document}forms C2F5radicals which are removed byCompetitive studies over the range of 74–146°C gave ratios ofk10/k9, and these were combined with values obtained previously by different methods at higher temperatures upto 515°C to give\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log(}k_{10} /k_9) = (- 0.47 \pm 0.03) - (12,500 \pm 300)/\theta $$\end{document}where θ = 2.303RTJ/mol. A value is assigned to the activation energyE10, and this, with other data, leads to\documentclass{article}\pagestyle{empty}\begin{document}$$ D{\rm (C}_{\rm 2} {\rm F}_{\rm 5} - {\rm H}) = 429.8 \pm 2.1{\rm KJ}/{\rm mol} $$\end{document}at 25°C. This result is in excellent agreement with two previous independent determina