Thermochemistry fluorocarbons

Reactivity and Thermochemistry of Selected Metal/Fluorocarbon Systems... 

In Table I, we also estimate the probabilities that the collisions between these reactant pairs lead to reaction. Except for the reactions of CF2, we see that the F or F transfer reactions observed in perfluorinated alkanes are extremely inefficient. This low reaction probability is especially striking when compared with the efficiencies of the corresponding reactions in hydrocarbon systems ( ). The methyl ion reaction with ethane corresponding to reaction 4 occurs at every collision between the reactant pair the hydride transfer reactions from propane to vinyl ions or ethyl ions, corresponding to reactions 6 and 7, occur with efficiencies of about 0.5. These differences between the efficiencies of ion-molecule reactions in fluoroalkanes and alkanes can be explained in terms of the thermochemistry of these systems, remembering that endothermic or thermoneutral ion-molecule reactions are quite inefficient, and often can not even be seen on the time scale of ion collection in a mass spectrometer. The highly efficient hydride transfer reactions observed in hydrocarbon systems are all exothermic. In the fluorocarbon systems, o the other j hand, the F transfer reactions listed for 2 3 2 5 actually slightly endothermic, as... 

That is, hydrocarbon carbonium ions will nearly always undergo exothermic hydride transfer reactions with alkanes having a larger number of carbon atoms, but this is apparently not the case In fluorocarbon systems. An examination of the thermochemistry of these reactions explains these di fering trends.Table X contrasts the nergy gained in going from R to RH for, and sec-... 

It may seem, at first glance, somewhat incongruous that a paper about the thermochemistry of fluorocarbon free radicals should appear in a volume nominally devoted to the kinetics of these radicals. However, for an elementary reaction such as (1)... 

---