Intermediates of thermal transformations of perfluoro-organic compounds. New spectral data and reactions

Chain elongation during thermolysis of tetrafluoroethylene and hexafluoropropylene: Modeling of mechanistic hypotheses and elucidation of data needs

“…The 1,3-biradical: Recent computations by Wei and coworkers [71] support earlier suggestions [94,96] that step (7), contrary to the general behavior of singlet carbenes, is not concerted but proceeds through a specially stabilized singlet 1,3-biradical intermediate which was described as a C 2v "bond-stretched invertomer" of c-C 3 F 6…”

“…For the first stage, the modeling target was the data at 600 • C [16] shown in Fig. 1 [29,60,72,91,93,96,102]. Option A is the concerted insertion of CF 2 : into the C-F bond of C 2 F 4 in step (-10c) (we add the "c" suffix to distinguish this concerted option from the mechanistically undefined global process).…”

“…12) with rate-limiting dissociation step (14). However, the Russian group [60,93,96] later supported Option A. For completeness, we also add step (-15).…”

Coherent Oscillation and Ultrafast Internal Conversion of Tetrafluoroethene after Excitation at 197 nm

“…[33,34] This state was therefore assigned to a "diradical" form of C 2 F 4 . We argue that a singlet diradical would not behave as such a discrete intermediate, because it does not correspond to a minimum on the potential surface: Actually every point lying farther out on the curve that correlates with the two triplet CF 2 (with their opposed spins combining to a singlet) in Figure 4 would correspond to such a singlet diradical; along the twist coordinate there is probably only a saddle point connecting the two S 0 minima at 0 and 1808, such as in ethene.…”

“…However, the transient UV spectrum [32] seems to be inconsistent with the spectrum of tetrafluoroethylidene. [34] The nature of the intermediate belonging to the transient UV spectrum is hence not yet clear. Spin-allowed dissociation of the triplet leads to one singlet and one triplet CF 2 (broken line in Figure 4), which is higher by 2.15 eV than the lowest dissociation channel.…”