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1.
Using a relative rate technique, rate constants have been determined for the gas-phase reactions of Cl atoms with the cholorethenes and ethane at 298 ± 2 K and 735 torr total pressure of air. Using a rate constant of 1.97 × 10?10 cm3 molecule?1 s?1 for the reaction of Cl atoms with n-butane, the following rate constants (in units of 10?11 cm3 molecule?1 s?1) were obtained: vinyl chloride, 12.7 ± 0.2; 1,1-dichloroethene, 14.0 ± 0.2; cis-1,2-dichloroethene, 9.65 ± 0.10; trans-1,2-dichloroethene, 9.58 ± 0.18; trichloroethene, 8.08 ± 0.10; tetrachloroethene, 4.13 ± 0.23; and ethane, 6.17 ± 0.08 (where the indicated error limits do not include the uncertainties in the rate constant for n-butane). A small amount of cis-trans isomerization was observed for the reactions involving the cis- and trans-1,2-dichloroethenes. These data are compared and discussed with the available literature data.  相似文献   

2.
The gas-phase thermal isomerization of N-propylidenecyclopropylamine has been studied in the temerature range of 573° to 635°K. The reaction is homogeneous and kinetically first order and yields 5-ethyl-1-pyrroline as the sole product. The rate constants are independent of pressure in the range of 2.5 to 55 torr and fit the Arrhenius relationship log k(sec?1) = (14.05 ± 0.06) - (47.77 ± 0.16)/θ where θ = 2.303 RT in units of kcal/mole, or log k(sec?1) = (14.05 ± 0.06) - (199.9 ± 0.7)/θ, where θ = 2.303RT in kJ/mole. From considerations of a biradical pathway it is concluded that the resonance stabilization energy of the substituted 2-aza-allyl radical is very similar to that of the methallyl radical.  相似文献   

3.
Relative rate constants for the gas-phase reactions of Cl-atom with thirteen atmospherically interesting alkanes (C2? C8) have been determined at 296 ± 2 K based on GC/FID measurements of their relative decays in the UV (λ ≥ 300 nm) photolysis of mixtures containing Cl2 and the entire series of the selected alkanes in the mtorr range in 750 torr of N2. The following absolute rate constants (in units of 10?10 cm3 molecule?1 s?1) have been derived from the relative rate constants combined with the value of 1.94 × 10?10 cm3 molecule?1 s?1 for the Cl + n-butane reaction: ethane (0.57 ± 0.05); propane (1.27 ± 0.02); 2-methyl propane (1.30 ± 0.01), 2-methyl butane ((1.96 ± 0.02)), n-pentane (2.50 ± 0.02); 2,3-dimethyl butane (2.00 ± 0.06); 2-methyl pentane (2.58 ± 0.08); n-hexane (3.05 ± 0.04); 2-methyl hexane (3.12 ± 0.04); n-heptane (3.65 ± 0.06); 2,2,4-trimethyl pentane (2.25 ± 0.08); and n-octane (4.09 ± 0.12). The uncertainties indicated are two least-squares standard deviations (2σ). These rate constants are compared with literature values and their applicability to Arctic tropospheric conditions is discussed. © 1995 John Wiley & Sons, Inc.  相似文献   

4.
Rate constants of Br atom reactions have been determined using a relative kinetic method in a 20 l reaction chamber at total pressures between 25 and 760 torr in N2 + O2 diluent over the temperature range 293–355 K. The measured rate constants for the reactions with alkynes and alkenes showed dependence upon temperature, total pressure, and the concentration of O2 present in the reaction system. Values of (6.8 ± 1.4) × 10?15, (3.6 ± 0.7) × 10?14, (1.5 ± 0.3) × 10?12, (1.6 ± 0.3) × 10?13, (2.7 ± 0.5) × 10?12, (3.4 ± 0.7) × 10?12, and (7.5 ± 1.5) × 10?12 (units: cm3 s?1) have been obtained as rate constants for the reactions of Br with 2,2,4-trimethylpentane, acetylene, propyne, ethene, propene, 1-butene, and trans-2-butene, respectively, in 760 torr of synthetic air at 298 K with respect to acetaldehyde as reference, k = 3.6 × 10?12 cm3 s?1. Formyl bromide and glyoxal were observed as primary products in the reaction of Br with acetylene in air which further react to form CO, HBr, HOBr, and H2O2. Bromoacetaldehyde was observed as an primary product in the reaction of Br with ethene. Other observed products included CO, CO2, HBr, HOBr, BrCHO, bromoethanol, and probably bromoacetic acid.  相似文献   

5.
The reactions of hydroxyl radicals with eight substituted aromatic hydrocarbons and four olefins were studied utilizing the flash photolysis–resonance fluorescence technique. The rate constants were measured at 298°K using either Ar or He as the diluent gas. The values of the rate constants (k × 1012) in the units of cm3/molec. sec are
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6.
The thermal isomerization of the title compounds was studied in the vapor phase. Over the temperature range from 445.1 to 477.5°K, 1,4-dimethylbicyclo[2.2.0]hexane underwent a homogeneous unimolecular reaction to 2,5-dimethyl-1,5-hexadiene, the rate constants being represented by the equation: k = 1.86 × 1011 exp (?31000 ± 1800/RT) sec?1. Over the temperature range from 630.0 to 662.2°K, 1,4-dimethylbicyclo[2.1.1]-hexane also underwent a unimolecular isomerization to the same product, the rate constants being given by the equation: k = 8.91 × 1014 exp (?56000 ± 900/RT) sec?1. The pyrolysis of 1,4-dimethylbicyclo[2.1.0]pentane gave 1,3-dimethylcyclopentene-1 and 2,4-dimethyl-1,4-pentadiene in the ratio of 9:1. The former reaction was influenced by surface effects but the latter was not. The rate constants for the formation of 2,4-dimethyl-1,4-pentadiene fitted the equation: k = 1.66 × 1017 exp (?57400 ± 3100/RT) sec?1. The effect of the two methyl groups at the bridgehead positions in these molecules in influencing the rate of decomposition is discussed in terms of the non-bonded repulsive forces between the substituents.  相似文献   

7.
Direct kinetic measurements have been made on the reaction: 2NO2 = N2O4. Equilibrium mixtures of NO2 and N2O4 at (224 ± 2) K were perturbed by flash photolysis of a fraction of the N2O4. The rate of relaxation back to equilibrium was monitored by observing the transmittance of the 14P(11) line from a cw CO laser selected to coincide with the v9 band of N2O4. Measurements were made in the presence of 350–750 torr of He, N2, or CF4. Within this limited pressure range, the kinetics were consistent with third-order behavior with the following rate constants (cm3 molecule?1 s?1): k0 = (2.4 ± 0.5) × 10?34 [He]; (1.0 ± 0.1) × 10?33 [N2]; (1.8 ± 0.3) × 10?33 [CF4].  相似文献   

8.
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   

9.
The kinetics of the gas-phase reactions of O3 with a series of alkenes have been investigated at atmospheric pressure (ca. 740 torr) of air and 296 ± 2 K, using a relative rate method in the presence of sufficient n-octane to scavenge any OH radicals generated in these reactions. Relative to k(O3 + propene) = 1.00, the rate constants obtained were: 1-butene, 0.975 ± 0.030; 2-methylpropene, 1.14 ± 0.04; 2-methyl-1,3-butadiene (isoprene), 1.21 ± 0.02; 1,4-cyclohexadiene, 4.75 ± 0.23; cyclohexene, 7.38 ± 0.48; cis-2-butene, 12.8 ± 0.8; trans-2-butene, 21.5 ± 1.5; 2-methyl-2-butene, 42.1 ± 2.8; cyclopentene, 64.9 ± 4.3; and 2,3-dimethyl-2-butene, 123 ± 11. These relative rate constants have been placed on an absolute basis using a rate constant for the reaction of O3 with propene of 1.01 × 10?17 cm3 molecule?1 s?1 at 296 K derived from an analysis of the available literature data. The resulting rate constants then lead to a self-consistent set of room temperature data for the reactions of O3 with these alkenes. © John Wiley & Sons, Inc.  相似文献   

10.
The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with nitro methane, nitro ethane, nitro propane, nitro butane, nitro pentane, ethyl nitrate, isopropyl nitrate, n-propyl nitrate, 2-pentyl nitrate, and 2-heptyl nitrate. Decay rates of these organic species were measured relative to one or more of the following reference compounds; n-butane, ethane, chloroethane, and methane. Using rate constants of 2.25 × 10?10 5.7 × 10?11, 8.04 × 10?12, and 1.0 × 10?13 cm3 molecule?1 s?1 for the reaction of Cl atoms with n-butane, ethane, chloroethane, and methane, respectively, the following rate constants were derived, in units of cm3 molecule?1 s?1: nitro methane, <7 × 10?15; nitro ethane, (2.05 ± 0.14) × 10?13; nitro propane, (1.13 ± 0.05) × 10?11; nitro butane, (5.13 ± 0.68) × 10?11; nitro pentane, (1.40 ± 0.14) × 10?10; ethyl nitrate, (3.70 ± 0.24) × 10?12; n-propyl nitrate, (2.15 ± 0.13) × 10?11; i-propyl nitrate, (3.94 ± 0.48) × 10?12; 2-pentyl nitrate, (1.00 ± 0.06) × 10?10; and 2-heptyl nitrate, (2.84 ± 0.50) × 10?10. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure (?740 torr) of synthetic air. The results are discussed with respect to the previous literature data and to the modeling of these compounds in the atmosphere.  相似文献   

11.
A variety of relative and absolute techniques have been used to measure the reactivity of fluorine atoms with a series of halogenated organic compounds and CO. The following rate constants were derived, in units of cm3 molecule?1 s?1: CH3F, (3.7 ± 0.8) × 10?11, CH3Cl, (3.3 ± 0.7) × 10?11; CH3Br, (3.0 ± 0.7) × 10?11; CF2H2, (4.3 ± 0.9) × 10?12; CO, (5.5 ± 1.0) × 10?13 (in 700 torr total pressure of N2 diluent); CF3H, (1.4 ± 0.4) × 10?13; CF3CCl2H (HCFC-123), (1.2 ± 0.4) × 10?12; CF3CFH2 (HFC-134a), (1.3 ± 0.3) × 10?12, CHF2CHF2 (HFC-134), (1.0 ± 0.3) × 10?12; CF2ClCH3 (HCFC-42b), (3.9 ± 0.9) × 10?12, CF2HCH3 (HFC-152a), (1.7 ± 0.4) × 10?11; and CF3CF2H (HFC-125), (3.5 ± 0.8) × 10?13. Quoted errors are statistical uncertainties (2σ). For rate constants derived using relative rate techniques, an additional uncertainty has been added to account for potential systematic errors in the reference rate constants used. Experiments were performed at 295 ± 2 K. Results are discussed with respect to the previous literature data and to the interpretation of laboratory studies of the atmospheric chemistry of HCFCs and HFCs. © 1993 John Wiley & Sons, Inc.  相似文献   

12.
Atomic absorption and fluorescence spectrophotometry have been routinely used in kinetic investigations as probes of relative, rather than absolute, atom concentration. The calibration of a Lyman-α photometer for measurement of absolute hydrogen atom concentrations at levels [H] ι ≤ 1.8 × 1014 atoms/cm2 and total pressure of 1.5 torr He is described. The photometer is characterized in terms of a two-level emission source and an absorption region in which only Doppler broadening of the transition is considered. The modifications due to pressure broadening by high pressures (500 ≤ P ≤ 1500 torr) in the absorption region are discussed in detail. Application of the technique is reported for the recombination of hydrogen atoms in the presence of six nonreactive heat bath gases. Experiments were performed in a static reaction cell at pressures of 500–1500 torr of heat bath gas, and hydrogen atoms were produced by Hg (3P1) photosensitization of H2. The technique is critically evaluated and the mechanistic implications of the hydrogen atom recombination results are examined. The measured room temperature recombination rate constants in H2, He, Ne, Ar, Kr, and N2 are 8.5 ± 1.2, 6.9 ± 1.5, 5.9 ± 1.5, 8.0 ± 0.8, 10.2 ± 0.9, and 9.6 ± 1.4, respectively, where the units are 1033 cm6/molec2 · sec.  相似文献   

13.
Using relative rate techniques the reactions of chlorine and fluorine atoms with HC(O)F have been determined to proceed with rate constants of k1 = (1.9 ± 0.2) × 10−15 and k2 = (8.3 ± 1.7) × 10−13 cm3 molecule−1 s−1, respectively. Stated errors reflect statistical uncertainty; possible systematic uncertainties could add additional 10% and 20% ranges to the values of k1 and k2, respectively. Experiments were performed at 295 ± 2 K and 700 torr total pressure of air. The results are discussed with respect to the design and interpretation of laboratory studies of the atmospheric chemistry of CFC replacements. © 1997 John Wiley & Sons, Inc.  相似文献   

14.
The reaction of NO with the peroxy radical CFCl2CH2O2, and with CH3CFClO2 was investigated at 8(SINGLEBOND)20 torr and 263(SINGLEBOND)321 K by UV flash photolysis of CFCl2CH3/O2/NO gas mixtures. The kinetics were determined from observations of the growth rate of the CFCl2CH2O radical and the decay rate of NO by time-resolved mass spectrometry. The temperature dependence of the bimolecular rate coefficients, with their statistical uncertainties, can be expressed as (2.9 ± 0.7) e(435±96)/T × 10−12 cm3 molecule −1s−1, or (1.3 ± 0.2) (T/300)&minus(1.5±0.2) × 10−11 cm3 molecule−1 s−1 for NO + CFCl2CH2O2, and (3.3 ± 0.6)e(516±73)/T × 10−12 cm3 molecule−1 s−1, or (2.0 ± 0.3) (T/300)&minus(1.8±0.3) × 10−11 cm3 molecule−1 s−1 for NO + CH3CFClO2. No pressure dependence of the rate coefficients could be detected over the 8(SINGLEBOND)20 torr range investigated. © 1996 John Wiley & Sons, Inc.  相似文献   

15.
The kinetics of the gas-phase reaction of Cl atoms with CF3I have been studied relative to the reaction of Cl atoms with CH4 over the temperature range 271–363 K. Using k(Cl + CH4) = 9.6 × 10?12 exp(?2680/RT) cm3 molecule?1 s?1, we derive k(Cl + CF3I) = 6.25 × 10?11 exp(?2970/RT) in which Ea has units of cal mol?1. CF3 radicals are produced from the reaction of Cl with CF3I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments were k(Cl + C2F5I)/k(Cl + CF3I) = 11.0 ± 0.6 and k(Cl + C2F5I)/k(Cl + C2H5Cl) = 0.49 ± 0.02. The reaction of CF3 radicals with Cl2 was studied relative to that with O2 at pressures from 4 to 700 torr of N2 diluent. By using the published absolute rate constants for k(CF3 + O2) at 1–10 torr to calibrate the pressure dependence of these relative rate constants, values of the low- and high-pressure limiting rate constants have been determined at 296 K using a Troe expression: k0(CF3 + O2) = (4.8 ± 1.2) × 10?29 cm6 molecule?2 s?1; k(CF3 + O2) = (3.95 ± 0.25) × 10?12 cm3 molecule?1 s?1; Fc = 0.46. The value of the rate constant k(CF3 + Cl2) was determined to be (3.5 ± 0.4) × 10?14 cm3 molecule?1 s?1 at 296 K. The reaction of Cl atoms with CF3I is a convenient way to prepare CF3 radicals for laboratory study. © 1995 John Wiley & Sons, Inc.  相似文献   

16.
The reactions Br + NO2 + M → BrNO2 + M (1) and I + NO2 + M → INO2 + M (2) have been studied at low pressure (0.6-2.2 torr) at room temperature and with helium as the third body by the discharge-flow technique with EPR and mass spectrometric analysis of the species. The following third order rate constants were found k1(0) = (3.7 ± 0.7) × 10?31 and k2(0) = (0.95 ± 0.35) × 10?31 (units are cm6 molecule?2 s?1). The secondary reactions X + XNO2X2 + NO2 (X = Br, I) have been studied by mass spectrometry and their rate constants have been estimated from product analysis and computer modeling.  相似文献   

17.
The reaction 2NO2 + ROH = RONO + HNO3 (R = CH3 or C2H5) has been studied using the FTIR method at reactant pressures from 0.1 to 1.0 torr at 25°C. The termolecular rate constant for the forward reaction was determined to be (5.7 ± 0.6) × 10?37 cm6/molec2·s for CH3OH and (5.7 ± 0.8) × 10?37 cm6/molec2·s for C2H5OH, that is, d[RONO]/dt = k[NO2]2[ROH]. The corresponding equilibrium constants were measured as 1.36 ± 0.06 and 0.550 ± 0.025 torr?1, respectively. These results are consistent with those of a previous study based on the NO2 decay measurements at reactant pressures from 1 to 10 torr.  相似文献   

18.
The third order rate coefficients for the addition reaction of Cl with NO2, Cl + NO2 + M → ClNO2 (ClONO) + M; k1, were measured to be k1(He) = (7.5 ± 1.1) × 10?31 cm6 molecule?2 s?1 and k1(N2) = (16.6 ± 3.0) × 10?31 cm6 molecule?2 s?1 at 298 K using the flash photolysis-resonance fluorescence method. The pressure range of the study was 15 to 500 torr He and 19 to 200 torr N2. The temperature dependence of the third order rate coefficients were also measured between 240 and 350 K. The 298 K results are compared with those from previous low pressure studies.  相似文献   

19.
Reactions of Cu2 with several small molecules have been studied in the gas phase, under thermalized conditions at room temperature, in a fast-flow reactor. They fall into one of two categories. Cu2 does not react with O2, N2O, N2, H2, and CH4 at pressures up to 6 torr. This implies bimolecular rate constants of less than 5 × 10?15 cm3 s?1 at 6 torr He. Cu2 reacts with CO, NH3, C2H4, and C3H6 in a manner characteristic of association reactions. Second-order rate constants for all four of these reagents are dependent on total pressure. The reactions with CO, NH3, and C2H4 are in their low pressure limit at up to 6 torr He buffer gas pressure. The reaction with C3H6 begins to show fall-off behavior at pressures above 3 torr. Limiting low-pressure, third-order rate constants are 0.66 ± 0.10, 8.8 ± 1.2, 9.3 ± 1.4, and 85 ± 15 × 10?30 cm6 s?1 in He for CO, NH3, C2H4, and C3H6, respectively. Modeling studies of these rate constants imply that the association complexes are bound by at least 20 kcal mol?1 in the case of C2H4 and C3H6 and at least 25 kcal mol?1 in the other cases. The implications of these results for Cu-ligand bonding are developed in comparison with existing work on the interactions of these ligands with Cu atoms, larger clusters, and surfaces. © 1994 John Wiley & Sons, Inc.  相似文献   

20.
The rate constants for the reactions have been measured directly by flash photolysis and kinetic spectroscopy. At room temperature, k3 = (3.4 ± 0.1) × 109 L/mol·s, independent of pressure in the range of 55–400 torr, and k6 = (2.1 ± 0.2) × 109 L/mol·s.  相似文献   

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