摘要:

AbstractThe kinetics of dissociation oftris‐2,2′‐bipyridyl‐iron(II) complex ion have been examined in aqueous acetic acid solutions. The reaction is first order in the complex ion; the dependence of rate on H+is somewhat like that observed in aqueous solutions approaching a limiting value at higher H+concentrations. The influence of solvent composition on the reaction rate under acid‐dependent and acid‐independent conditions shows an initial retardation by acetic acid. The argument of ion‐pair formation based on decrease of dielectric constant proposed to explain the kinetics in other aqueous solvent media was found useless to explain the behavior in acetic acid solutions. Other solvent parameters also did not provide satisfactory correlation with the kinetic results, thus, indicating the operation of more complex microscopic solute‐solvent and solvent‐solvent interactions. While solvent effects play some part in the rate process, the rate of reaction would tend to zero in the absence of H2O and H+. This interesting observation proved useful in proposing a reaction mechanism that is consistent with the rate behavior over the entire range of solvent composition. The activity of water in the reaction medium is controlled by the content of acetic acid which can effect the structure of water through operation of hydrophobic forces and formation of hydrates. While acetic acid cannot possibly fulfill the role of water in occupying the vacated coordination position, the anomalous rise in rate even under some water deficient conditions seems to be related to the coordinating ability of HSO4−derived from H2SO4pres

ISSN:0538-8066    

DOI:10.1002/kin.550241102

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of tetrahydrofurfuryl alcohol by dihydroxydiperiodatonickelate (IV) complex in the temperature range of 20–35°C has been studied by spectrophotometry in aqueous alkaline medium. The reaction order in [Ni(IV)] was found to be unity and that in [alcohol]to be 1.64–1.69. The rate of oxidation increases with increase in [OH−] and decreases with increase in [IO4−], indicating that dihydroxymonoperiodatonickelate (IV) complex is the reactive species of oxidant. Salt effect studies indicated that the reaction is of ion‐dipole type. Under the protection of nitrogen the reaction system does not induce polymerization of acrylonitrile or acrylamide, which indicates that a one‐step two‐electron transfer mechanism without free radical intermediate may be in operation. A mechanism involving a preequilibrium of an adduct formation between Ni(IV) and alcohol has been proposed. All the experimental phenomena can be explained by the equation derived from the mechanism. The activation parameters of the rate‐determining step have been calculated. © Joh

ISSN:0538-8066    

DOI:10.1002/kin.550241103

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe products of the reaction of OH with CH3SSCH3(DMDS) were investigated at 298 K using a flow tube reactor coupled to a photoionization mass spectrometer and a pulsed photolysis‐pulsed laser induced fluorescence apparatus. The results from the former apparatus were semi‐quantitative and showed that CH3S and CH3SOH are produced in the title reaction. The latter apparatus was used to quantify the yield of CH3S in the title reaction. The measured yield was 0.28 ± 0.20, independent of pressure and buffer gas, suggesting that products other than CH3S and CH3SOH are also important in this reaction. The quoted uncertainty is at the 95% confidence level and includes estimated systematic errors. © John Wiley&Sons

ISSN:0538-8066    

DOI:10.1002/kin.550241104

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of ethylS‐phenylmercapto acetate and several para‐, meta‐, and ortho‐substituted ethylS‐phenylmercaptoacetates by chloramine‐B have been studied in 50% (V/V) aqueous ethanol medium containing phosphate buffer. This oxidation is of first order with respect to substrate and zero order with respect to oxidant. A catalytic effect of mercury is observed and the order with respect to mercury is fractional (0.74). The increase in pH decreases the rate of oxidation and the order with respect to H+is 0.05. In general electron‐releasing substituents accelerate the rate while electron‐attracting groups retard the rate. A good correlation is found to exist between logk1and Hammett constants. Susceptibility of the reaction to the steric effect of ortho‐substituents has been analyzed in the light of application of Taft's steric energy parameters. © Jo

ISSN:0538-8066    

DOI:10.1002/kin.550241105

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of Aspartic acid by bismuth(V) studied in HClO4‐HF mixture iodometrically exhibit complex dependence with respect to aspartic acid (AA). The rate law (i) accounts for all the experimental observations.where [Bi(V)] and [AA]are the gross analytical concentration of all fluorobismuth(V) species and the equilibrium concentration of aspartic acid, respectively. The oxidation product of the amino acid was identified to be an aldehyde. HF and F−do not affect the rate of the reaction. © John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550241106

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe rate constants for the reaction H + HBr → H2+ Br were measured between 217 and 383 K using pulsed laser photolysis of HBr and cw resonance fluorescence detection of H(2S). The temporal profiles of the product Br atoms were also monitored to obtain the rate constant at 298 K. The yield of Br from the reaction was determined to be unity. The rate coefficient as a function of temperature is given by the Arrhenius expression,k1= (2.96 ± 0.44) × 10−11exp(−(460 ± 40)/T) cm3molecule−1s−1. The quoted errors are at the 95% confidence level and include estimated systematic errors. Our results are compared with those from previous direct measurements. © John Wi

ISSN:0538-8066    

DOI:10.1002/kin.550241107

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractUsing a relative rate method, rate constants for the gas‐phase reactions of the OH radical withtrans‐pinane [(1R, 2R)‐2, 6, 6‐trimethylbicyclo[3.1.1]heptane], tricyclene (1, 7, 7‐trimethyltricyclo[2.2.1.02, 6]heptane), and quadricyclane (quadricyclo[2.2.1.02, 6.03, 5]heptane) of (1.34 ± 0.29) × 10−11cm3molecule−1s−1, (2.86 ± 0.62) × 10−12cm3molecule−1s−1and (1.83 ± 0.41) × 10−12cm3molecule−1s−1, respectively, have been determined at 296 ± 2 K. These rate constants are compared with values calculated from an empirical estimation method and used to refine this estimation technique for the calculation of OH radical reaction rate constants for polycycl

ISSN:0538-8066    

DOI:10.1002/kin.550241108

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics of the disproportionation of N  Cl‐n‐propylamine and N – Cl‐isopropylamine to the correspondingN, N‐dichloramines were found to be a second order with respect to theN‐chloramine. The influence of amine concentration, pH, buffers, ionic strength, and temperature were also studied. The observed influence of pH supports a reaction mechanism which allowed estimation of the protonation constants of the chloramines studied. The influence of buffers, which was studied for both the above chloramines and N  Cl‐3‐aminopropanol, reflects general acid catalysis, for which a mechanism is proposed. Bronsted's equation was fitted to the catalytic constants obtained therefrom so as to estimate the values of the parameter α for these threeN‐chloramines.

ISSN:0538-8066    

DOI:10.1002/kin.550241109

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA detailed kinetic study of the reaction of toluidine blue (tolonium chloride) (TB+Cl−) with thiourea (TU) in aqueous hydrochloric acid solution is reported. The reaction was first order with respect to toluidine blue and the reductant and second order with respect to [H+]. Thiourea had a 2:1 stoichiometric ratio with TB+. Toluidine blue was reduced to a colorless base in two one‐electron reduction steps and TU was oxidized to thioformamidinium ion, which dimerized rapidly to give stable dithioformamidinium ion. The energy parameters obtained for TB+‐TU reaction were mean energy of activation (Ea′) = 26.7 ± 2.4 kJ M−1; enthalpy of activation (ΔH#) = 24.2 kJ M−1; frequency factor (A) = 1.04 × 104M−3s−1; and entropy of activation (ΔS#) = −176.35 J M−1s−

ISSN:0538-8066    

DOI:10.1002/kin.550241110

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe ultraviolet absorption spectrum and the self reaction kinetics of CF3O2radicals have been studied in the gas phase at 298 K using the pulse radiolysis technique. Long pathlength Fourier transform infrared (FTIR) spectroscopy was used to identify and quantify reaction products. Absorption cross sections were quantified over the wavelength range 215–270 nm. The measured cross section at 230 nm was;\documentclass{article}\pagestyle{empty}\begin{document}$$ \sigma_{{\rm CF3O2}} (230\,{\rm nm) = (2}{\rm .06} \pm {\rm 0}{\rm .40)}\times {\rm 10}^{{\rm - 18}} {\rm cm}^{\rm 2}\, {\rm molecule}^{{\rm -1}} $$\end{document}Errors represent statistical (2σ) together with our estimate of potential systematic errors. The absorption cross section data were then used to derive the observed self reaction rate constant for reaction (1), defined as −d[CF3O2]/dt= 2kobs[CF3O2]2klobs= (3.6 ± 0.9) × 10−12cm3molecule−1s−1. The only carbon containing product observed by FTIR spectroscopy was CF3OOOCF3. Consideration of the loss of CF3O2radicals to form the trioxide CF3OOOCF3allows derivation of the true bimolecular rate constant for reaction (1);k1= (1.8 ± 0.5) × 10−12cm3molecule−1s−1. These results are discussed with respect to previous studies of the absorption spectra of peroxy radicals, the kinetics, and mechanisms of their self reaction. ©

ISSN:0538-8066    

DOI:10.1002/kin.550241111

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY