1493-11-4Relevant articles and documents
Temperature dependence of the gas phase reactions of CF3O with CH4 and NO
Jensen,Hanson,Howard
, p. 8574 - 8579 (1994)
A temperature-regulated flow tube reactor coupled to a chemical ionization mass spectrometer (CIMS) was used to investigate reactions of CF3O with CH4 and NO. The reaction rate for the CF3O + CH4 reaction was measured in the temperature range 231-385 K and found to be k3(T) = (3.1 ± 0.5) × 10-12 exp[(-1470 ± 250) K/T]cm3 molecule-1 s-1, with k3(298 K) = (2.2 ± 0.4) × 10-14 cm3 moleculeMIN1 (where the uncertainties represents our estimated accuracy at the 95 % confidence level). The latter is in good agreement with recently reported measurements at room temperature. The reaction rate constant for the CF3O + NO reaction was measured in the temperature range 231-393 K and found to be k4(T) = (4.1 ± 0.6) × 10-11 disagrees with two previously reported values by a factor of about 2.5 but is in good agreement with three recently reported values. The results reported in this study are important in establishing the fate of the CF3Ox radicals produced as degradation products from hydroflurocarbons (HFC's) in the atmosphere.
Proton affinity and absolute heat of formation of trifluoromethanol
Chyall,Squires
, p. 16435 - 16440 (1996)
The proton affinity and absolute heat of formation of trifluoromethanol have been derived from translational energy threshold measurements for reactions involving oxygen-protonated trifluoromethanol. The reaction of ionized iodotrifluoromethane with water was used to prepare CF3OH2+ in the flow tube of a flowing afterglow triple-quadrupole instrument. The isomeric cluster ion, (HF)CF2OH+, was shown to be more stable than CF3OH2+ by the base-catalyzed conversion of CF3 OH2+ to (HF)CF2OH+ using either SO2 or OCS as the catalyst. The proton affinity of CF3OH at oxygen was determined from the enthalpy change for the endothermic proton transfer reaction CF3OH2+ + CO → CF3OH + HCO+. The measured enthalpy change, was combined with the known value for the proton affinity of CO (141.9 kcal mol-1) to yield a value for the oxygen proton affinity of CF3OH. The dissociation energy for the loss of water from CF3OH2+ was measured by energy-resolved collision-induced dissociation. This value was used in a thermochemical cycle along with the measured proton affinity of CF3OH to derive the gas-phase heat of formation of CF3OH. This experimental value is slightly lower than, but in good agreement with, the 298 K heat of formation of CF3OH that is predicted by high-level molecular orbital calculations.
UV absorption spectrum, and kinetics and mechanism of the self reaction of CF3CF2O2 radicals in the gas phase at 295 K
Sehested,Ellermann,Nielsen
, p. 701 - 717 (1993)
The ultraviolet absorption spectrum, kinetics and mechanism of the self reaction of CF3CF2O2 radicals have been studied in the gas phase at 295 K. Two techniques were used; pulse radiolysis UV absorption to measure the spectrum and kinetics, and long-path length FTIR spectroscopy to identify and quantify the reaction products. Absorption cross sections were quantified over the wavelength range 220-270 nm. At 230 nm, ΣCF3CF2O2 =(2.74±0.46)×10-18 cm2 molecule-1. The observed products following the self reaction of CF3CF2O2 radicals were COF2CF3O3CF3, CF3O3C2F5, and CF3OH. CF3O2CF3 was tentatively identified as a product. The carbon balance was 90-100%. The self reaction of CF3CF2O2 radicals was found to proceed via one channel to produce CF3CF2O radicals which then decompose to give CF3 radicals and COF2. In the presence of O2, CF3 radicals are converted into CF3O radicals. CF3O radicals have several fates; self reaction to give CF3O2CF3; reaction with CF3O2 radicals to give CF3O3CF3; reaction with C2F5O2 radicals to give CF3O3C2F5; or reaction with CF3CF2H to give CF3OH. As part of this work a rate constant (2.5±0.6)×10-16 cm3 molecule-s- was measured for the reaction of Cl atoms with CF3CHF2 using a relative rate technique. Results are discussed with respect to the atmospheric chemistry of CF3CF2H(HFC-125).
