Kinetics of OH radical reaction with anthracene and anthracene-d10

Using a refined pulsed laser photolysis/pulsed laser-induced fluorescence (PLP/PLIF) technique, the kinetics of the reaction of a surrogate three-ring polynuclear aromatic hydrocarbons (PAH), anthracene (and its deuterated form), with hydroxyl (OH) radicals was investigated over the temperature range of 373 to 1200 K. This study represents the first examination of the OH kinetics for this class of reactions at elevated temperatures (>470 K). The results indicate a complex temperature dependence similar to that observed for simpler aromatic compounds, e.g., benzene. At low temperatures (373-498 K), the rate measurements exhibited Arrhenius behavior (k = 1.82 x 10(-11) exp(542.35/T) in units of cm3 molecule(-1) s(-1)), and the kinetic isotope effect (KIE) measurements were consistent with an OH-addition mechanism. The low-temperature results are extrapolated to atmospheric temperatures and compared with previous measurements. Rate measurements between 673 and 923 K exhibited a sharp decrease in the magnitude of the rate coefficients (a factor of 9). KIE measurements under these conditions were still consistent with an OH-addition mechanism. The following modified Arrhenius equation is the best fit to our anthracene measurements between 373 and 923 K (in units of cm3 molecule(-1) s(-1)): k(1) (373-923 K) = 8.17 x 10(14) T(-8.3) exp(-3171.71/T). For a limited temperature range between 1000 and 1200 K, the rate measurements exhibited an apparent positive temperature dependence with the following Arrhenius equation, the best fit to the data (in units of cm3 molecule(-1) s(-1)): k1 (999-1200 K) = 2.18 x 10(-11) exp(-1734.11/T). KIE measurements above 999 K were slightly larger than unity but inclusive regarding the mechanism of the reaction. Theoretical calculations of the KIE indicate the mechanism of reaction at these elevated temperatures is dominated by OH addition with H abstraction being a minor contributor.     

Kinetics of hydrogen abstraction reaction between trifluoromethyl formate and OH radical: A theoretical investigation

Kinetics and mechanism of the hydrogen abstraction reaction between trifluoromethyl formate, CF₃OCHO, and OH radical have been investigated by using ab initio molecular orbital theory up to G2(MP2) level. The hydrogen abstraction rate constant has been calculated for the first time over a temperature range of 250–450 K by using standard transition state theory including the tunneling correction. Arrhenius parameters of the reaction have been estimated from the temperature dependence of the calculated rate constant. The calculated value for the rate constant (2.0 × 10^?14 cm³ molecule^?1 s^?1) at 298 K is found to be in very good agreement with the recent experimental results. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 500–507, 2002     

Kinetics study of the aromatic bicyclic peroxy radical + NO reaction: overall rate constant and nitrate product yield measurements

The measurements of the overall bicyclic peroxy radical + NO rate constant for the 1,3,5-trimethylbenzene (1,3,5-TMB) system and of the nitrate product yields for the benzene, toluene, p-xylene, and 1,3,5-TMB systems were performed via the turbulent flow chemical ionization mass spectrometry technique. While the overall rate constant was found to be consistent with the value used in the most detailed aromatic oxidation kinetic model (Master Chemical Mechanism, MCM), the nitrate product yields were found to be generally lower than predicted by the MCM and to have a different aromatic species-specific dependence than the MCM predicts.     

CN radical reaction rate measurements by time-resolved FM spectroscopy

Time-resolved frequency-modulation spectroscopy is shown to be an effective method for measuring the rates of gas-phase reactions. As an example, the rate constant for the reaction of CN with C₂H₄ at 298 K is measured to be 2.5 ± 0.2 × 10⁻¹⁰ cm³s⁻¹, in good agreement with other literature values. The efficiency and sensitivity of this technique will be of interest to the chemical kineticist. © 1997 John Wiley & Sons, Inc.     

Formation of 3-Methylfuran from the gas-phase reaction of OH radicals with isoprene and the rate constant for its reaction with the OH radical

3-Methylfuran has been identified as a product of the gas-phase reaction of the OH radical with isoprene, and under simulated atmospheric conditions a formation yield of 0.044 ± 0.006 was determined. In an analogous manner, the OH radical reaction with 1,3-butadiene formed furan with a yield of 0.039 ± 0.011. Using a relative rate method, a rate constant for the reaction of the OH radical with 3-methylfuran of 9.35 × 10^?11 cm³ molecule^?1 s^?1 (with an estimated overall uncertainty of ±20%) at 296 ± 2 K was also determined. These data show that 3-methylfuran is a reactive compound which will be present in the troposphere at concentrations ?5% of those of its isoprene precursor.     

Kinetics of the reaction of OH with HCl

The rate constant of the reaction OH + HCl → H₂O + Cl was measured in a flow tube over the temperature range 224 to 460°K using resonance fluorescence detection of OH. An Arrhenius expression k₁ = (2.0 ± 0.1) × 10^?12 exp [?(620 ± 20 cal/mole)/RT] was obtained. Stratospheric and reaction kinetic implications are discussed briefly.     

High temperature measurements of the rate of the reaction of OH with NH3

Low pressure (4.67 kPa) CH₄/O₂/Ar flames were seeded with approximately 5300 ppm NH₃. The concentration profiles of stable and radical species in lean (? = 0.92) and rich (? = 1.13) flames were determined by molecular beam sampling mass spectrometry. Temperature profiles in these flames were measured with thermocouples whose readings were corrected for radiative losses by the Na-line reversal method. Regions of the flames were selected where the principal reaction leading to the destruction of NH₃ was By correcting the measured concentrations for diffusion, the net rate of NH₃ loss rate was determined in the temperature range 2080–2360 K. The rate constant k₁ was determined from the net loss rate with correction for the reaction using measured values of (O) and k₂ values given by Salimian, Hanson, and Kruger [1]. The best-fit Arrhenius expression for k₁ in the temperature range 2080–2360 K is 10^13.88 exp(?4539/T) cm³/mol-s. The results of this study combined with previous lower temperature data confirm the non-Arrhenius behavior of k₁ suggested by Salimian, Hanson, and Kruger [1]. The best-fit modified three parameter expression for the range 300–2360 K is 10^6.33±0.2 T² exp(?169/T) cm³/mol-s.     

Kinetics and mechanism of the reaction of OH with ClO

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

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.     

Kinetics of the gas-phase reaction of OH with HCl

The reaction of hydroxyl radicals with hydrogen chloride (reaction 1) has been studied experimentally using a pulsed-laser photolysis/pulsed-laser-induced fluorescence technique over a wide range of temperatures, 298-1015 K, and at pressures between 5.33 and 26.48 kPa. The bimolecular rate coefficient data set obtained for reaction 1 demonstrates no dependence on pressure and exhibits positive temperature dependence that can be represented with modified three-parameter Arrhenius expression within the experimental temperature range: k1 = 3.20 x 10(-15)T0.99 exp(-62 K/T) cm3 molecule(-1) s(-1). The potential-energy surface has been studied using quantum chemical methods, and a transition-state theory model has been developed for the reaction 1 on the basis of calculations and experimental data. The model results in modified three-parameter Arrhenius expressions: k1 = 8.81 x 10(-16)T1.16 exp(58 K/T) cm3 molecule(-1) s(-1) for the temperature range 200-1015 K and k1 = 6.84 x 10(-19)T2.12 exp(646 K/T) cm3 molecule(-1) s(-1) for the temperature dependence of the reaction 1 rate coefficient extrapolation to high temperatures (500-3000 K). A temperature dependence of the rate coefficient of the Cl + H2O --> HCl + OH reaction has been derived on the basis of the experimental data, modeling, and thermochemical information.     

High accuracy measurements of OH reaction rate constants and IR absorption spectra: substituted 2-propanols

Rate constants for the gas phase reactions of OH radicals with 2-propanol and three fluorine substituted 2-propanols, (CH(3))(2)CHOH (k(0)), (CF(3))(2)CHOH (k(1)), (CF(3))(2)C(OH)CH(3) (k(2)), and (CF(3))(3)COH (k(3)), were measured using a flash photolysis resonance-fluorescence technique over the temperature range 220-370 K. The Arrhenius plots were found to exhibit noticeable curvature for all four reactions. The temperature dependences of the rate constants can be represented by the following expressions: k(0)(T) = 1.46 × 10(-11) exp{-883/T} + 1.30 × 10(-12) exp{+371/T} cm(3) molecule(-1) s(-1); k(1)(T) = 1.19 × 10(-12) exp{-1207/T} + 7.85 × 10(-16) exp{+502/T } cm(3) molecule(-1) s(-1); k(2)(T) = 1.68 × 10(-12) exp{-1718/T} + 7.32 × 10(-16) exp{+371/T} cm(3) molecule(-1) s(-1); k(3)(T) = 3.0 × 10(-20) × (T/298)(11.3) exp{+3060/T} cm(3) molecule(-1) s(-1). The atmospheric lifetimes due to reactions with tropospheric OH were estimated to be 2.4 days and 1.9, 6.3, and 46 years, respectively. UV absorption cross sections were measured between 160 and 200 nm. The IR absorption cross sections of the three fluorinated compounds were measured between 450 and 1900 cm(-1), and their global warming potentials were estimated.     

The gas-phase reaction of hydrazine and ozone: A nonphotolytic source of OH radicals for measurement of relative OH radical rate constants

The homogeneous gas-phase reaction of N₂H₄ with O₃ in air atmospheric pressure has been used to generate OH radicals in the dark, allowing the determination of relative OH radical rate constants for compounds which photolyze rapidly. This technique was first validated by determining the OH radical rate constant ratios for n-butane/cyclohexane and methanol/dimethyl ether, both of which are in excellent agreement with the literature values. The rate constant for the reaction of OH radicals with methyl nitrite at 300 ± 3 K was then determined relative to those for the reaction of OH radicals with n-hexane and dimethyl ether. The resulting rate constant of 1.8 × 10^?13 cm³/molecule·s is about seven times lower than those of previous measurements which employed a different nonphotolytic relative rate method.     

Kinetics of the reaction of OH with pernitric and nitric acids

The absolute rate constants for the reactions of OH + HO₂NO₂ (1) and OH + HNO₃ (2) have been measured with the technique of flash photolysis resonance fluorescence over the temperature ranges of 240–330 K at 760 torr He for reaction (1) and of 240–370 K at 50 and 760 torr He for reaction (2). Reactant concentrations were monitored continuously by ultraviolet and infrared spectrophotometry. The data can be fitted to the following Arrhenius expressions: These results are in very good agreement with recent studies of reaction (2), and also of reaction (1) at 295 K.     

Kinetics of the OH + HCNO reaction

The kinetics of the OH + HCNO reaction was studied. The total rate constant was measured by LIF detection of OH using two different OH precursors, both of which gave identical results. We obtain k = (2.69 +/- 0.41) x 10(-12) exp[(750.2 +/- 49.8)/T] cm(3) molecule(-1) s(-1) over the temperature range 298-386 K, with a value of k = (3.39 +/- 0.3) x 10(-11) cm(3) molecule(-1) s(-1) at 296 K. CO, H(2)CO, NO, and HNO products were detected using infrared laser absorption spectroscopy. On the basis of these measurements, we conclude that CO + H(2)NO and HNO + HCO are the major product channels, with a minor contribution from H(2)CO + NO.     

Kinetics of the reaction of methyl radical with hydroxyl radical and methanol decomposition

The CH3 + OH bimolecular reaction and the dissociation of methanol are studied theoretically at conditions relevant to combustion chemistry. Kinetics for the CH3 + OH barrierless association reaction and for the H + CH2OH and H + CH3O product channels are determined in the high-pressure limit using variable reaction coordinate transition state theory and multireference electronic structure calculations to evaluate the fragment interaction energies. The CH3 + OH --> 3CH2 + H2O abstraction reaction and the H2 + HCOH and H2 + H2CO product channels feature localized dynamical bottlenecks and are treated using variational transition state theory and QCISD(T) energies extrapolated to the complete basis set limit. The 1CH2 + H2O product channel has two dynamical regimes, featuring both an inner saddle point and an outer barrierless region, and it is shown that a microcanonical two-state model is necessary to properly describe the association rate for this reaction over a broad temperature range. Experimental channel energies for the methanol system are reevaluated using the Active Thermochemical Tables (ATcT) approach. Pressure dependent, phenomenological rate coefficients for the CH3 + OH bimolecular reaction and for methanol decomposition are determined via master equation simulations. The predicted results agree well with experimental results, including those from a companion high-temperature shock tube determination for the decomposition of methanol.     

The rate of the reaction of OH with HCl

The absolute rate constant for the OH + HCl reaction has been measured from 240 to 295 K utilizing the techniques of laser/flash photolysis-resonance fluorescence. The HCl concentrations were monitored continuously by ultraviloet and infrared spectrophotometry. The results can be fit to the following Arrhenius expression: The rate constant values obtained in this study are 20–30% larger than those recommended previously for modeling of stratospheric chemistry.     

OH radical reaction rate constants for polycyclic alkanes: Effects of ring strain and consequences for estimation methods

Using a relative rate method, rate constants for the gas-phase reactions of the OH radical with trans-pinane [(1R, 2R)-2, 6, 6-trimethylbicyclo[3.1.1]heptane], tricyclene (1, 7, 7-trimethyltricyclo[2.2.1.0^{2, 6}]heptane), and quadricyclane (quadricyclo[2.2.1.0^{2, 6}.0^{3, 5}]heptane) of (1.34 ± 0.29) × 10^?11 cm³ molecule^?1 s^?1, (2.86 ± 0.62) × 10^?12 cm³ molecule^?1 s^?1 and (1.83 ± 0.41) × 10^?12 cm³ molecule^?1 s^?1, respectively, have been determined at 296 ± 2 K. These rate constants are compared with values calculated from an empirical estimation method and used to refine this estimation technique for the calculation of OH radical reaction rate constants for polycyclic systems. © John Wiley & Sons, Inc.     

Kinetics and products of the reactions of selected diols with the OH radical

Using a relative rate method, rate constants have been measured at 296 ± 2 K for the gas‐phase reactions of OH radicals with 1,2‐butanediol, 2,3‐butanediol, 1,3‐butanediol, and 2‐methyl‐2,4‐pentanediol, with rate constants (in units of 10^?12 cm³ molecule^?1 s^?1) of 27.0 ± 5.6, 23.6 ± 6.3, 33.2 ± 6.8, and 27.7 ± 6.1, respectively, where the error limits include the estimated overall uncertainty of ±20% in the rate constant for the reference compound. Gas chromatographic analyses showed the formation of 1‐hydroxy‐2‐butanone from 1,2‐butanediol, 3‐hydroxy‐2‐butanone from 2,3‐butanediol, 1‐hydroxy‐3‐butanone from 1,3‐butanediol, and 4‐hydroxy‐4‐methyl‐2‐pentanone from 2‐methyl‐2,4‐pentanediol, with formation yields of 0.66 ± 0.11, 0.89 ± 0.09, 0.50 ± 0.09, and 0.47 ± 0.09, respectively, where the indicated errors are the estimated overall uncertainties. Pathways for the formation of these products are presented, together with a comparison of the measured and estimated rate constants and product yields. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 310–316, 2001