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1.
A high‐resolution IR diode laser in conjunction with a Herriot multiple reflection flow‐cell has been used to directly determine the rate coefficients for simple alkanes with Cl atoms at room temperature (298 K). The following results were obtained: k(Cl + n‐butane) = (1.91 ± 0.10) × 10?10 cm3 molecule?1 s?1, k(Cl + n‐pentane) = (2.46 ± 0.12) × 10?10 cm3 molecule?1 s?1, k(Cl + iso‐pentane) = (1.94 ± 0.10) × 10?10 cm3 molecule?1 s?1, k(Cl + neopentane) = (1.01 ± 0.05) × 10?10 cm3 molecule?1 s?1, k(Cl + n‐hexane) = (3.44 ± 0.17) × 10?10 cm3 molecule?1 s?1 where the error limits are ±1σ. These values have been used in conjunction with our own previous measurements on Cl + ethane and literature values on Cl + propane and Cl + iso‐butane to generate a structure activity relationship (SAR) for Cl atom abstraction reactions based on direct measurements. The resulting best fit parameters are kp = (2.61 ± 0.12) × 10?11 cm3 molecule?1 s?1, ks = (8.40 ± 0.60) × 10?11 cm3 molecule?1 s?1, kt = (5.90 ± 0.30) × 10?11 cm3 molecule?1 s?1, with f( ? CH2? ) = f (? CH2? ) = f (?C?) = f = 0.85 ± 0.06. Tests were carried out to investigate the potential interference from production of excited state HCl(v = 1) in the Cl + alkane reactions. There is some evidence for HCl(v = 1) production in the reaction of Cl with shape n‐hexane. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 86–94, 2002 相似文献
2.
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: k1b = (9.7 ± 4.1) × 10?14 exp{(600 ± 120)/T} cm3 molecule?1 s?1 (with k1b = (7.3 ± 2.2) × 10?13 cm3 molecule?1 s?1 and k1b/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 Hf,298(HO2) = 3.0 ± 0.4 kcal mol?1. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 587–599, 2001 相似文献
3.
The kinetics of C2H5O2 and C2H5O2 radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis. The temporal profiles of C2H5O were monitored by LIF. The rate constant for C2H5O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k2 = (1.25±0.04) × 10?11, (1.66±0.06) × 10?11, (1.81±0.06) × 10?11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm3 molecule?1 s?1). The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C2H5O + NO + M → C2H5ONO + M (2a), C2H5O + NO → CH3CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k2a and for k2b : k = (2.6±1.0) × 10?28 cm6 molecule?2 s?1, k = (3.1±0.8) × 10?11 cm3 molecule?1 s?1 and k2b ca. 8 × 10?12 cm3 molecule?1 s?1. The present value of k, obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10?27 cm6 molecule?2 s?1 recommended in air. The rate constant for the reaction C2H5O2 + NO → C2H5O + NO2 (3) has been measured at 1 torr of He from the simulation of experimental C2H5O profiles. The value obtained for k3 = (8.2±1.6) × 10?12 cm3 molecule?1 s?1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc. 相似文献
4.
The rate constant for the reactions of atomic chlorine with 1,4‐dioxane (k1), cyclohexane (k2), cyclohexane‐d12(k3), and n‐octane (k4) has been determined at 240–340 K using the relative rate/discharge fast flow/mass spectrometer (RR/DF/MS) technique developed in our laboratory. Essentially, no temperature dependence for these reactions was observed over this temperature range, with an average of k1 = (1.91 ± 0.20) × 10?10 cm3 molecule?1 s?1, k2 = (2.91 ± 0.31) × 10?10 cm3 molecule?1 s?1, k3 = (2.73 ± 0.30) × 10?10 cm3 molecule?1 s?1, and k4 = (3.22 ± 0.36) × 10?10 cm3 molecule?1 s?1, respectively. The kinetic isotope effect of the reaction of cyclohexane with atomic chlorine has also been determined to be 1.14 by directly monitoring the decay of both cyclohexane and cyclohexane‐d12 in the presence of chlorine atoms, which is consistent with the literature value of 1.20. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 386–398, 2006 相似文献
5.
This paper presents an experimental procedure to study state-to-state collisional dynamics by using tunable and pulsed laser techniques and time-resolved and dispersed fluorescence methods. For the first time, the decay processes of electronically excited iodine, B3IIou+ (v′ = 19), to the adjacent vibrational states in collisions with He molecules have been directly observed in real time. The rate constants for the state-to-state vibrational energy transfer obtained are, k,vHe(19→18) = (2.76±0.05)x10?11cm3s?1 molecule?1 and kvHe(19→20) = (1.65±0.04) × 10?11 cm3s?1 molecule?1. These results are in satisfactory agreement with the detailed balance principle. 相似文献
6.
The rate coefficients for the gas-phase reactions of C2H5O2 and n-C3H7O2 radicals with NO have been measured over the temperature range of (201–403) K using chemical ionization mass spectrometric detection of the peroxy radical. The alkyl peroxy radicals were generated by reacting alkyl radicals with O2, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C2H5 radicals were generated through the dissociation of iodoethane in a low-power radio frequency discharge. The discharge source was also tested for the i-C3H7O2 + NO reaction, yielding k298 K = (9.1 ± 1.5) × 10−12 cm3 molecule−1 s−1, in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 ± 0.4) × 10−12 exp{(380 ± 70)/T} cm3 molecule−1 s−1 and k(T) = (2.9 ± 0.5) × 10−12 exp{(350 ± 60)/T} cm3 molecule−1 s−1 for the reactions of C2H5O2 and n-C3H7O2 radicals with NO, respectively. The rate coefficients at 298 K derived from these Arrhenius expressions are k = (9.3 ± 1.6) × 10−12 cm3 molecule−1 s−1 for C2H5O2 radicals and k = (9.4 ± 1.6) × 10−12 cm3 molecule−1 s−1 for n-C3H7O2 radicals. © 1996 John Wiley & Sons, Inc. 相似文献
7.
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
8.
A kinetic study of the reactions of H atoms with CH3SH and C2H5SH has been carried out at 298 K by the discharge flow technique with EPR and mass spectrometric analysis of the species. The pressure was 1 torr. It was found: k1 = (2.20 ± 0.20) × 10?12 for the reaction H + CH3SH (1) and k2 = (2.40 ± 0.16) × 10?12 for the reaction H + C2H5SH (2). Units are cm3 molecule?1 s?1. A mass spectrometric analysis of the reaction products and a computer simulation of the reacting systems have shown that reaction (1) proceeds through two mechanisms leading to the formation of CH3S + H2 (1a) and CH3 + H2S (1b). 相似文献
9.
Pd-catalyzed double carbomethoxylation of the Diels-Alder adduct of cyclo-pentadiene and maleic anhydride yielded the methyl norbornane-2,3-endo-5, 6-exo-tetracarboxylate ( 4 ) which was transformed in three steps into 2,3,5,6-tetramethyl-idenenorbornane ( 1 ). The cycloaddition of tetracyanoethylene (TCNE) to 1 giving the corresponding monoadduct 7 was 364 times faster (toluene, 25°) than the addition of TCNE to 7 yielding the bis-adduct 9 . Similar reactivity trends were observed for the additions of TCNE to the less reactive 2,3,5,6-tetramethylidene-7-oxanorbornane ( 2 ). The following second order rate constants (toluene, 25°) and activation parameters were obtained for: 1 + TCNE → 7 : k1 = (255 + 5) 10?4 mol?1 · s?1, ΔH≠ = (12.2 ± 0.5) kcal/mol, ΔS≠ = (?24.8 ± 1.6) eu.; 7 + TCNE → 9 , k2 = (0.7 ± 0.02) 10?4 mol?1 · s?1, ΔH≠ = (14.1 ± 1.0) kcal/mol, ΔS≠ = ( ?30 ± 3.5) eu.; 2 + TCNE → 8 : k1 = (1.5 ± 0.03) 10?4 mol?1 · s?1, ΔH≠ = (14.8 ± 0.7) kcal/mol, ΔS≠ = (?26.4 ± 2.3) eu.; 8 + TCNE → 10 ; k2 = (0.004 ± 0.0002) 10?4 mol?1 · s?1, ΔH≠ = (17 ± 1.5) kcal/mol, ΔS≠ = (?30 ± 4) eu. The possible origins of the relatively large rate ratios k1/k2 are discussed briefly. 相似文献
10.
Absolute rate constants are measured for the reactions: OH + CH2O, over the temperature range 296–576 K and for OH + 1,3,5-trioxane over the range 292–597 K. The technique employed is laser photolysis of H2O2 or HNO3 to produce OH, and laser-induced fluorescence to directly monitor the relative OH concentration. The results fit the following Arrhenius equations: k (CH2O) = (1.66 ± 0.20) × 10?11 exp[?(170 ± 80)/RT] cm3 s?1 and k(1,3,5-trioxane) = (1.36 ± 0.20) × 10?11 exp[?(460 ± 100)/RT] cm3 s?1. The transition-state theory is employed to model the OH + CH2O reaction and extrapolate into the combustion regime. The calculated result covering 300 to 2500 K can be represented by the equation: k(CH2O) = 1.2 × 10?18 T2.46 exp(970/RT) cm3 s?1. An estimate of 91 ± 2 kcal/mol is obtained for the first C? H bond in 1,3,5-trioxane by using a correlation of C? H bond strength with measured activation energies. 相似文献
11.
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
12.
Using Fourier transform infrared spectroscopy, the ethene yield from the reaction of C2H5 radicals with O2 has been determined to be 1.50 ± 0.09%, 0.85 ± 0.11%, and <0.1% at total pressures of 25, 50, and 700 torr, respectively. Additionally, the rate constant of the reaction of C2H5 radicals with molecular chlorine was measured relative to that with molecular oxygen. (1) A ratio k6/k7 = 1.99 ± 0.14 was measured at 700 torr total pressure which, together with the literature value of k7 = 4.4 × 10?12 cm3 molecule?1s?1, yields k6 = (8.8 ± 0.6) × 10?12 cm3 molecule?1s?1. Quoted errors represent 2σ. These results are discussed with respect to previous kinetic and mechanistic studies of C2H5 radicals. 相似文献
13.
The absolute rate constants of the reactions F + H2CO → HF + HCO (1) and Br + H2CO → HBr + HCO (2) have been measured using the discharge flow reactor-EPR method. Under pseudo-first-order conditions (¦H2CO¦?¦F¦or¦Br¦), the following values were obtained at 298 K: k1 = (6.6 ± 1.1) × 10?11 and k2 = (1.6± 0.3) × 10?12, Units are cm3 molecule?1s?1. The stratospheric implication of these data is discussed and the value obtained for k makes reaction (2) a possible sink for Br atoms in the stratosphere. 相似文献
14.
The overall rate coefficient k of the self recombination of BrO radicals has been measured at 298 K with use of the discharge flow/mass spectrometry technique. The rate coefficient k2 for the reaction channel forming Br2 has been also determined. The results are: k = (3.2 ± 0.5) × 10?12 and k2 = (4.7 ± 1.5) × 10?13 (in cm3 molecule?1 s?1). These results are discussed with respect to previous literature data. 相似文献
15.
Rate coefficients, k, and ClO radical product yields, Y, for the gas‐phase reaction of O(1D) with CClF2CCl2F (CFC‐113) (k2), CCl3CF3 (CFC‐113a) (k3), CClF2CClF2 (CFC‐114) (k4), and CCl2FCF3 (CFC‐114a) (k5) at 296 K are reported. Rate coefficients for the loss of O(1D) were measured using a competitive reaction technique, with n‐butane (n‐C4H10) as the reference reactant, employing pulsed laser photolysis production of O(1D) combined with laser‐induced fluorescence detection of the OH radical temporal profile. Rate coefficients were measured to be k2 = (2.33 ± 0.40) × 10?10 cm3 molecule?1 s?1, k3 = (2.61 ± 0.40) × 10?10 cm3 molecule?1 s?1, k4 = (1.42 ± 0.25) × 10?10 cm3 molecule?1 s?1, and k5 = (1.62 ± 0.30) × 10?10 cm3 molecule?1 s?1. ClO radical product yields for reactions (2)–(5) were measured using pulsed laser photolysis combined with cavity ring‐down spectroscopy to be 0.80 ± 0.10, 0.79 ± 0.10, 0.85 ± 0.12, and 0.79 ± 0.10, respectively. The quoted errors in k and Y are at the 2σ (95% confidence) level and include estimated systematic errors. © 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 43: 393–401, 2011 相似文献
16.
The kinetics of reactions of OH radical with n‐heptane and n‐hexane over a temperature range of 240–340K has been investigated using the relative rate combined with discharge flow/mass spectrometry (RR/DF/MS) technique. The rate constant for the reaction of OH radical with n‐heptane was measured with both n‐octane and n‐nonane as references. At 298K, these rate constants were determined to be k1, octane = (6.68 ± 0.48) × 10?12 cm3 molecule?1 s?1 and k1, nonane = (6.64 ± 1.36) × 10?12 cm3 molecule?1 s?1, respectively, which are in very good agreement with the literature values. The rate constant for reaction of n‐hexane with the OH radical was determined to be k2 = (4.95 ± 0.40) × 10?12 cm3 molecule?1 s?1 at 298K using n‐heptane as a reference. The Arrhenius expression for these chemical reactions have been determined to be k1, octane = (2.25 ± 0.21) × 10?11 exp[(?293 ± 37)/T] and k2 = (2.43 ± 0.52) × 10?11 exp[(?481.2 ± 60)/T], respectively. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 489–497, 2011 相似文献
17.
A jet-stream kinetic technique and the resonance fluorescence method applied to detection of iodine atoms were used to measure the rate constants of the reactions of the IO· radical with the halohydrocarbons CHFCl-CF2Cl (k = (3.2 ± 0.9) × 10?16 cm3 molecule s?1) and CH2ClF (k = (9.4 ± 1.3) × 10?16 cm3 molecule s?1), the hydrogen-containing haloethers CF3-O-CH3 (k = (6.4 ± 0.9) × 10?16 cm3 molecule s?1) and CF3CH2-O-CHF2 (k = (1.2 ± 0.6) × 10?15 cm3 molecule s?1), and hydrogen iodide (k = (1.3 ± 0.9) × 10?12 cm3 molecule s?1) at 323 K. 相似文献
18.
Manolis N. Romanias Vassileios G. Stefanopoulos Dimitrios K. Papanastasiou Vassileios C. Papadimitriou Panos Papagiannakopoulos 《国际化学动力学杂志》2010,42(12):724-734
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
19.
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
20.
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