Interactions of methyl and difluoromethyl radicals and the elimination of hydrogen fluoride from "hot" 1,1-difluoroethane

Follmer

Meleason

et al. 1992

Mixtures of 1,1,3,3-tetrafluoroacetone and perf luorodi-n-propyl ketone have been photolyzed together over the temperature range 50" to 200"C, and the disproportionation/combination ratio for n-C3F7 and CFzH radicals has been determined to be A(n-CsF7, CFZH) = 0.072 ? 0.003. A reevaluation of existing data on CH3 and CFzH radicals leads to a value of A(CH3, CFzH) = 0.35. The large variations in A for the reactions of alkyl and perfluoroalkyl radicals with CFzH radicals are discussed. 0 1992 John Wiley & Sons, Inc.

Section: Re-examination Of A(ch3 Cf2h)mentioning

confidence: 99%

Disproportionation reactions between alkyl and fluoroalkyl radicals. VII. Difluoromethyl with perfluoro‐n‐propyl and methyl radicals

Follmer

Meleason

et al. 1992

“…Certainly there seems to be little basis for prior discussions [5,[11][12][13] concerning a correlation between the effects of c(-and @-fluorination with variation in E*, particularly in view of the fact that some of this discussion [l l-131 was based on E* = 51 kcalmole-l for C2H6F*. Internal Energv.…”

Section: Tschuikow-roux [34]mentioning

confidence: 99%

The elimination of HF from vibrationally excited fluoroethanes. The decomposition of 1,1,1‐trifluoroethane‐d₀ and d₃

1970

The vibrationally excited molecules CF,CH,* and CF,CD,* have been synthesized by radical combination (produced by ketone photolysis), and HF and DF elimination from them studied as a function of temperature and pressure. Using RRK theory many calculations have recently been made of critical energies for the decomposition of "hot" fluoroethane molecules. Taking CF,CH,* as an example, it is concluded that the empiricism involved in such calculations renders results of doubtful significance. The non-equilibrium kinetic isotope effect is k,/k, = 3.1 at 470°K. Arrhenius parameters are also presented for radical abstraction reactions from the ketone source molecules.

“…The previous values were k,/k;/' = 2.2 x 103 e-6,900/RT mole-'/' cc sec-1/2 for TFA [2] and k;/ki1/' = 5.1 x lo3 e-8000/RT mole-'/' cc sec-1'2 for DFA [3]. We now consider that our original TFA data are in error due to the presence of an impurity in the TFA sample [7]. In the two TFA systems the experimental values of k,/ki/z tend to agree at the highest temperatures, which would be expected, since the presence of a impurity with a labile hydrogen would be relatively more important at low temperatures.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Some hydrogen atom abstraction reactions of CF₂H and CFH₂ radicals, and the CH bond dissociation energy in CF₂H₂

1969