Quantum chemical characterization of the ground and lowest excited singlet and triplet states of CH3CF and CF3CF and their photochemical isomerization and dissociation pathways

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

“…However, these values are suspect because the first [28] was based on data fitting to an assumed Option C, a premise later abandoned by these authors in favor of Option A [60,93,96], and the second [63] was replaced shortly thereafter by the same authors [69] by a value of ≈−125 kcal/mol. In contrast, the computed values of f H 298 (CF 3 CF:) [52][53][54]61,69,70] cluster nicely around ≈−123 kcal/mol (Table S-1), which lead to a "low" value of (17); ----: Pathway to C2F4 (Fig. 9).…”

“…As a result of these reinforcing effects, the C C double bond in C 2 F 4 is unusually weak with DH 298 (CF 2 CF 2 ) ≈ 69.0 kcal/mol compared with DH 298 (CH 2 CH 2 ) = 172.1 kcal/mol; it is notably weaker than even the C-C single bond in CF 3 -CF 3 , ≈98 kcal/mol [52,53,70,[76][77][78]. The net result is the ubiquity of CF 2 : as a key intermediate in thermolysis reactions of perfluorocarbons.…”

“…In spite of considerable scatter, the computational studies (first 4 entries in Table 4) suggest a significant endothermicity as well as a significant kinetic barrier in the reverse exothermic direction (in contrast to 1,2-H migration in hydrocarbenes which is very rapid [104]). For a simulation based on computational data (Option C1), we chose the E parameters of Bacskay [70] for which the computational value of r H 13 most closely matched the "computational" value from Table 1 (37.5 kcal/mol), and we assumed A 13 = 1E13 s −1 for a rather tight bridged transition state for F migration. The value of r S 13 = 5.1 cal/mol K (Table 1) (15) was not included in this initial simulation.…”

Mass spectrometric investigation and formation mechanisms of high-mass species in the downstream region of Ar/CF4/O2plasmas

“…This reaction is accompanied with the emission of a photon in a visible light region through the allowed electronic transition, having a significantly large probability. The potential energy surface, including zero point corrections, for the formation reaction of C 2 F 4 obtained by accurate calculations, 42 is summarized in Fig. 7.…”

“…7. The UV-vis absorption spectrum of CF 3 CF 42 observed in an argon matrix at 12 K has peak maxima at 465 and 235 nm. 43 The onset of the absorption band with a peak at 465 nm is about 540 nm, which agrees very well with the calculated energy gap between the singlet ground state and the lowest excited singlet states of CF 3 CF, 2.29 eV (541 nm).…”