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 for the gas‐phase reactions of chlorine atoms with 1,4‐cyclohexadiene and 1,5‐cyclooctadiene at 298 K

Rate constants for the reactions of Cl atoms with two cyclic dienes, 1,4‐cyclohexadiene and 1,5‐cyclooctadiene, have been determined, at 298 K and 800 Torr of N₂, using the relative rate method, with n‐hexane and 1‐butene as reference molecules. The concentrations of the organics are followed by gas chromatographic analysis. The ratios of the rate constants of reactions of Cl atoms with 1,4‐cyclohexadiene and 1,5‐cyclooctadiene to that with n‐hexane are measured to be 1.29 ± 0.06 and 2.19 ± 0.32, respectively. The corresponding ratios with respect to 1‐butene are 1.50 ± 0.16 and 2.36 ± 0.38. The absolute values of the rate constants of the reaction of Cl atom with n‐hexane and 1‐butene are considered as (3.15 ± 0.40) × 10^?10 and (3.21 ± 0.40) × 10^{? 10} cm³ molecule^?1s^?1, respectively. With these, the calculated values are k(Cl + 1,4‐cyclohexadiene) = (4.06 ± 0.55) × 10^?10 and k(Cl + 1,5‐cyclooctadiene) = (6.90 ± 1.33) × 10^?10 cm³ molecule^?1 s^?1 with respect to n‐hexane. The rate constants determined with respect to 1‐butene are marginally higher, k(Cl + 1,4‐cyclohexadiene) = (4.82 ± 0.80) × 10^{? 10} and k(Cl + 1,5‐cyclooctadiene) = (7.58 ± 1.55) × 10^{? 10} cm³ molecule^?1 s^?1. The experiments for each molecule were repeated three to five times, and the slopes and the rate constants given above are the average values of these measurements, with 2σ as the quoted error, including the error in the reference rate constant. The relative rate ratios of 1,4‐cyclohexadiene with both the reference molecules are found to be higher in the presence of oxygen, and a marginal increase is observed in the case of 1,5‐cyclooctadiene. Benzene is identified as one major product in the case of 1,4‐cyclohexadiene. Considering that the cyclohexadienyl radical, a product of the hydrogen abstraction reaction, is quantitatively converted to benzene in the presence of oxygen, the fraction of Cl atoms that reacts by abstraction is estimated to be 0.30 ± 0.04. The atmospheric implications of the results are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 431–440, 2011     

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     

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     

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.     

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     

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.     

Kinetics of the reactions of C2H5, n‐C3H7, and n‐C4H9 radicals with Cl2 at the temperature range 190–360 K

The kinetics of the C₂H₅ + Cl₂, n‐C₃H₇ + Cl₂, and n‐C₄H₉ + Cl₂ reactions has been studied at temperatures between 190 and 360 K using laser photolysis/photoionization mass spectrometry. Decays of radical concentrations have been monitored in time‐resolved measurements to obtain reaction rate coefficients under pseudo‐first‐order conditions. The bimolecular rate coefficients of all three reactions are independent of the helium bath gas pressure within the experimental range (0.5–5 Torr) and are found to depend on the temperature as follows (ranges are given in parenthesis): k(C₂H₅ + Cl₂) = (1.45 ± 0.04) × 10^?11 (T/300 K)^{?1.73 ± 0.09} cm³ molecule^?1 s^?1 (190–359 K), k(n‐C₃H₇ + Cl₂) = (1.88 ± 0.06) × 10^?11 (T/300 K)^{?1.57 ± 0.14} cm³ molecule^?1 s^?1 (204–363 K), and k(n‐C₄H₉ + Cl₂) = (2.21 ± 0.07) × 10^?11 (T/300 K)^{?2.38 ± 0.14} cm³ molecule^?1 s^?1 (202–359 K), with the uncertainties given as one‐standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are ±20%. Current results are generally in good agreement with previous experiments. However, one former measurement for the bimolecular rate coefficient of C₂H₅ + Cl₂ reaction, derived at 298 K using the very low pressure reactor method, is significantly lower than obtained in this work and in previous determinations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 614–619, 2007     

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.     

Kinetic investigation of gas‐phase reactions between the OH‐radical and o‐, m‐, p‐ethyltoluene and n‐nonane in air

We have carried out relative rate experiments (T = 294 ± 2 K, atmospheric pressure) to investigate the OH‐oxidation of o‐, m‐, and p‐ethyltoluene and n‐nonane (k₁, k₂, k₃, and k₄ respectively). The experiments were performed in a 2‐m³ smog chamber with Teflon coated walls. The rate constants obtained are (in cm³ molecule^?1 s^?1 with two sigma uncertainties): k₁ = (1.36 ± 0.07) × 10^?11; k₂ = (2.12 ± 0.26) × 10^?11; k₃ = (1.47 ± 0.04) × 10^?11, and k₄ = (0.95 ± 0.02) × 10^?11. The measured rate constants are in accordance with previously published data, so that a coherent group of values for the compounds studied can be established. Atmospheric implications, ozone, and particle production are discussed. In addition, we have determined the amount of o‐, m‐, and p‐ethyltoluenes in different types of gasoline. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 367–378 2004     

Gas‐Phase Reaction of Monomethylhydrazine with Ozone: Kinetics and OH Radical Formation

The gas‐phase reaction of monomethylhydrazine (CH₃NH? NH₂; MMH) with ozone was investigated in a flow tube at atmospheric pressure and a temperature of 295 ± 2 K using N₂/O₂ mixtures (3–30 vol% O₂) as the carrier gas. Proton transfer reaction–mass spectrometry (PTR‐MS) and long‐path FT‐IR spectroscopy served as the main analytical techniques. The kinetics of the title reaction was investigated with a relative rate technique yielding k_MMH+O3 = (4.3 ± 1.0) × 10^?15 cm³ molecule^?1 s^?1. Methyldiazene (CH₃N?NH; MeDia) has been identified as the main product in this reaction system as a result of PTR‐MS analysis. The reactivity of MeDia toward ozone was estimated relative to the reaction of MMH with ozone resulting in k_MeDia+O3 = (2.7 ± 1.6) × 10^?15 cm³ molecule^?1 s^?1. OH radicals were followed indirectly by phenol formation from the reaction of OH radicals with benzene. Increasing OH radical yields with increasing MMH conversion have been observed pointing to the importance of secondary processes for OH radical generation. Generally, the detected OH radical yields were definitely smaller than thought so far. The results of this study do not support the mechanism of OH radical formation from the reaction of MMH with ozone as proposed in the literature.     

Kinetic study of the gas‐phase reaction of hydroxyl radical with CF3CH2OCH2CF3 using the laser photolysis–laser induced fluorescence method

The laser photolysis‐laser‐induced fluorescence method was used for measuring the kinetic parameters of the reaction of OH radicals with CF₃CH₂OCH₂CF₃ (2,2,2‐trifluoroethyl ether), in the temperature range of 298–365 K. The bimolecular rate coefficient at 298 K, k_II(298), was measured to be (1.47 ± 0.03) × 10^?13 cm³ molecule^?1 s^?1, and the temperature dependence of k_II was determined to be (4.5 ± 0.8) × 10^?12exp [?(1030 ± 60)/T] cm³ molecule^?1 s^?1. The error quoted is 1σ of the linear regression of the respective plots. The rate coefficient at room temperature is very close to the average of the three previous measurements, whereas the values of E_a/R and the A‐factor are higher than the two previously reported values. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 519–525, 2010     

Gas‐phase ozonolysis: Rate coefficients for a series of terpenes and rate coefficients and OH yields for 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene

The kinetics of the gas‐phase reactions of O₃ with a series of selected terpenes has been investigated under flow‐tube conditions at a pressure of 100 mbar synthetic air at 295 ± 0.5 K. In the presence of a large excess of m‐xylene as an OH radical scavenger, rate coefficients k(O₃+terpene) were obtained with a relative rate technique, (unit: cm³ molecule^?1 s^?1, errors represent 2σ): α‐pinene: (1.1 ± 0.2) × 10^?16, ³Δ‐carene: (5.9 ± 1.0) × 10^?17, limonene: (2.5 ± 0.3) × 10^?16, myrcene: (4.8 ± 0.6) × 10^?16, trans‐ocimene: (5.5 ± 0.8) × 10^?16, terpinolene: (1.6 ± 0.4) × 10^?15 and α‐terpinene: (1.5 ± 0.4) × 10^?14. Absolute rate coefficients for the reaction of O₃ with the used reference substances (2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene) were measured in a stopped‐flow system at a pressure of 500 mbar synthetic air at 295 ± 2 K using FT‐IR spectroscopy, (unit: cm³ molecule^?1 s^?1, errors represent 2σ ): 2‐methyl‐2‐butene: (4.1 ± 0.5) × 10^?16 and 2,3‐dimethyl‐2‐butene: (1.0 ± 0.2) × 10^?15. In addition, OH radical yields were found to be 0.47 ± 0.04 for 2‐methyl‐2‐butene and 0.77 ± 0.04 for 2,3‐dimethyl‐2‐butene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 394–403, 2002     

Rate coefficients for the OH + acetaldehyde (CH3CHO) reaction between 204 and 373 K

The rate coefficient, k₁, for the gas‐phase reaction OH + CH₃CHO (acetaldehyde) → products, was measured over the temperature range 204–373 K using pulsed laser photolytic production of OH coupled with its detection via laser‐induced fluorescence. The CH₃CHO concentration was measured using Fourier transform infrared spectroscopy, UV absorption at 184.9 nm and gas flow rates. The room temperature rate coefficient and Arrhenius expression obtained are k₁(296 K) = (1.52 ± 0.15) × 10^?11 cm³ molecule^?1 s^?1 and k₁(T) = (5.32 ± 0.55) × 10^?12 exp[(315 ± 40)/T] cm³ molecule^?1 s^?1. The rate coefficient for the reaction OH (ν = 1) + CH₃CHO, k₇(T) (where k₇ is the rate coefficient for the overall removal of OH (ν = 1)), was determined over the temperature range 204–296 K and is given by k₇(T) = (3.5 ± 1.4) × 10^?12 exp[(500 ± 90)/T], where k₇(296 K) = (1.9 ± 0.6) × 10^?11 cm³ molecule^?1 s^?1. The quoted uncertainties are 2σ (95% confidence level). The preexponential term and the room temperature rate coefficient include estimated systematic errors. k₇ is slightly larger than k₁ over the range of temperatures included in this study. The results from this study were found to be in good agreement with previously reported values of k₁(T) for temperatures <298 K. An expression for k₁(T), suitable for use in atmospheric models, in the NASA/JPL and IUPAC format, was determined by combining the present results with previously reported values and was found to be k₁(298 K) = 1.5 × 10^?11 cm³ molecule^?1 s^?1, f(298 K) = 1.1, E/R = 340 K, and Δ E/R (or g) = 20 K over the temperature range relevant to the atmosphere. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 635–646, 2008     

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     

Absolute rate constants for the gas‐phase ozonolysis of isoprene and methylbutenol

The reactions of the biogenic organic compounds isoprene and 2‐methyl‐3‐buten‐2‐ol (MBO) with ozone have been investigated under controlled conditions for pressure (atmospheric pressure) and temperature (293 ± 2 K), using FTIR spectrometry. CO was added to scavenge hydroxyl radical formation during the ozonolysis experiments. Reaction rate constants were determined by absolute rate technique, by measuring both ozone and the organic compound concentrations. The measured values were k₁ = (1.19 ± 0.09) × 10^?17 cm³ molecule^?1 s^?1 for the reaction between ozone and isoprene and k₂ = (8.3 ± 1.0) × 10_?18 cm³ molecule^?1 s^?1 for the reaction between ozone and MBO. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 152–156 2004     

Rate coefficients and mechanisms of the reaction of cl‐atoms with a series of unsaturated hydrocarbons under atmospheric conditions

Rate coefficients and/or mechanistic information are provided for the reaction of Cl‐atoms with a number of unsaturated species, including isoprene, methacrolein ( MACR ), methyl vinyl ketone ( MVK ), 1,3‐butadiene, trans‐2‐butene, and 1‐butene. The following Cl‐atom rate coefficients were obtained at 298 K near 1 atm total pressure: k(isoprene) = (4.3 ± 0.6) × 10^?10cm³ molecule^?1 s^?1 (independent of pressure from 6.2 to 760 Torr); k( MVK ) = (2.2 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1; k( MACR ) = (2.4 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1; k(trans‐2‐butene) = (4.0 ± 0.5) × 10^?10 cm³ molecule^?1 s^?1; k(1‐butene) = (3.0 ± 0.4) × 10^?10 cm³ molecule^?1 s^?1. Products observed in the Cl‐atom‐initiated oxidation of the unsaturated species at 298 K in 1 atm air are as follows (with % molar yields in parentheses): CH₂O (9.5 ± 1.0%), HCOCl (5.1 ± 0.7%), and 1‐chloro‐3‐methyl‐3‐buten‐2‐one (CMBO, not quantified) from isoprene; chloroacetaldehyde (75 ± 8%), CO₂ (58 ± 5%), CH₂O (47 ± 7%), CH₃OH (8%), HCOCl (7 ± 1%), and peracetic acid (6%) from MVK ; CO (52 ± 4%), chloroacetone (42 ± 5%), CO₂ (23 ± 2%), CH₂O (18 ± 2%), and HCOCl (5%) from MACR ; CH₂O (7 ± 1%), HCOCl (3%), acrolein (≈3%), and 4‐chlorocrotonaldehyde (CCA, not quantified) from 1,3‐butadiene; CH₃CHO (22 ± 3%), CO₂ (13 ± 2%), 3‐chloro‐2‐butanone (13 ± 4%), CH₂O (7.6 ± 1.1%), and CH₃OH (1.8 ± 0.6%) from trans‐2‐butene; and chloroacetaldehyde (20 ± 3%), CH₂O (7 ± 1%), CO₂ (4 ± 1%), and HCOCl (4 ± 1%) from 1‐butene. Product yields from both trans‐2‐butene and 1‐butene were found to be O₂‐dependent. In the case of trans‐2‐butene, the observed O₂‐dependence is the result of a competition between unimolecular decomposition of the CH₃CH(Cl)? CH(O?)? CH₃ radical and its reaction with O₂, with k_decomp/k_O2 = (1.6 ± 0.4) × 10¹⁹ molecule cm^?3. The activation energy for decomposition is estimated at 11.5 ± 1.5 kcal mol^?1. The variation of the product yields with O₂ in the case of 1‐butene results from similar competitive reaction pathways for the two β‐chlorobutoxy radicals involved in the oxidation, ClCH₂CH(O?)CH₂CH₃ and ?OCH₂CHClCH₂CH₃. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 334–353, 2003     

Kinetic study of the reactions of atomic chlorine with several volatile organic compounds at 240–340 K

The rate constant for the reactions of atomic chlorine with 1,4‐dioxane (k₁), cyclohexane (k₂), cyclohexane‐d₁₂(k₃), and n‐octane (k₄) has been determined at 240–340 K using the relative rate/discharge fast flow/mass spectrometer (RR/DF/MS) technique developed in our laboratory. Essentially, no temperature dependence for these reactions was observed over this temperature range, with an average of k₁ = (1.91 ± 0.20) × 10^?10 cm³ molecule^?1 s^?1, k₂ = (2.91 ± 0.31) × 10^?10 cm³ molecule^?1 s^?1, k₃ = (2.73 ± 0.30) × 10^?10 cm³ molecule^?1 s^?1, and k₄ = (3.22 ± 0.36) × 10^?10 cm³ molecule^?1 s^?1, respectively. The kinetic isotope effect of the reaction of cyclohexane with atomic chlorine has also been determined to be 1.14 by directly monitoring the decay of both cyclohexane and cyclohexane‐d₁₂ in the presence of chlorine atoms, which is consistent with the literature value of 1.20. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 386–398, 2006     

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