The photolysis of 1,3-difluoro- and 1,1,3,3-tetrofluoro-acetone at low pressure

Abstract

The data on ZIÍczFíHz/RczFiHi with added Nz at 391°K may well be better represented by a small positive intercept at ~0.05, but it is apparent that a large number of runs would have to be performed (see for instance ref 22) to permit a clear-cut determination as to the existence of an intercept, or not.(32) Similarly, so did plots of ñcia/ñczFsHs and Rtram/RciFtSi, although any difference in behavior of these two functions would certainly not be anticipated.(33) The data in Figure 7 only show the ratio of the products, but the absolute amount of elimination products is, of course, reduced with increasing pressure.

Disproportionation reactions between CF2H and C2H5radicals in the gas phase

“…Possible products are C2F3H and 1-fluoropropene, which can be formed via H F elimination reactions from the vibrationally excited intermediates in reactions ( 3 ) and (5), and these would comprise a part of the two combination processes. Trifluoroethylene was not expected to be formed as the half-quenching pressure for the hot C2F4H2* intermediate is <0.04 torr a t 30°C [23,41]. Our failure to observe any 1-fluoropropene places an upper limit on the half-quenching pressure for the CF2HC2HS* intermediate a t <1.0 torr a t room temperature, which is in agreement with other estimates for the chemically activated molecule formed by radical combination [42,43].…”

The photolysis of 2‐fluorocyclohexanone in the 313‐nm region. The elimination of hydrogen fluoride from vibrationally excited fluorocyclopentane

“…The observation that internal hydrogen abstraction is favored over cyclization has been noted previously [29,30], and the value of 1.2 for FCH is consistent with this. The value is based upon the sum of the two products which result from the initial combination step [31]. There is some evidence for a small inverse temperature effect on the disproportionation-to-combination ratio (1.42 f 0.07 at 30"C, 1.17 f 0.19 at 120°C, and Configurational effects may also be involved.…”

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

“…$ In experiments involving deuterium it is possible to measure the CF,HD directly by mass spectrometry, rather than to make a correction to the methylene fluoride yield, as in equation (5). These alternative approaches are referred to [ 101 as Methods I1 and I respectively.…”

“…In the DFA photolysis, the reaction scheme is similar to that for TFA, except that reaction (3) must be replaced by (3') (3') 2 CFH, -+ C,F,H4 or C,FH3 + HF since HF elimination can occur from the vibrationally excited intermediate C2F2Hq* before collisional stabilization takes place under the reaction conditions [3]. A disproportionation reaction, analogous to reaction (2), does not occur with CFH, radicals [5].…”