摘要:

AbstractThe oxidation of Fe(bpy)22+by peroxodisulphate (bpy = 2,2′‐bipyridine) has been studied in a variety of sodiumbis(2‐ethylhexyl)sulfosuccinate(aerosol‐OT or AOT)‐oil‐water microemulsions by changing the nature of the oil phase, the surfactant concentration, and the molar ratiow= [H2O]/[AOT]. Kinetic results show that the influence of surfactant concentration is due to a dilution effect. On the other hand, the comparison between the reaction rate in conventional aqueous solution with that in AOTw/omicroemulsions seems to indicate that the iron(II) species is distributed between the aqueous phase and the interphase. © 1995 John Wil

ISSN:0538-8066    

DOI:10.1002/kin.550270602

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe rate constants for the reaction of electron pulse produced solvated electrons and a number of solutes in water‐isopropanol mixtures have been measured. The quenching of the singlet excited state of naphthalene has also been studied in the same mixtures, using triethylamine and acrylamide as quenchers. The variation of the bimolecular solvated electron reaction rate constants with the composition of the solvent has been compared with the variation in the quenching constants with the composition of the solvent. Both these variations are surprisingly similar, with acrylamide behaving in a reverse manner (to the other solutes) in both the cases. It has been possible to quantitatively correlate both sets of data using dielectric constant (ϵ) as a measure of polarity and the viscosity (η) as an index of the microstructure. The curves obtained provide insights with respect to the nature of charge transfer processes involved. © 1995 John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550270603

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAtomic resonance absorption spectroscopy (ARAS) was applied to measure S atoms, behind shock waves in COS/H2pyrolysis or CS2/H2photolysis systems. Both the pyrolysis of COS and the photolysis CS2was used to generate the S atoms, which subsequently reacts with H2via the reaction:The photolysis experiments were designed to provide clear first‐order conditions for reaction (R3); i.e., the H2concentration exceeds that of S by at least a factor of 100. The S atom profiles obtained during pyrolysis of highly diluted COS/H2/Ar mixtures were analyzed by computer simulations based on a simplified reaction mechanism using the rate coefficientk3as a fitting parameter. Both groups of experiments covered the temperature range of 1257 K ⩽T⩽ 3137 K and lead to a rate coefficient of:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 \,\, = \,\,6.0 \times 10^{14} \,{\rm exp}\left({ - 12070{{\rm K} \mathord{\left/ {\vphantom {{\rm K} T}} \right. \kern-\nulldelimiterspace} T}} \right){\rm cm}^{\rm 3} \,{\rm mol}^{ - 1} \,{\rm s}^{ - 1} $$\end{document}. © 1995 John Wiley&Son

ISSN:0538-8066    

DOI:10.1002/kin.550270604

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of some monosaccharides viz., D‐ribose, D‐xylose, and D‐arabinose, D‐glucose, D‐fructose, D‐galactose, 2‐deoxyglucose, and α‐methyl glucopyranoside by MnO42−in aqueous alkaline medium have been studied. The rate of oxidation has been found to be first‐order both with respect to [oxidant] and [sugar]. The rate is independent of [OH−] under experimental conditions of [OH−]>0.5 M where the oxidant is stable. The effect of ionic strength is negligible on the rate. A mechanism involving the formation of a 5‐membered cyclic intermediate complex between MnO42−and 1,2‐enediol form of the sugar is proposed. The intermediate complex decomposes to give products in the subsequent slow step. The involvement of 1,2‐enediol form receives support from the reaction of α‐methyl glucopyranoside, which exists in ring structure in alkaline solution reacting much slower than glucose with MnO42−under similar conditions. Second‐order rate constantk″ and activation parameters have been evaluated. The series of reactions exhibits a clear demonstration of applicability of isokinetic phenomenon where Arrhenius plots for all the reactions are found to intersect at a common p

ISSN:0538-8066    

DOI:10.1002/kin.550270605

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe oscillatory reaction between potassium bromate and gallic acid in sulfuric acid medium has been studied calorimetrically with and without ferroin indicator. Enthalpy changes during oscillations have increased with increasing bromate concentration in presence and absence of the indicator. Prominent catalytic activity of the indicator has been observed. An initial large enthalpy change has been observed in both uncatalyzed and catalyzed conditions prior to the starting of oscillation. Attempts have been made to correlate the main thermal events with the proposed mechanism of the reaction. © 1995 John Wiley&Sons, Inc

ISSN:0538-8066    

DOI:10.1002/kin.550270606

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractKinetic study on the dissolution of CO2from the surface of a liquid CO2droplet in water was conducted, and a mechanism of the decay of CO2hydrate was proposed. The model was applied to the experimental data which showed that the radius of liquid CO2droplets in water reduced linearly with time. It was proved that the dissolution rate of CO2into water is dominated by the decay of CO2hydrate on the surface of the droplet. The rate constant of the decay of CO2hydrate was estimated to be 1.25 × 10−6m s−1. From a viewpoint of liquid CO2disposal in the deep ocean, it is predicted that the thin membrane of CO2hydrate at the interface between seawater and liquid CO2will control the dissolution of CO2into seawater. © 1995 John Wiley&Sons

ISSN:0538-8066    

DOI:10.1002/kin.550270607

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractIn an extension of our earlier studies at lower temperatures [4,5] the title reaction was measured directly in a flow reactor at temperatures of 600 and 700 K. The pressure of 0.65 mb was chosen that low in order to reduce the contribution of the stabilization channel. OH was used in an excess over CH3. Both reactants along with the reaction products were monitored by mass spectrometry. CH3profiles served as the major observable quantity for the extraction of rate data. This had to be done by using computer simulation since it was impossible to work under pseudo‐first‐order conditions.The obtained total rate coefficients were divided into channel rate coefficients by means of branching ratios as determined by the mass spectrometric measurement of the reaction products. For CH3+ OH, this led to a rate coefficient,k1ainto the stabilization channel, and another one,k1e + freferring to the sum of two H2‐eliminating channels yielding the biradical HCOH and to a minor extent H2CO. These latter channels have not been measured before.In order to distinguish between them we switched over from OH to OD to getso that the biradical and/or aldehyde channels could be determined by their by‐products H2and HD, respectively. The use of OD makes it also possible to measure the channelthrough its by‐product, HDO.A comparison of the rate coefficients of both systems, i.e., CH3+ OH and CH3+ OD, indicates that within our error limits no significant isotope effect takes place.For the rate coefficient into the HCOH channel, we arrive at a preliminary Arrhenius expression in units of cm, molec, and s:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1{\rm e}} \,\, = \,\,9.1 \times 10^{ - 11} \,{\rm exp}\left({{{ - 15000} \mathord{\left/ {\vphantom {{ - 15000} T}} \right. \kern-\nulldelimiterspace} T}} \right) $$\end{document}. The H2CO channel could not be detected at our lower temperature rendering us with a rate coefficient at 700 K:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1{\rm f}} \left({700\,{\rm K}} \right)\,\, = \,\,1.7 \times 10^{ - 12} $$\end{document}. Since simulation is needed for the deduction of the total rate coefficients as well as of the branching ratios, an uncertainty factor of 1.5 has to be attributed to these numbers. © 1995 John Wiley

ISSN:0538-8066    

DOI:10.1002/kin.550270608

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractA dependence of the activation energy upon the extent of conversion has been discovered for the thermal decomposition of Cu4OCl6L4with piperidine (1), morpholine (2), and triphenylphosphine oxide (3) as the ligand (L). Within the interval of conversions 0–0.3 the process shows a decrease in the activation energy (230–130 (1), 130–50 (2), and 200–100 (3) kJ mol−1). The processes considered show an isokinetic relationship withTiso= 255 ± 15 K which corresponds to a vibrational frequency of viso= 177 ± 10 cm−1. This value accords well with IR absorption bands assigned to the stretching vibration in the trigonal CuCl3chromophore as predicted by theory. Based on this, an assumption about the CuCl3‐group as a central site of the reaction can be made. The IR‐ and X‐ray data are presented to support the assumption made. © 1995

ISSN:0538-8066    

DOI:10.1002/kin.550270609

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of the acqueous‐phase reactions of the free radicals ·OH, ·Cl 2−, and SO 4−· with the halogenated acetates, CH2FCOO−, CHF2COO−, CF3COO−, and with CH2ClCOO−, CHCl2COO−, CCl3COO−were investigated. Generally, the reactivity decreases with increasing halogen substitution and is in the orderk(·OH)>k(SO 4−·)>k(·Cl 2−), but there is no general relation between the effect on reactivity of chlorine and fluorine substi

ISSN:0538-8066    

DOI:10.1002/kin.550270610

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractRate constants for the gas‐phase reactions of the Cl atom with a series of alkanes have been determined at 296 ± 2 K using a relative rate method. Using a rate constant for the Cl atom reaction withn‐butane of 1.94 × 10−10cm3molecule−1s−1, the rate constants obtained (in units of 10−11cm3molecule−1s−1) were: 2‐methylpentane, 25.0 ± 0.8; 3‐methylpentane, 24.8 ± 0.6; cyclohexane, 30.8 ± 1.2; cyclohexane‐d12, 25.6 ± 0.8; 2,4‐dimethylpentane, 25.6 ± 1.2; 2,2,3‐trimethylbutane, 17.9 ± 0.7; methylcyclohexane, 34.7 ± 1.2;n‐octane, 40.5 ± 1.2; 2,2,4‐trimethylpentane, 23.1 ± 0.8; 2,2,3,3‐tetramethylbutane, 15.6 ± 0.9;n‐nonane, 42.9 ± 1.2;n‐decane, 48.7 ± 1.8; andcis‐bicyclo[4.4.0]decane, 43.1 ± 0.8, where the indicated errors are two least‐squares standard deviations and do not include the uncertainties in then‐butane rate constant. These data have been combined with rate constants obtained previously for ten C2C7alkanes and this entire data set has been used to develop an estimation method allowing the room temperature rate constants for the reactions of the Cl atom

ISSN:0538-8066    

DOI:10.1002/kin.550270611

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY