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1.
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 kOH = 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; kOH = 9.8 × 10?13 exp[(1166 ± 248)/T]; 301–373 K; p-cresol; kOH = 2.21 × 10?12 exp[(943 ± 449)/T]; 301–373 K; and phenol, kOH = 3.7 × 10?13 exp[(1267 ± 233)/T]; 301–373 K. The rate coefficient for benzaldehyde kOH = 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 kOH = 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, kOH = 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.  相似文献   

2.
Laser flash photolysis combined with competition kinetics with SCN? as the reference substance has been used to determine the rate constants of OH radicals with three fluorinated and three chlorinated ethanols in water as a function of temperature. The following Arrhenius expressions have been obtained for the reactions of OH radicals with (1) 2‐fluoroethanol, k1(T) = (5.7 ± 0.8) × 1011 exp((?2047 ± 1202)/T) M?1 s?1, (2) 2,2‐difluoroethanol, k2(T) = (4.5 ± 0.5) × 109 exp((?855 ± 796)/T) M?1 s?1, (3) 2,2,2‐trifluoroethanol, k3(T) = (2.0 ± 0.1) × 1011 exp((?2400 ± 790)/T) M?1 s?1, (4) 2‐chloroethanol, k4(T) = (3.0 ± 0.2) × 1010 exp((?1067 ± 440)/T) M?1 s?1, (5) 2, 2‐dichloroethanol, k5(T) = (2.1 ± 0.2) × 1010 exp((?1179 ± 517)/T) M?1 s?1, and (6) 2,2,2‐trichloroethanol, k6(T) = (1.6 ± 0.1) × 1010 exp((?1237 ± 550)/T) M?1 s?1. All experiments were carried out at temperatures between 288 and 328 K and at pH = 5.5–6.5. This set of compounds has been chosen for a detailed study because of their possible environmental impact as alternatives to chlorofluorocarbon and hydrogen‐containing chlorofluorocarbon compounds in the case of the fluorinated alcohols and due to the demonstrated toxicity when chlorinated alcohols are considered. The observed rate constants and derived activation energies of the reactions are correlated with the corresponding bond dissociation energy (BDE) and ionization potential (IP), where the BDEs and IPs of the chlorinated ethanols have been calculated using quantum mechanical calculations. The errors stated in this study are statistical errors for a confidence interval of 95%. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 174–188, 2008  相似文献   

3.
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   

4.
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   

5.
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.  相似文献   

6.
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?17T1.85exp(–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?18T2.2exp(260/T) at T= 248–900 K and k3 = 2.7 × 10?16T1.7exp(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?17T1.93exp(–114/T), k2 = 9.0 × 10?17T1.8 exp(120/T), and k3 = 3.75 × 10?16 T1.65 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.  相似文献   

7.
The rate constants of the reaction between OH and H2S in He, N2, and O2 over the temperature range 245–450 K have been determined using the discharge flow-resonance fluorescence technique. At 299 K, k1 = (4.4 ± 0.7) × 10?12 cm3 molecule?1 s?1. The temperature dependence of the rate constant can be fitted either by k1 = 5.6 × 10?12 exp(?57/T) or by k1 = (3.8 × 10?19)T2.43 exp(732/T) to within 8 and 9%, respectively. However, the non-Arrhenius behavior can be confidently confirmed. The absence of the pressure dependence and the third-body effect at low temperature suggest that the complex formation mechanism is not important over the temperature range of our study.  相似文献   

8.
Single pulse shock tube studies of the thermal dehydrochlorination reactions (chlorocyclopentane → cyclopentene + HCl) and (chlorocyclohexane → cyclohexene + HCl) at temperatures of 843–1021 K and pressures of 1.4–2.4 bar have been carried out using the comparative rate technique. Rate constants have been measured relative to (2‐chloropropane → propene + HCl) and the decyclization reactions of cyclohexene, 4‐methylcyclohexene, and 4‐vinylcyclohexene. Absolute rate constants have been derived using k(cyclohexene → ethene + butadiene) = 1.4 × 1015 exp(?33,500/T) s?1. These data provide a self‐consistent temperature scale of use in the comparison of chemical systems studied with different temperature standards. A combined analysis of the present results with the literature data from lower temperature static studies leads to
  • k(2‐chloropropane) = 10(13.98±0.08) exp(?26, 225 ± 130) K/T) s?1; 590–1020 K; 1–3 bar
  • k(chlorocylopentane) = 10(13.65 ± 0.10) exp(?24,570 ± 160) K/T) s?1; 590–1020 K; 1–3 bar
  • k(chlorocylohexane) = 10(14.33 ± 0.10) exp(?25,950 ± 180) K/T) s?1; 590–1020 K; 1–3 bar
Including systematic uncertainties, expanded standard uncertainties are estimated to be about 15% near 600 K rising to about 25% at 1000 K. At 2 bar and 1000 K, the reactions are only slightly under their high‐pressure limits, but falloff effects rapidly become significant at higher temperatures. On the basis of computational studies and Rice–Ramsperger–Kassel–Marcus (RRKM)/Master Equation modeling of these and reference dehydrochlorination reactions, reported in more detail in an accompanying article, the following high‐pressure limits have been derived:
  • k (2‐chloropropane) = 5.74 × 109T1.37 exp(?25,680/T) s?1; 600–1600 K
  • k (chlorocylopentane) = 7.65 × 107T1.75 exp(?23,320/T) s?1; 600–1600 K
  • k (chlorocylohexane) = 8.25 × 109T1.34 exp(?25,010/T) s?1; 600–1600 K
© 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 44: 351–368, 2012  相似文献   

    9.
    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 T2.98 exp (1750/T) cm3 mol?1 s?1 (200–400 K) and 3.22 × 10‐18 T2.11 exp(849/T) cm3 mol?1 s?1 (400–3000 K) for the H‐abstraction process and k2 = 1.05 × 10‐17 T1.63 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  相似文献   

    10.
    The rate constants and activation energies for the reactions of some thiophenes with the NO3 radical were measured using the absolute fast‐flow discharge technique at 263–335 K and low pressure. The proposed Arrhenius expressions for 2‐ethylthiophene, 2‐propylthiophene, 2,5‐dimethylthiophene, and 2‐chlorothiophene are k = (4.2 ± 0.28) ×10?16 exp[(2280 ± 70)]/T, k = (7.0 ± 2) × 10?18 exp[(3530 ± 70)]/T, k = (1 ± 1) × 10?14 exp[(1648 ± 240)]/T, and k = (8 ± 2) × 10?17 exp[(2000 ± 200)]/T (k = cm3 molecule?1 s?1), respectively. The reactions of this radical with 2‐chlorothiophene and 3‐chlorothiophene were also studied by a relative method in a Teflon static reactor at room temperature and atmospheric pressure. The effect of substitution on thiophene reactivity is discussed, and a relationship between the rate constants and the ionization potential (IP = ?EHOMO) has been proposed. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 570–576, 2006  相似文献   

    11.
    Far-infrared rotational transitions in ClO(X23/2, υ = 0) have been observed using laser magnetic resonance (LMR) with an optically pumped spectrometer. Five observed transitions at wavelengths between 444 and 713 µm have been compared with values predicted with spectroscopic constants from the literature. LMR detection of ClO has been used to study its reactions with NO and NO2 in a discharge flow system under pseudo-first-order conditions for ClO. The measured rate constants are k(ClO + NO) = (7.1 ± 1.4) × 10?12 exp[(270 ± 50)/T] cm3/molec·s for the temperature range of 202 < T < 393 K; k(ClO + NO2 + M) = (2.8 ± 0.6) × 10?33 exp[(1090 ± 80)/T] cm6/molec2·s (M = He, 250 < T < 387 K), (3.5 ± 0.6) × 10?33 exp[(1180 ± 80)/T] (M = O2, 250 < T < 416 K), and (2.09 ± 0.3) × 10?31 (M = N2, T = 297 K). All measurements were made at low pressures, between 0.6 and 6.6 torr. These results are compared with those from other studies.  相似文献   

    12.
    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 k1a(T) = 1.24 × 10?15T1.24exp(?304.81/T), k2a(T) = 7.27 × 10?15T0.37exp(?630.69/T), and k3a(T) = 2.84 × 10?19T2.51 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  相似文献   

    13.
    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 Fcent = 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 krec,0 = [N2] 3.7 × 10?30 (T/300)?4.1 cm6/molec2·s and krec,∞ = 1.6 × 10?12 (T/300)+0.2 cm3/molec·s.  相似文献   

    14.
    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   

    15.
    The mechanisms for reactions of H, HO, and Cl with HOClO3, important elementary processes in the early stages of the ammonium perchlorate (AP) combustion reaction, have been investigated at the CCSD(T)/6‐311+G(3df,2p)//PW91PW91/6‐311+G(3df) level of theory. The rate constants for the low‐energy channels have been calculated by statistical theory. For the reaction of H and HOClO3, the main channels are the production of H2 + ClO4 (k1a) and HO + HOClO2 (k1b); k1a and k1b can be represented as 1.07 × 10?17 T1.97 exp(?7484/T) and 6.08 × 10?17T1.96 exp(?7729/T) cm3 molecule?1 s?1, respectively. For the HO + HOClO3 reaction, the main pathway is the H2O + ClO4 (k2a) production process, with the predicted rate constant k2a = 1.24 × 10 ?8 T?2.99 exp(1664/T) for 300–500 K and k2a = 1.27×10?19 T2.12 exp(?1474/T) for 500–3000 K. For the Cl + HOClO3 reaction, the formation of HOCl + ClO3 (k3a) and HCl + ClO4 (k3b) is dominant, with k3a = 1.33×10?12 T0.67 exp(?9658/T) and k3b = 1.75×1016 T1.63 exp(?11156/T) cm3 molecules?1 in the range of 300–3000 K. In addition, the heats of formation of ClO3 and HOClO3 have been predicted based on several isodesmic and/or isogyric reactions with ΔfHo0 (ClO3) = 47.0 ± 1.0 and ΔfHo0 (HOClO3) = 5.5 ± 1.5 kcal/mol, respectively. These data may be used for kinetic simulation of the AP decomposition and combustion reaction. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 253–261, 2010  相似文献   

