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1.
Rate constants have been measured in several aqueous/organic solvent mixtures for the addition reaction of Cl2˙? radicals with 2-propen-1-o1 and 2-buten-1-o1 as a function of temperature and with 2, 3-dimethyl-2-butene at room temperature. The rate constants were in the range of 106–109 L mol?1 s?1, the activation energies were relatively low (1–10 kJ mol?1), and the pre-exponential factors varied over the range log A = 7.9 to 9.4. The rate constants (k) decreased (by up to a factor of 30) upon increasing the fraction of organic solvent and log k correlated linearly with the dielectric constant for a given water/organic solvent system, but the lines for the different solvent systems had different slopes. A better correlation of log k was found with a combination of the solvatochromic factor, ET(30), and the hydrogen-bond donor acidity factor, α. This suggests that the rate of reaction is influenced by the solvent polarity and also by specific solvation of the ionic reactant and product. Solvent effect on the reaction of SO4˙? with 2-propen-1-o1 was studied for comparison. © 1993 John Wiley & Sons, Inc.  相似文献   

2.
The solid‐liquid equilibria in the quinary system Na+, K+//Cl?, SO2?4, B4O2?7‐H2O at 298 K had been studied experimentally using the method of isothermal solution saturation. Solubilities and densities of the solution of the quinary system were measured experimentally. Based on the experimental data, the dry‐salt phase diagram and water content diagram of the quinary system were constructed, respectively. In the equilibrium diagram of the quinary system Na+, K+//Cl?, SO2?4, B4O2?7‐H2O at 298 K, there are five invariant points F1, F2, F3, F4 and F5; eleven univariant curves E1F1, E2F2, E3F3, E4F5, E5F2, E6F4, E7F5, F1F4, F2F4 F1F3 and F3F5, and seven fields of crystallization saturated with Na2B4O7 corresponding to Na2SO4, Na2SO4·10H2O, Na2SO4·3K2SO4 (Gla), K2SO4, K2B4O7·4H2O, NaCl and KCl. The experimental results show that Na2SO4·3K2SO4 (Gla), K2SO4 and K2B4O7·4H2O have bigger crystallization fields than other salts in the quinary system Na+, K+//Cl?, SO2?4, B4O2?7‐H2O at 298 K.  相似文献   

3.
The N2 negative ion chemical ionization (NICI) mass spectra of aniline, aminonaphthalenes, aminobiphenyls and aminoanthracenes show an unexpected addition appearing at [M + 11]. This addition is also observed in the N2 positive chemical ionization (PCI) mass spectra. An ion at [M – 15]? is found in the NICI spectra of aminoaromatics such as aniline, 1- and 2-aminonaphthalene and 1- and 2-aminoanthracene. Ion formation was studied using labeled reagents, variation of ion source pressure and temperature and examination of ion chromatograms. These experiments indicate that the [M + 11], [M – 15] and [M + 11] ions result from the ionization of analytes altered by surface-assisted reactions. Experiments with 15N2, [15N] aniline, [2,3,4,5,6-2H5] aniline and [13C6] aniline show that the [M + 11] ion corresponds to [M + N – 3H]. The added nitrogen originates from the N2 buffer gas and the addition occurs with loss of one ring and two amino group hydrogens. Fragmentation patterns in the N2 PCI mass spectrum of aniline suggest that the neutral product of the surface-assisted reaction is 1,4-dicyanobuta-1,3-diene. Experiments with diamino-substituted aromatics show analogous reactions resulting in the formation of [M – 4H] ions for aromatics with ortho-amino groups. Experiments with methylsubstituted aminoaromatics indicate that unsubstituted sites ortho to the amino group facilitate nitrogen addition, and that methyl groups provide additional sites for nitrogen addition.  相似文献   

4.
Pulsed laser photolysis, time-resolved laser-induced fluorescence experiments have been carried out on the reactions of CN radicals with CH4, C2H6, C2H4, C3H6, and C2H2. They have yielded rate constants for these five reactions at temperatures between 295 and 700 K. The data for the reactions with methane and ethane have been combined with other recent results and fitted to modified Arrhenius expressions, k(T) = A′(298) (T/298)n exp(?θ/T), yielding: for CH4, A′(298) = 7.0 × 10?13 cm3 molecule?1 s?1, n = 2.3, and θ = ?16 K; and for C2H6, A′(298) = 5.6 × 10?12 cm3 molecule?1 s?1, n = 1.8, and θ = ?500 K. The rate constants for the reactions with C2H4, C3H6, and C2H2 all decrease monotonically with temperature and have been fitted to expressions of the form, k(T) = k(298) (T/298)n with k(298) = 2.5 × 10?10 cm3 molecule?1 s?1, n = ?0.24 for CN + C2H4; k(298) = 3.4 × 10?10 cm3 molecule?1 s?1, n = ?0.19 for CN + C3H6; and k(298) = 2.9 × 10?10 cm3 molecule?1 s?1, n = ?0.53 for CN + C2H2. These reactions almost certainly proceed via addition-elimination yielding an unsaturated cyanide and an H-atom. Our kinetic results for reactions of CN are compared with those for reactions of the same hydrocarbons with other simple free radical species. © John Wiley & Sons, Inc.  相似文献   

5.
The recombination reaction O + O2 → O3 was studied by laser flash photolysis of pure O2 in the pressure range 3–20 atm, and of N2O? O2 mixtures in the bath gases Ar, N2, (CO2, and SF6) in the pressure range 3–200 atm. Fall-off curves of the reaction have been derived. Low-pressure rate coefficients were found to agree well with literature data. A high-pressure rate coefficient of k = (2.8 ± 1.0) × 10?12 cm3 molecule?1 s?1 was obtained by extrapolation.  相似文献   

6.
The gas-phase reaction of the NO3 radical with NO2 was investigated, using a flash photolysis-visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10?13 cm3 molecule?1 s?1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N2 and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O2. These data show that the third-body efficiencies of N2 and O2 are identical, within the error limits, and that previous evaluations for M = N2 are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO3 radical with methanol, ethanol, and propan-2-ol of ?6 × 10?16, ?9 × 10?16, and ?2.3 × 10?15 cm3 molecule?1 s?1, respectively, at 298 ± 2 K.  相似文献   

7.
The [C4H6O] ion of structure [CH2?CHCH?CHOH] (a) is generated by loss of C4H8 from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔHf of [CH2?CHCH?CHOH] was estimated to be 736 kJ mol?1. The isomeric ion [CH2?C(OH)CH?CH2] (b) was shown to have ΔHf, ? 761 kJ mol?1, 54 kJ mol?1 less than that of its keto analogue [CH3COCH?CH2]. Ion [CH2?C(OH)CH?CH2] may be generated by loss of C2H4 from ionized hex-1-en-3-one or by loss of C4H8 from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C4H6O] ion generated by loss of C2H4 from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH2?CHCH?CHOH] and [CH2?C(OH)CH?CH2] ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH3˙ and CO, [CH2?CHCH?CHOH]+˙ and [CH2?C(OH)CH?CH2] do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C4H6O] ion [CH2?C?CHCH2OH] are also reported.  相似文献   

8.
Rate constants have been measured for the reactions of the sulfate radical, SO4˙?, with alkanes, alkenes, alcohols, ethers, and amines in 95% acetonitrile solution. The rate constants were in the range of 106 L mol?1 s?1 for the abstraction reactions and 107?109 L mol?1 s?1 for the addition and electron transfer reactions. These values are 20 to 80 times lower than those measured in aqueous solutions. Furthermore, the rate constants for the reactions of SO4˙? with the primary alcohols increase with the number of carbon atoms and then level off, in contrast to the behavior observed in aqueous solution, where the rate constant increases more sharply for the larger alcohols. © 1993 John Wiley & Sons, Inc.  相似文献   

9.
Unstable 2-hydroxpropene was prepared by retro-Diels-Alder decomposition of 5-exo-methyl-5-norbornenol at 800°C/2 × 10?6 Torr. The ionization energy of 2-hydroxypropene was measured as 8.67±0.05 eV. Formation of [C2H3O]+ and [CH3]+ ions originating from different parts of the parent ion was examined by means of 13C and deuterium labelling. Threshold-energy [H2C?C(OH)? CH3] ions decompose to CH3CO++CH3˙ with appearance energy AE(CH3CO+) = 11.03 ± 0.03 eV. Higher energy ions also form CH2?C?OH+ + CH3 with appearance energy AE(CH2?C?OH+) = 12.2–12.3 eV. The fragmentation competes with hydrogen migration between C(1) and C(3) in the parent ion. [C2H3O]+ ions containing the original methyl group and [CH3]+ ions incorporating the former methylene and the hydroxyl hydrogen atom are formed preferentially, compared with their corresponding counterparts. This behaviour is due to rate-determining isomerization [H2C?C(OH)? CH3] →[CH3COCH3], followed by asymmetrical fragmentation of the latter ions. Effects of internal energy and isotope substitution are discussed.  相似文献   

10.
Electron pulse radiolysis at ?298°K of 2 atm H2 containing 5 torr O2 produces HO2 free radical whose disappearance by reaction (1), HO2 + HO2 →H2O2 + O2, is monitored by kinetic spectrophotometry at 230.5 nm. Using a literature value for the HO2 absorption cross section, the values k1 = 2.5×10?12 cm3/molec·sec, which is in reasonable agreement with two earlier studies, and G(H) G(HO2) ?13 are obtained. In the presence of small amounts of added H2O or NH3, the observed second-order decay rate of the HO2 signal is found to increase by up to a factor of ?2.5. A proposed kinetic model quantitatively explains these data in terms of the formation of previously unpostulated 1:1 complexes, HO2 + H2O ? HO2·H2O (4a) and HO2 + NH3? HO2·NH3 (4b), which are more reactive than uncomplexed HO2 toward a second uncomplexed HO2 radical. The following equilibrium constants, which agree with independent theoretical calculations on these complexes, are derived from the data: 2×10?20?K4a?6.3 × 10?19 cm3/molec at 295°K and K4b = 3.4 × 10?18 cm3/molec at 298°K. Several deuterium isotope effects are also reported, including kH/kD = 2.8 for reaction (1). The atmospheric significance of these results is pointed out.  相似文献   

11.
O2 in the A3Σu+ state has been prepared in a discharge flow system by recombining oxygen atoms on a nickel surface. The decay of this excited state was followed by observing the emission between 280 and 400 nm. The wall deactivation was observed to approach unit efficiency. Rate constants were determined to be 0.9 × 10?11, 2.9 × 10?13, and 8.6 × 10?16 cm3/molecule sec for the quenching of O2(A3Σu+) by O, O2, and Ar, respectively.  相似文献   

12.
The distonic ions HO+?CHCH2C˙H2 (1) and CH3C(?O+H)CH2C˙H2 (2) were directly generated, their decompositions characterized and their appearance energies determined by photoionization. Heats of formation derived from the appearance energies were 757 kJ mol?1 for 1 and 692 kJ mol?1 for 2. Deuterium labeling demonstrates that both ions decompose at low energies in the same ways as their isomers with the same skeletal structures, consistent with proposals that 1 and 2 are intermediates in the decompositions of those systems. Surprisingly, the values of the translational energy releases accompanying the formation of CH3CO+ and C2H5CO+ from 2 appear to be inversely proportional to the available excess energy. The 1,2-H-shift RC(?O+H)CH2C˙H2 → RC(?O+H)C˙HCH3 is compared to the corresponding, non-occurring 1,2-H-shift in alkyl free radicals.  相似文献   

13.
14.
The kinetics and mechanism of Cl-atom-initiated reactions of CHO? CHO were studied using the FTIR detection method to monitor the photolysis of Cl2–CHO? CHO mixtures in 700 torr of N2–O2 diluent at 298 ± 2 K. The observed product distribution in the [O2] pressure of 0–700 torr combined with relative rate measurements provide evidence that: (1) the primary step is Cl + CHO? CHO → HCl + CHO? CO with a rate constant of [3.8 ± 0.3(σ)] × 10?11 cm3 molecule?1 s?1; (2) the primary product CHO? CO unimolecularly dissociates to CHO and CO with an estimated lifetime of ≤ca. 1 × 10?7 s; (3) alternatively, the CHO? CO reacts with O2 leading to the formation of CO, CO2, and most likely the HO radical, but no stable products containing two carbon atoms; (4) the HO2 radical, formed in the secondary reaction CHO + O2 → HO2 + CO, reacts with the CHO? CHO with a rate constant ca. 5 × 10?16 cm3 molecule?1 s?1 to form HCOOH and a new transient product resembling that detected previously in the HO2 reaction with HCHO.  相似文献   

15.
Preparation of μ-Sulfurdisulfonium Salts [(CH3)2S? Sx? S(CH3)2]2+2A? (x = 1–3, A? = AsF6?, SbF6?, SbCl6?). On the Analogy of the Reactivity of Sulfanes and Sulfonium Salts The preparation of the μ-sulfurdisulfonium salts [(CH3)2S? Sx? S(CH3)2]2+(A?)2 with x = 1–3 and A? = AsF6?, SbF6?, SbCl6? is reported. The salts are formed by reaction of (CH3)2SH+A? and (CH3)2SSH+A? with SCl2 and S2Cl2, resp. They are characterized by vibrational spectroscopic measurements. [(CH3)2S? S2? S(CH3)2]2+(SbF6?)2 crystallizes in the space group C2/c with a = 1 884.5(7) pm, b = 1 302.8(5) pm, c = 1 477.2(5) pm, β = 98.62(3)° und Z = 8.  相似文献   

16.
A novel-pulsed electrolyte cathode atmospheric pressure discharge (pulsed-ECAD) plasma source driven by an alternating current (AC) power supply coupled with a high-voltage diode was generated under normal atmospheric pressure between a metal electrode and a small-sized flowing liquid cathode. The spatial distributions of the excitation, vibrational, and rotational plasma temperatures of the pulsed-ECAD were investigated. The electron excitation temperature of H Texc(H), vibrational temperature of N2 Tvib(N2), and rotational temperature of OH Trot(OH) were from 4900?±?36 to 6800?±?108 K, from 4600?±?86 to 5800?±?100 K, and from 1050?±?20 to 1140?±?10 K, respectively. The temperature characteristics of the dc solution cathode glow discharge (dc-SCGD) were also studied for the comparison with the pulsed-ECAD. The effects of operating parameters, including the discharge voltage and discharge frequency, on the plasma temperatures were investigated. The electron number densities determined in the discharge system and dc-SCGD were 3.8–18.9?×?1014?cm–3 and 2.6?×?1014 to 17.2?×?1014?cm–3, respectively.  相似文献   

17.
An explicit function has been derived for the potential-energy surface of the ground state of ClO3 with the six interatomic distances as variables. This surface is valid over all configurations of the atoms. The surface has been used to calculate classical trajectories for the reactions R1: O(3P2)+ClO(2Π3/2)→ O2(3∑)+Cl(2)P3/2 and R2: Cl(2P3/2)+O3(1A1)→ClO(2Π3/2)+O2(3∑). An appreciable fraction (~1/3) of the reactive trajectories for R1 go through a long-lived complex ClOO(2A″). The cross section decreases with increasing rotational state of the ClO; and 37% of the energy release is vibrational. The calculated rate constant at 298°K is 2.6 × 10?11 cm3/molecule sec. For reaction R2 there is no evidence of long-lived complexes. The product ClO is predominantly found in the backward-scattering direction. Most of the internal energy is carries off by ClO but O2 carried off most translational energy. An Arrhenius expression has been deduced from calculations at 220 and 300°K to give an A factor of 2.488 × 10?11 cm3/molecule sec and an activation energy of 1.543 kJ/mol.  相似文献   

18.
Rate constants (k's) of the thermal cyclodimerization of ten meta-substituted trifluorostyrenes (m-Y-TFS's) have been measured in the temperature range 110–160°C. On the basis of these k's and the σmb values derived from 19F NMR data the spin-delocalization substituent constant σ˙m values of these ten meta-substituents have been calculated. The averaged σ˙m values are: m-Et, 0.09; m-t-Bu, 0.11; m-F, 0.03; m-Cl,?0.05; m-Br, 0.12: m-CF3, ?0.07; m-OMe, 0.10; m-NO2, ?0.002; m-CN, 0.11 and m-CO2Me, 0.08. Both the smallness of these values and the nonexistence of correlation between Hammett-Type polar σX and these σ˙m values support our belief that the σj?J approach is reliable and trustworthy.  相似文献   

19.
Ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence electron correlation have been employed to examine the [C2H2O] potential energy surface. Four [C2H2O] isomers have been identified as potentially stable, observable ions. These are the experimentally well-known ketene radical cation, [CH2?C?O] (a), and the presently unknown ethynol radical cation, [CH2?C? OH] (b), the oxirene radical cation (c) and an ion resembling a complex of CO with [CH2], (d). The calculated energies of b, c and d relative to a are 189, 257 and 259 kJ mol?1, respectively. Dissociation of ions a and d is found to occur without reverse activation energy.  相似文献   

20.
The kinetics of the gas‐phase reactions of O3 with a series of selected terpenes has been investigated under flow‐tube conditions at a pressure of 100 mbar synthetic air at 295 ± 0.5 K. In the presence of a large excess of m‐xylene as an OH radical scavenger, rate coefficients k(O3+terpene) were obtained with a relative rate technique, (unit: cm3 molecule?1 s?1, errors represent 2σ): α‐pinene: (1.1 ± 0.2) × 10?16, 3Δ‐carene: (5.9 ± 1.0) × 10?17, limonene: (2.5 ± 0.3) × 10?16, myrcene: (4.8 ± 0.6) × 10?16, trans‐ocimene: (5.5 ± 0.8) × 10?16, terpinolene: (1.6 ± 0.4) × 10?15 and α‐terpinene: (1.5 ± 0.4) × 10?14. Absolute rate coefficients for the reaction of O3 with the used reference substances (2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene) were measured in a stopped‐flow system at a pressure of 500 mbar synthetic air at 295 ± 2 K using FT‐IR spectroscopy, (unit: cm3 molecule?1 s?1, errors represent 2σ ): 2‐methyl‐2‐butene: (4.1 ± 0.5) × 10?16 and 2,3‐dimethyl‐2‐butene: (1.0 ± 0.2) × 10?15. In addition, OH radical yields were found to be 0.47 ± 0.04 for 2‐methyl‐2‐butene and 0.77 ± 0.04 for 2,3‐dimethyl‐2‐butene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 394–403, 2002  相似文献   

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