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1.
The dissociation of N2O/Ar mixtures, with and withoutadded CO, has been studied by monitoring both infrared and ultraviolet emissions behind reflected shock waves. Initial temperatures ranged from 1850 to 2535°K, and the total concentrations were 1.94–2.40 × 1018 molecule/cm3. The infrared emission, corrected if necessary for CO, was observed to decay exponentially, and an apparent rate constant Kapp was obtained. Addition of CO had no effect upon kapp and all the data can be described by the followingArrhenius parameters (in units of cm3/molecule.sec): log A=?9.31±0.12 and EA=219.1±5.2 kJ/mole. Ultraviolet emission data, in runs with added CO, indicate that the atomic oxygen concentration reached a constant value at t < 600 μsec for T0 > 2050°K. Numerical integration of the mechanism allowed comparison of calculated and observed parameters relating to both infrared and ultraviolet data. A consistent fit to these data was obtained with k1=1.3×10?9 exp (?238 kJ/RT) and k2=k3=1.91×10?11 exp(?105 kJ/RT). The concentration of atomic oxygen produced by N2O dissociation is shown to be a sensitive function of k1 through k3. Upper limits are also set for the rate constants of the following reactions:   相似文献   

2.
Abstract

The kinetics and stability constants of l-tyrosine complexation with copper(II), cobalt(II) and nickel(II) have been studied in aqueous solution at 25° and ionic strength 0.1 M. The reactions are of the type M(HL)(3-n)+ n-1 + HL- ? M(HL)(2-n)+n(kn, forward rate constant; k-n, reverse rate constant); where M=Cu, Co or Ni, HL? refers to the anionic form of the ligand in which the hydroxyl group is protonated, and n=1 or 2. The stability constants (Kn=kn/k-n) of the mono and bis complexes of Cu2+, Co2+ and Ni2+ with l-tyrosine, determined by potentiometric pH titration are: Cu2+, log K1=7.90 ± 0.02, log K2=7.27 ± 0.03; Co2+, log K1=4.05 ± 0.02, log K2=3.78 ± 0.04; Ni2+, log K1=5.14 ± 0.02, log K2=4.41 ± 0.01. Kinetic measurements were made using the temperature-jump relaxation technique. The rate constants are: Cu2+, k1=(1.1 ± 0.1) × 109 M ?1 sec?1, k-1=(14 ± 3) sec?1, k2=(3.1 ± 0.6) × 108 M ?1 sec?1, k?2=(16 ± 4) sec?1; Co2+, k1=(1.3 ± 0.2) × 106 M ?1 sec?1, k-1=(1.1 ± 0.2) × 102 sec?1, k2=(1.5 ± 0.2) × 106 M ?1 sec?1, k-2=(2.5 ± 0.6) × 102 sec?1; Ni2+, k1=(1.4 ± 0.2) × 104 M ?1 sec?1, k-1=(0.10 ± 0.02) sec?1, k2=(2.4 ± 0.3) × 104 M ?1 sec?1, k-2=(0.94 ± 0.17) sec?1. It is concluded that l-tyrosine substitution reactions are normal. The presence of the phenyl hydroxyl group in l-tyrosine has no primary detectable influence on the forward rate constant, while its influence on the reverse rate constant is partially attributed to substituent effects on the basicity of the amine terminus.  相似文献   

3.
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   

4.
The flash photolysis of azo?n?propane and of azoisopropane has been studied by kinetic spectroscopy. Transient absorption spectra in theregion of 220–260 nm have been assigned to the n-propyl and isopropyl radicals. For the n-propyl radical, ?max = 744 ± 39 l/mol cm at 245 nm and the rate constants for the mutual reactions were measured to be kc = (1.0 ± 0.1) × 1010 l/mol sec (combination) and kd = (1.9 ± 0.2) × 109 l/mol sec (disproportionation). For the isopropyl radical, ?max = 1280 ± 110 l/mol cm at 238 nm, with kc = (7.7 ± 1.6) × 109 l/mol sec and kd = (5.0 ± 1.2) × 109 l/mol sec The rate constant for the dissociation of the vibrationally excited triplet state of the azopropanes into radicals was measured from the variation in the quantum yield of radicals with pressure. For azo-n-propane k = (6.6 ± 1.3) × 107 sec?1, and for azoisopropane k = (1.6 ± 0.4) × 108 sec?1. Collisional deactivation of the vibrationally excited singlet and triplet states was found to occur on every collision for n-pentane; but nitrogen and argon were inefficient with a rate constant of 1.1 × 1010 l/mol sec. Spectra observed in the region of 220–260 and 370–400 nm areattributed to the cis isomers of the parent trans-azopropanes. These are formed, as permanent products, in increasing amounts as the pressure is increased.  相似文献   

5.
The kinetics of the title reactions have been studied using the discharge-flow mass spectrometic method at 296 K and 1 torr of helium. The rate constant obtained for the forward reaction Br+IBr→I+Br2 (1), using three different experimental approaches (kinetics of Br consumption in excess of IBr, IBr consumption in excess of Br, and I formation), is: k1=(2.7±0.4)×10−11 cm3 molecule−1s−1. The rate constant of the reverse reaction: I+Br2→Br+IBr (−1) has been obtained from the Br2 consumption rate (with an excess of I atoms) and the IBr formation rate: k−1=(1.65±0.2)×10−13 cm3molecule−1s−1. The equilibrium constant for the reactions (1,−1), resulting from these direct determinations of k1 and k−1 and, also, from the measurements of the equilibrium concentrations of Br, IBr, I, and Br2, is: K1=k1/k−1=161.2±19.7. These data have been used to determine the enthalpy of reaction (1), ΔH298°=−(3.6±0.1) kcal mol−1 and the heat of formation of the IBr molecule, ΔHf,298°(IBr)=(9.8±0.1) kcal mol−1. © 1998 John Wiley & sons, Inc. Int J Chem Kinet 30: 933–940, 1998  相似文献   

6.
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   

7.
A kinetic study of the reduction of pyrocatechol and catechin by dpph? radical has been carried out in various ratios of CH3OH/H2O mixed solvent at pH 5.5–7.5, μ = 0.10 M [(n‐Bu)4N]ClO4, and T = 25°C. The rate constants of oxidation in aqueous solvent, k, were obtained from the extrapolation of the linear plots of the specific rate constants k vs. % H2O plots at each pH value. A linear relationship between k and 1/[H+] was observed for both flavonoids with k = k1Ka1/[H+], where Ka1 was the first acid dissociation constant on the catechol ring and k1 is the rate constant of the oxidation of the mononegative species HX?. The values of k1 obtained from the slopes of the plots are (8.2 ± 0.2) × 105 and (6.1 ± 0.1) × 105 M?1 s?1 for pyrocatechol and catechin, respectively. The analysis of the reaction on the basis of Marcus theory for an outer‐sphere electron transfer reaction yielded a value of 3.7 × 103 M?1 s?1 for the self‐exchange rate constant of dpph?/dpphH couple. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 147–153, 2011  相似文献   

8.
Kinetics of the substitution reaction of solvent molecule in uranyl(VI) Schiff base complexes by tri‐n‐butylposphine as the entering nucleophile in acetonitrile at 10–40°C was studied spectrophotometrically. The second‐order rate constants for the substitution reaction of the solvent molecule were found to be (8.8 ± 0.5) × 10?3, (5.3 ± 0.2) × 10?3, (7.5 ± 0.3) × 10?3, (6.1 ± 0.3) × 10?3, (13.5 ± 1.6) × 10?3, (13.2 ± 0.9) × 10?3, (52.9 ± 0.2) × 10?3, and (88.1 ± 0.6) × 10?3 M?1 s?1 at 40°C for [UO2(Schiff base)(CH3CN)], where Schiff base = L1–L8, respectively. In a temperature dependence study, the activation parameters ΔH# and ΔS# for the reaction of uranyl complexes with PBu3 were determined. From the linear rate dependence on the concentration of PBu3, the span of k2 values and the large negative values of the activation entropy, an associative (A) mechanism is deduced for the solvent substitution. By comparing the second‐order rate constants k2, it was concluded that the steric and the electronic properties of the complexes were important for the rate of the reactions.  相似文献   

9.
Some relative rate experiments have been carried out at room temperature and at atmospheric pressure. This concerns the OH-oxidation of some oxygenated volatile organic compounds including methanol (k1), ethanol (k2), MTBE (k3), ethyl acetate (k4), n-propyl acetate (k5), isopropyl acetate (k6), n-butyl acetate (k7), isobutyl acetate (k8), and t-butyl acetate (k9). The experiments were performed in a Teflon-film bag smog chamber. The rate constants obtained are (in cm3 molecule−1 s−1): k1=(0.90±0.08)×10−12; k2=(3.88±0.11)×10−12; k3=(2.98±0.06)×10−12; k4=(1.73±0.20)×10−12; k5=(3.56±0.15)×10−12; k6=(3.97±0.18)×10−12; k7=(5.78±0.15)×10−12; k8=(6.77±0.30)×10−12; and k9=(0.56±0.11)×10−12. The agreement between the obtained rate constants and some previously published data has allowed for most of the studied compounds to point out a coherent group of values and to suggest recommended values. Atmospheric implications are also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 839–847, 1998  相似文献   

10.
The alkanolysis of ionized phenyl salicylate, PS?, has been studied in the presence and absence of micelles of sodium dodecyl sulphate, SDS, at 0.05 M NaOH, 30 or 32°C and within the alkanol, ROH, (ROH = HOCH2CH2OH and CH3OH) contents of 15–74 or 92%, v/v. The alkanolysis of PS? involves intramolecular general base catalysis. At a constant concentration of SDS, [SDS]T, the observed pseudo first-order rate constants, kobs, for the reactions of ROH with PS? obtained at different concentration of ROH, [ROH]T, obey the relationship: kobs = k[ROH]T/(1 + KA[ROH]T) where k is the apparent second-order rate constant and KA is the association constant for dimerization of ROH molecules. Both k and KA decrease with increase in [SDS]T. At a constant [ROH]T, the rate constants, kobs, show a decrease of nearly 2-fold with increase in [SDS]T from 0.0–0.3M. These results are explained in terms of pseudo-phase model of micelle. The rate constants for alkanolysis of PS? in micellar pseudophase are insignificant compared with the corresponding rate constants in aqueous-alkanol pseudophase. This is attributed largely to considerably low value of [ROH] in the specific micellar environment where micellar bound PS? molecules exist. The increase in [ROH]T decrease the value of the binding constant of PS? with SDS micelle. The effects of anionic micelles on the rates of alkanolysis of PS? are explained in terms of the porous cluster micellar structure.  相似文献   

11.
We have developed a technique for generating high concentrations of gaseous OH radicals in a reaction chamber. The technique, which involves the UV photolysis of O3 in the presence of water vapor, was used in combination with the relative rate method to obtain rate constants for reactions of OH radicals with selected species. A key improvement of the technique is that an O3/O2 (3%) gas mixture is continuously introduced into the reaction chamber, during the UV irradiation period. An important feature is that a high concentration of OH radicals [(0.53–1.2) × 1011 radicals cm?3] can be produced during the irradiation in continuous, steady‐state experiment. Using the new technique in conjunction with the relative rate method, we obtained the rate constant for the reaction of CHF3 (HFC‐23) with OH radicals, k1. We obtained k1(298 K) = (3.32 ± 0.20) × 10?16 and determined the temperature dependence of k1 to be (0.48 ± 0.13) × 10?12 exp[?(2180 ± 100)/T] cm3 molecule?1 s?1 at 253–328 K using CHF2CF3 (HFC‐125) and CHF2Cl (HCFC‐22) as reference compounds in CHF3–reference–H2O gas mixtures. The value of k1 obtained in this study is in agreement with previous measurements of k1. This result confirms that our technique for generating OH radicals is suitable for obtaining OH radical reaction rate constants of ~10?16 cm3 molecule?1 s?1, provided the rate constants do not depend on pressure. In addition, it also needed to examine whether the reactions of sample and reference compound with O3 interfere the measurement when selecting this technique. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 317–325, 2003  相似文献   

12.
Rate constants for the reactions of Cl atoms with two cyclic dienes, 1,4‐cyclohexadiene and 1,5‐cyclooctadiene, have been determined, at 298 K and 800 Torr of N2, using the relative rate method, with n‐hexane and 1‐butene as reference molecules. The concentrations of the organics are followed by gas chromatographic analysis. The ratios of the rate constants of reactions of Cl atoms with 1,4‐cyclohexadiene and 1,5‐cyclooctadiene to that with n‐hexane are measured to be 1.29 ± 0.06 and 2.19 ± 0.32, respectively. The corresponding ratios with respect to 1‐butene are 1.50 ± 0.16 and 2.36 ± 0.38. The absolute values of the rate constants of the reaction of Cl atom with n‐hexane and 1‐butene are considered as (3.15 ± 0.40) × 10?10 and (3.21 ± 0.40) × 10? 10 cm3 molecule?1s?1, respectively. With these, the calculated values are k(Cl + 1,4‐cyclohexadiene) = (4.06 ± 0.55) × 10?10 and k(Cl + 1,5‐cyclooctadiene) = (6.90 ± 1.33) × 10?10 cm3 molecule?1 s?1 with respect to n‐hexane. The rate constants determined with respect to 1‐butene are marginally higher, k(Cl + 1,4‐cyclohexadiene) = (4.82 ± 0.80) × 10? 10 and k(Cl + 1,5‐cyclooctadiene) = (7.58 ± 1.55) × 10? 10 cm3 molecule?1 s?1. The experiments for each molecule were repeated three to five times, and the slopes and the rate constants given above are the average values of these measurements, with 2σ as the quoted error, including the error in the reference rate constant. The relative rate ratios of 1,4‐cyclohexadiene with both the reference molecules are found to be higher in the presence of oxygen, and a marginal increase is observed in the case of 1,5‐cyclooctadiene. Benzene is identified as one major product in the case of 1,4‐cyclohexadiene. Considering that the cyclohexadienyl radical, a product of the hydrogen abstraction reaction, is quantitatively converted to benzene in the presence of oxygen, the fraction of Cl atoms that reacts by abstraction is estimated to be 0.30 ± 0.04. The atmospheric implications of the results are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 431–440, 2011  相似文献   

13.
Absolute (flash photolysis) and relative (FTIR-smog chamber and GC) rate techniques were used to study the gas-phase reactions of Cl atoms with C2H6 (k1), C3H8 (k3), and n-C4H10 (k2). At 297 ± 1 K the results from the two relative rate techniques can be combined to give k2/k1 = (3.76 ± 0.20) and k3/k1 = (2.42 ± 0.10). Experiments performed at 298–540 K give k2/k1 = (2.0 ± 0.1)exp((183 ± 20)/T). At 296 K the reaction of Cl atoms with C3H8 produces yields of 43 ± 3% 1-propyl and 57 ± 3% 2-propyl radicals, while the reaction of Cl atoms with n-C4H10 produces 29 ± 2% 1-butyl and 71 ± 2% 2-butyl radicals. At 298 K and 10–700 torr of N2 diluent, 1- and 2-butyl radicals were found to react with Cl2 with rate coefficients which are 3.1 ± 0.2 and 2.8 ± 0.1 times greater than the corresponding reactions with O2. A flash-photolysis technique was used to measure k1 = (5.75 ± 0.45) × 10−11 and k2 = (2.15 ± 0.15) × 10−10 cm3 molecule−1 s−1 at 298 K, giving a rate coefficient ratio k2/k1 = 3.74 ± 0.40, in excellent agreement with the relative rate studies. The present results are used to put other, relative rate measurements of the reactions of chlorine atoms with alkanes on an absolute basis. It is found that the rate of hydrogen abstraction from a methyl group is not influenced by neighboring groups. The results are used to refine empirical approaches to predicting the reactivity of Cl atoms towards hydrocarbons. Finally, relative rate methods were used to measure rate coefficients at 298 K for the reaction of Cl atoms with 1- and 2-chloropropane and 1- and 2-chlorobutane of (4.8 ± 0.3) × 10−11, (2.0 ± 0.1) × 10−10, (1.1 ± 0.2) × 10−10, and (7.0 ± 0.8) × 10−11 cm3 molecule−1 s−1, respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 43–55, 1997.  相似文献   

14.
An experimental setup that coupled IR multiple‐photon dissociation (IRMPD) and laser‐induced fluorescence (LIF) techniques was implemented to study the kinetics of the recombination reaction of dichlorocarbene radicals, CCl2, in an Ar bath. The CCl2 radicals were generated by IRMPD of CDCl3. The time dependence of the CCl2 radicals’ concentration in the presence of Ar was determined by LIF. The experimental conditions achieved allowed us to associate the decrease in the concentration of radicals to the self‐recombination reaction to form C2Cl4. The rate constant for this reaction was determined in both the falloff and the high‐pressure regimes at room temperature. The values obtained were k0 = (2.23 ± 0.89) × 10?29 cm6 molecules?2 s?1 and k = (6.73 ± 0.23) × 10?13 cm3 molecules?1 s?1, respectively.  相似文献   

15.
Ultrasound‐mediated atom transfer radical polymerization (sono‐ATRP) in miniemulsion media is used for the first time for the preparation of complex macromolecular architectures by a facile two‐step synthetic route. Initially, esterification reaction of sucrose or lactulose with α‐bromoisobutyryl bromide (BriBBr) is conducted to receive multifunctional ATRP macroinitiators with 8 initiation sites, followed by polymerization of n‐butyl acrylate (BA) forming arms of the star‐like polymers. The brominated lactulose‐based molecule was examined as an ATRP initiator by determining the activation rate constant (ka) of the catalytic process in the presence of a copper(II) bromide/tris(2‐pyridylmethyl)amine (CuIIBr2/TPMA) catalyst in both organic solvent and for the first time in miniemulsion media, resulting in ka = (1.03 ± 0.01) × 104 M?1 s?1 and ka = (1.16 ± 0.56) × 103 M?1 s?1, respectively. Star‐like macromolecules with a sucrose or lactulose core and poly(n‐butyl acrylate) (PBA) arms were successfully received using different catalyst concentration. Linear kinetics and a well‐defined structure of synthesized polymers reflected by narrow molecular weight distribution (Mw/Mn = 1.46) indicated 105 ppm wt of catalyst loading as concentration to maintain controlled manner of polymerization process. 1H NMR analysis confirms the formation of new sugar‐inspired star‐shaped polymers.  相似文献   

