共查询到20条相似文献,搜索用时 46 毫秒
1.
The electrooxidation of L -dopa at GC electrode was studied by in situ UV-vis spectroelectrochemistry (SEC) and cyclic voltammetry. The mechanism of electrooxidation and some reaction parameters were obtained. The results showed that the whole electrooxidation reaction of L -dopa at glassy carbon (GC) electrode was an irreversible electrochemical process followed by a chemical reaction in neutral solution (EC mechanism). The spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E0=228 mV, the apparent electron-transfer number of the electrooxidation reaction αn=0.376 (R=0.99, SD=0.26), the standard electrochemical rate constant k0=(3.93±0.12)×10−4 cm s−1 (SD=1.02×10−2), and the formation equilibrium constant of the following chemical reaction kc=(5.38±0.34)×10−1 s−1 (SD=1.02×10−2) were also obtained. 相似文献
2.
Electrochemical Investigation of Cytochrome c Immobilized onto Self‐Assembled Monolayer of Captopril
The electrochemical behavior of cytochrome c (cyt‐c) that was electrostatically immobilized onto a self‐assembled monolayer (SAM) of captopril (capt) on a gold electrode has been investigated. Cyclic voltammetry, scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy were employed to evaluate the blocking property of the capt SAM. SECM was used to measure the bimolecular electron transfer (ET) kinetics (kBI) between a solution‐based redox probe and the immobilized protein. In addition, the tunneling ET between the immobilized protein and the underlying gold electrode was calculated. A kBI value of (5.0±0.6)×108 mol?1 cm3 s?1 for the bimolecular ET and a standard tunneling rate constant (k0) of 46.4±0.2 s?1 for the tunneling ET have been obtained. 相似文献
3.
The rate constants for the reactions of OH with dimethyl ether (k1), diethyl ether (k2), di-n-propyl ether (k3), di-isopropyl ether (k4), and di-n-butyl ether (k5) have been measured over the temperature range 230–372 K using the pulsed laser photolysis-laser induced fluorescence (PLP-LIF) technique. The temperature dependence of k1,k4, can be expressed in the Arrhenius plots form: k1 = (6.30 ± 0.10) × 10?12 exp[?(234 ± 34)/T] and k4 = (4.13 ± 0.10) × 10?12 exp[(274 ± 26)/T]. The Arrhenius plots for k2,k3, and k5, were curved and they were fitted to the three parameter expressions: k2 = (1.02 ± 0.08) × 10?17 T2 exp[(797 ± 24)/T], k3 = (1.84 ± 0.23) × 10?17T2 exp[(767 ± 34)/T], and k5 = (6.29 ± 0.74) × 10?18T2 exp[(1164 ± 34)/T]. The values at 298 K are (2.82 ± 0.21) × 10?12, (1.36 ± 0.11) × 10?11,(2.17 ± 0.16) × 10?11, (1.02 ± 0.10) × 10?11, and (2.69 ± 0.22) × 10?11 for k1, k2, k3, k4, and k5, respectively, (in cm3 molecule?1 s?1). These results are compared to the literature data. © 1995 John Wiley & Sons, Inc. 相似文献
4.
A new electrochemical method was proposed for the determination of adenosine‐5′‐triphosphate (ATP) based on the electrooxidation at a molecular wire (MW) modified carbon paste electrode (CPE), which was fabricated with diphenylacetylene (DPA) as the binder. A single well‐defined irreversible oxidation peak of ATP appeared on MW‐CPE with adsorption‐controlled process and enhanced electrochemical response in a pH 3.0 Britton‐Robinson buffer solution, which was due to the presence of high conductive DPA in the electrode. The electrochemical parameters of ATP were calculated with the electron transfer coefficient (α) as 0.54, the electron transfer number (n) as 1.9, the apparent heterogeneous electron transfer rate constant (ks) as 2.67 × 10?5 s?1 and the surface coverage (ΓT) as 4.15 × 10?10 mol cm?2. Under the selected conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0 × 10?7 mol L?1 to 2.0 × 10?3 mol L?1 with the detection limit as 1.28 × 10?8 mol L?1 (3σ) by sensitive differential pulse voltammetry. The proposed method showed good selectivity without the interferences of coexisting substances and was successful applied to the ATP injection samples detection. 相似文献
5.
R. K. Talukdar A. Mellouki T. Gierczak S. Barone S-Y. Chiang A. R. Ravishankara 《国际化学动力学杂志》1994,26(10):973-990
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 k3 – k5 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
6.
