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1.
C2H5ONO was photolyzed with 366 nm radiation at ?48, ?22, ?2.5, 23, 55, 88, and 120°C in a static system in the presence of NO, O2, and N2. The quantum yield of CH3CHO, Φ{CH3CHO}, was measured as a function of reaction conditions. The primary photochemical act is and it proceeds with a quantum yield ?1a = 0.29 ± 0.03 independent of temperature. The C2H5O radicals can react with NO by two routes The C2H5O radical can also react with O2 via Values of k6/k2 were determined at each temperature. They fit the Arrhenius expression: Log(k6/k2) = ?2.17 ± 0.14 ? (924 ± 94)/2.303 T. For k2 ? 4.4 × 10?11 cm3/s, k6 becomes (3.0 ± 1.0) × 10?13 exp{?(924 ± 94)/T} cm3/s. The reaction scheme also provides k8a/k8 = 0.43 ± 0.13, where 相似文献
2.
Anthony M. Dean 《国际化学动力学杂志》1976,8(3):459-474
N2O decay has been monitored via infrared emission for a series of mixtures containing N2O/Ar and N2O/H2/Ar. These mixtures were studied behind reflected shock waves in the temperature interval of 1950–3075°K with total concentrations ranging from 1.2 to 2.5 × 1018 molec/cm3. In all cases the N2O decayed exponentially, and a rate constant kobs was obtained. Runs without added H2 could be described by the following Arrhenius parameters: log A = ?9.72 ± 0.08 (in units of cm3/molec · sec) and EA = 203.5 ± 3.6 kJ/mole. Addition of 0.01% and 0.1% H2 was observed to increase the decay rate; the largest increase occurred between 2250 and 2500°K with 0.1% H2, where kobs doubled. Mixtures with no added H2 were analyzed by numerical integration of the following reactions: Quantitative agreement between calculations and observations were obtained with both high and low choices for k2 and k3. The additional reactions were included in the analysis of the mixtures containing H2. Here agreement was obtained only when low values were assigned to k2 and k3. The combinations of k1 ← k3 which agreed with all the data were k1 = 3.25 × 10?10 exp (?215 kJ/RT) and k2 = k3 = 1.91 × 10?11 exp (-105 kJ/RT). 相似文献
3.
n-C3H7ONO was photolyzed with 366 nm radiation at ?26, ?3, 23, 55, 88, and 120°C in a static system in the presence of NO, O2, and N2. The quantum yields of C2H5CHO, C2H5ONO, and CH3CHO were measured as a function of reaction conditions. The primary photochemical act is and it proceeds with a quantum yield ?1 = 0.38 ± 0.04 independent of temperature. The n-C3H7O radicals can react with NO by two routes The n-C3H7O radical can decompose via or react with O2 via Values of k4/k2 ? k4b/k2 were determined to be (2.0 ± 0.2) × 1014, (3.1 ± 0.6) × 1014, and (1.4 ± 0.1) × 1015 molec/cm3 at 55, 88, and 120°C, respectively, at 150-torr total pressure of N2. Values of k6/k2 were determined from ?26 to 88°C. They fit the Arrhenius expression: For k2 ? 4.4 × 10?11 cm3/s, k6 becomes (2.9 ± 1.7) × 10?13 exp{?(879 ± 117)/T} cm3/s. The reaction scheme also provides k4b/k6 = 1.58 × 1018 molec/cm3 at 120°C and k8a/k8 = 0.56 ± 0.24 independent of temperature, where 相似文献
4.
Mixtures of cyanogen and nitrous oxide diluted in argon were shock-heated to measure the rate constants of A broad-band mercury lamp was used to measure CN in absorption at 388 nm [B2Σ+(v = 0) ← X2Σ+(v = 0)], and the spectral coincidence of a CO infrared absorption line [v(2 ← 1), J(37 ← 38)] with a CO laser line [v(6 → 5), J(15 → 16)] was exploited to monitor CO in absorption. The CO measurement established that reaction (3) produces CO in excited vibrational states. A computer fit of the experiments near 2000 K led to An additional measurement of NO via infrared absorption led to an estimate of the ratio k5/k6: with k5/k6 ? 103.36±0.27 at 2150 K. Mixtures of cyanogen and oxygen diluted in argon were shock heated to measure the rate constant of and the ratio k5/k6 by monitoring CN in absorption. We found near 2400 K: and The combined measurements of k5/k6 lead to k5/k6 ? 10?3.07 exp(+31,800/T) (±60%) for 2150 ≤ T ≤ 2400 K. 相似文献
5.
The rate coefficient for the reaction has been determined in mixtures of nitric acid (HNO3) and argon in incident shock wave experiments. Quantitative OH time-histories were obtained by cw narrow-linewidth uv laser absorption of the R1(5) line of the A2 σ+ ← X2 Πi (0,0) transition at 32606.56 cm?1 (vacuum). The experiments were conducted over the temperature range 1050–2380 K and the pressure range 0.18–0.60 atm. The second-order rate coefficient was determined to be with overall uncertainties of +11%, ?16% at high temperatures and +25%, ?22% at low temperatures. By incorporating data from previous investigations in the temperature range 298–578 K, the following expression is determined for the temperature range 298–2380 K © 1994 John Wiley & Sons, Inc. 相似文献
6.
CH and C-atom time histories in dilute hydrocarbon pyrolysis: Measurements and kinetics calculations
CH and C-atom concentration-time histories were measured during pyrolysis of highly dilute mixtures (6 to 100 ppm) of ethane or methane in argon behind reflected shock waves over the temperature range 2500 to 3800 K and pressure range 0.5 to 1.3 atm. CH was detected using narrow-linewidth laser absorption at 431 nm. C-atom concentrations were measured using atomic resonance absorption spectroscopy (ARAS) at 156.1 nm. These data allow improved understanding of dilute hydrocarbon pyrolysis. A pyrolysis reaction mechanism was developed which fits essential characteristics of the CH and C-atom profiles (time to peak, peak concentration, and 50% decay time) within ±25%. Critical reactions for which rate coefficient data were not previously available are: Best-fit rate coefficients, valid over the range 2500 to 3800 K, are: k4 = 5.0 × 1015 exp(?42800 K/T), k5 = 4.0 × 1015 exp(?41800 K/T), k6 = 1.3 × 1014 exp(?29700 K/T), and k7 = 1.9 × 1014 exp(?33700 K/T) cm3 mol?1 s?1 相似文献
7.
D. A. Parkes 《国际化学动力学杂志》1977,9(3):451-469
Using the technique of molecular modulation spectrometry, we have measured directly the rate constants of several reactions involved in the oxidation of methyl radicals at room temperature: k1 is in the fall-off pressure regime at our experimental pressures (20–760 torr) where the order lies between second and third and we obtain an estimate for the second-orderlimit of (1.2 ± 0.6) × 10?12 cm3/molec · sec, together with third-order rate constants of (3.1 ± 0.8) × 10?31 cm6/molec2 · sec with N2 as third body and (1.5 ± 0.8) × 10?30 with neopentane; we cannot differentiate between k2a and k2c and we conclude k2a + (k2c) = (3.05 ± 0.8) × 10?13 cm3/molec · sec and k2b = (1.6 ± 0.4) × 10?13 cm3/molec · sec; k3 = (6.0 ± 1.0) × 10?11 cm3/molec · sec. 相似文献
8.
N2O was photolyzed at 2139 Å to produce O(1D) atoms in the presence of H2O and CO. The O(1D) atoms react with H2O to produce HO radicals, as measured by CO2 production from the reaction of OH with CO. The relative importance of the various possible O(1D )–H2O reactions is The relative rate constant for O(1D) removal by H2O compared to that by N2O is 2.1, in good agreement with that found earlier in our laboratory. In the presence Of C3H6, the OH can be removed by reaction with either CO or C3H6: From the CO2 yield, k3/k2 = 75,0 at 100°C and 55.0 at 200°C to within ± 10%. When these values are combined with the value of k2 = 7.0 × 10?13exp (–1100/RT) cm3/sec, k3 = 1.36 × 10?11 exp (–100/RT) cm3/sec. At 25°C, k3 extrapolates to 1.1 × 10?11 cm3/sec. 相似文献
9.
i-C4H9ONO was photolyzed with 366-nm radiation at ?8, 23, 55, 88, and 120°C in a static system in the presence of NO, O2, and N2. The quantum yield of i-C3H7CHO, Φ{i-C3H7CHO}, was measured as a function of reaction of reaction conditions. The primary photochemical act is and it proceeds with a quantum yield ?1 = 0.24 ± 0.02 independent of temperature. The i-C4H9O radicals can react with NO by two routes The i-C4H9O radical can decompose via or react with O2 via Values of k4/k2 ? k4b/k2 were determined to be (2.8 ± 0.6) × 1014, (1.7 ± 0.2) × 1015, and (3.5 ± 1.3) × 1015 molec/cm3 at 23 55, and 88°C, respectively, at 150-torr total pressure of N2. Values of k6/k2 were determined from ?8 to 120°C. They fit the Arrhenius expression: For k2 ? 4.4 × 1011 cm3/s, k6 becomes (3.2 ± 2.0) × 10?13 exp{?(836 ± 159)/T} cm3/s. The reaction scheme also provides k4b/k6 = 3.59 × 1018 and 5.17 × 1018 molec/cm3 at 55 and 88°C, respectively, and k8b/k8 = 0.66 ± 0.12 independent of temperature, where 相似文献
10.
