Kinetics of the reactions of CCl3 with O and O2 and of CCl3O2 with NO at 295 K

The reactions of CCl₃ with O(³P) and O₂ and those of CCl₃O₂ with NO have been studied at 295 K using discharge flow methods with helium as the bath gas. The rate coefficient for the reaction of CCl₃ with O was found to be (4.2 ± 0.6) × 10^?11 cm³/s and that for CCl₃O₂ with NO was (18.6 ± 2.8) × 10^?12 cm³/s with both coefficients independent of [He]. For reaction between CCl₃ and O₂ the rate coefficient was found to increase from 1.51 7times; 10^?14 cm³/s to 7.88 × 10^?14 cm³/s as the [He] increased from 3.5 × 10¹⁶ cm^?3 to 2.7 × 10¹⁷ cm^?3. There was no evidence for a direct two-body reaction, and it is concluded that the only product of this reaction is CCl₃O₂. Examination of these results for CCl₃ + O₂ in terms of current simplified falloff treatment suggests that the high-pressure limit for this reaction is ～ 2.5 × 10^?12 cm³/s, which may be compared with a direct measurement of the high-pressure limit of 5 × 10^?12 cm³/s. A value of (5.8 ± 0.6) × 10^?31 cm⁶/s has been obtained for k₀, the coefficient in the low-pressure region. This value is compared with corresponding values found earlier for the (CH₃, O₂) and (CF₃, O₂) systems and with estimates based on unimolecular rate theory.     

1,1,1,3,3,-pentafluorobutane (HFC-365mfc): atmospheric degradation and contribution to radiative forcing

The rate constant for the reaction of the hydroxyl radical with 1,1,1,3,3-pentafluorobutane (HFC-365mfc) has been determined over the temperature range 278–323K using a relative rate technique. The results provide a value of k(OH+CF₃CH₂CF₂CH₃)=2.0×10⁻¹²exp(−1750±400/T) cm³ molecule⁻¹ s⁻¹ based on k(OH+CH₃CCl₃)=1.8×10⁻¹² exp (−1550±150/T) cm³ molecule⁻¹ s⁻¹ for the rate constant of the reference reaction. Assuming the major atmospheric removal process is via reaction with OH in the troposphere, the rate constant data from this work gives an estimate of 10.8 years for the tropospheric lifetime of HFC-365mfc. The overall atmospheric lifetime obtained by taking into account a minor contribution from degradation in the stratosphere, is estimated to be 10.2 years. The rate constant for the reaction of Cl atoms with 1,1,1,3,3-pentafluorobutane was also determined at 298±2 K using the relative rate method, k(Cl+CF₃CH₂CF₂CH₃)=(1.1±0.3)×10⁻¹⁵ cm³ molecule⁻¹ s⁻¹. The chlorine initiated photooxidation of CF₃CH₂CF₂CH₃ was investigated from 273–330 K and as a function of O₂ pressure at 1 atmosphere total pressure using Fourier transform infrared spectroscopy. Under all conditions the major carbon-containing products were CF₂O and CO₂, with smaller amounts of CF₃O₃CF₃. In order to ascertain the relative importance of hydrogen abstraction from the (SINGLE BOND)CH₂(SINGLE BOND) and (SINGLE BOND)CH₃ groups in CF₃CH₂CF₂CH₃, rate constants for the reaction of OH radicals and Cl atoms with the structurally similar compounds CF₃CH₂CCl₂F and CF₃CH₂CF₃ were also determined at 298 K k(OH+CF₃CH₂CCl₂F)=(8±3)×10⁻¹⁶ cm³ molecule⁻¹ s⁻¹; k(OH+CF₃CH₂CF₃)=(3.5±1.5)×10⁻¹⁶ cm³ molecule⁻¹ s⁻¹; k(Cl+CF₃CH₂CCl₂F)=(3.5±1.5)×10⁻¹⁷ cm³ molecule⁻¹ s⁻¹]; k(Cl+CF₃CH₂CF₃)<1×10⁻¹⁷ cm³ molecule⁻¹ s⁻¹. The results indicate that the most probable site for H-atom abstraction from CF₃CH₂CF₂CH₃ is the methyl group and that the formation of carbonyl compounds containing more than a single carbon atom will be negligible under atmospheric conditions, carbonyl difluoride and carbon dioxide being the main degradation products. Finally, accurate infrared absorption cross-sections have been measured for CF₃CH₂CF₂CH₃, and jointly used with the calculated overall atmospheric lifetime of 10.2 years, in the NCAR chemical-radiative model, to determine the radiative forcing of climate by this CFC alternative. The steady-state Halocarbon Global Warming Potential, relative to CFC-11, is 0.17. The Global Warming Potentials relative to CO₂ are found to be 2210, 790, and 250, for integration time-horizons of 20, 100, and 500 years, respectively. © 1997 John Wiley & Sons, Inc.     

EPR kinetic study of the reactions of CF3Br with H atoms and OH radicals

Reactions of CF₃Br with H atoms and OH radicals have been studied at room temperature at 1–2 torr pressures in a discharge flow reactor coupled to an EPR spectrometer. The rate constant of the reaction H + CF₃Br → CF₃ + HBr (1) was found to be k₁ = (3.27 ± 0.34) × 10^?14 cm³/molec·sec. For the reaction of OH with CF₃Br (8) an upper limit of 1 × 10^?15 cm³/molec·sec was determined for k₈. When H atoms were in excess compared to NO₂, used to produce OH radicals, a noticeable reactivity of OH was observed as a result of the reaction OH + HBr → H₂O + Br, HBr being produced from reaction (1).     

Atmospheric chemistry of CCl2FCH2CF3 (HCFC-234fb): Kinetics and mechanism of reactions with Cl atoms and OH radicals

The atmospheric chemistry of CCl₂FCH₂CF₃ (HFCF-234fb) was examined using FT-IR/relative-rate methods. Hydroxyl radical and chlorine atom rate coefficients of k(CCl₂FCH₂CF₃+OH)= (2.9 ± 0.8) × 10⁻¹⁵ cm³ molecule^–1 s^–1 and k(CCl₂FCH₂CF₃+Cl)= (2.3 ± 0.6) × 10⁻¹⁷ cm³ molecule^–1 s^–1 were determined at 297 ± 2 K. The OH rate coefficient determined here is two times higher than the previous literature value. The atmospheric lifetime for CCl₂FCH₂CF₃ with respect to reaction with OH radicals is approximately 21 years using the OH rate coefficient determined in this work, estimated Arrhenius parameters and scaling it to the atmospheric lifetime of CH₃CCl₃. The chlorine atom initiated oxidation of CCl₂FCH₂CF₃ gives C(O)F₂ and C(O)ClF as stable secondary products. The halogenated carbon balance is close to 80% in our system. The integrated IR absorption cross-section for CCl₂FCH₂CF₃ is 1.87 × 10⁻¹⁶ cm molecule⁻¹ (600–1600 cm⁻¹) and the radiative efficiency was calculated to 0.26 W m⁻² ppb¹. A 100-year Global Warming Potential (GWP) of 1460 was determined, accounting for an estimated stratospheric lifetime of 58 years and using a lifetime-corrected radiative efficiency estimation.     

Kinetic study of the reaction of chlorine atoms with CF3I and the reactions of CF3 radicals with O2, Cl2 and NO at 296 K

The kinetics of the gas-phase reaction of Cl atoms with CF₃I have been studied relative to the reaction of Cl atoms with CH₄ over the temperature range 271–363 K. Using k(Cl + CH₄) = 9.6 × 10^?12 exp(?2680/RT) cm³ molecule^?1 s^?1, we derive k(Cl + CF₃I) = 6.25 × 10^?11 exp(?2970/RT) in which E_a has units of cal mol^?1. CF₃ radicals are produced from the reaction of Cl with CF₃I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments were k(Cl + C₂F₅I)/k(Cl + CF₃I) = 11.0 ± 0.6 and k(Cl + C₂F₅I)/k(Cl + C₂H₅Cl) = 0.49 ± 0.02. The reaction of CF₃ radicals with Cl₂ was studied relative to that with O₂ at pressures from 4 to 700 torr of N₂ diluent. By using the published absolute rate constants for k(CF₃ + O₂) at 1–10 torr to calibrate the pressure dependence of these relative rate constants, values of the low- and high-pressure limiting rate constants have been determined at 296 K using a Troe expression: k₀(CF₃ + O₂) = (4.8 ± 1.2) × 10^?29 cm⁶ molecule^?2 s^?1; k_∞(CF₃ + O₂) = (3.95 ± 0.25) × 10^?12 cm³ molecule^?1 s^?1; F_c = 0.46. The value of the rate constant k(CF₃ + Cl₂) was determined to be (3.5 ± 0.4) × 10^?14 cm³ molecule^?1 s^?1 at 296 K. The reaction of Cl atoms with CF₃I is a convenient way to prepare CF₃ radicals for laboratory study. © 1995 John Wiley & Sons, Inc.     

Kinetics and mechanism for the oxidation of 1,1,1-trichloroethane

The reaction mechanisms for oxidation of CH₃CCl₂ and CCl₃CH₂ radicals, formed in the atmospheric degradation of CH₃CCl₃ have been elucidated. The primary oxidation products from these radicals are CH₃CClO and CCl₃CHO, respectively. Absolute rate constants for the reaction of hydroxyl radicals with CH₃CCl₃ have been measured in 1 atm of Argon at 359, 376, and 402 K using pulse radiolysis combined with UV kinetic spectroscopy giving ??(OH + CH₃CCl₃) = (5.4 ± 3) 10^?12 exp(?3570 ± 890/RT) cm³ molecule^?1 s^?1. A value of this rate constant of 1.3 × 10^?14 cm³ molecule^?1 s^?1 at 298 K was calculated using this Arrhenius expression. A relative rate technique was utilized to provide rate data for the OH + CH₃ CCl₃ reaction as well as the reaction of OH with the primary oxidation products. Values of the relative rate constants at 298 K are: ??(OH + CH₃CCl₃) = (1.09 ± 0.35) × 10^?14, ??(OH + CH₃CClO) = (0.91 ± 0.32) × 10^?14, ??(OH + CCl₃CHO) = (178 ± 31) × 10^?14, ??(OH + CCl₂O) < 0.1 × 10^?14; all in units of cm³ molecule^?1 s^?1. The effect of chlorine substitution on the reactivity of organic compounds towards OH radicals is discussed.     

Synthesis and polymerization of racemic and optically active β-substituted β-propiolactones. II: β-monosubstituted and β-disubstituted monomers and polymers with different optical purities

β-(trichloromethyl)-β-propiolactone (CCl₃-PL), β-(trifluoromethyl,methyl)-β-propiolactone (CF₃, Me-PL) and β-(trifluoromethyl,ethyl)-β-propiolactone (CF₃,Et-PL) have been obtained by the reaction of ketene with chloral, 1,1,1-trifluoroacetone and 1,1,1-trifluorobutanone, respectively. Chiral catalysis lead to optically active monomers. The enantiomeric excess of the lactones has been measured by ¹H-NMR spectroscopy, in the presence of 2,2,2-trifluoro-1-(9-anthryl)ethanol or an europium chiral shift reagent. Polymerizations have been carried out in bulk or in toluene, at 60°C or 80°C, using mainly organometallic initiators. The Polymers become insoluble and crystalline at enantiomeric excesses over 80% for CCl₃-PL and 70% for CF₃,Me-PL. Melting temperatures were recorded from 238 to 268°C for poly(CCl₃-PL) and from 78 to 100°C for poly(CF₃,Me-PL), depending upon the molecular weight and the enantiomeric excess. The ¹³C-NMR specroscopy of poly(CCL₃-PL) indicates that the polymerization of the corresponding lactone leads to polymers of increasing degrees of isotacticity with the enantiomeric excess of the monomer.     

The kinetics of the reaction of O(3P) and D atoms with cyclohexane

The kinetics of the reactions of O(³P) and D atoms with cyclohexane have been investigated using fast-flow techniques. The rates of reaction were computed by monitoring changes in both atom and cyclohexane concentrations using electron spin resonance and mass spectrometric methods, respectively. The O(³P) + C₆H₁₂ reaction was studied over a temperature range of 344 to 513°K and we obtain a specific rate constant of (3.2±0.6) × 10¹⁴ exp (?4400±400/RT) cm³/mole˙sec for this reaction. The only reaction product detectable mass spectrometrically under flow conditions of excess oxygen atoms is formaldehyde. The D + C₆H₁₂ reaction was studied over a temperature range of 297 to 596°K. A specific rate constant of (4.1±1.0) × 10¹³ exp (?4000±300/RT) cm³/mole˙sec was obtained for this reaction. On the basis of the results obtained in these studies, the important primary process in both the O(³P) and D atom reactions is concluded to be abstraction of a hydrogen atom from the cyclohexane molecule.     

Kinetics and mechanism of the thermal gas-phase reaction between trifluoromethylhypofluorite,CF3OF,and tetrachloroethene

The thermal gas-phase reaction of CF₃OF with CCl₂CCl₂ has been studied between 313.8 and 343.8 K. The initial pressure of CF₃OF was varied between 10.8 and 77.5 torr and that of CCl₂CCl₂ between 3.7 and 26.8 torr. CF₃OF was always present in excess, varying the initial ratio of CF₃OF to that of CCl₂CCl₂ from 1.3 to 10. Three products were formed: CF₃OCCl₂CCl₂F, CCl₂FCCl₂F, and CF₃O(CCl₂CCl₂) ₂OCF₃. The yields of CF₃OCCl₂CCl₂F were 98–99.5%, based on the sum of the products. The reaction was a homogeneous chain reaction not affected by the total pressure. In presence of O₂ the oxidation of CCl₂CCl₂ to CCl₃C(O)Cl and COCl₂ occurred. The proposed basic reaction steps are: generation of the radicals CF₃O˙ and CCl₂FCCl₂˙ (κ₁) in a biomolecular process between CF₃OF and CCl₂CCl₂, formation of the radical CF₃OCCl₂CCl₂˙ by addition of CF₃O˙ to CCl₂CCl₂, chain generation of CF₃O˙ by abstraction of fluorine atom from CF₃OF by CF₃OCCl₂CCl₂˙ (κ₄), and chain termination by recombination of the radicals CF₃OCCl₂CCl₂˙. The expressions obtained for the constants κ₁ and κ₄ are κ₁ = 3.16 ± 0.6 × 10⁷ exp(−15.2 ± 1.7 Kcal mol⁻¹/RT) dm³ mol⁻¹ s⁻¹, κ₄ = 3.7 ± 0.5 × 10⁹ exp(−6.0 ± 1.1 Kcal mol⁻¹/RT) dm³ mol⁻¹ s⁻¹. © 1996 John Wiley & Sons, Inc.     

Kinetics of the gas‐phase reactions of chlorine atoms with CH2F2, CH3CCl3, and CF3CFH2 over the temperature range 253–553 K

Relative rate techniques were used to study the title reactions in 930–1200 mbar of N₂ diluent. The reaction rate coefficients measured in the present work are summarized by the expressions k(Cl + CH₂F₂) = 1.19 × 10^?17 T² exp(?1023/T) cm³ molecule^?1 s^?1 (253–553 K), k(Cl + CH₃CCl₃) = 2.41 × 10^?12 exp(?1630/T) cm³ molecule^?1 s^?1 (253–313 K), and k(Cl + CF₃CFH₂) = 1.27 × 10^?12 exp(?2019/T) cm³ molecule^?1 s^?1 (253–313 K). Results are discussed with respect to the literature data. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 401–406, 2009     

The rate constant for the recombination of trifluoromethyl radicals at T = 296 K

The high-pressure rate constant of the CF₃ + CF₃ → C₂F₆ reaction at T = 296 K was measured in the pulse photolysis (λ = 694.3 nm, ruby laser) of CF₃NO in the presence of NO by means of the time-resolved detection of CF₃NO by the intracavity absorption of He(SINGLE BOND)Ne laser radiation (λ = 632.8 nm). The obtained value is k_2∞ = (3.9 ± 1.3) × 10⁻¹² cm³/s. © 1996 John Wiley & Sons, Inc.     

Kinetics and mechanism for the atmospheric oxidation of 1,1,2-trifluoroethane (HFC 143)

The rate constant for the reaction of the hydroxyl radical with 1,2,2-trifuoroethane has been determined over the temperature range 278–323 K using a relative rate technique. The results provide a value of k(OH + CH₂FCHF₂) = 2.65 × 10^?12 exp(?1542 ± 500/T) cm³ molecule^?1 s^?1 based on k(OH + CH₃CCl₃) = 1.2 × 10^?12 exp(?1400 ± 200/T) cm³ molecule^?1 s^?1 for the rate constant of the reference reaction. The chlorine atom initiated photooxidation of CH₂CHF₂ was investigated from 255 to 330 K and as a function of O₂ pressure at 1 atmosphere total pressure using Fourier transform infrared spectroscopy. The major carbon-containing products were CHFO and CF₂O suggesting that the alkoxy radicals CH₂FCF₂O and CHF₂CHFO, formed in the reaction, react predominantly by carbon-carbon bond cleavage. The results indicate that formation of CHF₂CFO from the reaction of CHF₂CHFO radicals with O₂ will be unimportant under all atmospheric conditions. © 1995 John Wiley & Sons, Inc.     

Azide mechanisms for the production of NCl metastables

The production of both the b¹Σ⁺ and a¹Δ states of NCl has been observed from the reaction of HN₃ with flowing streams of Cl and F atoms. The results suggest that a two-step reaction sequence is responsible for the production of excited NCl, as follows: The rate contant (all products) for the first step is k(F + HN₃) > 1 × 10^?11 cm³/molecule sec. Comparison of this value to results obtained in a previous study of the F + HN₃ system yields a value k(F + N₃) = 2 × 10^?12 cm³/molecule sec. The rate constant for the reaction of chlorine atoms with HN₃ was determined to be k(Cl + HN₃) 1 × 10^?12 cm³/molecule sec. The difference between the Cl + HN₃ and F + HN₃ rates is interpreted in terms of an addition–elimination mechanism.     

Kinetics and mechanism of the reaction of CF3 radicals with NO2

The reaction of CF₃ with NO₂ was studied at 296 ± 2K using two different absolute techniques. Absolute rate constants of (1.6 ± 0.3) × 10⁻¹¹ and (2.1 _−0.3⁺⁰⁷) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ were derived by IR fluorescence and UV absorption spectroscopy, respectively. The reaction proceeds via two reaction channels: CF₃ + NO₂ → CF₂O + FNO, (70 ± 12)% and CF₃ + NO₂ → CF₃O + NO, (30 ± 12)%. An upper limit of 11% for formation of other reaction products was determined. The overall rate constant was within the uncertainty independent of total pressure between 0.4 to 760 torr. © 1996 John Wiley & Sons, Inc.     

Measurement of the solubility of water in 2,2-dichloro-1,1,1-trifluoroethane (HCFC 123)

A metal ebulliometer has been used to measure the solubility of water in 2,2-dichloro-1,1,1-trifluoroethane (HCFC 123) over the temperature range 297–354 K. Solubilities varied from 9.5×10⁻³ to 3.75×10⁻² (mole fraction). Activity coefficients (γ^∞) and distribution coefficients (K^∞) were estimated. The results were used to resolve a discrepancy found in the literature concerning the vapor pressure of HCFC 123.     

ab initio calculations and thermochemical analysis on C1 atom abstractions of chlorine from chlorocarbons and the reverse alkyl abstractions: Cl2 + R· ↔ Cl· + RCl

Thermodynamic properties (ΔH°_f(298), S°₍₂₉₈₎ and Cp(T) from 300 to 1500 K) for reactants, adducts, transition states, and products in reactions of CH₃ and C₂H₅ with Cl₂ are calculated using CBSQ//MP2/6‐311G(d,p). Molecular structures and vibration frequencies are determined at the MP2/6‐311G(d,p), with single‐point calculations for energy at QCISD(T)/6‐311 + G(d,p), MP4(SDQ)/CbsB4, and MP2/CBSB3 levels of calculation with scaled vibration frequencies. Contributions of rotational frequencies for S°₍₂₉₈₎ and Cp(T)'s are calculated based on rotational barrier heights and moments of inertia using the method of Pitzer and Gwinn [1]. Thermodynamic parameters, ΔH°_f(298), S°₍₂₉₈₎, and C_P(T), are evaluated for C₁ and C₂ chlorocarbon molecules and radicals. These thermodynamic properties are used in evaluation and comparison of Cl₂ + R· → Cl· + RCl (defined forward direction) reaction rate constants from the kinetics literature for comparison with the calculations. Data from some 20 reactions in the literature show linearity on a plot of Ea_fwd vs. ΔH_rxn,fwd, yielding a slope of (0.38 ± 0.04) and intercept of (10.12 ± 0.81) kcal/mole. A correlation of average Arrhenius preexponential factor for Cl· + RCl → Cl₂ + R· (reverse rxn) of (4.44 ± 1.58) × 10¹³ cm³/mol‐sec on a per‐chlorine basis is obtained with Ea_Rev = (0.64 ± 0.04) × ΔH_rxn,Rev + (9.72 ± 0.83) kcal/mole, where Ea_Rev is 0.0 if ΔH_rxn,Rev is more than 15.2 kcal/mole exothermic. Kinetic evaluations of literature data are also performed for classes of reactions. Ea_fwd = (0.39 ± 0.11) × ΔH_rxn,fwd + (10.49 ± 2.21) kcal/mole and average A_fwd = (5.89 ± 2.48) × 10¹² cm³/mole‐sec for hydrocarbons: Ea_fwd = (0.40 ± 0.07) × ΔH_rxn,fwd + (10.32 ± 1.31) kcal/mole and average A_fwd = (6.89 ± 2.15) × 10¹¹ cm³/mole‐sec for C₁ chlorocarbons: Ea_fwd = (0.33 ± 0.08) × ΔH_rxn,fwd + (9.46 ± 1.35) kcal/mole and average A_fwd = (4.64 ± 2.10) × 10¹¹ cm³/mole‐sec for C₂ chlorocarbons. Calculation results on the methyl and ethyl reactions with Cl₂ show agreement with the experimental data after an adjustment of +2.3 kcal/mole is made in the calculated negative Ea's. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 548–565, 2000     

UV absorption spectra,kinetics, and mechanisms of the self reaction of CF3O2 radicals in the gas phase at 295 K

The ultraviolet absorption spectrum and the self reaction kinetics of CF₃O₂ radicals have been studied in the gas phase at 298 K using the pulse radiolysis technique. Long pathlength Fourier transform infrared (FTIR) spectroscopy was used to identify and quantify reaction products. Absorption cross sections were quantified over the wavelength range 215–270 nm. The measured cross section at 230 nm was; Errors represent statistical (2σ) together with our estimate of potential systematic errors. The absorption cross section data were then used to derive the observed self reaction rate constant for reaction (1), defined as ?d[CF₃O₂]/dt = 2k _obs[CF₃O₂]² k_lobs = (3.6 ± 0.9) × 10^?12 cm³ molecule^?1 s^?1. The only carbon containing product observed by FTIR spectroscopy was CF₃OOOCF₃. Consideration of the loss of CF₃O₂ radicals to form the trioxide CF₃OOOCF₃ allows derivation of the true bimolecular rate constant for reaction (1); k₁ = (1.8 ± 0.5) × 10^?12 cm³ molecule^?1 s^?1. These results are discussed with respect to previous studies of the absorption spectra of peroxy radicals, the kinetics, and mechanisms of their self reaction. © John Wiley & Sons, Inc.     

Rate constants for the gas‐phase reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals at 250–430 K

The rate constants k₁ for the reaction of CF₃CF₂CF₂CF₂CF₂CHF₂ with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250–430 K using the flash photolysis–laser‐induced fluorescence (FP‐LIF) technique and the laser photolysis–laser‐induced fluorescence (LP‐LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253–328 K in an 11.5‐dm³ reaction chamber with either CHF₂Cl or CH₂FCF₃ as a reference compound. OH radicals were produced by UV photolysis of an O₃–H₂O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k₁ (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10^?15 cm³ molecule^?1 s^?1 (FP‐LIF method) and (1.72 ± 0.07) × 10^?15 cm³ molecule^?1 s^?1 (LP‐LIF method), whereas the K₁ (298 K) values determined by the relative method were (1.87 ± 0.11) × 10^?15 cm³ molecule^?1 s^?1 (CHF₂Cl reference) and (2.12 ± 0.11) × 10^?15 cm³ molecule^?1 s^?1 (CH₂FCF₃ reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K₁ = (4.71 ± 0.94) × 10^?13 exp[?(1630 ± 80)/T] cm³ molecule^?1 s^?1. Using kinetic data for the reaction of tropospheric CH₃CCl₃ with OH radicals [k₁ (272 K) = 6.0 × 10^?15 cm³ molecule^?1 s^?1, tropospheric lifetime of CH₃CCl₃ = 6.0 years], we estimated the tropospheric lifetime of CF₃CF₂CF₂CF₂CF₂CHF₂ through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26–33, 2004     

FTIR studies of the kinetics and mechanism for the reaction of Cl atom with formylchloride

The rate constant for the reaction Cl + CHClO → HCl + CClO was determined from relative decay rates of CHClO and CH₃Cl inthe photolysis of mixtures containing Cl₂ (～1 torr), CH₃Cl (～1 torr), and O₂ (～0.1 torr) in 700 torr N₂. In such mixtures CHClO was generated in situ as a principal product prior to complete consumption of O₂. The value of k(Cl + CHClO)/k(Cl + CH₃Cl) = 1.6 ± 0.2(3σ) combined with the literature value of k(Cl + CH₃Cl) = 4.9 × 10^?13 cm³/molecule sec gives k(Cl + CHClO) = 7.8 × 10^?13 cm³/molecule sec at 298 ± 2 K, in excellent agreement with a previous value of (7.9 ± 1.5) × 10^?13 cm³/molecule sec determined by Sanhueza and Heicklen [J. Phys. Chem., 79 , 7 (1975)]. Thus this reaction is approximately 100 times slower than the corresponding reactions of aldehydes and alkanes with comparable C? H bond energies (≤95 kcal/mol).     

A kinetic study of the reaction of fluorine atoms with CH3F,CH3Cl,CH3Br,CF2H2, CO,CF3H,CF3CHCl2, CF3CH2F,CHF2CHF2, CF2ClCH3, CHF2CH3, and CF3CF2H at 295 ± 2 K

A variety of relative and absolute techniques have been used to measure the reactivity of fluorine atoms with a series of halogenated organic compounds and CO. The following rate constants were derived, in units of cm³ molecule^?1 s^?1: CH₃F, (3.7 ± 0.8) × 10^?11, CH₃Cl, (3.3 ± 0.7) × 10^?11; CH₃Br, (3.0 ± 0.7) × 10^?11; CF₂H₂, (4.3 ± 0.9) × 10^?12; CO, (5.5 ± 1.0) × 10^?13 (in 700 torr total pressure of N₂ diluent); CF₃H, (1.4 ± 0.4) × 10^?13; CF₃CCl₂H (HCFC-123), (1.2 ± 0.4) × 10^?12; CF₃CFH₂ (HFC-134a), (1.3 ± 0.3) × 10^?12, CHF₂CHF₂ (HFC-134), (1.0 ± 0.3) × 10^?12; CF₂ClCH₃ (HCFC-42b), (3.9 ± 0.9) × 10^?12, CF₂HCH₃ (HFC-152a), (1.7 ± 0.4) × 10^?11; and CF₃CF₂H (HFC-125), (3.5 ± 0.8) × 10^?13. Quoted errors are statistical uncertainties (2σ). For rate constants derived using relative rate techniques, an additional uncertainty has been added to account for potential systematic errors in the reference rate constants used. Experiments were performed at 295 ± 2 K. Results are discussed with respect to the previous literature data and to the interpretation of laboratory studies of the atmospheric chemistry of HCFCs and HFCs. © 1993 John Wiley & Sons, Inc.