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1.
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 ktotal = 1.69 × 10?20 × T2.34 exp(1612/T) cm3 molecule?1 s?1 at T = 300–650 K and 8.04 × 10?22 × T3.36 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 × T4.25 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  相似文献   

2.
The kinetics and mechanism for the reaction of NH2 with HNO 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 major products of this reaction were found to be NH3 + NO formed by H‐abstraction via a long‐lived H2N???HNO complex and the H2NN(H)O radical intermediate formed by association with 26.9 kcal/mol binding energy. The rate constants for formation of primary products in the temperature range of 300–3000 K were predicted by variational transition state or RRKM theories. The predicted total rate constants at the 760 Torr Ar pressure can be represented by ktotal = 3.83 × 10?20 × T+2.47exp(1450/T) at T = 300–600 K; 2.58 × 10?22 × T+3.15 exp(1831/T) cm3 molecule?1 s?1 at T = 600?3000 K. The branching ratios of major channels at 760 Torr Ar pressure are predicted: k1 + k3 + k4 producing NH3 + NO accounts for 0.59–0.90 at T = 300–3000 K peaking around 1000 K, k2 accounts for 0.41–0.03 at T = 300–600 K decreasing with temperature, and k5 accounts for 0.07–0.27 at T > 600 K increasing gradually with temperature. The NH3 + NO formation rate constant was found to be a factor of 3–10 smaller than that of the isoelectronic reaction CH3 + HNO producing CH4 + NO, which has been shown to take place by barrierless H‐abstraction without involving a hydrogen‐bonding complex as in the NH2 case. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 677–677, 2009  相似文献   

3.
The kinetics of reactions of HCCl with NO and NO2 were investigated over the temperature ranges 298–572 k and 298–476 k, respectively, using laser‐induced fluorescence spectroscopy to measure total rate constants and time‐resolved infrared diode laser absorption spectroscopy to probe reaction products. Both reactions are fast, with k(HCCl + NO) = (2.75 ± 0.2) × 10?11 cm3 molecule?1 s?1 and k(HCCl + NO2) = (1.10 ± 0.2) × 10?10 cm3 molecule?1 s?1 at 296 K. Both rate constants displayed only a slight temperature dependence. Detection of products in the HCCl + NO reaction at 296 K indicates that HCNO + Cl is the major product with a branching ratio of ? = 0.68 ± 0.06, and NCO + HCl is a minor channel with ? = 0.24 ± 0.04. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 12–17, 2002  相似文献   

4.
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: k1b = (8.6 ± 3.2) × 10?11 exp[?(660 ± 100)/T] cm3 molecule?1 s?1 (with k1b = (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  相似文献   

5.
Rate coefficients for the reactions of CH3 + Br2 (k2), CH3CO + Br2 (k3), and Cl + Br2 (k5) were measured using the laser‐pulsed photolysis method combined with detection of the product Br atoms using resonance fluorescence. For the reactions involving organic radicals, the rate coefficients were observed to increase with decreasing temperature and within the temperature range explored, were adequately described by Arrhenius‐like expressions: k2 (224–358 K) = 1.83 × 10?11 exp(252/T) and k3 (228–298 K) = 2.92 × 10?11 exp(361/T) cm3 molecule?1 s?1. The total, temperature‐independent uncertainty for each reaction (including possible systematic errors in Br2 concentration measurement) was estimated as ~7% for k2 and 10% for k3. Accurate data on k5 was obtained at 298 K, with a value of 1.88 × 10?10 cm3 molecule?1 s?1 obtained (with an associated error of 6%). A limited data set at 228 K suggests that k5 is, within experimental uncertainty, independent of temperature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 575–585, 2010  相似文献   

6.
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  相似文献   

7.
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  相似文献   

8.
Relative rate techniques were used to study the kinetics of the reaction of OH radicals with acetylene at 296 K in 25–8000 Torr of air, N2/O2, or O2 diluent. Results obtained at total pressures of 25–750 Torr were in good agreement with the literature data. At pressures >3000 Torr, our results were substantially (~35%) lower than that reported previously. The kinetic data obtained over the pressure range 25–8000 Torr are well described (within 15%) by the Troe expression using ko = (2.92 ± 0.55) × 10?30 cm6 molecule?2 s?1, k = (9.69 ± 0.30) × 10?13 cm3 molecule?1 s?1, and Fc = 0.60. At 760 Torr total pressure, this expression gives k = 8.49 × 10?13 cm molecule?1 s?1. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 191–197, 2003  相似文献   

9.
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  相似文献   

10.
The rate coefficients of the reactions of CN and NCO radicals with O2 and NO2 at 296 K: (1) CN + O2 → products; (2) CN + NO2 → products; (3) NCO + O2 → products and (4) NCO + NO2 → products have been measured with the laser photolysis-laser induced fluorescence technique. We obtained k1 = (2.1 ± 0.3) × 10?11 and k2 = (7.2 ± 1.0) × 10?11 cm3 molecule?t s?1 which agree well with published results. As no reaction was observed between NCO and O2 at 297 K, an upper limit of k3 < 4 × 10?17 cm3 molecule?1 S?1 was estimated. The reaction of NCO with NO2 has not been investigated previously. We measured k4 = (2.2 ± 0.3) × 10?11 cm3 molecule?1 s?1 at 296 K.  相似文献   

11.
Rate coefficients, k, for the gas‐phase reaction CH3CO + Cl2 → products (2) were measured between 253 and 384 K at 55–200 Torr (He). Rate coefficients were measured under pseudo‐first‐order conditions in CH3CO with CH3CO produced by the 248‐nm pulsed‐laser photolysis of acetone, CH3C(O)CH3, or 2,3‐butadione, CH3C(O)C(O)CH3. The loss of CH3CO was monitored by cavity ring‐down spectroscopy (CRDS) at 532 nm. Rate coefficients were determined by first‐order kinetic analysis of the CH3CO temporal profiles for [Cl2] < 1 × 1014 molecule cm?3 and the analysis of the CRDS profiles by the simultaneous kinetics and ring‐down method for experiments performed with [Cl2] > 1 × 1014 molecule cm?3. k2(T) was found to be independent of pressure, with k2(296 K) = (3.0 ± 0.5) × 10?11 cm3 molecule?1 s?1. k2(T) showed a weak negative temperature dependence that is well reproduced by the Arrhenius expression k2(T) = (2.2 ± 0.8) × 10?11 exp[(85 ± 120)/T] cm3 molecule?1 s?1. The quoted uncertainties in k2(T) are at the 2σ level (95% confidence interval) and include estimated systematic errors. A comparison of the present work with previously reported rate coefficients for the CH3CO + Cl2 reaction is presented. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 543–553, 2009  相似文献   

12.
Rate coefficients, k(T), for the OH + CHF=CF2 (trifluoroethylene, HFO‐1123) gas‐phase reaction were measured under pseudo–first‐order conditions using pulsed laser photolysis to produce OH radicals and pulsed laser induced fluorescence to measure the OH radical temporal profile. Rate coefficients were measured over the temperature range 212–375 K at total pressures between 20 and 500 Torr (He, N2 bath gas). The rate coefficient was found to be independent of pressure over this range of pressure with a temperature dependence that is described by the Arrhenius expression (3.04 ± 0.30) × 10–12 exp[(312 ± 25)/T] cm3 molecule–1 s1 with k(296 K) measured to be (8.77 ± 0.80) × 10–12 cm3 molecule–1 s1 (quoted uncertainties are 2σ and include estimated systematic errors). Rate coefficients for the reaction of CHF=CF2 with 18OH and OD were also measured as part of this study at 296 and 373 K and a total pressure of ~25 Torr (He). The isotope measurements were used to evaluate the observed OH radical regeneration. CHF=CF2 is a very short‐lived substance with an atmospheric lifetime of ~1 day with respect to OH reactive loss, whereas the actual lifetime of CHF=CF2 will depend on the time and location of its emission. The global warming potential for CHF=CF2 on the 100‐year time horizon (GWP100) was estimated using the present results and a lifetime correction factor to be 3.9 × 10?3.  相似文献   

13.
The gas-phase reaction of the NO3 radical with NO2 was investigated, using a flash photolysis-visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10?13 cm3 molecule?1 s?1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N2 and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O2. These data show that the third-body efficiencies of N2 and O2 are identical, within the error limits, and that previous evaluations for M = N2 are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO3 radical with methanol, ethanol, and propan-2-ol of ?6 × 10?16, ?9 × 10?16, and ?2.3 × 10?15 cm3 molecule?1 s?1, respectively, at 298 ± 2 K.  相似文献   

14.
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  相似文献   

15.
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  相似文献   

16.
The rate constants k1 for the reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250–430 K using the flash photolysis–laser‐induced fluorescence (FP‐LIF) technique and the laser photolysis–laser‐induced fluorescence (LP‐LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253–328 K in an 11.5‐dm3 reaction chamber with either CHF2Cl or CH2FCF3 as a reference compound. OH radicals were produced by UV photolysis of an O3–H2O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k1 (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10?15 cm3 molecule?1 s?1 (FP‐LIF method) and (1.72 ± 0.07) × 10?15 cm3 molecule?1 s?1 (LP‐LIF method), whereas the K1 (298 K) values determined by the relative method were (1.87 ± 0.11) × 10?15 cm3 molecule?1 s?1 (CHF2Cl reference) and (2.12 ± 0.11) × 10?15 cm3 molecule?1 s?1 (CH2FCF3 reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K1 = (4.71 ± 0.94) × 10?13 exp[?(1630 ± 80)/T] cm3 molecule?1 s?1. Using kinetic data for the reaction of tropospheric CH3CCl3 with OH radicals [k1 (272 K) = 6.0 × 10?15 cm3 molecule?1 s?1, tropospheric lifetime of CH3CCl3 = 6.0 years], we estimated the tropospheric lifetime of CF3CF2CF2CF2CF2CHF2 through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26–33, 2004  相似文献   

17.
Rate coefficients, k, for the gas‐phase reaction of O(3P) atoms with Cl2O (dichlorine monoxide) over a range of temperatures (230–357 K) at pressures between 12 and 32 Torr (N2) are reported. Rate coefficients were measured under pseudo‐first‐order conditions in O(3P) using pulsed laser photolysis to produce O(3P) atoms and atomic resonance fluorescence to detect its temporal profile. The rate coefficient temperature dependence is given by the Arrhenius expression k(T) = (1.51 ± 0.20) × 10?11 exp[?(477 ± 30)/T] cm3 molecule?1 s?1, and k(296 K) was measured to be (2.93 ± 0.30) × 10?12 cm3 molecule?1 s?1. The quoted uncertainty limits are at the 2σ (95% confidence) level and include estimated systematic errors. The rate coefficients determined in the present study, under conditions that minimized secondary losses of O(3P), are compared with previous results from other laboratories and the discrepancies are discussed. © 2011 Wiley Peiodicals, 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: 312–321, 2011  相似文献   

    18.
    The rate constant for the reaction or NH3 + OH → NH2 + H2O has been measured in a high temperature fast flow reactor over the range 294–1075 K k = (5.41 ± 0.86) × 10-12 exp[?(2120 ± 143) cal mole?1/RT cm3 molecule?1 s?1. This result is compared with literature values and discussed.  相似文献   

    19.
    The kinetics of iodine dioxide (OIO) reactions with nitric oxide (NO), nitrogen dioxide (NO2), and molecular chlorine (Cl2) are studied in the gas‐phase by cavity ring‐down spectroscopy. The absorption spectrum of OIO is monitored after the laser photodissociation, 266 or 355 nm, of the gaseous mixture, CH2I2/O2/N2, which generates OIO through a series of reactions. The second‐order rate constant of the reaction OIO + NO is determined to be (4.8 ± 0.9) × 10?12 cm3 molecule?1 s?1 under 30 Torr of N2 diluent at 298 K. We have also measured upper limits for the second‐order rate constants of OIO with NO2 and Cl2 to be k < 6 × 10?14 cm3 molecule?1 s?1 and k < 8 × 10?13 cm3 molecule?1 s?1, respectively. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 688–693, 2007  相似文献   

    20.
    Absolute and relative rate techniques were used to study the reactivity of Cl atoms with cyclohexanone in 6 Torr of argon or 800–950 Torr of N2 at 295 ± 2 K. The absolute rate experiments gave k(Cl + cyclohexanone) = (1.88 ± 0.38) × 10?10, whereas the relative rate experiments gave k(Cl + cyclohexanone) = (1.66 ± 0.26) × 10?10 cm3 molecule?1 s?1. Cyclohexanone has a broad UV absorption band with a maximum cross section of (4.0 ± 0.3) × 10?20 cm2 molecule?1 near 285 nm. The results are discussed with respect to the literature data. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 223–229, 2008  相似文献   

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