The rate coefficient, k, of the reaction has been determined in the temperature range 2460–2840 K using a shock tube technique. C2N2? H2O? Ar mixtures were heated behind incident shock waves and the CN and OH concentration time histories were monitored simultaneously using broad-band absorption near 388 nm (CN) and narrow-line laser absorption at 306.67 nm (OH). The rate coefficient expression providing the best fit to the data was with uncertainty limits of about ±45% in the temperature range 2460–2840 K. The rate coefficient of the reverse reaction was calculated using detailed balancing, and its extrapolation to lower temperatures was compared with previously published results. 相似文献
11.
L. F. Phillips 《国际化学动力学杂志》1978,10(8):899-904
The rate of disappearance of C2N2 in the presence of a large excess of H atoms has been measured in a discharge-flow system at pressures near 1 torr and temperatures in the range of 282–338 K. Under these conditions the reaction has a small negative temperature coefficient. A transition from second-order to third-order kinetics with decreasing pressure occurs at pressures near 1 torr. The results are discussed in terms of the mechanism where k7 = (1.5 ± 0.2) × 10–15 cm3/molec1·sec is found for the forward rate of reaction (7). The results also give k7k8/k?7 = 3.7 × 10?31 cm6/molec2·sec and k7k9/k?7 = 3.0 × 10?32 cm6/molec2·sec, the first being probably an upper limit and the second probably a lower limit; hence k8/k9 = 12 is found as an upper limit. 相似文献
12.
Mixtures of N2O, CO, and NO in excess H2 were photolyzed at 213.9 nm and 298°K. The initially formed O(1D) atoms from the photolysis of N2O abstract an H atom from H2 permitting a study of the competition: From the CO2 yield the relative rate coefficient k1/k2 is obtained. It is found to be slightly dependent on pressure for total pressures (mainly H2) of 95.5 to 768 torr. However, the values are near the high-pressure limiting value which is found by extrapolation to give k1∞ = 1.2 × 10?11 cm3/sec based on k2∞ = 3.55 × 10?13 cm3/sec. 相似文献
13.
The reaction of O(3P), prepared from the Hg photosensitization of N2O, with C2HCl3 was studied at 25°C. The products of the reaction in the absence of O2 were CO, CHCl3, and polymer (as well as N2 from the N2O). The quantum yields of CO and CHCl3 were 0.23 ± 0.01 and 0.14 ± 0.05, is respectively independent of reaction conditions. The reaction mechanism is with k14a/k14 = 0.23, where k14a + k14b. Most of the HCl and CCl2 combine to form CHCl3, but some other products must also be formed to account for the difference in the CO and CHCl3 quantum yields. The C2HCl3O* adduct polymerizes without involving additional C2HCl3 molecules, since the quantum yield of C2HCl3 disappearance, ? Φ{C2HCl3}, was about 1.0 at high values of [N2O]/[C2HCl3]. The rate coefficient for the reaction of O(3P) with C2HCl3 is 0.10 that for the reaction of O(3P) with C2F4. In the presence of O2 the free radical chain oxidation occurs because of the reaction The main product is CHCl2CCl(O) with smaller amounts of CO and CCl2O, and some CO2. The chain lengths were long and values of ? Φ {C2HCl3} up to 90 were observed. 相似文献
14.
Direct determinations of the rate constants (cm3/molec · sec) k1, k2, and k3 from 298 to 299°K are reported, using atomic resonance fluorescence in discharge flow systems: 1 One standard deviation. The rate constant k1, which has not been determined previously, was found to possess an insignificant temperature coefficient (EA = (0 ± 700) J/mole) in the range of 299 to 619°K. The present result for k2 agrees well with reinterpreted values from the one previous determination. Measurements of O atom consumption rates and Br atom production rates in the O + Br2 reaction are interpreted to give an estimate of the rate constant k4, which has not been reported previously, at 298°K: k3 has been measured at three temperatures between 299 and 602°K. The present and previous results for k3 were combined to give the following rate expression: 相似文献
15.
The deprotonation rate 1/τ of the title compounds, [4 – R – Py H]+, where R = NH2, t-Bu, Me, Cl, Br or CN, is measured using the coalescence of the pyridinic α-protons, in a mixture CF3COOH/H2O/HClO4 of variable acidity Ho, at 38°C. 1/τ is a linear function k/ho of the acidity 1/ho. k is approximately proportional to the water content and independent of the salt concentration, which seems to be evidence for an exchange with an intermediate pyridine hydrate, according to: . After a preliminary ionisation step: k values, like KA, fit a Hammett relationship (ρ = 5,05), except for R ? NH2, and are very sensitive to the nature of R (k = 3,44 × 102 for R = NH2 and k = 3,14 × 108 M?1 s?1 for R ? CN), while kH values (1010 s?1) are not. 相似文献
16.
Mixtures of N2O, H2, O2, and trace amounts of NO and NO2 were photolyzed at 213.9 nm, at 245°–328°K, and at about 1 atm total pressure (mostly H2). HO2 radicals are produced from the photolysis and they react as follows: Reaction (1b) is unimportant under all of our reaction conditions. Reaction (1a) was studied in competition with reaction (3) from which it was found that k1a/k31/2 = 6.4 × 10?6 exp { z?(1400 ± 500)/RT} cm3/2/sec1/2. If k3 is taken to be 3.3 × 10?12 cm3/sec independent of temperature, k1a = 1.2 × 10?11 exp {?(1400 ± 500)/RT} cm3/sec. Reaction (2a) is negligible compared to reaction (2b) under all of our reaction conditions. The ratio k2b/k1 = 0.61 ± 0.15 at 245°K. Using the Arrhenius expression for k1a given above leads to k2b = 4.2 × 10?13 cm3/sec, which is assumed to be independent of temperature. The intermediate HO2NO2 is unstable and induces the dark oxidation of NO through reaction (?2b), which was found to have a rate coefficient k?2b = 6 × 1017 exp {?26,000/RT} sec?1 based on the value of k1a given above. The intermediate can also decompose via Reaction (10b) is at least partially heterogeneous. 相似文献
17.
The decomposition of ethane sensitized by isopropyl radicals was studied in the temperature range of 496–548°K. The rate of formation of n-butane, isopentane, and 2,3-dimethylbutane were measured. The expression k1/k2½ was found to be where k1 and k2 are rate constants of The decomposition of propylene sensitized by isopropyl radicals was studied between 494 and 580°K by determination of the initial rates of formation of the main products. The ratio of k13/k21/2 was evaluated to be where k13 is the rate constant for The isomerization of the isopropyl radical was investigated by studying the decomposition of azoisopropane. The decomposition of the iso-C3H7 radical into C2H4 and CH3 was followed by measuring the rate of formation of C2H4. On the basis of the experimental data, obtained in the range of 538–666° K, k15/k2½ was found: where k15 is the rate constant of 相似文献
18.
The decomposition of dimethyl peroxide (DMP) was studied in the presence and absence of added NO2 to determine rate constants k1 and k2 in the temperature range of 391–432°K: The results reconcile the studies by Takezaki and Takeuchi, Hanst and Calvert, and Batt and McCulloch, giving log k1(sec?1) = (15.7 ± 0.5) - (37.1 ± 0.9)/2.3 RT and k2 ≈ 5 × 104M?1· sec?1. The disproportionation/recombination ratio k7b/k7a = 0.30 ± 0.05 was also determined: When O2 was added to DMP mixtures containing NO2, relative rate constants k12/k7a were obtained over the temperature range of 396–442°K: A review of literature data produced k7a = 109.8±0.5M?1·sec?1, giving log k12(M?1·sec?1) = (8.5 ± 1.5) - (4.0 ± 2.8)/2.3 RT, where most of the uncertainty is due to the limited temperature range of the experiments. 相似文献
19.
The kinetics of dimethyl sulfoxide (DMSO) oxidation by peroxomonophosphoric acid (PMPA) in aqueous medium at 308 K and I = 0.4 mol/dm3 follow the rate expressions In the pH range from 0 to 2, where k1 and k2 are 5.092 × 10?1 dm3/mol sec and ? 0, respectively; in the pH range from 4 to 7, where k2 = 8.127 × 10?3 and k3 = 2.90 × 10?3 dm3/mol sec; and in the pH range from 10 to 13.6, where k4 ? 0, and k5 = 3.08 × 10?2 dm3/mol sec. The reaction is interpreted in terms of mechanisms involving an electrophilic and a nucleophilic attack of the peroxomonophosphoric acid species, respectively, in acid and alkaline regions, on the sulfur atom of the sulfoxide molecule giving rise to S-type transition states followed by oxygen-oxygen bond fission to form the products. 相似文献
20.
The reaction of peroxomonophosphoric acid and hydrazinium ion in acid perchlorate solutions occurs as per stoichiometry (i), and the rate law (ii) at large [N2H5 +], where K′d is the first acid dissociation constant of H3PO5 and k 1 and k 2 are rate constants found to be 2.6 × 10?4 s?1 and 5.0 × 10?2 M?1 s?1, respectively, at 35°. The reaction is greatly catalyzed by iodide ions. The mechanism involves a redox cycle I?/I2 and the rate is independent of [N2H5 +] in the presence of iodide ions. K′d was found to be 0.55 M?1 and independent of temperature. 相似文献