Relative rate constants for the reactions of hydroxyl radicals and chlorine atoms with a series of aliphatic alcohols

Rate constants for the gas‐phase reactions of hydroxyl radicals and chlorine atoms with a series of alcohols have been determined by using the relative method. The experiments were performed at 295 ± 2 K and at 1 atmospheric pressure. The obtained values of the rate constants in units of 10^?12 cm³ molecule^?1 s^?1 are as follows:

Gas‐phase rate coefficients for a series of alkyl cyclohexanes with OH radicals and Cl atoms

The rate coefficients of the reactions of OH radicals and Cl atoms with three alkylcyclohexanes compounds, methylcyclohexane (MCH), trans‐1,4‐dimethylcyclohexane (DCH), and ethylcyclohexane (ECH) have been investigated at (293 ± 1) K and 1000 mbar of air using relative rate methods. A majority of the experiments were performed in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC), a stainless steel chamber using in situ FTIR analysis and online gas chromatography with flame ionization detection (GC‐FID) detection to monitor the decay of the alkylcyclohexanes and the reference compounds. The studies were undertaken to provide kinetic data for calibrations of radical detection techniques in HIRAC. The following rate coefficients (in cm³ molecule⁻¹ s⁻¹) were obtained for Cl reactions: k_(Cl+MCH) = (3.51 ± 0.37) × 10^–10, k_(Cl+DCH) = (3.63 ± 0.38) × 10⁻¹⁰, k_(Cl+ECH) = (3.88 ± 0.41) × 10⁻¹⁰, and for the reactions with OH radicals: k_(OH+MCH) = (9.5 ± 1.3) × 10^–12, k_(OH+DCH) = (12.1 ± 2.2) × 10⁻¹², k_(OH+ECH) = (11.8 ± 2.0) × 10⁻¹². Errors are a combination of statistical errors in the relative rate ratio (2σ) and the error in the reference rate coefficient. Checks for possible systematic errors were made by the use of two reference compounds, two different measurement techniques, and also three different sources of OH were employed in this study: photolysis of CH₃ONO with black lamps, photolysis of H₂O₂ at 254 nm, and nonphotolytic trans‐2‐butene ozonolysis. For DCH, some direct laser flash photolysis studies were also undertaken, producing results in good agreement with the relative rate measurements. Additionally, temperature‐dependent rate coefficient investigations were performed for the reaction of methylcyclohexane with the OH radical over the range 273‐343 K using the relative rate method; the resulting recommended Arrhenius expression is k_{(OH + MCH)} = (1.85 ± 0.27) × 10^–11 exp((–1.62 ± 0.16) kJ mol⁻¹/RT) cm³ molecule⁻¹ s⁻¹. The kinetic data are discussed in terms of OH and Cl reactivity trends, and comparisons are made with the existing literature values and with rate coefficients from structure‐activity relationship methods. This is the first study on the rate coefficient determination of the reaction of ECH with OH radicals and chlorine atoms, respectively.     

Kinetics of the reactions of hydroxyl radicals (OH) and of chlorine atoms (Cl) with methylethylether over the temperature range 274–345 K

The rate constants for the gas-phase reactions between methylethylether and hydroxyl radicals (OH) and methylethylether and chlorine atoms (Cl) have been determined over the temperature range 274–345 K using a relative rate technique. In this range the rate constants vary little with temperature and average values of k_MEE+OH = (6.60_−2.62^+3.88) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ and k_MEE+Cl= (34.9 ± 6.7) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ were obtained. The atmospheric lifetimes of methylethylether have been estimated with respect to removal by OH radicals and Cl atoms to be ca. 2 days and ca. 30–40 days, respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 231–236, 1997.     

Kinetics and mechanisms of the tropospheric reactions of menthol, borneol, fenchol, camphor, and fenchone with hydroxyl radicals (OH) and chlorine atoms (Cl)

Relative kinetic techniques have been used to measure the rate coefficients for the reactions of oxygenated terpenes (menthol, borneol, fenchol, camphor, and fenchone) and cyclohexanol with hydroxyl radicals (OH) and chlorine atoms (Cl) at 298 ± 2 K and atmospheric pressure. The rate coefficients obtained for the reactions of the title compounds with OH are the following (in units of 10(-11) cm(3) molecule(-1) s(-1)): (1.48 ± 0.31), (2.65 ± 0.32), (2.49 ± 0.30), (0.38 ± 0.08), (0.39 ± 0.09) for menthol, borneol, fenchol, camphor, and fenchone, respectively. For the corresponding reactions with Cl atoms the rate coefficients are as follows (in units of 10(-10) cm(3) molecule(-1) s(-1)): (3.21 ± 0.26), (3.40 ± 0.28), (2.72 ± 0.13), (2.93 ± 0.17), (1.59 ± 0.10), and (1.86 ± 0.29) for cyclohexanol, menthol, borneol, fenchol, camphor, and fenchone, respectively. The reported error is twice the standard deviation. Product studies of the reactions were performed using multipass in situ FTIR (Fourier transform infrared spectroscopy) and solid-phase microextraction (SPME) with analysis by GC-MS (gas chromatography-mass spectrometry). A detailed mechanism is proposed to justify the observed reaction products.     

Kinetics of the reactions of pinonaldehyde with OH radicals and with Cl atoms

The rate constant for the reaction of OH radicals with pinonaldehyde has been measured at 293 ± 6 K using the relative rate method in the laboratory in Wuppertal (Germany) using photolytic sources for the production of OH radicals and in the EUPHORE smog chamber facility in Valencia (Spain) using the in situ ozonolysis of 2,3‐dimethyl‐2‐butene as a dark source of OH radicals. In all the experiments pinonaldehyde and the reference compounds were monitored by FTIR spectroscopy, and in addition in the EUPHORE smog chamber the decay of pinonaldehyde was monitored by the HPLC/DNPH method and the reference compound by GC/FID. The results from all the different series of experiments were in good agreement and lead to an average value of k(pinonaldehyde + OH) = (4.0 ± 1.0) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. This result lead to steady‐state estimates of atmospheric pinonaldehyde concentrations in the ppbV range (1 ppbV ≈ 2.5 × 10¹⁰ molecule cm⁻³ at 298 K and 1 atm) in regions with substantial α‐pinene emission. It also implies that atmospheric sinks of pinonaldehyde by reaction with OH radicals could be half as important as its photolysis. The rate constant of the reaction of pinonaldehyde with Cl atoms has been measured for the first time. Relative rate measurements lead to a value of k(pinonaldehyde + Cl) = (2.4 ± 1.4) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. In contrast to previous studies which suggested enhanced kinetic reactivity for pinonaldehyde compared to other aldehydes, the results from both the OH‐ and Cl‐initiated oxidation of pinonaldehyde in the present work are in line with predictions using structure‐activity relationships. © 1999 John Wiley & Sons, Inc., Int J Chem Kinet 31: 291–301, 1999     

A relative rate study of the reaction of Cl atoms with a series of alkyl nitrates and nitro alkanes in air at 295 ± 2 K

The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with nitro methane, nitro ethane, nitro propane, nitro butane, nitro pentane, ethyl nitrate, isopropyl nitrate, n-propyl nitrate, 2-pentyl nitrate, and 2-heptyl nitrate. Decay rates of these organic species were measured relative to one or more of the following reference compounds; n-butane, ethane, chloroethane, and methane. Using rate constants of 2.25 × 10^?10 5.7 × 10^?11, 8.04 × 10^?12, and 1.0 × 10^?13 cm³ molecule^?1 s^?1 for the reaction of Cl atoms with n-butane, ethane, chloroethane, and methane, respectively, the following rate constants were derived, in units of cm³ molecule^?1 s^?1: nitro methane, <7 × 10^?15; nitro ethane, (2.05 ± 0.14) × 10^?13; nitro propane, (1.13 ± 0.05) × 10^?11; nitro butane, (5.13 ± 0.68) × 10^?11; nitro pentane, (1.40 ± 0.14) × 10^?10; ethyl nitrate, (3.70 ± 0.24) × 10^?12; n-propyl nitrate, (2.15 ± 0.13) × 10^?11; i-propyl nitrate, (3.94 ± 0.48) × 10^?12; 2-pentyl nitrate, (1.00 ± 0.06) × 10^?10; and 2-heptyl nitrate, (2.84 ± 0.50) × 10^?10. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure (?740 torr) of synthetic air. The results are discussed with respect to the previous literature data and to the modeling of these compounds in the atmosphere.     

Absolute reaction rate of chlorine atoms with neopentane

The reaction of atomic chlorine with neopentane was studied in the gas phase with the Very Low Pressure Reactor (VLPR) technique over the temperature range 273–333 K. The absolute reaction rate was found to be temperature-independent, and the average rate constant was k₁ = (1.11± 0.13) × 10^?10 cm³ molecule^?1 s^?1 within experimental error. The reaction proceeds via metathesis of a hydrogen atom with no activation energy, and leads to the formation of HCl and neopentyl radical. © 1995 John Wiley & Sons, Inc.     

Kinetics of the reaction of OH radicals with a series of ethers under simulated atmospheric conditions at 295 K

Ethers are being increasingly used as motor fuel additives to increase the octane number and to reduce CO emissions. Since their reaction with hydroxyl radicals (OH) is a major loss process for these oxygenated species in the atmoshpere, we have conducted a relative rate study of the kinetics of the reactions of OH radicals with a series of ethers and report the results of these measurements here. Experiments were performed under simulated atmospheric conditions; atmospheric pressure (? 740 torr) in synthetic air at 295 K. Using rate constants of 2.53 × 10^?12, and 1.35 × 10^?11 cm³ molecule^?1 s^?1 for the reaction of OH radicals with n-butane and diethyl ether, the following rate constants were derived, in units of 10^?11 cm³ molecule^?1 s^?1: dimethylether, (0.232 ± 0.023); di-n-propylether, (1.97 ± 0.08); di-n-butylether, (2.74 ± 0.32); di-n-pentylether, (3.09 ± 0.26); methyl-t-butylether, (0.324 ± 0.008); methyl-n-butylether, (1.29 ± 0.03); ethyl-n-butylether, (2.27 ± 0.09); and ethyl-t-butylether, (0.883 ± 0.026). Quoted errors represent 2σ from the least squares analysis and do not include any systematic errors associated with uncertainties in the reference rate constants used to place our relative measurements on an absolute basis. The implications of these results for the atmospheric chemistry of ethers are discussed.     

A shock tube study of the reaction of methyl radicals with hydroxyl radicals

The reaction of CH₃ with OH has been studied near 1200 K and 1 atmosphere pressure in shock tube experiments in which UV absorption was used to monitor [OH]. A rate coefficient of (1.1 ± 0.3) × 10¹³ cm³/mol-s was measured for removal of OH by CH₃. This measured value is compared with previous experimental data and calculations. Several possible reaction channels are discussed, and although products were not monitored, it seems probable, on the basis of other work and theoretical estimates, that the primary mechanism (?75%) for the removal of OH by CH₃ at these conditions is their combination to form CH₃OH. Rate coefficients of (5.3 ± 0.8) × 10¹² and (9.0 ± 1.4) × 10¹² cm³/mol-s were measured for the reactions of OH with acetone and ethane, respectively, at the same temperature and pressure.     

A kinetic and mechanistic study of the reactions of OH radicals and Cl atoms with 3,3,3-trifluoropropanol under atmospheric conditions

Product distribution studies of the OH radical and Cl atom initiated oxidation of CF3CH2CH2OH in air at 1 atm and 298 +/- 5 K have been carried out in laboratory and outdoor atmospheric simulation chambers in the presence and absence of NOx. The results show that CF3CH2CHO is the only primary product and that the aldehyde is fairly rapidly removed from the system. In the absence of NOx the major degradation product of CF3CH2CHO is CF3CHO, and the combined yields of the two aldehydes formed from CF3CH2CH2OH are close to unity (0.95 +/- 0.05). In the presence of NOx small amounts of CF3CH2C(O)O2NO2 were also observed (<15%). At longer reaction times CF3CHO is removed from the system to give mainly CF2O. The laser photolysis-laser induced fluorescence technique was used to determine values of k(OH + CF3CH2CH2OH) = (0.89 +/- 0.03) x 10(-12) and k(OH + CF3CH2CHO) = (2.96 +/- 0.04) x 10(-12) cm3 molecule(-1) s(-1). A relative rate method has been employed to measure the rate coefficients k(OH + CF3CH2CH2OH) = (1.08 +/- 0.05) x 10(-12), k(OH + C6F13CH2CH2OH) = (0.79 +/- 0.08) x 10(-12), k(Cl + CF3CH2CH2OH) = (22.4 +/- 0.4) x 10(-12), and k(Cl + CF3CH2CHO) = (25.7 +/- 0.4) x 10(-12) cm3 molecule(-1) s(-1). The results from this investigation are discussed in terms of the possible importance of emissions of fluorinated alcohols as a source of fluorinated carboxylic acids in the environment.     

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     

Determination of the rate constants for the gas-phase reactions of methyl butenol with OH radicals,ozone, NO3 radicals,and Cl atoms

Using a relative rate method, rate constants for the gas-phase reactions of 2-methyl-3-buten-2-ol (MBO) with OH radicals, ozone, NO₃ radicals, and Cl atoms have been investigated using FTIR. The measured values for MBO at 298±2 K and 740±5 torr total pressure are: k_OH=(3.9±1.2)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹, k_O3=(8.6±2.9)×10⁻¹⁸ cm³ molecule⁻¹ s⁻¹, k=(8.6±2.9)×10⁻¹⁵ cm³ molecule⁻¹ s⁻¹, and k_Cl=(4.7±1.0)×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. Atmospheric lifetimes have been estimated with respect to the reactions with OH, O₃, NO₃, and Cl. The atmospheric relevance of this compound as a precursor for acetone is, also, briefly discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 589–594, 1998     

Rate constants and atmospheric lifetimes for the reactions of OH radicals and Cl atoms with haloalkanes

Rate constants for the reactions of Cl atoms and OH radicals with haloalkanes were measured using the relative rate technique. From these values the atmospheric lifetimes of the organics with respect to Cl atoms and OH radicals were calculated. Cl atoms were produced by the photolysis of chlorine gas, and photolysis of methyl nitrite was the source of OH radicals. The rate constants were measured for a series of brominated and chlorinated alkanes for which measurements have not yet been reported excepting: k(Cl + 1-chloropropane) and k(OH + 1-chloropropane, 2-chloropropane, and bromoethane). The organics studied were 1-chloropropane, 2-chloropropane, 1,3 dichloropropane, 2-chloro 2methylpropane, bromoethane, 1-bromopropane, 2-bromopropane, 1-bromobutane, 1-bromopentane, and 1-bromohexane. Cl atom reactions were measured at 298 K, the OH radical reactions were measured at temperatures between 298–308 K. © 1993 John Wiley & Sons, Inc.     

Rate constants for reactions of OH radicals with a series of asymmetrical ethers and tert-Butyl alcohol

Absolute rate constants for the reactions of OH radicals with butyl ethyl ether (k₁), methyl tert-butyl ether (k₂), ethyl tert-butyl ether (k₃) tert-amyl methyl ether (k₄) and tert-butyl alcohol (k₅) have been measured over the temperature range 230–372 K using a pulsed laser photolysis-laser induced fluorescence (PLP-LIF) technique. The temperature dependence of k₁ − k₅ when expressed in Arrhenius form gave: k₁ = (6.59 ± 0.66) × 10 ⁻¹² exp|(362 ± 60)/T|, k₂ = (5.03 ± 0.27) × 10⁻¹² exp|&minus(133 ± 30)/T|, k₃ = (4.40 ± 0.24) × 10⁻¹² exp|(210 ± 37)/T|,k⁴ = (4.7 ± 0.7) × 10⁻¹² exp|(82 ± 85)/T|, and k₅ = (2.66 ± 0.48) × 10⁻¹² exp| −(270 ± 130)/T|. However, the Arrhenius plots for k₁–k₅, were slightly curved and are best fitted by the three parameter fits which are given in the article. The room temperature values of k₁, k₂, k₃, k₄, and k₅ are (2.08 ± 0.23) × 10⁻¹¹, (3.13 ± 0.36) × 10⁻¹², (8.80 ± 0.50) × 10⁻¹², (6.28 ± 0.45) × 10⁻¹², and (1.08 ± 0.10) × 10⁻¹², respectively, in cm³ molecule⁻¹ s⁻¹. © 1996 John Wiley & Sons, Inc.     

Approximate values of the rate constants of radiation reaction of hydrogen atoms and hydroxyl radicals in aqueous solutions

Russian Chemical Bulletin -     

Kinetics and mechanism of the reaction of propylene oxide with chlorine atoms and hydroxy radicals

The kinetics and mechanism of gas‐phase propylene oxide (PPO) reactions were studied in a 142‐L reaction chamber by long‐path Fourier transform infrared spectroscopy at atmospheric pressure and 298 K. Rate coefficients for the reaction of PPO with ozone (O₃), chlorine atoms (Cl), and hydroxyl radicals (OH) were measured using the relative rate technique. Product yields of acetic acid, acetic formic anhydride, formic acid, and carbon monoxide were determined for the following reactions: PPO with Cl both in the presence and absence of NO, PPO with OH and NO, methyl acetate with Cl both in the presence and absence of NO, and ethyl formate with Cl both in the presence and absence of NO. The measured rate coefficients for PPO with O₃, Cl, and OH are <3.5 × 10^?21 cm³ molecule^?1 s^?1, (3.0 ± 0.7) × 10^?11 cm³ molecule^?1 s^?1, and (3.0 ± 1.0) × 10^?13 cm³ molecule^?1 s^?1, respectively. The carbon balance for the products measured ranged from 10% (for OH + PPO) to 100% (for Cl + methyl acetate in the absence of NO). The mechanistic and atmospheric implications of these measurements are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 507–521, 2011     

Atmospheric chemistry of di-tert-butyl ether: Rates and products of the reactions with chlorine atoms,hydroxyl radicals,and nitrate radicals

The rate constants for the gas-phase reactions of di-tert-butyl ether (DTBE) with chlorine atoms, hydroxyl radicals, and nitrate radicals have been determined in relative rate experiments using FTIR spectroscopy. Values of k_(DTBE+CI) = (1.4 ± 0.2) × 10⁻¹⁰,k_(DTBE+OH) = (3.7 ± 0.7) × 10⁻¹², and k_(DTBE+N03) = (2.8 ± 0.9) × 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹ were obtained. Tert-butyl acetate was identified as the major product of both Cl atom and OH radical initiated oxidation of DTBE in air in the presence of NO_x. The molar tert-butyl acetate yield was 0.85 ± 0.11 in the Cl atom experiments and 0.84 ± 0.11 in OH radical experiments. As part of this work the rate constant for reaction of Cl atoms with tert-butyl acetate at 295 K was determined to be (1.6 ± 0.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The stated errors are two standard deviations (2σ). © 1996 John Wiley & Sons, Inc.     

Rate constants for the gas‐phase reactions of Cl atoms with a series of ethers

The laser photolysis–resonance fluorescence technique has been used to determine the absolute rate coefficient for the Cl atom reaction with a series of ethers, at room temperature (298 ± 2) K and in the pressure range 15–60 Torr. The rate coefficients obtained (in units of cm³ molecule⁻¹ s⁻¹) are dimethyl ether (1.3 ± 0.2) × 10⁻¹⁰, diethyl ether (2.5 ± 0.3) × 10⁻¹⁰, di‐n‐propyl ether (3.6 ± 0.4) × 10⁻¹⁰, di‐n‐butyl ether (4.5 ± 0.5) × 10⁻¹⁰, di‐isopropyl ether (1.6 ± 0.2) × 10⁻¹⁰, methyl tert‐butyl ether (1.4 ± 0.2) × 10⁻¹⁰, and ethyl tert‐butyl ether (1.5 ± 0.2) × 10⁻¹⁰. The results are discussed in terms of structure–reactivity relationship. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 105–110, 2000     

An absolute and relative rate study of the reaction of oh radicals with dimethyl sulfide

The gas phase reaction of OH radicals with dimethyl sulfide (CH₃SCH₃, DMS) has been studied using both an absolute and a relative technique at 295 ± 2 K and a total pressure of 1 atm. The absolute rate technique of pulse radiolysis combined with kinetic spectroscopy was applied. Using this technique a rate constant of (3.5 ± 0.2) × 10^?12 cm³ molecule^?1 s^?1 was obtained. For the relative rate method, rate constants for the reaction of OH with DMS were found to increase with increasing concentrations of added NO. These results are compared with the large body of kinetic and mechanistic data previously reported in the literature.