Chemistry of Nuclear Recoil 18F Atoms. IV. Hot F‐to‐HF and F‐to‐F2 Abstraction in CH3CF3

Abstract

New hot abstraction reaction channels have been demonstrated for nuclear recoil ¹⁸F atoms reacting with fluorocarbon substrates. Hot F‐to‐HF abstraction in CH₃CF₃ is a very efficient process with an absolute hot yield of $\text{51\%±3\%}$ . Hot F‐to‐F₂ reactions also occur, but with much lower efficiencies. The F‐to‐F₂ absolute hot yields in CH₃CF₃, C₂F₆, and C₃F₆ are $\text{5.4\%±0.3\%, 6.9\%±0.8\%}$ , and $\text{11.7\%±0.5\%}$ , respectively. In good agreement with theoretical expectations, translational excitation appears to be much more effective as a driving force for the exoergic F‐to‐HF process in comparison with the endoergic F‐to‐F₂ process. The Arrhenius activation energy for thermal F‐to‐HF abstraction in CH₃CF₃ is at least $\text{2.1±0.1}\mathrm{kcal}/\mathrm{mole}$ larger than the value associated with the thermal ¹⁸F‐atom pi‐addition process in C₃F₆.