Rate of decomposition of hexafluoroazomethane and the absolute rate of recombination of trifluoromethyl radical at higher temperatures

Abstract

The unimolecular homogeneous decomposition of hexafluoroazomethane was studied in a VLPP apparatus in the temperature range 720-1050 K and is consistent with the following Arrhenius parameters: log k(sec-') = 16.2 -55.2/0 a t 900 K, where the A factor was assumed to he the same as for 2,2'-azoisobutane. The homogeneous rate of recombination of CF3 radicals a t temperatures around 1000 K was also studied under VLPP conditions and was found to be in the fall-off region, corresponding to k / k = 8.5 X when a rotational transition-state model was used. This model predicts an essentially constant value of k;" of over the temperature range 300-1000 K.

Substituent effects on the disproportionation-combination rate constant ratios for gas-phase halocarbon radicals. II. Reactions of ?CF3 +CF3CH2CH2? and CF3CH2CH2? + CF3CH2CH2?

“…Steric repulsion of substituents can cause the k, to decrease which would increase the kdlk,, all other factors remaining constant. At room temperature, the most reliable k, measurements show a decline in kc's with increasing halogenation with Cl's having a much greater effect than fluorine; 3.6 X 10'" M -' s -' for two CH3 radicals [21,22], 0.5 X lo1" M-ls-' and 1.4 X 10"' M-ls-' f or two CF3 radicals [23,24], <0.6 X 10'" M-'s-I for CH3 + CC13 radicals [25] and 0.2 X 10'' M-'s-' for CC13 radicals [27]. The smaller k,.…”

Novel Source of Trifluoromethyl Radical As Efficient Initiator for the Polymerization of Vinylidene Fluoride

“…Usually, the radical brings the polymer end‐groups that may play a role on its properties. However, available sources of perfluoroalkyl radicals are in general either too stable, too unstable, or are difficult and expensive to prepare 29. Among different strategies to incorporate a specific end‐group as a function or a label, telomerization is an attractive method.…”

Synthesis and pyrolysis of perfluoroazo‐2‐propane

“…The average value for the preexponential factor is 1016.4'0.2 s-'. This is in keeping with such a bond breaking process whether a "vibrational" or a "rotational" model [131 These values and D(R-H) are listed in Table IV. It is clear from Figure 3 that the activation energy for R = t-Bu derived from kinetic data does not provide a good fit with the data for the other azoalkanes.…”