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  • 1
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The apparent rate constants of formation (k1) and hydrolysis (k2) of the Schiff bases formed between pyridoxal and polyallylamine has been fitted to a kinetic scheme that involve the different protonated species in the reaction medium and the individual rate constants of formation (k1i) and hydrolysis (k2i). The (k1i) values precludes an acid catalyzed intramolecular process. The effects of hydrophobic medium due to the presence of the macromolecule on the reaction is also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 1-6, 1998.
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  • 2
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 21-29 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase reaction of ozone with a series of unsaturated oxygenates and with 1-pentene has been studied at ambient T (287-296 K) and p=1 atm. of air. Reaction rate constants, in units of 10-18 cm3 molecule-1 s-1, are 0.22±0.05 for 2 (5H)-furanone, 1.08±0.20 for methacrolein, 1.74±0.20 for crotonaldehyde, 5.84±0.39 for methylvinyl ketone, 1.05±0.15 for methyl acrylate, 3.20±0.47 for vinyl acetate, 59.0±8.7 for cis-3-hexenyl acetate, 154±30 for ethylvinyl ether, ≥(315±23) for linalool, and 10.9±1.4 for 1-pentene. The results are compared to literature data for the compounds studied and for other unsaturated oxygenates, and are discussed in terms of reactivity toward ozone as a function of the nature, number, and position of the oxygen-containing substituents (SINGLEBOND)CHO, (SINGLEBOND)C(O)R, (SINGLEBOND)C(O)OR, and (SINGLEBOND)OC(O)R. Atmospheric implications are briefly examined. © 1998 John Wiley & Sons, Inc. Int. J Chem Kinet: 30: 21-29, 1998.
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  • 3
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 47-54 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new linear regression method is applied to determine the rate constants from time-dependent profiles. The method is effective for obtaining the rate constants of such consecutive processes as vibrational relaxation. The ambiguity of ordinary nonlinear analysis is eliminated by the linearization of regression equations. Because the new method also determines relative detectivity, the nascent vibrational distributions immediately following reactions or photolysis can be obtained simultaneously. In order to demonstrate the reliability of the new method under practical conditions, several examples of analysis of the data with noise are shown in detail. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 47-54, 1998.
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  • 4
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    International Journal of Chemical Kinetics 30 (1998), S. 69-88 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Decomposition studies of trichlorosilane, dichlorosilane, and monochlorosilane at 921 K, 872 K, and 806 K, respectively, are reported. The studies were made at fixed reactant pressures over a range of total pressures in a wall conditioned, quartz reactor connected to a quadrupole mass-spectrometer. Products were monitored sequentially and continuously in time. The dichlorosilane decomposition was also studied by the comparative-rate single-pulse shock-tube method at temperatures around 1250 K. Two mechanisms of decomposition are considered: a silylene based mechanism initiated by molecular elimination reactions (Scheme I), and a free radical based mechanism initiated by bond fission reactions (Scheme V). Modeling tests of these mechanisms show that only the former is consistent with the experimental data. The decompositions are shown to be essentially nonchain processes initiated by the following pressure dependent reactions: HSiCl3(SINGLEBOND)4→ SiCl2+HCl, H2SiCl2(SINGLEBOND)1→ SiCl2+H2 and H3SiCl(SINGLEBOND)5→ HSiCl+H2. High pressure Arrhenius parameters recommended for these reactions are A4,∞=A1,∞=A5,∞=1014.5±0.5 s-1, E4,∞=71.9±2.1 kcal/mol, E1,∞=69.2±2.0 kcal/mol, and E5,∞=60.6±1.8 kcal/mol. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 69-88, 1998.
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  • 5
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    International Journal of Chemical Kinetics 30 (1998), S. 111-120 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The detailed kinetics of the reaction of toluidine blue {phenothiazine-5-ium, 3-amino-7(dimethylamino)-2-methyl chloride, tolonium chloride, TB+Cl-} with potassium bromate and with aqueous bromine reaction were studied. In most of the experiments, the kinetics were monitored by following the rate of consumption of TB+ at 590 nm with excess acid and bromate. The reaction exhibited complex kinetic behavior. Initial reaction was slow and after an induction time, the TB+ concentration decreased fast. It had first-order dependence on both TB+ and bromate, and second-order dependence on H+. Under excess bromate conditions, the stoichiometric ratio of TB+ to bromate was 1:1. Demethylated sulfoxides were found at the reaction products. Sharp increase in the overall potential synchronized with the increase in bromine levels and the fast depletion of [TB+]. The role of bromide ion and bromine in the reaction was established. A multi-step reaction mechanism is proposed consistent with the experimental results. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 111-120, 1998.
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  • 6
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    International Journal of Chemical Kinetics 30 (1998), S. 137-143 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of tert-amyl methyl ether (TAME) from methanol (MeOH) and tert-amyl alcohol (TAA) in the liquid phase was studied by using an ion exchange resin, Amberlyst15 (A15) in the H+ form. Experiments were carried out in a stirred batch reactor under atmospheric pressure. The effects of catalyst size, agitation speed, temperatures, feed ratio and water on the reaction rate were investigated. Both of intraparticle and external diffusion effects could be neglected in this system. The dehydration of TAA could be decreased by increasing the ratio of MeOH/TAA and the reaction rates were greatly inhibited by water.A kinetic model which considered the inhibition of water was proposed. The experimental results agreed well with the model. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 137-143, 1998.
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  • 7
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    International Journal of Chemical Kinetics 30 (1998), S. 171-177 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A high-pressure, high-temperature reactor unit was developed to test batch-wise inter-conversions of hydrocarbons. A major ambiguity characterizes this reactor, as it does all similar units that have been described, determination of the time-temperature profile for the reacting mixture. Here we report on a solution to this problem - use of a “chemical thermometer,” based on the kinetics of dissociation of C4F8. We propose a revised set of rate constants that permit calibration of the reactor operation. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 171-177, 1998.
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  • 8
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of proton transfer between poly(A - AH) (partially protonated double-stranded polyadenylic acid) and CPR (chlorophenol red), and between poly(C - H - C) (partially protonated double-stranded polycytidylic acid) and the indicators CPR, BCP (bromocresol purple), and BCG (bromocresol green) have been investigated at 25°C and ionic strength 0.1 M (NaClO4) by the temperature-jump method. The acidic proton of poly(C - H - C) is engaged in a hydrogen bond (N3H+----N3) which is believed to contribute to stabilizing the double-strand conformation, whereas the acidic proton of poly(A - A - H) does not form hydrogen bonds. The analysis of the dependence of the relaxation times on the concentrations of the reactants has enabled the evaluation of the rate constants for the direct proton transfer and for the protolysis paths. The rate constants for proton recombination with the deprotonated forms of the polynucleotides and the indicators are of the order of magnitude expected for diffusion controlled processes involving oppositely charged ions (k2=(0.2-1.6)×1010 M-1s-1). The direct proton transfer from poly(C - H - C) to BCG is thermodynamically disfavored and its rate constant, k1, is lower than k2 by about three orders of magnitude. The (thermodynamically favored) proton transfers from poly(A - A - H) to CPR and from poly(C - H - C) to CPR and BCP are characterized by similar values of k1. This result indicates that the hydrogen bonds in poly(C - H - C) are very weak and suggests that the stabilization of the double-stranded conformation of this polynucleotide could be ascribed to the large number of hydrogen bonds rather than to their specific strength. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 161-169, 1998.
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  • 9
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    International Journal of Chemical Kinetics 30 (1998), S. 207-214 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Manganese(II) is oxidized by ozone in acid solution, k=(1.5±0.2)×103 M-1 s-1 in HClO4 and k=(1.8±0.2)×103M-1 s-1 in H2SO4. The plausible mechanism is an oxygen atom transfer from O3 to Mn2+ producing the manganyl ion MnO2+, which subsequently reacts rapidly with Mn2+ to form Mn(III). No free OH radicals are involved in the mechanism. The spectrum of Mn(III) was obtained in the wave length range 200-310 nm. The activation energy for the initial reaction is 39.5 kJ/mol. Manganese(III) is reduced by hydrogen peroxide to Mn(II) with k(Mn(III)+H2O2)=2.8×103M-1 s-1 at pH 0-2. The mechanism of the reaction involving formation of the manganese(II)-superoxide complex and reaction of H2O2 with Mn(IV) species formed due to reversible disproportionation of Mn(III), is suggested. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 207-214, 1998.
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  • 10
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    International Journal of Chemical Kinetics 30 (1998), S. 273-276 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic micelles of cetyltrimethylammonium bromide, CTABr, speed attack of hydroxide ion upon coumarin by a factor of c.a-2, due to a concentration effect. The first-order rate constants, kobs, at a given hydroxide ions concentration go through maxima with increasing surfactant concentration. The overall micellar effects in these cationic micelles can be treated in terms of the pseudo-phase ion exchange model. Analysis of the data shows that second-order rate constant at the micellar surface is smaller than the second-order rate constant in water. Anionic micelles of sodium dodecyi sulfate, SDS, inhibit the same reaction. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 273-276, 1998.
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  • 11
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    International Journal of Chemical Kinetics 30 (1998), S. 285-290 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of oxidation of four vicinal diols, four nonvicinal diols, and one of their monoethers by pyridinium bromochromate (PBC) have been studied in dimethyl sulfoxide. The main product of oxidation is the corresponding hydroxyaldehyde. The reaction is first-order with respect to each the diol and PBC. The reaction is acid-catalyzed and the acid dependence has the form: kobs=a+b[H+]. The oxidation of [1,1,2,2-2H4]ethanediol exhibited a primary kinetic isotope effect (kH/k D=6.70 at 298 K). The reaction has been studied in 19 organic solvents including dimethyl sulfoxide and the solvent effect has been analyzed using multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 285-290, 1998.
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  • 12
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    International Journal of Chemical Kinetics 30 (1998), S. 291-300 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oscillatory behavior of a [Fe(phen)3]2+-catalyzed/bromomalonic acid/acidic bromate Belousov-Zhabotinsky system in aerated batch conditions has been reinvestigated. An 18-step skeleton mechanism is proposed. Reactions involving oxygen in the aqueous phase as well as reactions involving organic radicals are included in the skeleton mechanism. The numerical treatment of the corresponding differential equations leads to simulated behaviors in satisfactory agreement with the experimental ones. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 291-300, 1998.
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  • 13
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    International Journal of Chemical Kinetics 30 (1998), S. 309-310 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 14
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    International Journal of Chemical Kinetics 30 (1998), S. 329-333 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficients for the reactions CHFO+F, CFO+F and the self-reaction of CFO were determined over the temperature range of 222-298 K. A computer controlled discharge-flow system with mass spectrometric detection was used. The results are expressed in the Arrhenius form (with energies in J):CHFO+F→CFO+HF:k1(T)=(9.7±0.7)·10-12 exp[-(5940±150)/RT] cm3 molecule-1 s-1CFO+F+M→CF2O+M:FORMULA DISC=“MATH”〉k2(T)=(2.60±1.17)·10-10 exp[-(10110±1250)/RT cm3 molecule-1 s-1FORMULACFO+CFO→CF2O+CO:k3(T)=(3.77±2.7)·10-10 exp[-(8350±2800)/RT] cm3 molecule-1 s-1© 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 329-333, 1998
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  • 15