A photoionization study of trifluoromethanol, CF3OH, trifluoromethyl hypofluorite, CF3OF, and trifluoromethyl hypochlorite, CF3OCl
Asher, Robert L.,Appelman, Evan H.,Tilson, Jeffrey L.,Litorja, Maritoni,Berkowitz, Joseph,Ruscic, Branko
, p. 9111 - 9121 (1997)
CF3OH, an important and controversial by-product of atmospheric decomposition of CF3CFH2 (HFC-134a) and other hydrofluorocarbons, has been examined by photoionization mass spectrometry. The ionization onset is characterized by a broad Franck-Condon distribution, arising primarily from a substantial elongation of the C-O bond upon ionization. An upper limit to the adiabatic ionization potential (IP) of ≤ 13.08 ± 0.05 eV has been established. The appearance potentials (APs) of the first two fragments have been accurately determined by fitting with appropriate model functions as AP0(CF2OH+/CF 3OH)≤13.830±0.005 eV and AP0(CF+3/CF 3OH)≤13.996±0.005 eV. While the exact nature of the lowest-energy fragment (nominally CF2OH+) is not clear, the CF+3 fragment threshold leads unambiguously to ΔH°f 298(CF3OH)≥-217.2±0.9 kcal/mol and D298(CF3-OH)≤115.2±0.3 kcal/mol. With previously derived ΔH°f 298(CF3O)=-151.8+1.7-1.1 kcal/mol, this yields D298(CF3O-H) =117.5+1.9-1.4 kcal/mol, very close to, or only slightly weaker than the O-H bond energy in water: D298(CF3O-H)-D298(HO-H)=-1.8 +1.9-1.4 kcal/mol≈0 kcal/mol. Similarly, with the recently redetermined value for ΔH°f(CF2O), this implies a 298 K reaction enthalpy for the 1,2-elimination of HF from CF3OH of 2.81+1.7-1.1 kcal/mol. CF3OF and CF3OCl have also been examined by photoionization. CF3OF produces a very weak parent, with an apparent adiabatic IP(CF3OF) ≤12.710±0.007 eV. An analysis of the CF+3 and CF2O+ fragments from CF3OF, when combined with literature data, suggests ΔH°f 298(CF3OF)=-176.9+1.8-1.3 kcal/mol. The fitted value for the appearance potential of CF+3 from CF3OCl, AP0(CF+3/CF 3OCl)≤12.85±0.01 eV, leads to ΔH°f 298(CF3OCl)≥-175.6±1.0 kcal/mol, D298(CF3-OCl)≤88.4±0.3 kcal/mol, and D298(CF3O-Cl)≤52.8+2.0-1.5 is kcal/mol.
Atmospheric Chemistry of CF3O Radicals: Reaction with CH4, CD4, CH3F, CF3H, (13)CO, C2H5F, C2D6, C2H6, CH3OH, i-C4H8, and C2H2
Wallington, Timothy J.,Ball, James C.
, p. 3201 - 3205 (1995)
A relative rate technique has been used to study the title reactions at 296 +/- 2 K.Using a reference rate constant of k(CF3O + CH4) = (2.2 +/- 0.2) x 1E-14 cm3 molecule-1 s-1, rate constants (in 700 Torr of air diluent) for the reactions of CF3O radicals with the following reactants were established; CD4, (5.1 +/- 1.6) x 1E-15; CH3F, (2.4 +/- 0.3) x 1E-14; CF3H, 3 molecule-1 s-1.The rate of the reaction of CF3O radicals with (13)CO was observed to be dependent on the total pressure.In 100 Torr of total pressure of air diluent, k(CF3O + (13)CO) = (4.6 +/- 0.5) x 1E-14 cm3 molecule-1 s-1.The reaction of CF3O with (13)CO gives (13)CO2 in a yield of 96 +/- 8percent.Implications for the atmospheric chemistry of CF3O radicals are discussed.
Redwood,Willis
, p. 1893,1897 (1965)
α-Fluoroalcohols: Synthesis and Characterization of Perfluorinated Methanol, Ethanol and n-Propanol, and their Oxonium Salts
Baxter, Amanda F.,Schaab, Jonas,Hegge, Joachim,Saal, Thomas,Vasiliu, Monica,Dixon, David A.,Haiges, Ralf,Christe, Karl O.
, p. 16737 - 16742 (2018)
The thermally unstable, primary perfluoroalcohols, CF3OH, C2F5OH, and nC3F7OH, were conveniently prepared from the corresponding carbonyl compounds in anhydrous HF solution. Experimental values for the reaction enthalpies and entropies were derived from the temperature dependence of the RfCOF+HF?RfCF2OH (Rf=F, CF3, CF3CF2) equilibria by NMR spectroscopy. Electronic structure calculations of the gas-phase and solution reaction energies, gas-phase acidities and heats of formation were carried out at the G3MP2 level, showing that these compounds are strong acids. Protonation of these alcohols in HF/SbF5 produced the perfluoroalkyl oxonium salts RfCF2OH2+SbF6?.
Kinetics of the Reactions of the CF3O Radical with Alkanes
Barone, Stephen B.,Turnipseed, Andrew A.,Ravishankara, A. R.
, p. 4602 - 4608 (1994)
Utilizing the technique of pulsed laser photolysis/pulsed laser induced fluorescence, we have investigated the atmospherically important reactions of the (trifluoromethyl)peroxy radical, CF3O, with several alkanes.The reaction rate coefficients for CF3O + CH4 (k3), C2H6 (k4), C3H8 (k5), (CH3)3CH (k6), and CD4 (k7) were measured, as functions of temperature, to be k3 = (1.92 +/- 0.33) x E-12 exp cm3 molecule-1 s-1, k4 = (4.84 +/- 1.11) x E-12 exp cm3 molecule-1 s-1, k5 = (5.12 +/- 1.12) x E-12 exp cm3 molecule-1 s-1, k6 = (4.32 +/- 0.42) x E-12 exp cm3 molecule-1 s-1, and k7 = (0.91 +/- 0.31) E-12 exp cm3 molecule-1 s-1, respectively.These kinetic data are compared with results from previous studies.The atmospheric implications of these findings are discussed.