《Journal of Coordination Chemistry》2012,65(4):263-270
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
7.
The kinetics of OH reactions with furan (k1), thiophene (k2), and tetrahydrothiophene (k3), have been investigated over the temperature range 254–425 K. OH radicals were produced by flash photolysis of water vapor at λ > 165 nm and detected by timeresolved resonance fluorescence spectroscopy. The following Arrhenius expressions adequately describe the measured rate constants as a function of temperature (units are cm3 molecule?1 S?1): k1 = (1.33 ± 0.29) × 10?11 exp[(333 ± 67)/T], k2 = (3.20 ± 0.70) × 10?12 exp[(325 ± 71)/T], k3 = (1.13 ± 0.35) × 10?11 exp[(166 ± 97)/T]. The results are compared with previous investigations and their implications regarding reaction mechanisms and atmospheric residence times are discussed. 相似文献
8.
Rate constants for the reactions of OH and NO3 radicals with CH2?CHF (k1 and k4), CH2?CF2 (k2 and k5), and CHF?CF2 (k3 and k6) were determined by means of a relative rate method. The rate constants for OH radical reactions at 253–328 K were k1 = (1.20 ± 0.37) × 10?12 exp[(410 ± 90)/T], k2 = (1.51 ± 0.37) × 10?12 exp[(190 ± 70)/T], and k3 = (2.53 ± 0.60) × 10?12 exp[(340 ± 70)/T] cm3 molecule?1 s?1. The rate constants for NO3 radical reactions at 298 K were k4 = (1.78 ± 0.12) × 10?16 (CH2?CHF), k5 = (1.23 ± 0.02) × 10?16 (CH2?CF2), and k6 = (1.86 ± 0.09) × 10?16 (CHF?CF2) cm3 molecule?1 s?1. The rate constants for O3 reactions with CH2?CHF (k7), CH2?CF2 (k8), and CHF?CF2 (k9) were determined by means of an absolute rate method: k7 = (1.52 ± 0.22) × 10?15 exp[?(2280 ± 40)/T], k8 = (4.91 ± 2.30) × 10?16 exp[?(3360 ± 130)/T], and k9 = (5.70 ± 4.04) × 10?16 exp[?(2580 ± 200)/T] cm3 molecule?1 s?1 at 236–308 K. The errors reported are ±2 standard deviations and represent precision only. The tropospheric lifetimes of CH2?CHF, CH2?CF2, and CHF?CF2 with respect to reaction with OH radicals, NO3 radicals, and O3 were calculated to be 2.3, 4.4, and 1.6 days, respectively. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 619–628, 2010 相似文献
9.
The equilibrium constant for the reaction CH2(COOH)2 + I3? ? CHI(COOH)2 + 2I? + H+, measured spectrophotometrically at 25°C and ionic strength 1.00M (NaClO4), is (2.79 ± 0.48) × 10?4M2. Stopped-flow kinetic measurements at 25°C and ionic strength 1.00M with [H+] = (2.09-95.0) × 10?3M and [I?] = (1.23-26.1) × 10?3M indicate that the rate of the forward reaction is given by (k1[I2] + k3[I3?]) [HOOCCH2COO?] + (k2[I2] + k4[I3?]) [CH(COOH)2] + k5[H+] [I3?] [CH2(COOH)2]. The values of the rate constants k1-k5 are (1.21 ± 0.31) × 102, (2.41 ± 0.15) × 101, (1.16 ± 0.33) × 101, (8.7 ± 4.5) × 10?1M?1·sec?1, and (3.20 ± 0.56) × 101M?2·sec?1, respectively. The rate of enolization of malonic acid, measured by the bromine scavenging technique, is given by ken[CH2(COOH)2], with ken = 2.0 × 10?3 + 1.0 × 10?2 [CH2(COOH)2]. An intramolecular mechanism, featuring a six-member cyclic transition state, is postulated to account for the results on the enolization of malonic acid. The reactions of the enol, enolate ion, and protonated enol with iodine and/or triodide ion are proposed to account for the various rate terms. 相似文献
10.
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
11.
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
12.
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
13.
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
14.