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    International Journal of Chemical Kinetics 30 (1998), S. 349-358 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Models that simulate atmospheric photochemistry require the use of a stiff ordinary differential equations (ODEs) solver. Since the simulation of the chemical transformations taking place in the system takes up to 80 percent of the CPU time, the numerical solver must be computationally fast. Also, the residual error from the solver must be small. Because most accurate solvers are relatively slow, modelers continue to search for timely, yet accurate integration methods. Over the past years an extensive number of articles have been dedicated to this subject. One of the highly debated questions is whether one should construct specialized algorithms or instead use general methods for stiff ODEs. In the present article we use the second alternative. We apply three linearly (semi-)implicit methods from the classical stiff ODE literature which we modified to implement the sparse routines to solve the system of equations describing a complex kinetic mechanism. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 349-358, 1998
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  • 16
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vacuum line kinetic studies of the reaction of p-toluenesulfonyl chloride and benzene or toluene, using aluminum chloride as the catalyst and dichloromethane as the solvent were determined at 25°C by means of gas chromatography. The reaction is first-order in arene, tosyl chloride, and in AlCl3 as catalyst. Noncompetitive results are kT/kB=22±7 with a product sulfone isomer distribution: ortho, 14±1%; meta, 4.3±0.2%; and para 82±1%. With hexadeuteriobenzene kH/kD was determined to be 1.8±0.1. Rate constant ratios and product isomer distributions were also determined competitively: with AlCl3, kT/kB=30±2; % ortho, 13±1; % meta, 4.0±0.5; % para, 84±3; with SbCl5, kT/kB=40±4; % ortho 10.3±0.4; % meta, 4.7±0.2; and % para, 85.0±0.5. The kT/kB ratio for AlCl3 and the meta sulfone product percentages for both AlCl3 and SbCl5 are considerably higher than those reported in the literature. NMR and Raman studies suggest a molecular complex between p-tosyl chloride and AlCl3, with coordination through oxygen as the dominant species and the probable electrophile in CH2Cl2. A reaction mechanism consistent with the kinetic and spectroscopic results is proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 367-372,1998
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  • 17
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    International Journal of Chemical Kinetics 30 (1998), S. 385-406 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The investigation of high-pressure autoignition of combustible mixtures is of importance in providing both practical information in the design of combustion systems and fundamental measurements to verify and develop chemical kinetic models. The autoignition characteristics of hydrogen-oxygen mixtures at low pressures have been explored extensively, whereas few measurements have been made at high pressures. The present measurements extend the range of pressures up to 4 MPa, where few measurements have yet been reported.Using a rapid compression machine equipped with a specially designed piston head, hydrogen autoignition pressure traces were measured at pressures above the second explosion limit (p=0.6-4 MPa, T=950-1050 K). The measured pressure records show a more gradual pressure increase during induction time in this regime than in the low-pressure regime, indicating that the energy release becomes significant at conditions over the second explosion limit.By comparing the measurements and a thermodynamic model which incorporates the heat transfer and energy release, a modified reaction rate constant for H2O2+H=HO2+H2, one of the most important reactions for hydrogen oxidation at high pressure, and the reaction with the largest uncertainty, is suggested in this work as k17=2.3 . 1013exp(-4000/T) cm3/mol-s. The modeled pressure history with the modified reaction rate agrees well with the measured values during the induction period over the range of conditions tested. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 385-406, 1998
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  • 18
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    International Journal of Chemical Kinetics 30 (1998), S. 419-423 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aminolysis reactions of O-ethyl S-(Z-phenyl) dithiocarbonates (Z=p-CH3, H, p-Cl, and p-NO2) with anilines (AN) and N,N-dimethylanilines (DMA) in acetonitrile at 30.0°C are investigated. Relatively small values of βX (βnuc,0.4 ca. 0.7) and βZ (βlg -0.1 ca. -0.4) for both ANs and DMAs, significantly large kH/kD values (1.1 ca. 1.9) involving deuterated anilines, and large negative ρXZ values for ANs (-0.56) are interpreted to indicate a concerted mechanism for both ANs and DMAs but with a hydrogen bonded four-center type transition state (TS) for ANs. The relative leaving ability, k(Z=p-NO2)/k(Z=p-CH3), is smaller for ANs than for DMAs, especially for a weaker nucleophile (1.9 and 4.7 for AN and DMA, respectively, with X=p-Cl). This suggests that the rate enhancement by the hydrogen-bond formation in the four-center type TS for AN is greater for a weaker nucleofuge (Z=p-CH3), especially when the nucleophile (X=p-Cl) is weaker. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 419-423,1998
