Kinetics of phenyl radical reactions with propane,n‐butane,n‐hexane,and n‐octane: Reactivity of C6H5 toward the secondary C?H bond of alkanes

The kinetics of C₆H₅ reactions with n‐C_nH_2n+2 (n = 3, 4, 6, 8) have been studied by the pulsed laser photolysis/mass spectrometric method using C₆H₅COCH₃ as the phenyl precursor at temperatures between 494 and 1051 K. The rate constants were determined by kinetic modeling of the absolute yields of C₆H₆ at each temperature. Another major product C₆H₅CH₃ formed by the recombination of C₆H₅ and CH₃ could also be quantitatively modeled using the known rate constant for the reaction. A weighted least‐squares analysis of the four sets of data gave k (C₃H₈) = (1.96 ± 0.15) × 10¹¹ exp[?(1938 ± 56)/T], and k (n‐C₄H₁₀) = (2.65 ± 0.23) × 10¹¹ exp[?(1950 ± 55)/T] k (n‐C₆H₁₄) = (4.56 ± 0.21) × 10¹¹ exp[?(1735 ± 55)/T], and k (n?C₈H₁₈) = (4.31 ± 0.39) × 10¹¹ exp[?(1415 ± 65)T] cm³ mol^?1 s^?1 for the temperature range studied. For the butane and hexane reactions, we have also applied the CRDS technique to extend our temperature range down to 297 K; the results obtained by the decay of C₆H₅ with CRDS agree fully with those determined by absolute product yield measurements with PLP/MS. Weighted least‐squares analyses of these two sets of data gave rise to k (n?C₄H₁₀) = (2.70 ± 0.15) × 10¹¹ exp[?(1880 ± 127)/T] and k (n?C₆H₁₄) = (4.81 ± 0.30) × 10¹¹ exp[?(1780 ± 133)/T] cm³ mol^?1 s^?1 for the temperature range 297‐‐1046 K. From the absolute rate constants for the two larger molecular reactions (C₆H₅ + n‐C₆H₁₄ and n‐C₈H₁₈), we derived the rate constant for H‐abstraction from a secondary C? H bond, k_s?CH = (4.19 ± 0.24) × 10¹⁰ exp[?(1770 ± 48)/T] cm³ mol^?1 s^?1. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 49–56, 2004     

Rate constants for the elementary reactions between CN radicals and CH4, C2H6, C2H4, C3H6, and C2H2 in the range: 295 ⩽ T/K ⩽ 700

Pulsed laser photolysis, time-resolved laser-induced fluorescence experiments have been carried out on the reactions of CN radicals with CH₄, C₂H₆, C₂H₄, C₃H₆, and C₂H₂. They have yielded rate constants for these five reactions at temperatures between 295 and 700 K. The data for the reactions with methane and ethane have been combined with other recent results and fitted to modified Arrhenius expressions, k(T) = A′(298) (T/298)ⁿ exp(?θ/T), yielding: for CH₄, A′(298) = 7.0 × 10^?13 cm³ molecule^?1 s^?1, n = 2.3, and θ = ?16 K; and for C₂H₆, A′(298) = 5.6 × 10^?12 cm³ molecule^?1 s^?1, n = 1.8, and θ = ?500 K. The rate constants for the reactions with C₂H₄, C₃H₆, and C₂H₂ all decrease monotonically with temperature and have been fitted to expressions of the form, k(T) = k(298) (T/298)ⁿ with k(298) = 2.5 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.24 for CN + C₂H₄; k(298) = 3.4 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.19 for CN + C₃H₆; and k(298) = 2.9 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.53 for CN + C₂H₂. These reactions almost certainly proceed via addition-elimination yielding an unsaturated cyanide and an H-atom. Our kinetic results for reactions of CN are compared with those for reactions of the same hydrocarbons with other simple free radical species. © John Wiley & Sons, Inc.     

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     

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     

Rate constants for the reactions of C2H5O,i‐C3H7O,and n‐C3H7O with NO and O2 as a function of temperature

The rate constants of the reactions of ethoxy (C₂H₅O), i‐propoxy (i‐C₃H₇O) and n‐propoxy (n‐C₃H₇O) radicals with O₂ and NO have been measured as a function of temperature. Radicals have been generated by laser photolysis from the appropriate alkyl nitrite and have been detected by laser‐induced fluorescence. The following Arrhenius expressions have been determined: (R₁) C₂H₅O + O₂ → products k₁ = (2.4 ± 0.9) × 10⁻¹⁴ exp(−2.7 ± 1.0 kJmol⁻¹/RT) cm³ s⁻¹ 295K < T < 354K p = 100 Torr (R₂) i‐C₃H₇O + O₂ → products k₂ = (1.6 ± 0.2) × 10⁻¹⁴ exp(−2.2 ± 0.2 kJmol⁻¹/RT) cm³ s⁻¹ 288K < T < 364K p = 50–200 Torr (R₃) n‐C₃H₇O + O₂ → products k₃ = (2.5 ± 0.5) × 10⁻¹⁴ exp(−2.0 ± 0.5 kJmol⁻¹/RT) cm³ s⁻¹ 289K < T < 381K p = 30–100 Torr (R₄) C₂H₅O + NO → products k₄ = (2.0 ± 0.7) × 10⁻¹¹ exp(0.6 ± 0.4 kJmol⁻¹/RT) cm³ s⁻¹ 286K < T < 388K p = 30–500 Torr (R₅) i‐C₃H₇O + NO → products k₅ = (8.9 ± 0.2) × 10⁻¹² exp(3.3 ± 0.5 kJmol⁻¹/RT) cm³ s⁻¹ 286K < T < 389K p = 30–500 Torr (R₆) n‐C₃H₇O + NO → products k₆ = (1.2 ± 0.2) × 10⁻¹¹ exp(2.9 ± 0.4 kJmol⁻¹/RT) cm³s⁻¹ 289K < T < 380K p = 30–100 Torr All reactions have been found independent of total pressure between 30 and 500 Torr within the experimental error. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 860–866, 1999     

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     

Kinetic study of reactions of C2H5O2 with NO at 298 K and 0.55 – 2 torr

The kinetics of C₂H₅O₂ and C₂H₅O₂ radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis. The temporal profiles of C₂H₅O were monitored by LIF. The rate constant for C₂H₅O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k₂ = (1.25±0.04) × 10^?11, (1.66±0.06) × 10^?11, (1.81±0.06) × 10^?11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm³ molecule^?1 s^?1). The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C₂H₅O + NO + M → C₂H₅ONO + M (2a), C₂H₅O + NO → CH₃CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k_2a and for k_2b : k = (2.6±1.0) × 10^?28 cm⁶ molecule^?2 s^?1, k = (3.1±0.8) × 10^?11 cm³ molecule^?1 s^?1 and k_2b ca. 8 × 10^?12 cm³ molecule^?1 s^?1. The present value of k, obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10^?27 cm⁶ molecule^?2 s^?1 recommended in air. The rate constant for the reaction C₂H₅O₂ + NO → C₂H₅O + NO₂ (3) has been measured at 1 torr of He from the simulation of experimental C₂H₅O profiles. The value obtained for k₃ = (8.2±1.6) × 10^?12 cm³ molecule^?1 s^?1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc.     

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.     

Kinetics of C6H5 radical reactions with 2‐methylpropane, 2,3‐dimethylbutane and 2,3,4‐trimethylpentane

The absolute bimolecular rate constants for the reactions of C₆H₅ with 2‐methylpropane, 2,3‐dimethylbutane and 2,3,4‐trimethylpentane have been measured by cavity ringdown spectrometry at temperatures between 290 and 500 K. For 2‐methylpropane, additional measurements were performed with the pulsed laser photolysis/mass spectrometry, extending the temperature range to 972 K. The reactions were found to be dominated by the abstraction of a tertiary C H bond from the molecular reactant, resulting in the production of a tertiary alkyl radical: C₆H₅ + CH(CH₃)₃ → C₆H₆ + t‐C₄H₉ (1) (1) C₆H₅ + (CH₃)₂CHCH(CH₃)₂ → C₆H₆ + t‐C₆H₁₃ (2) (2) C₆H₅ + (CH₃)₂CHCH(CH₃)CH(CH₃)₂ → C₆H₆ + t‐C₈H₁₇ (3) (3) with the following rate constants given in units of cm³ mol⁻¹ s⁻¹: k₁ = 10^{(11.45 ± 0.18)} e^{−(1512 ± 44)/T} k₂ = 10^{(11.72 ± 0.15)} e^{−(1007 ± 124)/T} k₃ = 10^{(11.83 ± 0.13)} e^{−(428 ± 108)/T} © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 645–653, 1999     

Kinetics and mechanism of the reactions of n‐butanal and n‐pentanal with chlorine atoms

The kinetics and mechanism of the reaction of chlorine atoms with n‐butanal and n‐pentanal have been investigated in a 142‐L reaction cell coupled to a Fourier transform infrared (FTIR) spectrometer at 298 ± 2 K and at 800 ± 3 Torr. The rate coefficients for Cl + n‐butanal and Cl + n‐pentanal were measured using the relative rate technique with isopropanol and ethene as the reference compounds. The yield of acyl radicals was determined by measuring yields of acid chloride and carbon monoxide products from the reaction of Cl + aldehyde in the absence of oxygen. The rate coefficients for Cl + n‐butanal and Cl + n‐pentanal are (1.63 ± 0.59) × 10^?10 cm³ molecule^?1 s^{? 1} and (2.37 ± 0.82) × 10^?10 cm³ molecule^?1 s^?1, respectively. The yields of acyl radicals from the reactions are 0.66 ± 0.04 for n‐butanal and 0.45 ± 0.04 for n‐pentanal. Under ambient conditions, the acyl radicals generated will react almost exclusively with oxygen. Mechanistic implications of these measurements are discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 133–141, 2009     

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     

Kinetics of the gas‐phase reactions of Cl atom with selected C2–C5 unsaturated hydrocarbons at 283 < T < 323 K

The reaction of Cl atoms with a series of C₂–C₅ unsaturated hydrocarbons has been investigated at atmospheric pressure of 760 Torr over the temperature range 283–323 K in air and N₂ diluents. The decay of the hydrocarbons was followed using a gas chromatograph with a flame ionization detector (GC‐FID), and the kinetic constants were determined using a relative rate technique with n‐hexane as a reference compound. The Cl atoms were generated by UV photolysis (λ ≥ 300 nm) of Cl₂ molecules. The following absolute rate constants (in units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, with errors representing ±2σ) for the reaction at 295 ± 2 K have been derived from the relative rate constants combined to the value 34.5 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ for the Cl + n‐hexane reaction: ethene (9.3 ± 0.6), propyne (22.1 ± 0.3), propene (27.6 ± 0.6), 1‐butene (35.2 ± 0.7), and 1‐pentene (48.3 ± 0.8). The temperature dependence of the reactions can be expressed as simple Arrhenius expressions (in units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹): k_ethene = (0.39 ± 0.22) × 10⁻¹¹ exp{(226 ± 42)/T}, k_propyne = (4.1 ± 2.5) × 10⁻¹¹ exp{(118 ± 45)/T}, k_propene = (1.6 ± 1.8) × 10⁻¹¹ exp{(203 ± 79)/T}, k_1‐butene = (1.1 ± 1.3) × 10⁻¹¹ exp{(245 ± 90)/T}, and k_1‐pentene = (4.0 ± 2.2) × 10⁻¹¹ exp{(423 ± 68)/T}. The applicability of our results to tropospheric chemistry is discussed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 478–484, 2000     

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     

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     

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     

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.     

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     

Experimental Study of the Reactions of OH Radicals with Propane,n‐Pentane,and n‐Heptane over a Wide Temperature Range

The kinetics of the reactions of propane, n‐pentane, and n‐heptane with OH radicals has been studied using a low‐pressure flow tube reactor (P = 1 Torr) coupled with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo–first‐order conditions, monitoring the kinetics of OH radical consumption in excess of the alkanes. A newly developed high‐temperature flow reactor was validated by the study of the OH + propane reaction, where the reaction rate constant, k₁ = 5.1 × 10^?17T^1.85exp(–160/T) cm³ molecule^?1 s^?1 (uncertainty of 20%), measured in a wide temperature range, 230–898 K, was found to be in excellent agreement with previous studies and current recommendations. The experimental data for the rate constants of the reactions of OH with n‐pentane and n‐heptane can be represented as three parameter expressions (in cm³ molecule^?1 s^?1, uncertainty of 20%): k₂ = 5.8 × 10^?18T^2.2exp(260/T) at T= 248–900 K and k₃ = 2.7 × 10^?16T^1.7exp(138/T) at T= 248–896 K, respectively. A combination of the present data with those from previous studies leads to the following expressions: k₁ = 2.64 × 10^?17T^1.93exp(–114/T), k₂ = 9.0 × 10^?17T^1.8 exp(120/T), and k₃ = 3.75 × 10^?16 T^1.65 exp(101/T) cm³ molecule^?1 s^?1, which can be recommended for k₁, k₂, and k₃ (with uncertainty of 20%) in the temperature ranges 190–1300, 240–1300, and 220–1300 K, respectively.     

Kinetics and Products of the Reactions of Ethyl and n‐Propyl Nitrates with OH Radicals

The kinetics of the reactions of ethyl (1) and n‐propyl (2) nitrates with OH radicals has been studied using a low‐pressure flow tube reactor combined with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo–first‐order conditions from kinetics of OH consumption in high excess of nitrates. The overall rate constants, k₁ = 1.14 × 10^?13 (T/298)^2.45 exp(193/T) and k₂ = 3.00 × 10^?13 (T/298)^2.50 exp(205/T) cm³ molecule^?1 s^?1 (with conservative 15% uncertainty), were determined at a total pressure of 1 Torr of helium over the temperature range (248–500) and (263–500) K, respectively. The yields of the carbonyl compounds, acetaldehyde and propanal, resulting from the abstraction by OH of an α‐hydrogen atom in ethyl and n‐propyl nitrates, followed by α‐substituted alkyl radical decomposition, were determined at T = 300 K to be 0.77 ± 0.12 and 0.22 ± 0.04, respectively.     

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