The interaction between mercuric ion and apoCopC in the absence or presence of cupric ion was investigated through difference UV spectra in Hepes buffer (10 mmol·L^-1) at pH 7.4. The results suggest that mercuric ion can bind to C- and N-terminal binding sites of apoCopC, and the conditional binding constants were calculated to be kN=(6.79± 1.12)× 10^6 mol^-1·L and kc=(3.06±0.05)× 10^5 mol^-1·L. Using urea as a chemical agent, the conformational stabilities of apoCopC and HgN^2+ -CopC-Hgc^2+ were monitored by fluorescence spectrum in Hepes buffer (50 mmol·L^-1) at pH 7.4. The free energy of stabilization is (14.69±0.85) and (16.66±0.55) kJ.mol^-1, respectively. HgN^2+ -CopC-Hgc^2+ is more stable than apoCopC. 相似文献
15.
By allowing dimethyl peroxide (10?4M) to decompose in the presence of nitric oxide (4.5 × 10?5M), nitrogen dioxide (6.5 × 10?5M) and carbon tetrafluoride (500 Torr), it has been shown that the ratio k2/k2′ = 2.03 ± 0.47: CH3O + NO → CH3ONO (reaction 2) and CH3O + NO2 → CH3ONO2 (reaction 2′). Deviations from this value in this and previous work is ascribed to the pressure dependence of both these reactions and heterogeneity in reaction (2). In contrast no heterogeneous effects were found for reaction (2′) making it an ideal reference reaction for studying other reactions of the methoxy radical. We conclude that the ratio k2/k2′ is independent of temperature and from k1 = 1010.2±0.4M?1 sec?1 we calculate that k2′ = 109.9±0.4M?1 sec?1. Both k2 and k2′ are pressure dependent but have reached their limiting high-pressure values in the presence of 500 Torr of carbon tetrafluoride. Preliminary results show that k4 = 10.9.0±0.6 10?4.5±1.1/ΘM?1 sec?1 (Θ = 2.303RT kcal mole?1) and by k4 = 108.6±0.6 10?2.4±1.1/ΘM?1 sec?1: CH3O + O2 → CH2O + HO2 (reaction 4) and CH3O + t-BuH → CH3OH + (t-Bu) (reaction 4′). 相似文献
16.
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
17.
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
18.
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
19.
The rate constants for the gas‐phase reactions of ground‐state oxygen atoms with CF2?CFCl (1), (E/Z)‐CFCl?CFCl (2), CFCl?CH2 (3), and (E/Z)‐CFH?CHCl (4) have been measured directly using a discharge flow tube coupled to a chemiluminescence detection system. The experiments were carried out under pseudo‐first‐order conditions with [O3P)]0 ? [ethene]0. The temperature dependences of the reactions were studied for the first time in the range 298–359 K. The proposed Arrhenius expressions (in units of cm3 molecule?1 s?1) were k1 = (1.07 ± 0.32) × 10?11 exp{?(8000±1600)/RT}, k2 = (0.56 ± 0.10) × 10?11 exp{?(8700±500)/RT}, k3 = (4.23 ± 1.25) × 10?11 exp{?(12,700 ± 800)/RT}, and k4 = (1.13 ± 0.62) × 10?11 exp{?(10,500 ± 1500)/RT}. All the rate coefficients display a positive temperature dependence, which highlights the importance of the irreversibility of the addition mechanism for these reactions. Halogen substitution in the ethene is discussed in terms of reactivity with O(3P). © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 763–769, 2005 相似文献
20.
Reactions of ozone with simple olefins have been studied between 6 and 800 mtorr total pressure in a 220-m3 reactor. Rate constants for the removal of ozone by an excess of olefin in the presence of 150 mtorr oxygen were determined over the temperature range 280 to 360° K by continuous optical absorption measurements at 2537 Å. The technique was tested by measuring the rate constants k1 and k2 of the reactions (1) NO + O3 → NO2 + O2 and (2) NO2 + O3 rarr; NO3 + O2 which are known from the literature. The results for NO, NO2, C2H4, C3H6, 2-butene (mixture of the isomers), 1,3→butadiene, isobutene, and 1,1 -difluoro-ethylene are 1.7 × 10?1 4 (290°K), 3.24 × 10?17 (289°K), 1.2 × 10?1 4 exp (–4.95 ± 0.20/RT), 1.1 × 10?1 4 exp (–3.91 ± 0.20/RT), 0.94 × 10?1 4 exp ( –2.28 ± 0.15/RT), 5.45 ± 10?1 4 exp ( –5.33 ± 0.20/RT), 1.8 ×10?17 (283°K), and 8 × 10?20 cm3/molecule ·s(290°K). Productformation from the ozone–propylene reaction was studied by a mass spectrometric technique. The stoichiometry of the reaction is near unity in the presence of molecular oxygen. 相似文献