16.
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   

17.
The rate constant for the reaction of CH3OCH2 radicals with O2 (reaction (1)) and the self reaction of CH3OCH2 radicals (reaction (5)) were measured using pulse radiolysis coupled with time resolved UV absorption spectroscopy. k1 was studied at 296K over the pressure range 0.025–1 bar and in the temperature range 296–473K at 18 bar total pressure. Reaction (1) is known to proceed through the following mechanism: CH3OCH2 + O2 ↔ CH3OCH2O2# → CH2OCH2O2H# → 2HCHO + OH (kprod) CH3OCH2 + O2 ↔ CH3OCH2O2# + M → CH3OCH2O2 + M (kRO2) k = kRO2 + kprod, where kRO2 is the rate constant for peroxy radical production and kprod is the rate constant for formaldehyde production. The k1 values obtained at 296K together with the available literature values for k1 determined at low pressures were fitted using a modified Lindemann mechanism and the following parameters were obtained: kRO2,0 = (9.4 ± 4.2) × 10−30 cm6 molecule−2 s−1, kRO2,∞ = (1.14 ± 0.04) × 10−11 cm3 molecule−1 s−1, and kprod,0 = (6.0 ± 0.5) × 10−12 cm3 molecule−1 s−1, where kRO2,0 and kRO2,∞ are the overall termolecular and bimolecular rate constants for formation of CH3OCH2O2 radicals and kprod,0 represents the bimolecular rate constant for the reaction of CH3OCH2 radicals with O2 to yield formaldehyde in the limit of low pressure. kRO2,∞ = (1.07 ± 0.08) × 10−11 exp(−(46 ± 27)/T) cm3 molecule−1 s−1 was determined at 18 bar total pressure over the temperature range 296–473K. At 1 bar total pressure and 296K, k5 = (4.1 ± 0.5) × 10−11 cm3 molecule−1 s−1 and at 18 bar total pressure over the temperature range 296–523K, k5 = (4.7 ± 0.6) × 10−11 cm3 molecule−1 s−1. As a part of this study the decay rate of CH3OCH2 radicals was used to study the thermal decomposition of CH3OCH2 radicals in the temperature range 573–666K at 18 bar total pressure. The observed decay rates of CH3OCH2 radicals were consistent with the literature value of k2 = 1.6 × 1013exp(−12800/T)s−1. The results are discussed in the context of dimethyl ether as an alternative diesel fuel. © 1997 John Wiley & Sons, Inc.  相似文献   

18.
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   

19.
Rate constants for the reaction of 1-chloro-2,3-epoxypropane with p-cresol in the presence of basic catalysts were studied at the temperature range of 71–100°C. It was found that in the presence of sodium p-cresolate, three consecutive reactions proceeded giving the following products: 1-chloro-3-(tolyloxy)-2-propanol (CTP), 1-(p-tolyloxy)-2,3-epoxypropane (TEP) as a main product, and 1,3-di(p-tolyloxy)-2-propanol (DTP). Their rate constants at 71°C were: k1 = 0.030 ± 0.009, k2 = 1.58 ± 0.02, and k3 = 0.033 ± 0.005 dm3/mol · min, respectively. In the presence of quaternary ammonium salts, this process consisted of 5 reactions which led to CTP as a main product as well as TEP and 1,3-dichloro-2-propanol (DCP). The rate constant of CTP formation at 71°C was established, k1 = 0.130 ± 0.030 dm3/mol · min, as were the ratios of the other rate constants k2/k−4 = 1.5 ± 0.2, k5/k−4 = 20.0 ± 5.0, and k4/k1 = 0.6 ± 0.7. Based on the changes in Cl ion concentration during the reaction, the catalystic activity of quaternary ammonium salts was explained. The kinetic model of these reactions in the presence of basic catalysts has been proposed and appropriate kinetic equations have been presented. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 73–79, 1997.  相似文献   

20.
Rate constants for the reactions of OH, NO3, and O3 with pinonaldehyde and the structurally related compounds 3-methylbutanal, 3-methylbutan-2-one, cyclobutyl-methylketone, and 2,2,3-trimethyl-cyclobutyl-1-ethanone have been measured at 300±5 K using on-line Fourier transform infrared spectroscopy. The rate constants obtained for the reactions with pinonaldehyde were: kOH=(9.1±1.8)×10−11 cm3 molecule−1 s−1, kNO3=(5.4±1.8)×10−14 cm3 molecule−1 s−1, and kO3=(8.9±1.4)×10−20 cm3 molecule−1 s−1. The results obtained indicate a chemical lifetime of pinonaldehyde in the troposphere of about two hours under typical daytime conditions, [OH]=1.6×106 molecule cm−3. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 527–533, 1997.  相似文献   

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