Hydrogen abstraction by fluorine atoms under conditions of thermal initiation: Hydrocarbons and fluorinated hydrocarbons

Abstract

Modified nuclear recoil techniques have been used to obtain accurate relative bimolecular rate coefficients for thermally induced hydrogen abstraction reactions by atomic fluorine. New results are reported for 12 hydrocarbons and partially fluorinated hydrocarbons studied a t 303'K.

Kinetics of the F + CH4Reaction in the Temperature Range 184−406 K

“…A value for k F+CH 4 / k F+D 2 at 298 K can also be calculated from the results of Manning et al They determined the rate constants for the F + D 2 and F + CH 4 reactions relative to the rate constant for the F + H 2 reaction. From the two relative rate constants reported by them a value of k F+CH 4 / k F+D 2 = 5.00 ± 0.18 can be calculated.…”

Chemical Kinetics and Hot Atom Chemistry — Present Status and Future Perspectives

“…The principal advantages of the radiotracer technique for the study of thermal reaction kinetics include extreme measurement sensitivity and freedom from complications such as self-heating [130,[133][134][135], The experimental sensitivity is such that direct calibration methods based upon literature data are not yet capable of revealing the quantitative importance of residual hot reaction contamination in moderated nuclear recoil experiments. Table 3 and Figure 13 show an indirect high sensitivity test for non-thermal contamination in the C 2 F 6 moderated CH4/C 3 F 6 [121 ].…”

“…The use of the moderated nuclear recoil technique in measurements of rate constants and Arrhenius parameters for thermal 18 F atom reactions has been well documented [53, [128][129][130][131][132][133][134][135][136][137][138], The kinetic behavior of thermalized 18 F atoms can be investigated in samples containing a large excess of a low reactivity polyatomic "moderator" such as SF 6 or C 2 F 6 . The moderator is supposed to provide source material for the nuclear reaction and to insure dissipation of the excess recoil atom translational energy.…”

Reactions of radioactive recoil atoms with (halo)methanes

“…The isotopic ratios for CH4/CD4 are (1.7 ± 0.4) and (2.06 ± 0.16), respectively, in accord with the established value of 1.47 as discussed before. Manning et al 178 measured rate constantsrelative to H2-for (fluoro)methanes: CH4 (2.58 ± 0.06), CD4 (1.66 ± 0.02), CH3F (1.49 x 0.03), CH2F2 (0.283 ± 0.013), and CHF3 (0.026 ± 0.006). The CH4/CD4 ratio is (1.55 ± 0.04).…”