Temperature‐dependent rate coefficients and mechanism for the gas‐phase reaction of chlorine atoms with acetone

The rate coefficient for the gas‐phase reaction of chlorine atoms with acetone was determined as a function of temperature (273–363 K) and pressure (0.002–700 Torr) using complementary absolute and relative rate methods. Absolute rate measurements were performed at the low‐pressure regime (～2 mTorr), employing the very low pressure reactor coupled with quadrupole mass spectrometry (VLPR/QMS) technique. The absolute rate coefficient was given by the Arrhenius expression k(T) = (1.68 ± 0.27) × 10^?11 exp[?(608 ± 16)/T] cm³ molecule^?1 s^?1 and k(298 K) = (2.17 ± 0.19) × 10^?12 cm³ molecule^?1 s^?1. The quoted uncertainties are the 2σ (95% level of confidence), including estimated systematic uncertainties. The hydrogen abstraction pathway leading to HCl was the predominant pathway, whereas the reaction channel of acetyl chloride formation (CH₃C(O)Cl) was determined to be less than 0.1%. In addition, relative rate measurements were performed by employing a static thermostated photochemical reactor coupled with FTIR spectroscopy (TPCR/FTIR) technique. The reactions of Cl atoms with CHF₂CH₂OH (3) and ClCH₂CH₂Cl (4) were used as reference reactions with k₃(T) = (2.61 ± 0.49) × 10^?11 exp[?(662 ± 60)/T] and k₄(T) = (4.93 ± 0.96) × 10^?11 exp[?(1087 ± 68)/T] cm³ molecule^?1 s^?1, respectively. The relative rate coefficients were independent of pressure over the range 30–700 Torr, and the temperature dependence was given by the expression k(T) = (3.43 ± 0.75) × 10^?11 exp[?(830 ± 68)/T] cm³ molecule^?1 s^?1 and k(298 K) = (2.18 ± 0.03) × 10^?12 cm³ molecule^?1 s^?1. The quoted errors limits (2σ) are at the 95% level of confidence and do not include systematic uncertainties. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 724–734, 2010     

Rate coefficients for the reactions of OH with butanols from 298 K to temperatures relevant for low-temperature combustion

Rate coefficients for the reactions of OH with n, s, and iso-butanol have been measured over the temperature range 298 to ∼650 K. The rate coefficients display significant curvature over this temperature range and bridge the gap between previous low-temperature measurements with a negative temperature dependence and higher temperature shock tube measurements that have a positive temperature dependence. In combination with literature data, the following parameterizations are recommended: k_{1,OH + n-butanol}(T) = (3.8 ± 10.4) × 10⁻¹⁹T^{2.48 ± 0.37}exp ((840 ± 161)/T) cm³ molecule⁻¹ s⁻¹ k_{2,OH + s-butanol}(T) = (3.5 ± 3.0) × 10⁻²⁰T^{2.76 ± 0.12}exp ((1085 ± 55)/T) cm³ molecule⁻¹ s⁻¹ k_{3,OH + i-butanol}(T) = (5.1 ± 5.3) × 10⁻²⁰T^{2.72 ± 0.14}exp ((1059 ± 66)/T) cm³ molecule⁻¹ s⁻¹ k_{4,OH + t-butanol}(T) = (8.8 ± 10.4) × 10⁻²²T^{3.24 ± 0.15}exp ((711 ± 83)/T) cm³ molecule⁻¹ s⁻¹ Comparison of the current data with the higher shock tube measurements suggests that at temperatures of ∼1000 K, the OH yields, primarily from decomposition of β-hydroxyperoxy radicals, are ∼0.3 (n-butanol), ∼0.3 (s-butanol) and ∼0.2 (iso-butanol) with β-hydroxyperoxy decompositions generating OH, and a butene as the main products. The data suggest that decomposition of β-hydroxyperoxy radicals predominantly occurs via OH elimination.     

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     

Direct measurement of the C2H5C(O)O2 + NO reaction rate coefficient using chemical ionization mass spectrometry

The rate coefficient for the reaction of the peroxypropionyl radical (C₂H₅C(O)O₂) with NO was measured with a laminar flow reactor over the temperature range 226–406 K. The C₂H₅C(O)O₂ reactant was monitored with chemical ionization mass spectrometry. The measured rate coefficients are k(T) = (6.7 ± 1.7) × 10⁻¹² exp{(340 ± 80)/T} cm³ molecule⁻¹ s⁻¹ and k(298 K) = (2.1 ± 0.2) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. Our results are comparable to recommended rate coefficients for the analogous CH₃C(O)O₂ + NO reaction. Heterogeneous effects, pressure dependence, and concentration gradients inside the flow reactor are examined. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet: 31: 221–228, 1999     

Temperature-dependent kinetics studies of the reactions of C2H5O2 and n-C3H7O2 radicals with NO

The rate coefficients for the gas-phase reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO have been measured over the temperature range of (201–403) K using chemical ionization mass spectrometric detection of the peroxy radical. The alkyl peroxy radicals were generated by reacting alkyl radicals with O₂, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C₂H₅ radicals were generated through the dissociation of iodoethane in a low-power radio frequency discharge. The discharge source was also tested for the i-C₃H₇O₂ + NO reaction, yielding k_{298 K} = (9.1 ± 1.5) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 ± 0.4) × 10⁻¹² exp{(380 ± 70)/T} cm³ molecule⁻¹ s⁻¹ and k(T) = (2.9 ± 0.5) × 10⁻¹² exp{(350 ± 60)/T} cm³ molecule⁻¹ s⁻¹ for the reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO, respectively. The rate coefficients at 298 K derived from these Arrhenius expressions are k = (9.3 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for C₂H₅O₂ radicals and k = (9.4 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for n-C₃H₇O₂ radicals. © 1996 John Wiley & Sons, Inc.     

The temperature dependence of the OH radical reactions with some aromatic compounds under simulated tropospheric conditions

The temperature dependence of the rate coefficients for the OH radical reactions with toluene, benzene, o-cresol, m-cresol, p-cresol, phenol, and benzaldehyde were measured by the competitive technique under simulated atmospheric conditions over the temperature range 258–373 K. The relative rate coefficients obtained were placed on an absolute basis using evaluated rate coefficients for the corresponding reference compounds. Based on the rate coefficient k(OH + 2,3-dimethylbutane) = 6.2 × 10^?12 cm³ molecule^?1s^?1, independent of temperature, the rate coefficient for toluene k_OH = 0.79 × 10^?12 exp[(614 ± 114)/T] cm³ molecule^?1 s^?1 over the temperature range 284–363 K was determined. The following rate coefficients in units of cm³ molecule^?1 s^?1 were determined relative to the rate coefficient k(OH + 1,3-butadiene) = 1.48 × 10^?11 exp(448/T) cm³ molecule^?1 s^?1: o-cresol; k_OH = 9.8 × 10^?13 exp[(1166 ± 248)/T]; 301–373 K; p-cresol; k_OH = 2.21 × 10^?12 exp[(943 ± 449)/T]; 301–373 K; and phenol, k_OH = 3.7 × 10^?13 exp[(1267 ± 233)/T]; 301–373 K. The rate coefficient for benzaldehyde k_OH = 5.32 × 10^?12 exp[(243 ± 85)/T], 294–343 K was determined relative to the rate coefficient k(OH + diethyl ether) = 7.3 × 10^?12 exp(158/T) cm³ molecule^?1 s^?1. The data have been compared to the available literature data and where possible evaluated rate coefficients have been deduced or updated. Using the evaluated rate coefficient k(OH + toluene) = 1.59 × 10^?12 exp[(396 ± 105)/T] cm³ molecule^?1 s^?1, 213–363 K, the following rate coefficient for benzene has been determined k_OH = 2.58 × 10^?12 exp[(?231 ± 84)/T] cm³ molecule^?1 s^?1 over the temperature range 274–363 K and the rate coefficent for m-cresol, k_OH = 5.17 × 10^?12 exp[(686 ± 231)/T] cm³ molecule^?1 s^?1, 299–373 K was determined relative to the evaluated rate coefficient k(OH + o-cresol) = 2.1 × 10^?12 exp[(881 ± 356)/T] cm³ molecule^?1 s^?1. The tropospheric lifetimes of the aromatic compounds studied were calculated relative to that for 1,1,1-triclorethane = 6.3 years at 277 K. The lifetimes range from 6 h for m-cresol to 15.5 days for benzene. © 1995 John Wiley & Sons, Inc.     

Kinetics of the gas‐phase reaction of Cl atoms with CF2ClCFClH at 263–313 K

Relative rate techniques were used to measure k(Cl + CF₂ClCFClH) = (1.4) × 10⁻¹¹ exp[−(2360 ± 400)/T] cm³ molecule⁻¹ s⁻¹; k(Cl + CF₂ClCFClH) = 5.1 × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹ at 298 K. This result is discussed with respect to the available data. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 785–788, 1999     

Rate coefficients for the reaction of OH with Cl2, Br2, and I2 from 235 to 354 K

Rate coefficients for the reaction of OH with Cl₂, (k₁), Br₂, (k₂) and I₂, (k₃), were measured under pseudo‐first‐order conditions in OH. OH was produced by pulsed laser photolysis of H₂O₂ (or HNO₃) and its temporal profile was monitored by laser‐induced fluorescence. The measured rate coefficients for k₁ (231–354 K) and k₂ (235–357 K) are: k₁ (T) = (3.77 ± 1.02) × 10⁻¹² exp[−(1228 ± 140)/T] cm³ molecule⁻¹ s⁻¹ k₂ (T) = (1.98 ± 0.51) × 10⁻¹¹ exp[(238 ± 70)/T] cm³ molecule⁻¹ s⁻¹ k₃ was independent of temperature between 240 and 348 K with an average value of (2.10 ± 0.60) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. The quoted uncertainties are 2σ (95% confidence limits, 1σ_A = Aσ_lnA) and include estimated systematic errors. Our measurements significantly im‐prove the accuracy of k₁. This is the first report of a slight negative temperature dependence for k₂ and of the temperature independence of k₃. © 1999 John Wiley & Sons, Inc.* Int J Chem Kinet 31: 417–424, 1999     

Relative Rate Studies of the Reactions of Atomic Chlorine with Acetone and Cyclic Ketones

Rate coefficients have been measured for Cl atom reactions under ambient conditions with acetone and four cyclic ketones. Cl was generated by UV photolysis of Cl₂, and other species were monitored by FT‐IR spectroscopy. The measurements yield k(Cl + acetone) = (2.0 ± 0.7) × 10⁻¹², k(Cl + cyclobutanone) = (10.1 ± 0.8) × 10⁻¹¹, k(Cl + cycloheptanone) = (24.0 ± 2.3) × 10⁻¹¹, k(Cl + 2‐methyl cyclopentanone) = (15.2 ± 1.2) × 10⁻¹¹, and k(Cl + 2‐methyl cyclohexanone) = (11.2 ± 1.0) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, where the uncertainties represent 95% confidence limits. These results are discussed in the context of structure‐activity relationships. We also present a prediction for Cl + cyclopropanone based on ab initio properties of the transition state.     

Kinetics and mechanism of the reaction of Cl atoms with HO2 radicals

The kinetic and mechanism of the reaction Cl + HO₂ → products (1) have been studied in the temperature range 230–360 K and at total pressure of 1 Torr of helium using the discharge‐flow mass spectrometric method. The following Arrhenius expression for the total rate constant was obtained either from the kinetics of HO₂ consumption in excess of Cl atoms or from the kinetics of Cl in excess of HO₂: k₁ = (3.8 ± 1.2) × 10^?11 exp[(40 ± 90)/T] cm³ molecule^?1 s^?1, where uncertainties are 95% confidence limits. The temperature‐independent value of k₁ = (4.4 ± 0.6) × 10^?11 cm³ molecule^?1 s^?1 at T = 230–360 K, which can be recommended from this study, agrees well with most recent studies and current recommendations. Both OH and ClO were detected as the products of reaction (1) and the rate constant for the channel forming these species, Cl + HO₂ → OH + ClO (1b), has been determined: k_1b = (8.6 ± 3.2) × 10^?11 exp[?(660 ± 100)/T] cm³ molecule^?1 s^?1 (with k_1b = (9.4 ± 1.9) × 10^?12 cm³ molecule^?1 s^?1 at T = 298 K), where uncertainties represent 95% confidence limits. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 317–327, 2001     

Temperature dependence of the rate coefficients for the reaction of chlorine atoms with chloromethanes

Rate coefficients for the reaction of Cl atoms with CH₃Cl (k₁), CH₂Cl₂ (k₂), and CHCl₃ (k₃) have been determined over the temperature range 222–298 K using standard relative rate techniques. These data, when combined with evaluated data from previous studies, lead to the following Arrhenius expressions (all in units of cm³ molecule⁻¹ s⁻¹): k₁ = (2.8 ± 0.3) × 10⁻¹¹ exp(−1200 ± 150/T); k₂ = (1.5 ± 0.2) × 10⁻¹¹ exp(−1100 ± 150/T); k₃ = (0.48 ± 0.05) × 10⁻¹¹ exp(−1050 ± 150/T). Values for k₁ are in substantial agreement with previous measurements. However, while the room temperature values for k₂ and k₃ agree with most previous data, the activation energies for these rate coefficients are substantially lower than previously recommended values. In addition, the mechanism of the oxidation of CH₂Cl₂ has been studied. The dominant fate of the CHCl₂O radical is decomposition via Cl‐atom elimination, even at the lowest temperatures studied in this work (218 K). However, a small fraction of the CHCl₂O radicals are shown to react with O₂ at low temperatures. Using an estimated value for the rate coefficient of the reaction of CHCl₂O with O₂ (1 × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹), the decomposition rate coefficient for CHCl₂O is found to be about 4 × 10⁶ s⁻¹ at 218 K, with the barrier to its decomposition estimated at 6 kcal/mole. As part of this work, the rate coefficient for Cl atoms with HCOCl was also been determined, k₇ = 1.4 × 10⁻¹¹ exp(−885/T) cm³ molecule⁻¹ s⁻¹, in agreement with previous determinations. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 515–524, 1999     

Kinetic studies of OH reactions with Iso-propyl,Iso-butyl,Sec-butyl,and Tert-butyl acetate

The temperature dependence of the rate coefficients for the OH radical reactions with iso-propyl acetate (k₁), iso-butyl acetate (k₂), sec-butyl acetate (k₃), and tert-butyl acetate (k₄) have been determined over the temperature range 253–372 K. The Arrhenius expressions obtained are: k₁=(0.30±0.03)×10⁻¹² exp[(770±52)/T]; k₂=(109±0.14)×10⁻¹² exp[(534±79)/T]; k₃=(0.73±0.08)×10⁻¹² exp[(640±62)/T]; and k₄=(22.2±0.34)×10⁻¹² exp[−(395±92)/T] (in units of cm³ molecule⁻¹ s⁻¹). At room temperature, the rate constants obtained (in units of 10⁻¹² cm³ molecule⁻¹ s⁻¹) were as follows: iso-propyl acetate (3.77±0.29); iso-butyl acetate (6.33±0.52); sec-butyl acetate (6.04±0.58); and tert-butyl acetate (0.56±0.05). Our results are compared with the previous determinations and discussed in terms of structure-activity relationships. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 683–688, 1997.     

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     

Daytime Reactions of 1,8‐Cineole in the Troposphere

Relative rate coefficients for the gas‐phase reaction of chlorine atoms (Cl) and hydroxyl radicals (OH) with 1,8‐cineole were determined by Fourier‐transform infrared (FTIR) spectroscopy between 285 and 313 K at atmospheric pressure. The temperature dependence of both reactions shows simple Arrhenius behaviour which can be represented by the following expressions (in units of cm³ molecule^?1s^?1): k(1,8‐cineole+OH)=(6.28±6.53)×10^?8exp[(?2549.3±155.7)/T] and k(1,8‐cineole+Cl)=(1.35±1.07)×10^?10exp[(?151.6±237.7)/T]. Major products of the titled reactions were identified by solid‐phase microextraction (SPME) coupled to a GC‐MS. Additionally, the first step of the reaction was theoretically studied by ab initio calculations and a reaction mechanism is proposed.     

Kinetic study of the gas‐phase reaction of the nitrate radical with methyl‐substituted thiophenes

The gas‐phase reactions of the NO₃ radical with 2‐methylthiophene, 3‐methylthiophene, and 2,5‐dimethylthiophene have been studied, using relative and absolute methods at 298 K. Determination of relative rate was performed using Teflon collapsible bag as the reaction chamber and gas chromatography as the analytical tool. For the absolute method, experiments were carried out using fast‐flow‐discharge technique with detection of NO₃ by laser‐induced fluorescence. The temperature dependence was studied by the absolute technique for the reactions of NO₃ with 2‐methylthiophene and 3‐methylthiophene in the range 263–335 K. The proposed Arrhenius expressions for the reaction of the nitrate radical with 2‐methylthiophene and 3‐methylthiophene are k = (4 ± 2) × 10^?16 exp[?(2200 ± 100)/T]] cm³ molecule^?1 s^?1 and k = (3 ± 2) × 10^?15 exp[?(1700 ± 200)/T]] cm³ molecule^?1 s^?1, respectively. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 286–293, 2003     

Kinetics and mechanism of the reaction of OH with ClO

The kinetics and mechanism of the following reactions have been studied in the temperature range 230–360 K and at total pressure of 1 Torr of helium, using the discharge‐flow mass spectrometric method: 1a : (1a) 1b : (1b) The following Arrhenius expression for the total rate constant was obtained from the kinetics of OH consumption in excess of ClO radical, produced in the Cl + O₃ reaction either in excess of Cl atoms or ozone: k₁ = (6.7 ± 1.8) × 10^?12 exp {(360 ± 90)/T} cm³ molecule^?1 s^?1 (with k₁ = (2.2 ± 0.4) × 10^?11 cm³ molecule^?1 s^?1 at T = 298 K), where uncertainties represent 95% confidence limits and include estimated systematic errors. The value of k₁ is compared with those from previous studies and current recommendations. HCl was detected as a minor product of reaction (1) and the rate constant for the channel forming HCl (reaction (1b)) has been determined from the kinetics of HCl formation at T = 230–320 K: k_1b = (9.7 ± 4.1) × 10^?14 exp{(600 ± 120)/T} cm³ molecule^?1 s^?1 (with k_1b = (7.3 ± 2.2) × 10^?13 cm³ molecule^?1 s^?1 and k_1b/k₁ = 0.035 ± 0.010 at T = 298 K), where uncertainties represent 95% confidence limits. In addition, the measured kinetic data were used to derive the enthalpy of formation of HO₂ radicals: Δ H_f,298(HO₂) = 3.0 ± 0.4 kcal mol^?1. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 587–599, 2001     

A laser flash photolysis/IR diode laser absorption study of the reaction of chlorine atoms with selected alkanes

A high‐resolution IR diode laser in conjunction with a Herriot multiple reflection flow‐cell has been used to directly determine the rate coefficients for simple alkanes with Cl atoms at room temperature (298 K). The following results were obtained: k(Cl + n‐butane) = (1.91 ± 0.10) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + n‐pentane) = (2.46 ± 0.12) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + iso‐pentane) = (1.94 ± 0.10) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + neopentane) = (1.01 ± 0.05) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + n‐hexane) = (3.44 ± 0.17) × 10^?10 cm³ molecule^?1 s^?1 where the error limits are ±1σ. These values have been used in conjunction with our own previous measurements on Cl + ethane and literature values on Cl + propane and Cl + iso‐butane to generate a structure activity relationship (SAR) for Cl atom abstraction reactions based on direct measurements. The resulting best fit parameters are k_p = (2.61 ± 0.12) × 10^?11 cm³ molecule^?1 s^?1, k_s = (8.40 ± 0.60) × 10^?11 cm³ molecule^?1 s^?1, k_t = (5.90 ± 0.30) × 10^?11 cm³ molecule^?1 s^?1, with f( ? CH₂^? ) = f (? CH₂^? ) = f (?C?) = f = 0.85 ± 0.06. Tests were carried out to investigate the potential interference from production of excited state HCl(v = 1) in the Cl + alkane reactions. There is some evidence for HCl(v = 1) production in the reaction of Cl with shape n‐hexane. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 86–94, 2002     

Gas‐phase reactions of Cl atoms with propane,n‐butane,and isobutane

Using the relative kinetic method, rate coefficients have been determined for the gas‐phase reactions of chlorine atoms with propane, n‐butane, and isobutane at total pressure of 100 Torr and the temperature range of 295–469 K. The Cl₂ photolysis (λ = 420 nm) was used to generate Cl atoms in the presence of ethane as the reference compound. The experiments have been carried out using GC product analysis and the following rate constant expressions (in cm³ molecule^?1 s^?1) have been derived: (7.4 ± 0.2) × 10^?11 exp [‐(70 ± 11)/ T], Cl + C₃H₈ → HCl + CH₃CH₂CH₂; (5.1 ± 0.5) × 10^?11 exp [(104 ± 32)/ T], Cl + C₃H₈ → HCl + CH₃CHCH₃; (7.3 ± 0.2) × 10^?11 exp[?(68 ± 10)/ T], Cl + n‐C₄H₁₀ → HCl + CH₃ CH₂CH₂CH₂; (9.9 ± 2.2) × 10^?11 exp[(106 ± 75)/ T], Cl + n‐C₄H₁₀ → HCl + CH₃CH₂CHCH₃; (13.0 ± 1.8) × 10^?11 exp[?(104 ± 50)/ T], Cl + i‐C₄H₁₀ → HCl + CH₃CHCH₃CH₂; (2.9 ± 0.5) × 10^?11 exp[(155 ± 58)/ T], Cl + i‐C₄H₁₀ → HCl + CH₃CCH₃CH₃ (all error bars are ± 2σ precision). These studies provide a set of reaction rate constants allowing to determine the contribution of competing hydrogen abstractions from primary, secondary, or tertiary carbon atom in alkane molecule. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 651–658, 2002     

Kinetic study of OH radical reaction with n‐heptane and n‐hexane at 240–340K using the relative rate/discharge flow/mass spectrometry (RR/DF/MS) technique

The kinetics of reactions of OH radical with n‐heptane and n‐hexane over a temperature range of 240–340K has been investigated using the relative rate combined with discharge flow/mass spectrometry (RR/DF/MS) technique. The rate constant for the reaction of OH radical with n‐heptane was measured with both n‐octane and n‐nonane as references. At 298K, these rate constants were determined to be k_{1, octane} = (6.68 ± 0.48) × 10^?12 cm³ molecule^?1 s^?1 and k_{1, nonane} = (6.64 ± 1.36) × 10^?12 cm³ molecule^?1 s^?1, respectively, which are in very good agreement with the literature values. The rate constant for reaction of n‐hexane with the OH radical was determined to be k₂ = (4.95 ± 0.40) × 10^?12 cm³ molecule^?1 s^?1 at 298K using n‐heptane as a reference. The Arrhenius expression for these chemical reactions have been determined to be k_{1, octane} = (2.25 ± 0.21) × 10^?11 exp[(?293 ± 37)/T] and k₂ = (2.43 ± 0.52) × 10^?11 exp[(?481.2 ± 60)/T], respectively. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 489–497, 2011     

Hydroxyl radical reactions with halogenated ethanols in aqueous solution: Kinetics and thermochemistry

Laser flash photolysis combined with competition kinetics with SCN^? as the reference substance has been used to determine the rate constants of OH radicals with three fluorinated and three chlorinated ethanols in water as a function of temperature. The following Arrhenius expressions have been obtained for the reactions of OH radicals with (1) 2‐fluoroethanol, k₁(T) = (5.7 ± 0.8) × 10¹¹ exp((?2047 ± 1202)/T) M^?1 s^?1, (2) 2,2‐difluoroethanol, k₂(T) = (4.5 ± 0.5) × 10⁹ exp((?855 ± 796)/T) M^?1 s^?1, (3) 2,2,2‐trifluoroethanol, k₃(T) = (2.0 ± 0.1) × 10¹¹ exp((?2400 ± 790)/T) M^?1 s^?1, (4) 2‐chloroethanol, k₄(T) = (3.0 ± 0.2) × 10¹⁰ exp((?1067 ± 440)/T) M^?1 s^?1, (5) 2, 2‐dichloroethanol, k₅(T) = (2.1 ± 0.2) × 10¹⁰ exp((?1179 ± 517)/T) M^?1 s^?1, and (6) 2,2,2‐trichloroethanol, k₆(T) = (1.6 ± 0.1) × 10¹⁰ exp((?1237 ± 550)/T) M^?1 s^?1. All experiments were carried out at temperatures between 288 and 328 K and at pH = 5.5–6.5. This set of compounds has been chosen for a detailed study because of their possible environmental impact as alternatives to chlorofluorocarbon and hydrogen‐containing chlorofluorocarbon compounds in the case of the fluorinated alcohols and due to the demonstrated toxicity when chlorinated alcohols are considered. The observed rate constants and derived activation energies of the reactions are correlated with the corresponding bond dissociation energy (BDE) and ionization potential (IP), where the BDEs and IPs of the chlorinated ethanols have been calculated using quantum mechanical calculations. The errors stated in this study are statistical errors for a confidence interval of 95%. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 174–188, 2008