    16.
    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   

    17.
    The rate constant of the gas-phase reaction Fe(a 5 D 4) + CO2 at 1180–2380 K and a total gas density of (7.0–10.0) × 10?6 mol/cm3 behind incident shock waves is k(Fe + CO2) = 1.4 × 1014.0 ± 0.3exp[?(14590 ± 1100)/T] cm3 mol?1 s?1, as determined by resonance atomic absorption photometry. Using thermochemical data available from the literature, the rate constant of the reverse reaction was calculated to be k(Fe + CO) = 9.2 × 1011.0 ± 0.3 (T/1000)0.57exp[?(490 ± 1100)/T] cm3 mol?1 s?1. The results are compared with data reported earlier.  相似文献   

    18.
    The kinetics of C6H5 reactions with n‐CnH2n+2 (n = 3, 4, 6, 8) have been studied by the pulsed laser photolysis/mass spectrometric method using C6H5COCH3 as the phenyl precursor at temperatures between 494 and 1051 K. The rate constants were determined by kinetic modeling of the absolute yields of C6H6 at each temperature. Another major product C6H5CH3 formed by the recombination of C6H5 and CH3 could also be quantitatively modeled using the known rate constant for the reaction. A weighted least‐squares analysis of the four sets of data gave k (C3H8) = (1.96 ± 0.15) × 1011 exp[?(1938 ± 56)/T], and k (n‐C4H10) = (2.65 ± 0.23) × 1011 exp[?(1950 ± 55)/T] k (n‐C6H14) = (4.56 ± 0.21) × 1011 exp[?(1735 ± 55)/T], and k (n?C8H18) = (4.31 ± 0.39) × 1011 exp[?(1415 ± 65)T] cm3 mol?1 s?1 for the temperature range studied. For the butane and hexane reactions, we have also applied the CRDS technique to extend our temperature range down to 297 K; the results obtained by the decay of C6H5 with CRDS agree fully with those determined by absolute product yield measurements with PLP/MS. Weighted least‐squares analyses of these two sets of data gave rise to k (n?C4H10) = (2.70 ± 0.15) × 1011 exp[?(1880 ± 127)/T] and k (n?C6H14) = (4.81 ± 0.30) × 1011 exp[?(1780 ± 133)/T] cm3 mol?1 s?1 for the temperature range 297‐‐1046 K. From the absolute rate constants for the two larger molecular reactions (C6H5 + n‐C6H14 and n‐C8H18), we derived the rate constant for H‐abstraction from a secondary C? H bond, ks?CH = (4.19 ± 0.24) × 1010 exp[?(1770 ± 48)/T] cm3 mol?1 s?1. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 49–56, 2004  相似文献   

    19.
    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 k3k5 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.  相似文献   

    20.
    The thermal decomposition of cyanogen azide (NCN3) and the subsequent collision‐induced intersystem crossing (CIISC) process of cyanonitrene (NCN) have been investigated by monitoring excited electronic state 1NCN and ground state 3NCN radicals. NCN was generated by the pyrolysis of NCN3 behind shock waves and by the photolysis of NCN3 at room temperature. Falloff rate constants of the thermal unimolecular decomposition of NCN3 in argon have been extracted from 1NCN concentration–time profiles in the temperature range 617 K <T< 927 K and at two different total densities: k(ρ ≈ 3 × 10?6 mol/cm3)/s?1=4.9 × 109 × exp (?71±14 kJ mol?1/RT) (± 30%); k(ρ ≈ 6 × 10?6 mol/cm3)/s?1=7.5 × 109 × exp (‐71±14 kJ mol?1/RT) (± 30%). In addition, high‐temperature 1NCN absorption cross sections have been determined in the temperature range 618 K <T< 1231 K and can be expressed by σ /(cm2/mol)= 1.0 × 108 ?6.3 × 104 K?1 × T (± 50%). Rate constants for the CIISC process have been measured by monitoring 3NCN in the temperature range 701 K <T< 1256 K resulting in kCIISC (ρ ≈ 1.8 ×10?6 mol/cm3)/ s?1=2.6 × 106× exp (‐36±10 kJ mol?1/RT) (± 20%), kCIISC (ρ ≈ 3.5×10?6 mol/cm3)/ s?1 = 2.0 × 106 × exp (?31±10 kJ mol?1/RT) (± 20%), kCIISC (ρ ≈ 7.0×10?6 mol/cm3)/ s?1=1.4 × 106 × exp (?25±10 kJ mol?1/RT) (± 20%). These values are in good agreement with CIISC rate constants extracted from corresponding 1NCN measurements. The observed nonlinear pressure dependences reveal a pressure saturation effect of the CIISC process. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 30–40, 2013  相似文献   

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