摘要:

AbstractThe reactions of OH radicals with dimethylsulfide (DMS) diethylsulfide (DES), tetrahydrothiophene (THT), and thiophene have been studied at room temperature for DES and THT, at 273, 293, and 318 K for DMS, and at 293 and 318 K for thiophene by the discharge flow EPR technique in a halocarbon wax coated reactor. The following rate constants were obtained at room temperature.For the reaction OH + DMS (1), a very low temperature dependence was noticed.Some additional results concerning the mass spectrometric analysis of the products are also reported.

ISSN:0538-8066    

DOI:10.1002/kin.550171202

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractKinetics of the complex formation of chromium(III) with alanine in aqueous medium has been studied at 45, 50, and 55°C, pH 3.3–4.4, and μ = 1 M (KNO3). Under pseudo first‐order conditions the observed rate constant (kobs) was found to follow the rate equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{{\rm obs}} = \frac{{(k_{{\rm an}} K_{{\rm IP}} K_a [{\rm H}^{\rm + }] + k'_{{\rm an}} K'_{{\rm IP}} K'_a K_a)[{\rm Alanine}]_T }}{{[{\rm H}^{\rm + }]^2 + [{\rm H}^{\rm + }]K_a + [{\rm H}^{\rm + }]K'_a + K_a K'_a + (K_{{\rm IP}} K_a [{\rm H}^{\rm + }] + K'_{{\rm JP}} K'_a K_a)[{\rm Alanine}]_{\rm T} }} $$\end{document}Values of the rate parameters (kan,k an′,KIP, andK IP′) were calculated. Activation parameters for anation rate constants, ΔH≠(kan) = 25 ± 1 kJ mol−1, ΔH≠(k an′) = 91 ± 3 kJ mol−1, and ΔS≠(kan) = −244 ± 3 JK−1mol−1, ΔS≠(k an′) = −30 ± 10 JK−1mol−1are indicative of an (Ia) mechanism forkanand (Id) mechanism fork an′routes (‥substrate Cr(H2O) 63+is involved in thekroute whereas Cr(H2O)5OH2+is involved ink′ route). Thermodynamic parameters for ion‐pair formation constants are found to be ΔH°(KIP) = 12 ± 1 kJ mol−1, ΔH°(K IP′) = −13

ISSN:0538-8066    

DOI:10.1002/kin.550171203

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550171204

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550171205

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractAbsolute rate coefficients for the reaction of OH with HCl (k1) have been measured as a function of temperature over the range 240–1055 K. OH was produced by flash photolysis of H2O at λ>165 nm, 266 nm laser photolysis of O3/H2O mixtures, or 266 nm laser photolysis of H2O2. OH was monitored by time‐resolved resonance fluorescenceor pulsed laser–induced fluorescence. In many experiments the HCl concentration was measuredin situin the slow flow reactor by UV photometry. Over the temperature range 240–363 K the following Arrhenius expression is an adequate representation of the data:k1= (2.4 ± 0.2) × 10−12exp[−(327 ± 28)/T]cm3molecule−1s−1. Over the wider temperature range 240–1055 K, the temperature dependence ofk1deviates from the Arrhenius form, but is adequately described by the expressionk1= 4.5 × 10−17T1.65exp(112/T) cm3molecule−1s−1. The error in a calculated rate coefficie

ISSN:0538-8066    

DOI:10.1002/kin.550171206

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractKinetic and spectrophotometric measurements made during the Fe3+ion catalyzed decomposition of H2O2have been analyzed using the computer simulation method. Improved values of the rate constants of the “complex scheme” and of the molar absorptivities ofthe intermediates were obtained:k3/KM= 4.94 M−1min−1,k4= 193 M−1min−1, εI/KM= 52.3 M−2cm−1, εII= 25.7 M−1cm−1. The simulation revealed details of the reaction which were unavailable by other means and which explained several features of its kinetics. The total amount of O2evolved in the reaction using [H2O2] ∼ 10−2M has been calculated and found to be nearly stoichiometric. O2evolution experiments in this region cannot, thus, distinguish between the “complex mechanism” predicting nearly stoichiometric evolution of O2and the “free radical mechanism” predicting exactly stoichiometricamounts of O2. There are discrepancies within the “free radical scheme” with regard to the correct values of the rate constants to fit the reactions of H2O2both with Fe2+and Fe3+ions, as well as other reactions

ISSN:0538-8066    

DOI:10.1002/kin.550171207

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe quenching rate constants of O2(1Δg) withn‐butylamine, diethylamine, dipropylamine, dibutylamine, and tripropylamine have been determined in a discharge flow system. The rate constants are found to be (1.6 ± 0.2) × 103, (8.5 ± 0.6) × 104, (9.8 ± 0.5) × 104, (2.1 ± 0.1) × 105, and (8.6 ± 0.5) × 1051 mol−1s−1, respectively. The rate constants are found to increase in the order, tertiary amine → secondary amine → primary amine. The “inductive effect” of alkyl substitution is also found to increase the rate constant in

ISSN:0538-8066    

DOI:10.1002/kin.550171208

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe kinetics of liquid phase chlorination of methane in a difluorodichloromethane medium has been studied in a temperature interval of 293–150 K. The value of activation energy found for the hydrogen abstraction stage by a chlorine atom (E1) equals 14.2 ± 2.5 kJ/mol, with the processes of chlorine atoms recombination and the cage effect being taken into account. The method of competitive reactions has been employed to assess the constants of reaction of chlorine atoms (k1) with ethane, propane, hexane, ethylene, allyl bromide, allyl chloride, ethyl chloride, and cyclohexane in nonpolar solvents, viz. difluorodichloromethane and 1,2‐dibromotetrafluoroethane. The values (k1) obtained in the liquid phaseare two to four orders lower than those in the gas phase, while the activation energy is 2–6 kJ/mol

ISSN:0538-8066    

DOI:10.1002/kin.550171209

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe rates of oxidation of four α‐keto acids, glyoxylic, pyruvic, phenylglyoxylic, and 2‐oxobutyric acids by Cerium(IV) in H2SO4HaHSO4and H2SO4HClO4solutions, have been studied spectrophotometrically. The rate data suggest that CeSO 42+is the most reactive of the Cerium(IV)‐sulfate complexes present in the H2SO4NaHSO4and H2SO4HClO4systems. The oxidation reaction is proposed to be a one‐electron process with the rate‐determining step being the decomposition of a α‐ketoacid‐Cerium(IV) complex to a free radical and carbon dioxide t

ISSN:0538-8066    

DOI:10.1002/kin.550171210

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe variational method of sensitivity analysis is applied to a recent chemical kinetic mechanism for photochemical smog. It is demonstrated that the variational method is capable of readily handling a large mechanism. The analysis can be applied to a single chemical species or to an arbitrarily large group of species contained in an objective function. Examples of the use of different objective functions are given. The variational method provides temporally distributed sensitivity coefficients. Therefore, the results are presented as a time‐dependent ranking of reactions in orderof decreasing importance with respect to the objective function species. This ranking permits the time‐dependent relative influence of each reaction to be readily determined by inspection. Particular attention is paid to reactions governing daytime O3formation and nighttime NO3and HONO format

ISSN:0538-8066    

DOI:10.1002/kin.550171211

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY