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.     

Analysis of the unimolecular reaction N2O5 + M ⇌ NO2 + NO3 + M

Recent experimental results on the thermal decomposition of N₂O₅ in N₂ are evaluated in terms of unimolecular rate theory. A theoretically consistent set of fall-off curves is constructed which allows to identify experimental errors or misinterpretations. Limiting rate constants k₀ = [N₂] 2.2 × 10^?3 (T/300)^?4.4 exp(?11,080/T) cm³/molec·s over the range of 220–300 K, k_∞ = 9.7 × 10¹⁴ (T/300)^+0.1 exp(?11,080/T) s^?1 over the range of 220–300 K, and broadening factors of the fall-off curve F_cent = exp(-T/250) + exp(?1050/T) over the range of 220–520 K have been derived. NO₂ + NO₃ recombination rate constants over the range of 200–300 K are k_rec,0 = [N₂] 3.7 × 10^?30 (T/300)^?4.1 cm⁶/molec²·s and k_rec,∞ = 1.6 × 10^?12 (T/300)^+0.2 cm³/molec·s.     

Kinetics of OH reactions with furan,thiophene, and tetrahydrothiophene

The kinetics of OH reactions with furan (k₁), thiophene (k₂), and tetrahydrothiophene (k₃), have been investigated over the temperature range 254–425 K. OH radicals were produced by flash photolysis of water vapor at λ > 165 nm and detected by timeresolved resonance fluorescence spectroscopy. The following Arrhenius expressions adequately describe the measured rate constants as a function of temperature (units are cm³ molecule^?1 S^?1): k₁ = (1.33 ± 0.29) × 10^?11 exp[(333 ± 67)/T], k₂ = (3.20 ± 0.70) × 10^?12 exp[(325 ± 71)/T], k₃ = (1.13 ± 0.35) × 10^?11 exp[(166 ± 97)/T]. The results are compared with previous investigations and their implications regarding reaction mechanisms and atmospheric residence times are discussed.     

Kinetics of the reactions of the hydroxyl radical with dimethyl ether and diethyl ether

Absolute rate coefficients for the reactions of the hydroxyl radical with dimethyl ether (k₁) and diethyl ether (k₂) were measured over the temperature range 295–442 K. The rate coefficient data, in the units cm³ molecule^?1 s^?1, were fitted to the Arrhenius equations k₁ (T) = (1.04 ± 0.10) × 10^?11 exp[?(739 ± 67 cal mol^?1)/RT] and k₂(T) = (9.13 ± 0.35) × 10^?12 exp[+(228 ± 27 kcal mol^?1)/RT], respectively, in which the stated error limits are 2σ values. Our results are compared with those of previous studies of hydrogen-atom abstraction from saturated hydrocarbons by OH. Correlations between measured reaction-rate coefficients and C? H bond-dissociation energies are discussed.     

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 reaction of OH with HCl from 240–1055 K

Absolute rate coefficients for the reaction of OH with HCl (k₁) have been measured as a function of temperature over the range 240–1055 K. OH was produced by flash photolysis of H₂O at λ > 165 nm, 266 nm laser photolysis of O₃/H₂O mixtures, or 266 nm laser photolysis of H₂O₂. OH was monitored by time-resolved resonance fluorescenceor pulsed laser–induced fluorescence. In many experiments the HCl concentration was measured in situ in the slow flow reactor by UV photometry. Over the temperature range 240–363 K the following Arrhenius expression is an adequate representation of the data: k₁ = (2.4 ± 0.2) × 10^?12 exp[?(327 ± 28)/T]cm³ molecule^?1 s^?1. Over the wider temperature range 240–1055 K, the temperature dependence of k₁ deviates from the Arrhenius form, but is adequately described by the expression k₁ = 4.5 × 10^?17 T^1.65 exp(112/T) cm³ molecule^?1 s^?1. The error in a calculated rate coefficient at any temperature is 20%.     

Kinetics of the reactions of NCO with NO and NO2

The rate coefficients of the reactions of NCO radicals with NO and NO₂: (1) NCO + NO → products (293–836 K) and : (2) NCO + NO₂ → products (294–774 K) were measured by means of laser photolysis and laser induced fluorescence technique in the indicated temperature ranges. NCO radicals were produced from the reaction of CN, from photodissociation of ICN or BrCN, with O₂. The concentration of NCO was monitored with a dye laser set at 414.95 nm. We determined k₁ = 1.73 × 10^?5 T^?2.01 exp(?470/T) cm³ molecule^?1 s^?1 that agrees with published results at room temperature and confirms the temperature dependence of an early report. A non-Arrhenius negative temperature dependence of k₂ was observed in this work that agrees satisfactorily with results for a shock tube¹⁸ near 1250 K. We obtained k₂ = 6.4 × 10^?10 T^?0.646 exp(164/T) cm³ molecule^?1 s^?1 for 1250 K ≥ T ≥ 294 K by combining data of these two measurements. Our result at 294 K and the temperature dependence disagree with results of two previous investigations. © 1995 John Wiley & Sons, Inc.     

Ab initio study of the OH + CH2O reaction: The effect of the OH··OCH2 complex on the H‐abstraction kinetics

Kinetics for the reaction of OH radical with CH₂O has been studied by single‐point calculations at the CCSD(T)/6‐311+G(3df, 2p) level based on the geometries optimized at the B3LYP/6‐311+G(3df, 2p) and CCSD/6‐311++G(d,p) levels. The rate constant for the reaction has been computed in the temperature range 200–3000 K by variational transition state theory including the significant effect of the multiple reflections above the OH··OCH₂ complex. The predicted results can be represented by the expressions k₁ = 2.45 × 10^‐21 T^2.98 exp (1750/T) cm³ mol^?1 s^?1 (200–400 K) and 3.22 × 10^‐18 T^2.11 exp(849/T) cm³ mol^?1 s^?1 (400–3000 K) for the H‐abstraction process and k₂ = 1.05 × 10^‐17 T^1.63 exp(?2156/T) cm³ mol^?1 s^?1 in the temperature range of 200–3000 K for the HO‐addition process producing the OCH₂OH radical. The predicted total rate constants (k₁ + k₂) can reproduce closely the recommended kinetic data for OH + CH₂O over the entire range of temperature studied. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 322–326, 2006     

Theoretical studies on the reactions CH3SCH3 with OH,CF3, and CH3 radicals

The multiple‐channel reactions OH + CH₃SCH₃ → products, CF₃ + CH₃SCH₃ → products, and CH₃ + CH₃SCH₃ → products are investigated by direct dynamics method. The optimized geometries, frequencies, and minimum energy path are all obtained at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the MC‐QCISD (single‐point) method. The rate constants for eight reaction channels are calculated by the improved canonical variational transition state theory with small‐curvature tunneling contribution over the temperature range 200–3000 K. The total rate constants are in good agreement with the available experimental data and the three‐parameter expressions k₁ = 4.73 × 10^?16T^1.89 exp(?662.45/T), k₂ = 1.02 × 10^?32T^6.04 exp(933.36/T), k₃ = 3.98 × 10^?35T^6.60 exp(660.58/T) (in unit of cm³ molecule^?1 s^?1) over the temperature range of 200–3000 K are given. Our calculations indicate that hydrogen abstraction channels are the major channels and the others are minor channels over the whole temperature range. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Theoretical study and rate constants calculation for the reactions X + CF3CH2OCF3 (X = F,Cl, Br)

The multiple‐channel reactions X + CF₃CH₂OCF₃ (X = F, Cl, Br) are theoretically investigated. The minimum energy paths (MEP) are calculated at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the MC‐QCISD (single‐point) method. The rate constants for major reaction channels are calculated by canonical variational transition state theory (CVT) with small‐curvature tunneling (SCT) correction over the temperature range 200–2000 K. The theoretical three‐parameter expressions for the three channels k_1a(T) = 1.24 × 10^?15T^1.24exp(?304.81/T), k_2a(T) = 7.27 × 10^?15T^0.37exp(?630.69/T), and k_3a(T) = 2.84 × 10^?19T^2.51 exp(?2725.17/T) cm³ molecule^?1 s^?1 are given. Our calculations indicate that hydrogen abstraction channel is only feasible channel due to the smaller barrier height among five channels considered. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2012     

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 and mechanism of the OH + CIO2reaction

The rate constant k₁ for the reaction of OH radicals with CIO₂ molecules was measured in a discharge flow system over the temperature range 293 ≤ T ≤ 473 K and at low pressures, 0.5 ≤ P ≤ 1.4 torr, using electron paramagnetic resonance or laser-induced fluorescence to monitor the pseudo first-order decay of OH concentrations. At 293 K, the value obtained for k₁ was (7.2 ± 0.5) × 10^?12 cm³ molecule^?1 s^?1. Within the temperature range of this study, a negative temperature dependence was observed: k₁ = (4.50 ± 0.75) × 10^?13 exp[(804 ± 114)/T] cm³ molecule^?1 s^?1. HOCl was detected by mass spectrometry as a product of the reaction and was titrated using OH + Cl₂ as a source in the calibration experiments. A simulation of the mechanism of the OH + ClO₂ reaction indicated that HOCl was mainly produced in the first reaction step. Both this result and the observed T dependence of k₁ suggest that this reaction proceeds via an intermediate adduct with a cyclic geometry.     

Kinetics of the reactions of OH with alkanes

The rate coefficients for the reactions of OH with ethane (k₁), propane (k₂), n-butane (k₃), iso-butane (k₄), and n-pentane (k₅) have been measured over the temperature range 212–380 K using the pulsed photolysis-laser induced fluorescence (PP-LIF) technique. The 298 K values are (2.43±0.20) × 10^?13, (1.11 ± 0.08) × 10^?12, (2.46 ± 0.15) × 10^?12, (2.06 ± 0.14) × 10^?12, and (4.10 ± 0.26) × 10^?12 cm³ molecule^?1 s^?1 for k₁, k₂, k₃, k₄, and k₅, respectively. The temperature dependence of k₁ and k₂ can be expressed in the Arrhenius form: k₁ = (1.03 ± 0.07) × 10^?11 exp[?(1110 ± 40)/T] and k₂ = (1.01 ± 0.08) × 10^?11 exp[?(660 ± 50)/T]. The Arrhenius plots for k₃ – k₅ were clearly curved and they were fit to three parameter expressions: k₃ = (2.04 ± 0.05) × 10^?17 T² exp[(85 ± 10)/T] k₄ = (9.32 ± 0.26) × 10^?18 T² exp[(275 ± 20)/T]; and k₅ = (3.13 ± 0.25) × 10^?17 T² exp[(115 ± 30)/T]. The units of all rate constants are cm³ molecule^?1 s^?1 and the quoted uncertainties are at the 95% confidence level and include estimated systematic errors. The present measurements are in excellent agreement with previous studies and the best values for atmospheric calculations are recommended. © 1994 John Wiley & Sons, Inc.     

Kinetics of OH radical reactions with a series of ethers

The rate constants for the reactions of OH with dimethyl ether (k₁), diethyl ether (k₂), di-n-propyl ether (k₃), di-isopropyl ether (k₄), and di-n-butyl ether (k₅) have been measured over the temperature range 230–372 K using the pulsed laser photolysis-laser induced fluorescence (PLP-LIF) technique. The temperature dependence of k₁,k₄, can be expressed in the Arrhenius plots form: k₁ = (6.30 ± 0.10) × 10^?12 exp[?(234 ± 34)/T] and k₄ = (4.13 ± 0.10) × 10^?12 exp[(274 ± 26)/T]. The Arrhenius plots for k₂,k₃, and k₅, were curved and they were fitted to the three parameter expressions: k₂ = (1.02 ± 0.08) × 10^?17 T² exp[(797 ± 24)/T], k₃ = (1.84 ± 0.23) × 10^?17T² exp[(767 ± 34)/T], and k₅ = (6.29 ± 0.74) × 10^?18T² exp[(1164 ± 34)/T]. The values at 298 K are (2.82 ± 0.21) × 10^?12, (1.36 ± 0.11) × 10^?11,(2.17 ± 0.16) × 10^?11, (1.02 ± 0.10) × 10^?11, and (2.69 ± 0.22) × 10^?11 for k₁, k₂, k₃, k₄, and k₅, respectively, (in cm³ molecule^?1 s^?1). These results are compared to the literature data. © 1995 John Wiley & Sons, Inc.     

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.     

Ab initio chemical kinetics for the NH2 + HNOx reactions,part II: Kinetics and mechanism for NH2 + HONO

The kinetics and mechanism for the reaction of NH₂ with HONO have been investigated by ab initio calculations with rate constant prediction. The potential energy surface of this reaction has been computed by single‐point calculations at the CCSD(T)/6‐311+G(3df, 2p) level based on geometries optimized at the CCSD/6‐311++G(d, p) level. The reaction producing the primary products, NH₃ + NO₂, takes place via precomplexes, H₂N???c‐HONO or H₂N???t‐HONO with binding energies, 5.0 or 5.9 kcal/mol, respectively. The rate constants for the major reaction channels in the temperature range of 300–3000 K are predicted by variational transition state theory or Rice–Ramsperger–Kassel–Marcus theory depending on the mechanism involved. The total rate constant can be represented by k_total = 1.69 × 10^?20 × T^2.34 exp(1612/T) cm³ molecule^?1 s^?1 at T = 300–650 K and 8.04 × 10^?22 × T^3.36 exp(2303/T) cm³ molecule^?1 s^?1 at T = 650–3000 K. The branching ratios of the major channels are predicted: k₁ + k₃ producing NH₃ + NO₂ accounts for 1.00–0.98 in the temperature range 300–3000 K and k₂ producing OH + H₂NNO accounts for 0.02 at T > 2500 K. The predicted rate constant for the reverse reaction, NH₃ + NO₂ → NH₂ + HONO represented by 8.00 × 10^?26 × T^4.25 exp(?11,560/T) cm³ molecule^?1 s^?1, is in good agreement with the experimental data. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 678–688, 2009     

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

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

Ab initio chemical kinetics for the NH2 + HNOx reactions,part III: Kinetics and mechanism for NH2 + HONO2

The kinetics and mechanism for the reaction of NH₂ with HONO₂ have been investigated by ab initio calculations with rate constant prediction. The potential energy surface of this reaction has been computed by single‐point calculations at the CCSD(T)/6‐311+G(3df, 2p) level based on geometries optimized at the B3LYP/6‐311+G(3df, 2p) level. The reaction producing the primary products, NH₃ + NO₃, takes place via a precursor complex, H₂N…HONO₂ with an 8.4‐kcal/mol binding energy. The rate constants for major product channels in the temperature range 200–3000 K are predicted by variational transition state or variational Rice–Ramsperger–Kassel–Marcus theory. The results show that the reaction has a noticeable pressure dependence at T < 900 K. The total rate constants at 760 Torr Ar‐pressure can be represented by k_total = 1.71 × 10^?3 × T^?3.85 exp(?96/T) cm³ molecule^?1 s^?1 at T = 200–550 K, 5.11 × 10^?23 × T^+3.22 exp(70/T) cm³ molecule^?1 s^?1 at T = 550–3000 K. The branching ratios of primary channels at 760 Torr Ar‐pressure are predicted: k₁ producing NH₃ + NO₃ accounts for 1.00–0.99 in the temperature range of 200–3000 K and k₂ + k₃ producing H₂NO + HONO accounts for less than 0.01 when temperature is more than 2600 K. The reverse reaction, NH₃ + NO₃ → NH₂ + HONO₂ shows relatively weak pressure dependence at P < 100 Torr and T < 600 K due to its precursor complex, NH₃…O₃N with a lower binding energy of 1.8 kcal/mol. The predicted rate constants can be represented by k_?1 = 6.70 × 10^?24 × T^+3.58 exp(?850/T) cm³ molecule^?1 s^?1 at T = 200–3000 K and 760 Torr N₂ pressure, where the predicted rate at T = 298 K, 2.8 × 10^?16 cm³ molecule^?1 s^?1 is in good agreement with the experimental data. The NH₃ + NO₃ formation rate constant was found to be a factor of 4 smaller than that of the reaction OH + HONO₂ producing the H₂O + NO₃ because of the lower barrier for the transition state for the OH + HONO₂. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 69–78, 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 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