摘要:

AbstractThe kinetics of electron transfer reactions between acetophenones with Ce(IV) have been studied in aqueous acetic acid medium in the presence of cationic micelle Cetylpyridinium chloride (CPyCl) at different temperatures. Kinetic data reveal first‐order dependence with respect to each of Ce(IV) and acetophenones. The cationic micelle, Cetylpyridinium chloride enhances the oxidation reactions. The catalysis fits to a model developed by Menger and Portnoy as well as Berezin's phase separation model. The binding and partition constants and the transfer free energy from water to micelle have been estimated and discussed, suggesting that the solubilization of both the reactants in the micellar phase, facilitates the oxidation. © 1993 John Wiley&Sons, I

ISSN:0538-8066    

DOI:10.1002/kin.550250802

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the present study the determination of the mechanism of the thermal decomposition of magnesium hydroxide from thermogravimetric experiments is attempted. For this purpose nonisothermal kinetic analysis of the dynamic experimental data is applied, using different methods, which are based on the best linearization of a functional form of the Arrhenius equation. The experiments were carried out under nonisothermal conditions in a thermogravimetric analyzer with nitrogen atmosphere, at five different heating rates, i.e., 3, 8, 15, 20, and 35 deg/min. The nonisothermal methods used for the kinetic analysis of the experimental data were the Coats‐Redfern method, the Romero et al., the improved Coats‐Redfern method, the differential method, the differential by Jerez et al., and a method using the heating rate as a variable. Applying each of these methods, the kinetic parameters and, in most cases, the form of the conversion function (kinetic model) which governs the dehydroxylation process of Mg(OH)2were determined. From the comparative study of the results of the above methods and using criteria about the credibility of each method, it was concluded that the kinetic model which represents the mechanism of the dehydroxylation of magnesium hydroxide, is that corresponding to the two dimensions nucleation with a reference value of activation energy 117.67 kJ/mol. © 1993 John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550250803

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe reaction of photochemically generated energetic hydrogen atoms with 1‐chloropropane, reaction (1),has been examined for translational energies of H* in the range 40 to 110 kJ mol−1. Integral probabilities for reaction (1) have been determined, and the phenomenological threshold energy is 47 ± 10 kJ mol−1. The moderating effect of CO2on reaction (1) for hydrogen atoms of initial energy 108 kJ mol−1has also been studied. © 1993 John Wiley&

ISSN:0538-8066    

DOI:10.1002/kin.550250804

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe products formed by the hydroxyl radical initiated photo‐oxidation of diethyl ether have been investigated by irradiating synthetic air mixtures containing diethyl ether and nitrous acid in amounts approaching ppbv levels in a smog chamber. The decay of reactants and formation of products were monitored by gas chromatography, HPLC, and by chemiluminescent analysis. The major products are ethyl formate and formaldehyde, minor products include ethyl acetate, acetaldehyde, peroxyacetyl nitrate, methyl nitrate, and ethyl nitrate. The products observed arise from the decomposition reactions of the 1‐ethoxyethoxy radical and its reaction with oxygen. One molecule of nitric oxide appears to be oxidized per molecule of diethyl ether reacted. This is lower than would be expected on the basis of the proposed mechanism and possible reasons for the discrepancy are discussed. © 1993 John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550250805

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractA 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 cm3molecule−1s−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 N2diluent); 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 ± 2K. Results are discussed with respect to the previous literature data and to the interpretation of laboratory studies of the atm

ISSN:0538-8066    

DOI:10.1002/kin.550250806

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractRelative rate experiments using UV photolysis of F2or Cl2have been used to determine rate constant ratios for several hydrofluorocarbon (HFC) reactions with Cl or F atoms and for HFC alkyl radicals with molecular halogens. For mixtures with F2present, dark reactions are, also, observed which are attributed to thermal dissociation of the F2to form F atoms. At 296 K, the rate of reaction (1a) [CF2HCH3+ F → CF2CH3+ HF] relative to (1b) [CF2HCH3+ F → CF2HCH2+ HF] isk1a/k1b= 0.73 (±0.13) and is independent ofT(= 262–348 K). At 296 K, the ratio of reaction (2a) [CF2HCH2F + F → products] to that of (k1a+k1b) is (k1a+k1b)/k2a= 2.7 (±0.4), and for reaction (2b) [CF3CH3+ F → products] (k1a+k1b)/k2b= 22 ± 12. The temperature dependence (263–365 K) of the rate constant of reaction (3) [CF3CFH2+ Cl → products] relative to reaction (4) [CF3CFClH + Cl → products] isk3/k4(±10%) = 1.55 exp(−300K/T). For the alkyl radicals formed from HFC 152a (CF2HCH2and CF2CH3) and from HFC 134a (CF3CFH), rate constants for the reactions with F2and Cl2were measured relative to their reactions with O2. The rate constant of reaction (5cl) [CF2CH3+ Cl2→ CF2ClCH3+ Cl] relative to (5o) [CF2CH3+ O2→ CF2(O2)CH3] isk5cl/k5o(±15%) = 0.3 exp(200K/T). For reaction (5f) [CF2CH3+ F2→ CF3CH3+ F],k5f/k5o(±35%) = 0.23. The ratio for reaction (6f) [CF2HCH2+ F2→ CF2HCH2F + F] relative to (6o) [CF2HCH2+ O2→ CF2HCH2O2] isk6f/k6o(±40%) = 1.23 exp(−730K/T). The rate constant ratio for reaction (8cl) [CF3CFH + Cl2→ CF3CFClH + Cl] relative to reaction (8o) [CF3CFH + O2→ CF3CFHO2] isk8cl/k8o(±18%) = 0.16 exp(−940K/T). For reaction (8f) [CF3CFH + F2→ CF3CF2H + F],k8f/k8o(±35%) =

ISSN:0538-8066    

DOI:10.1002/kin.550250807

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550250801

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY