Rate Measurement of the Reaction of CF2Cl Radicals with O2 (original) (raw)
Related papers
Photochemistry of fluorinated compounds: reaction between FCO and CF3CF2 radicals
Journal of Photochemistry and Photobiology A: Chemistry, 2002
CF 3 CF 2 C(O)F is a suitable source to generate the title radicals which can recombine to give back the precursor or lead to the formation of C 4 F 10 , CF 2 O and CO. We performed the photolysis of CF 3 CF 2 C(O)F pure and in the presence of c-C 6 H 12 or (FCO) 2 (oxalylfluoride), following the concentration of the different species by FTIR spectroscopy. The rate constant for the reaction CF 3 CF 2 + FCO → CF 3 CF 2 C(O)F was obtained through a simulation using both our experimental data and bibliography data available. The value found is (6.8 ± 0.8) × 10 −12 cm 3 molecule −1 s −1 and it is not substantially different from the rate constant (4.2 ± 0.5) × 10 −12 cm 3 molecule −1 s −1 obtained for the reaction of CF 3 and FCO radicals. Thus, it was concluded that the length of the carbon chain does not affect the mechanism nor the rate constant value when it is compared with the CF 3 + FCO system.
Journal of Chemical Physics, 1980
reactions were studied at room temperature with infrared chemiluminescence from a flowing afterglow apparatus. The HC1 and DCl vibrational energy distributions and the relative rate constants for C1 + PH,, GeH, and HI were measured. Since the rate constant for the C1 + HI reaction is available in the literature, the relative measurements can be converted to absolute rate constants. The HC1 distribution from C1 + HI was u1:u2:u3:u4 = 0.07:0.24:0.49:0.20, which is in good agreement with cold-wall, arrested-relaxation results. The vibrational energy distributions are ul:
Photochemistry of Long–Lived [(CF3)2CF]2C•C2F5 Radicals
Journal of Fluorine Chemistry, 2015
The mechanism of the photodecomposition of the long lived radical [(CF 3) 2 CF] 2 C C 2 F 5 is explored by UV and ESR spectroscopy and quantum chemical calculations. The kinetics of the photodecomposition of [(CF 3) 2 CF] 2 C C 2 F 5 are investigated in a matrix of glassy and liquid hexafluoropropylene trimer at 77 and 300 K, respectively. The mechanism of [(CF 3) 2 CF] 2 C C 2 F 5 photodecomposition does not depend on the phase state of the matrix but differs from the thermal decomposition of the radical. Under UV light with λ <300 nm, the CF 2-CF 3 bond of the perfluoro-ethyl group of [(CF 3) 2 CF] 2 C C 2 F 5 is broken. Thermal decomposition of the radical above 373 K occurs by breaking a CF-CF 3 bond in the perfluoro-isopropyl group. The experimental results are consistent with the calculated bond dissociation energies and UV-vis excitation spectra of the radical. Additional calculated CC BDEs for a number of fluorocarbon
Chemosphere, 1996
Laboratory experiments with H202/UV oxidation processes and photolysis at 253.7 nm wavelength have been carried out on dilute aqueous solutions (Co = 0.1 to 3.0 raM) of trifluorobenzene derivatives (1,3,5trifluorobenzene, 1,2,3 and 1,2,4-trifluorobenzene) and of ct,ct,tx-trifluorotoluene in the presence and in the absence of dissolved oxygen. The analyses of fluoride ions content during the oxidation experiments showed that the first steps lead to the production of about 2 tool of F-/mol of trifluorobenzene decomposed and of 1 mol of F-/mol of trifluorotoluene decomposed. Kinetic studies lead to the determination of the quantum yield for the photolysis of 1,3,5-trifluorobenzene, 1,2,3 and 1,2,4-trifluorobenzene (~ = 0.011, 0.010 and 0.015 respectively), and of trifluorotoluene (~ = 0.015). The rate constants for the reaction of hydroxyl radicals with these molecules, determined under specific experimental conditions, were found to range from 3.7 109 to 4.9 109 M-l.s-1). GC/MS analyses carried out on extracts at different irradiation time (UV, H202/UV) lead to the identification of numerous by-products from trifluorobenzene and trifluorotoluene. They consist mostly in hydroxylated and dehalogenated compounds. Dimers have also been observed during photolysis. Moreover, experiments carried out under oxygen limiting conditions revealed the formation of other compounds. For each case studied, a detailed mechanism involving radical intermediates and the different reaction sequences is proposed.
Experimental and theoretical study of the recombination reaction of FC(O)O radicals
Chemical Physics, 1996
The kinetics of the recombination reaction of FC(O)O radicals has been experimentally and theoretically investigated. The FC(O)O radicals were generated by excimer laser flash photolysis of mixtures of (FCO) 2 and 0 2 in excess of CO at 297 K and monitored by absorption spectroscopy at 545 nm. In agreement with the predictions from unimolecular rate theory, no appreciable falloff effects were observed for total pressures ranging from t I7 to 727 Tort. The measured limiting high pressure rate coefficient, krec~ =(7.0_+ 1.1)× 10 13 cm 3 molecule l s t, agrees very well with that predicted by a simplified version of the statistical adiabatic channel model. The influence of the dominant potential energy surface features on k,.~c.~ was examined between 200 and 600 K.
Journal of Photochemistry and Photobiology A-chemistry, 2001
The infrared multiphoton dissociation of C 3 F 6 has been studied through the analysis of the laser induced fluorescence of the produced CF, CF 2 and CF 3 radicals. The influence of buffer gases in the process has also been investigated. In the studied conditions, only unimolecular formation of these radicals has been detected. A discussion about the possible dissociation channels has been done. The obtained excitation spectra show that CF 2 is formed vibrationally hot and reveal the presence of the radical CF 3 . From the analysis of these spectra, different values of the vibrational temperature are obtained, for the two experimental employed arrangements.
Pulse radiolysis study of CF3CCI2 and CF3CCI2O2 radicals in the gas phase at 295K
Research on Chemical Intermediates, 1994
The ultraviolet absorption spectra and self reaction kinetics of CF3CCI z and CF3CCI202 radicals have been studied in the gas phase at 295K. Absorption cross sections were quantified over the wavelength range 220-300 nm. Measured cross sections near the absorption maxima were C~CF3CCn(230 rim) = (9.70 +_ 1.47) x 10-t8 and ~cF3cc~zo2(250 run) = (1.70 _+ 0.26) x 10-18 em 2 molecule-~. Errors are statistical (2~) together with our estimate of potential systematic errors. Rate constants for the self reaction of CF3CCI: and CF3CCI202 radicals were measured to be k~-(2.46 +-0.43) x 10 "~z and kTob~ = (3.33 + 0.53) x 10-lz cm 3 molecule-~ s-~, respectively. Results are discussed with respect to the existing database concerning halogenated peroxy radicals.
Kinetic Study of the CCl2 Radical Recombination Reaction by Laser‐Induced Fluorescence Technique
International Journal of Chemical Kinetics, 2013
ABSTRACTAn experimental setup that coupled IR multiple‐photon dissociation (IRMPD) and laser‐induced fluorescence (LIF) techniques was implemented to study the kinetics of the recombination reaction of dichlorocarbene radicals, CCl2, in an Ar bath. The CCl2 radicals were generated by IRMPD of CDCl3. The time dependence of the CCl2 radicals’ concentration in the presence of Ar was determined by LIF. The experimental conditions achieved allowed us to associate the decrease in the concentration of radicals to the self‐recombination reaction to form C2Cl4. The rate constant for this reaction was determined in both the falloff and the high‐pressure regimes at room temperature. The values obtained were k0 = (2.23 ± 0.89) × 10−29 cm6 molecules−2 s−1 and k∞ = (6.73 ± 0.23) × 10−13 cm3 molecules−1 s−1, respectively.
Journal of Physical Chemistry A, 2005
The laser-induced fluorescence (LIF) excitation spectra of the 4-methylcyclohexoxy and d11-cyclohexoxy radicals have been measured for the first time. LIF intensity was used as a probe in direct kinetic studies of the reaction of O 2 with trans-4-methylcyclohexoxy and d11-cyclohexoxy radicals from 228 to 301 K. Measured rate constants near room temperature are uniformly higher than the Arrhenius fit to the lower-temperature data, which can be explained by the regeneration of cyclic alkoxy radicals from the product of their-scission and the effect of O 2 concentration on the extent of regeneration. The Arrhenius expressions obtained over more limited ranges were k O 2) (1.4-1 +8) × 10-13 exp[(-810 (400)/T] cm 3 molecule-1 s-1 for trans-4methylcyclohexoxy (228-292 K) and k O 2) (3.7-1 +4) × 10-14 exp)[(-760 (400) /T] cm 3 molecule-1 s-1 for d11-cyclohexoxy (228-267 K) independent of pressure in the range 50-90 Torr. The room-temperature rate constant for the reaction of trans-4-methylcyclohexoxy radical with O 2 (obtained from the Arrhenius fit) is consistent with the commonly recommended value, but the observed activation energy is ∼3 times larger than the recommended value of 0.4 kcal/mol and half the value previously found for the reaction of normal cyclohexoxy radical with O 2 .