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     

Temperature-dependent rate coefficients for the gas-phase OH + furan-2,5-dione (C4H2O3, maleic anhydride) reaction

Rate coefficients, k₁(T), for the gas-phase reaction of the OH radical with furan-2,5-dione (maleic anhydride (MA), C₄H₂O₃), a biomass burning related compound, were measured under pseudo–first-order conditions in OH using the pulsed laser photolysis–laser-induced fluorescence method over a range of temperature (283-374 K) and bath gas pressure (50-200 Torr; He or N₂). k₁(T) was found to be independent of pressure over this range with k₁(283-374 K) = (1.55 ± 0.20) × 10⁻¹² exp[(−410 ± 44)/T) cm³ molecule⁻¹ s⁻¹ and k₁(296 K) = (3.93 ± 0.28) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹, where the uncertainties are 2σ and the preexponential term includes the estimated systematic error. The atmospheric lifetime of MA with respect to OH reactive loss is estimated to be ∼15 days. The present results are compared with a previous room temperature relative rate study of the OH + MA reaction, and the significant discrepancy between the studies is discussed; the present results are approximately a factor of 4 lower. It is also noteworthy that the experimentally measured k₁(296 K) value obtained in this work is nearly a factor of 110 less than estimated by a structure activity relationship based on trends in ionization potential. Based in part on a computational evaluation, an atmospheric degradation mechanism of MA is proposed.     

Rate coefficients and ClO radical yields in the reaction of O(1D) with CClF2CCl2F,CCl3CF3, CClF2CClF2, and CCl2FCF3

Rate coefficients, k, and ClO radical product yields, Y, for the gas‐phase reaction of O(¹D) with CClF₂CCl₂F (CFC‐113) (k₂), CCl₃CF₃ (CFC‐113a) (k₃), CClF₂CClF₂ (CFC‐114) (k₄), and CCl₂FCF₃ (CFC‐114a) (k₅) at 296 K are reported. Rate coefficients for the loss of O(¹D) were measured using a competitive reaction technique, with n‐butane (n‐C₄H₁₀) as the reference reactant, employing pulsed laser photolysis production of O(¹D) combined with laser‐induced fluorescence detection of the OH radical temporal profile. Rate coefficients were measured to be k₂ = (2.33 ± 0.40) × 10^?10 cm³ molecule^?1 s^?1, k₃ = (2.61 ± 0.40) × 10^?10 cm³ molecule^?1 s^?1, k₄ = (1.42 ± 0.25) × 10^?10 cm³ molecule^?1 s^?1, and k₅ = (1.62 ± 0.30) × 10^?10 cm³ molecule^?1 s^?1. ClO radical product yields for reactions (2)–(5) were measured using pulsed laser photolysis combined with cavity ring‐down spectroscopy to be 0.80 ± 0.10, 0.79 ± 0.10, 0.85 ± 0.12, and 0.79 ± 0.10, respectively. The quoted errors in k and Y are at the 2σ (95% confidence) level and include estimated systematic errors. © 2011 Wiley Periodicals, Inc.

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America

Int J Chem Kinet 43: 393–401, 2011     

Kinetics of the gas‐phase reactions of CHXCFX (X = H,F) with OH (253–328 K) and NO3 (298 K) radicals and O3 (236–308 K)

Rate constants for the reactions of OH and NO₃ radicals with CH₂?CHF (k₁ and k₄), CH₂?CF₂ (k₂ and k₅), and CHF?CF₂ (k₃ and k₆) were determined by means of a relative rate method. The rate constants for OH radical reactions at 253–328 K were k₁ = (1.20 ± 0.37) × 10^?12 exp[(410 ± 90)/T], k₂ = (1.51 ± 0.37) × 10^?12 exp[(190 ± 70)/T], and k₃ = (2.53 ± 0.60) × 10^?12 exp[(340 ± 70)/T] cm³ molecule^?1 s^?1. The rate constants for NO₃ radical reactions at 298 K were k₄ = (1.78 ± 0.12) × 10^?16 (CH₂?CHF), k₅ = (1.23 ± 0.02) × 10^?16 (CH₂?CF₂), and k₆ = (1.86 ± 0.09) × 10^?16 (CHF?CF₂) cm³ molecule^?1 s^?1. The rate constants for O₃ reactions with CH₂?CHF (k₇), CH₂?CF₂ (k₈), and CHF?CF₂ (k₉) were determined by means of an absolute rate method: k₇ = (1.52 ± 0.22) × 10^?15 exp[?(2280 ± 40)/T], k₈ = (4.91 ± 2.30) × 10^?16 exp[?(3360 ± 130)/T], and k₉ = (5.70 ± 4.04) × 10^?16 exp[?(2580 ± 200)/T] cm³ molecule^?1 s^?1 at 236–308 K. The errors reported are ±2 standard deviations and represent precision only. The tropospheric lifetimes of CH₂?CHF, CH₂?CF₂, and CHF?CF₂ with respect to reaction with OH radicals, NO₃ radicals, and O₃ were calculated to be 2.3, 4.4, and 1.6 days, respectively. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 619–628, 2010     

Vacuum ultraviolet laser‐induced fluorescence kinetic study of the reactions of Cl atoms with fluoroalkenes (CxF2x+1CHCH2, x = 1,2,4, 6, and 8) at low pressures

Pulsed laser photolysis/vacuum ultraviolet laser‐induced fluorescence techniques were used to measure rate coefficients for Cl atom reactions with a series of fluoroalkenes (C_xF_2x+1CH?CH₂, x = 1,2,4,6,8) in 6–10 Torr of CF₄ diluent at 295 ± 2 K. Rate coefficients (units of 10^?11 cm³ molecule^?1s^?1) of 4.49 ± 0.64, 6.58 ± 0.59, 8.91 ± 0.58, 9.27 ± 0.64, and 9.00 ± 0.87 were determined for C_xF_2x+1CH?CH₂ with x = 1,2,4,6, and 8, respectively. In 6–10 Torr of CF₄ diluent, the kinetics of the title reactions are at, or near, the high‐pressure limit for x = 4, 6, and 8, approximately 30% below the high‐pressure limit for x = 2, and approximately 50% below the high‐pressure limit for x = 1. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 328–332, 2007     

Kinetics of the gas‐phase reactions of cyclo‐CF2CFXCHXCHX – (X = H,F, Cl) with OH radicals at 253–328 K

Rate constants were determined for the reactions of OH radicals with halogenated cyclobutanes cyclo‐CF₂CF₂CHFCH₂? (k₁), trans‐cyclo‐CF₂CF₂CHClCHF? (k₂), cyclo‐CF₂CFClCH₂CH₂? (k₃), trans‐cyclo‐CF₂CFClCHClCH₂? (k₄), and cis‐cyclo‐CF₂CFClCHClCH₂? (k₅) by using a relative rate method. OH radicals were prepared by photolysis of ozone at a UV wavelength (254 nm) in 200 Torr of a sample reference H₂O? O₃? O₂? He gas mixture in an 11.5‐dm³ temperature‐controlled reaction chamber. Rate constants of k₁ = (5.52 ± 1.32) × 10^?13 exp[–(1050 ± 70)/T], k₂ = (3.37 ± 0.88) × 10^?13 exp[–(850 ± 80)/T], k₃ = (9.54 ± 4.34) × 10^?13 exp[–(1000 ± 140)/T], k₄ = (5.47 ± 0.90) × 10^?13 exp[–(720 ± 50)/T], and k₅ = (5.21 ± 0.88) × 10^?13 exp[–(630 ± 50)/T] cm³ molecule^?1 s^?1 were obtained at 253–328 K. The errors reported are ± 2 standard deviations, and represent precision only. Potential systematic errors associated with uncertainties in the reference rate constants could add an additional 10%–15% uncertainty to the uncertainty of k₁–k₅. The reactivity trends of these OH radical reactions were analyzed by using a collision theory–based kinetic equation. The rate constants k₁–k₅ as well as those of related halogenated cyclobutane analogues were found to be strongly correlated with their C? H bond dissociation enthalpies. We consider the dominant tropospheric loss process for the halogenated cyclobutanes studied here to be by reaction with the OH radicals, and atmospheric lifetimes of 3.2, 2.5, 1.5, 0.9, and 0.7 years are calculated for cyclo‐CF₂CF₂CHFCH₂? , trans‐cyclo‐CF₂CF₂CHClCHF? , cyclo‐CF₂CFClCH₂CH₂? , trans‐cyclo‐CF₂CFClCHClCH₂? , and cis‐cyclo‐CF₂CFClCHClCH₂? , respectively, by scaling from the lifetime of CH₃CCl₃. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 532–542, 2009     

Kinetics of the gas‐phase reaction of CF3OC(O)H with OH radicals at 242–328 K

The rate constants, k₁, of the reaction of CF₃OC(O)H with OH radicals were measured by using a Fourier transform infrared spectroscopic technique in an 11.5‐dm³ reaction chamber at 242–328 K. 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 UV irradiation. With CF₃OCH₃ as a reference compound, k₁ at 298 K was (1.65 ± 0.13) × 10^?14 cm³ molecule^?1 s^?1. The temperature dependence of k₁ was determined as (2.33 ± 0.42) × 10^?12 exp[?(1480 ± 60)/T] cm³ molecule^?1 s^?1; possible systematic uncertainty could add an additional 20% to the k₁ values. The atmospheric lifetime of CF₃OC(O)H with respect to reaction with OH radicals was calculated to be 3.6 years. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 337–344 2004     

Rate coefficients for the O(3P) + Cl2O gas‐phase reaction between 230 and 357 K

Rate coefficients, k, for the gas‐phase reaction of O(³P) atoms with Cl₂O (dichlorine monoxide) over a range of temperatures (230–357 K) at pressures between 12 and 32 Torr (N₂) are reported. Rate coefficients were measured under pseudo‐first‐order conditions in O(³P) using pulsed laser photolysis to produce O(³P) atoms and atomic resonance fluorescence to detect its temporal profile. The rate coefficient temperature dependence is given by the Arrhenius expression k(T) = (1.51 ± 0.20) × 10^?11 exp[?(477 ± 30)/T] cm³ molecule^?1 s^?1, and k(296 K) was measured to be (2.93 ± 0.30) × 10^?12 cm³ molecule^?1 s^?1. The quoted uncertainty limits are at the 2σ (95% confidence) level and include estimated systematic errors. The rate coefficients determined in the present study, under conditions that minimized secondary losses of O(³P), are compared with previous results from other laboratories and the discrepancies are discussed. © 2011 Wiley Peiodicals, Inc.

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

Int J Chem Kinet 43: 312–321, 2011     

FT‐IR kinetic and product study of the OH radical and Cl‐atom–initiated oxidation of dibasic esters

Using a relative kinetic technique, rate coefficients have been measured, at 296 ± 2 K and 740 Torr total pressure of synthetic air, for the gas‐phase reaction of OH radicals with the dibasic esters dimethyl succinate [CH₃OC(O)CH₂CH₂C(O)OCH₃], dimethyl glutarate [CH₃OC(O)CH₂CH₂CH₂C(O)OCH₃], and dimethyl adipate [CH₃OC(O)CH₂CH₂CH₂CH₂C(O)OCH₃]. The rate coefficients obtained were (in units of cm³ molecule^?1 s^?1): dimethyl succinate (1.89 ± 0.26) × 10^?12; dimethyl glutarate (2.13 ± 0.28) × 10^?12; and dimethyl adipate (3.64 ± 0.66) × 10^?12. Rate coefficients have been also measured for the reaction of chlorine atoms with the three dibasic esters; the rate coefficients obtained were (in units of cm³ molecule^?1 s^?1): dimethyl succinate (6.79 ± 0.93) × 10^?12; dimethyl glutarate (1.90 ± 0.33) × 10^?11; and dimethyl adipate (6.08 ± 0.86) × 10^?11. Dibasic esters are industrial solvents, and their increased use will lead to their possible release into the atmosphere, where they may contribute to the formation of photochemical air pollution in urban and regional areas. Consequently, the products formed from the oxidation of dimethyl succinate have been investigated in a 405‐L Pyrex glass reactor using Cl‐atom–initiated oxidation as a surrogate for the OH radical. The products observed using in situ Fourier transform infrared (FT‐IR) absorption spectroscopy and their fractional molar yields were: succinic formic anhydride (0.341 ± 0.068), monomethyl succinate (0.447 ± 0.111), carbon monoxide (0.307 ± 0.061), dimethyl oxaloacetate (0.176 ± 0.044), and methoxy formylperoxynitrate (0.032–0.084). These products account for 82.4 ± 16.4% C of the total reaction products. Although there are large uncertainties in the quantification of monomethyl succinate and dimethyl oxaloacetate, the product study allows the elucidation of an oxidation mechanism for dimethyl succinate. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 431–439, 2001     

Rate coefficients for the reaction of the acetyl radical,CH3CO,with Cl2 between 253 and 384 K

Rate coefficients, k, for the gas‐phase reaction CH₃CO + Cl₂ → products (2) were measured between 253 and 384 K at 55–200 Torr (He). Rate coefficients were measured under pseudo‐first‐order conditions in CH₃CO with CH₃CO produced by the 248‐nm pulsed‐laser photolysis of acetone, CH₃C(O)CH₃, or 2,3‐butadione, CH₃C(O)C(O)CH₃. The loss of CH₃CO was monitored by cavity ring‐down spectroscopy (CRDS) at 532 nm. Rate coefficients were determined by first‐order kinetic analysis of the CH₃CO temporal profiles for [Cl₂] < 1 × 10¹⁴ molecule cm^?3 and the analysis of the CRDS profiles by the simultaneous kinetics and ring‐down method for experiments performed with [Cl₂] > 1 × 10¹⁴ molecule cm^?3. k₂(T) was found to be independent of pressure, with k₂(296 K) = (3.0 ± 0.5) × 10^?11 cm³ molecule^?1 s^?1. k₂(T) showed a weak negative temperature dependence that is well reproduced by the Arrhenius expression k₂(T) = (2.2 ± 0.8) × 10^?11 exp[(85 ± 120)/T] cm³ molecule^?1 s^?1. The quoted uncertainties in k₂(T) are at the 2σ level (95% confidence interval) and include estimated systematic errors. A comparison of the present work with previously reported rate coefficients for the CH₃CO + Cl₂ reaction is presented. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 543–553, 2009     

Kinetics of the reaction of OH radicals with acetylene in 25–8000 torr of air at 296 K

Relative rate techniques were used to study the kinetics of the reaction of OH radicals with acetylene at 296 K in 25–8000 Torr of air, N₂/O₂, or O₂ diluent. Results obtained at total pressures of 25–750 Torr were in good agreement with the literature data. At pressures >3000 Torr, our results were substantially (～35%) lower than that reported previously. The kinetic data obtained over the pressure range 25–8000 Torr are well described (within 15%) by the Troe expression using k_o = (2.92 ± 0.55) × 10^?30 cm⁶ molecule^?2 s^?1, k_∞ = (9.69 ± 0.30) × 10^?13 cm³ molecule^?1 s^?1, and F_c = 0.60. At 760 Torr total pressure, this expression gives k = 8.49 × 10^?13 cm molecule^?1 s^?1. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 191–197, 2003     

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.     

Kinetics and mechanisms of OH‐initiated oxidation of small unsaturated alcohols

Smog chamber relative rate techniques were used to measure rate coefficients of (5.00 ± 0.54) × 10^?11, (5.87 ± 0.63) × 10^?11, and (6.49 ± 0.82) × 10^?11 cm³ molecule^?1 s^?1 in 700 Torr air at 296 ± 1 K for reactions of OH radicals with allyl alcohol, 1‐buten‐3‐ol, and 2‐methyl‐3‐buten‐2‐ol, respectively; the quoted uncertainties encompass the extremes of determinations using two different reference compounds. The OH‐initiated oxidation of allyl alcohol in the presence of NO_x gives glycolaldehyde in a molar yield of 0.85 ± 0.08; the quoted uncertainty is two standard deviations. Oxidation of 2‐methyl‐3‐buten‐2‐ol gives acetone and glycolaldehyde in molar yields of 0.66 ± 0.06 and 0.56 ± 0.05, respectively. The reaction of OH radicals with allyl alcohol, 1‐buten‐3‐ol, and 2‐methyl‐3‐buten‐2‐ol proceeds predominately via addition to the >C?CH₂ double bond with most of the addition occurring to the terminal carbon. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 151–158, 2010     

Trimethylchlorosilane, (CH3)3SiCl: OH reaction kinetics and infrared spectrum

Rate coefficients for the OH + (CH₃)₃SiCl (trimethylchlorosilane) gas-phase reaction were measured over the temperature range 295–375 K using a pulsed laser photolysis laser-induced fluorescence technique. The room temperature rate coefficient was determined to be k₁(295 K) = (2.51 ± 0.13) × 10⁻¹³ cm³ molecule^–1 s^–1. The Arrhenius expression k₁(T) = (7.06 ± 2.15) × 10⁻¹² exp[–(992 ± 101)/T] cm³ molecule^–1 s^–1, where the quoted uncertainties are 2σ fit precision, describes the measured temperature dependence very well. As part of this work, the infrared spectra of CH₃)₃SiCl was measured.     

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

Rate coefficients have been measured for the reactions of Cl atoms with methanol (k₁) and acetaldehyde (k₂) using both absolute (laser photolysis with resonance fluorescence) and relative rate methods at 295 ± 2 K. The measured rate coefficients were (units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹): absolute method, k₁ = (5.1 ± 0.4), k₂ = (7.3 ± 0.7); relative method k₁ = (5.6 ± 0.6), k₂ = (8.4 ± 1.0). Based on a critical evaluation of the literature data, the following rate coefficients are recommended: k₁ = (5.4 ± 0.9) × 10⁻¹¹ and k₂ = (7.8 ± 1.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ (95% confidence limits). The results significantly improve the confidence in the database for reactions of Cl atoms with these oxygenated organics. Rate coefficients were also measured for the reactions of Cl₂ with CH₂OH, k₅ = (2.9 ± 0.6) × 10⁻¹¹ and CH₃CO, k₆ = (4.3 ± 1.5) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, by observing the regeneration of Cl atoms in the absence of O₂. Based on these results and those from a previous relative rate study, the rate coefficient for CH₃CO + O₂ at the high pressure limit is estimated to be (5.7 ± 1.9) × 10⁻¹² cm³ molecule⁻¹ s⁻¹. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 776–784, 1999     

Kinetics of the reactions of OH with 3‐methyl‐2‐cyclohexen‐1‐one and 3,5,5‐trimethyl‐2‐cyclohexen‐1‐one under simulated atmospheric conditions

Relative rate coefficients for the reactions of OH with 3‐methyl‐2‐cyclohexen‐1‐one and 3,5,5‐trimethyl‐2‐cyclohexen‐1‐one have been determined at 298 K and atmospheric pressure by the relative rate technique. OH radicals were generated by the photolysis of methyl nitrite in synthetic air mixtures containing ppm levels of nitric oxide together with the test and reference substrates. The concentrations of the test and reference substrates were followed by gas chromatography. Based on the value k(OH + cyclohexene) = (6.77 ± 1.35) × 10^?11 cm³ molecule^?1 s^?1, rate coefficients for k(OH + 3‐methyl‐2‐cyclohexen‐1‐one) = (3.1 ± 1.0) × 10^?11 and k(OH + 3,5,5‐trimethyl‐2‐cyclohexen‐1‐one) = (2.4 ± 0.7) × 10^?11 cm³ molecule^?1 s^?1 were determined. To test the system we also measured k(OH + isoprene) = (1.11 ± 0.23) × 10^?10 cm³ molecule^?1 s^?1, relative to the value k(OH + (E)‐2‐butene) = (6.4 ± 1.28) × 10^?11 cm³ molecule^?1 s^?1. The results are discussed in terms of structure–activity relationships, and the reactivities of cyclic ketones formed in the photo‐oxidation of monoterpene are estimated. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 7–11, 2002     

Rate coefficients for the reactions of OH with n‐propanol and iso‐propanol between 237 and 376 K

The rate coefficients for the reaction OH + CH₃CH₂CH₂OH → products (k₁) and OH + CH₃CH(OH)CH₃ → products (k₂) were measured by the pulsed‐laser photolysis–laser‐induced fluorescence technique between 237 and 376 K. Arrhenius expressions for k₁ and k₂ are as follows: k₁ = (6.2 ± 0.8) × 10^?12 exp[?(10 ± 30)/T] cm³ molecule^?1 s^?1, with k₁(298 K) = (5.90 ± 0.56) × 10^?12 cm³ molecule^?1 s^?1, and k₂ = (3.2 ± 0.3) × 10^?12 exp[(150 ± 20)/T] cm³ molecule^?1 s^?1, with k₂(298) = (5.22 ± 0.46) × 10^?12 cm³ molecule^?1 s^?1. The quoted uncertainties are at the 95% confidence level and include estimated systematic errors. The results are compared with those from previous measurements and rate coefficient expressions for atmospheric modeling are recommended. The absorption cross sections for n‐propanol and iso‐propanol at 184.9 nm were measured to be (8.89 ± 0.44) × 10^?19 and (1.90 ± 0.10) × 10^?18 cm² molecule^?1, respectively. The atmospheric implications of the degradation of n‐propanol and iso‐propanol are discussed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 10–24, 2010     

Rate constants and Arrhenius parameters for the reactions of Cl atoms with the halogenated ethers: CF3CH2OCHF2, CF3CHClOCHF2, and CF3CH2OCClF2

Rate constants have been determined for the reactions of Cl atoms with the halogenated ethers CF₃CH₂OCHF₂, CF₃CHClOCHF₂, and CF₃CH₂OCClF₂ using a relative‐rate technique. Chlorine atoms were generated by continuous photolysis of Cl₂ in a mixture containing the ether and CD₄. Changes in the concentrations of these two species were measured via changes in their infrared absorption spectra observed with a Fourier transform infrared (FTIR) spectrometer. Relative‐rate constants were converted to absolute values using the previously measured rate constants for the reaction, Cl + CD₄ → DCl + CD₃. Experiments were carried out at 295, 323, and 363 K, yielding the following Arrhenius expressions for the rate constants within this range of temperature:Cl + CF₃CH₂OCHF₂: k = (5.1₅ ± 0.7) × 10⁻¹² exp(−1830 ± 410 K/T) cm³ molecule⁻¹ s⁻¹ Cl + CF₃CHClOCHF₂: k = (1.6 ± 0.2) × 10⁻¹¹ exp(−2450 ± 250 K/T) cm³ molecule⁻¹ s⁻¹ Cl + CF₃CH₂OCClF₂: k = (9.6 ± 0.4) × 10⁻¹² exp(−2390 ± 190 K/T) cm³ molecule⁻¹ s⁻¹ The results are compared with those obtained previously for the reactions of Cl atoms with other halogenated methyl ethyl ethers. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 165–172, 2001     

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.     

Rate coefficients for the gas-phase OH + furan (C4H4O) reaction between 273 and 353 K

Rate coefficients, k₁, for the gas-phase OH radical reaction with the heterocyclic ether C₄H₄O (1,4-epoxybuta-1,3-diene, furan) were measured over the temperature range 273–353 K at 760 Torr (syn. air). Experiments were performed using: (i) the photochemical smog chamber THALAMOS (thermally regulated atmospheric simulation chamber, IMT NE, Douai-France) equipped with Fourier Transform Infrared (FTIR) and Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) detection methods and (ii) a photochemical reactor coupled with FTIR spectroscopy (PCR, University of Crete, Greece). k₁(273–353 K) was measured using a relative rate (RR) method, in which the loss of furan was measured relative to the loss of reference compounds with well-established OH reaction rate coefficients. k₁(273–353 K) was found to be well represented by the Arrhenius expression (1.30 ± 0.12) × 10⁻¹¹ exp[(336 ± 20)/T] cm³ molecule⁻¹ s⁻¹, with k₁(296 K) measured to be (4.07 ± 0.32) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The k₁(296 K) and pre-exponential quoted error limits are 2σ and include estimated systematic errors in the reference rate coefficients. The observed negative temperature dependence is consistent with a reaction mechanism involving the OH radical association to a furan double bond. Quantum mechanical molecular calculations show that OH addition to the α-carbon (ΔH_r(296 K) = −121.5 kJ mol⁻¹) is thermochemically favored over the β-carbon (ΔH_r(296 K) = −52.9 kJ mol⁻¹) addition. The OH-furan adduct was found to be stable over the temperature range of the present measurements. Maleic anhydride (C₄H₂O₃) was identified as a minor reaction product, 3% lower-limit yield, demonstrating a non-ring-opening active reaction channel. The present results are critically compared with results from previous studies of the OH + furan reaction rate coefficient. The infrared spectrum of furan was measured as part of this study and its estimated climate metrics are reported.