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  • 19
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    International Journal of Chemical Kinetics 30 (1998), S. 425-437 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isobutane pyrolysis is studied in an unpacked Pyrex reactor at 20-100 torr initial pressures and 750-793 K. Results are interpreted in terms of a long chain radical mechanism and the reaction is modeled. The reaction selectivity or ratio of the initial production rate of isobutene (or hydrogen) to that of propene (or methane) is practically given by the ratio of the rate constant of abstraction of a tertiary hydrogen atom of isobutane to that of a primary one. A sensitivity analysis clearly shows that self-inhibition is essentially due to methylallyl radicals produced by hydrogen abstraction from isobutene. The model has been manually adjusted to experimental results and most of the adjusted rate constants are in agreement with literature data. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 425-437, 1998
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  • 20
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    International Journal of Chemical Kinetics 30 (1998), S. 463-469 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent effects on the kinetics of hydrolysis of isatin by sodium hydroxide have been investigated within the temperature range (30-55°C) in methanol-water and acetonitrile-water media of varying solvent compositions up to 70% (v/v) of the organic solvent component. The thermodynamic activation parameters were calculated and discussed in terms of solvation effects. The determined isokinetic temperatures, in both systems, revealed the existence of compensation effect arising from strong solute-solvent interactions; log k was correlated with both log [H2O] and the reciprocal of the dielectric constant. The first correlation was observed to be linear while the second was nonlinear. Finally a mechanism for the isatin ring opening was proposed, which accounts for the role and the effect of the solvent on the reaction rate. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 463-469, 1998
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  • 21
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    International Journal of Chemical Kinetics 30 (1998), S. 491-496 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photolysis of S2O8= in strong alkaline solutions (pH 〉 13) in the presence of molecular oxygen yields ozonide radical ions, \documentclass{article}\pagestyle{empty}\begin{document}$ \rm{O^{\textstyle{\cdot}-}_{3}} $\end{document}. These radicals show a complex decay rate sensitive to the peroxodisulfate concentration. A reaction mechanism, which includes the reaction of O•- and S2O8= with a rate constant k=(3-6)×106M-1s-1 and accounts for the experimental results is discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 491-496, 1998
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  • 22
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    International Journal of Chemical Kinetics 30 (1998), S. 503-522 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal reaction of propene was examined around 800 K in the presence of less than 20% oxygen. At initial time, the production of H2, CH4, C2H4, C2H6, allene, C3H8, 1,3-butadiene, butenes, 3- and 4-methylcyclopentene, a mixture of 1,4- and 1,5-hexadienes, methylcyclopentane (or dimethylcyclobutane), 4-methylpent-1-ene, and hex-1-ene, was observed along with hydrogen peroxide, CO, and small quantities of ethanal and CO2. Oxygen increases the initial production of hydrogen and of most hydrocarbons and, particularly, that of C6 dienes and of cyclenes. However, the production of allene, methylcyclopentane (or dimethylcyclobutane), and 4-methylpent-1-ene is practically not affected. A kinetic study confirms the mechanism proposed for the thermal reaction of propene. Formation of allene, thus, involves a four-center-unimolecular dehydrogenation of propene, that of 4-methylpent-1-ene is explained by an ene bimolecular reaction while methylcyclopentane (or dimethylcyclobutane) probably arises from a bimolecular process involving a biradical intermediate. Other products arise from a conventional chain radical mechanism.A kinetic scheme is proposed in which chains are primarily initiated by the bimolecular step:C3H6+O2→HO2·+C3H5·which competes with the second-order initiation of propene pyrolysis. Since allene production is not affected by oxygen, it is concluded that allyl radicals are not dehydrogenated by oxygen; but they oxidize in a branching step involving allylperoxyl radicals; r. radicals other than methyl, and allyl are dehydrogenated according to the conventional process:r·+O2→unsaturated+HO2·and account for the production of a large excess of C6 diolefins, methylcyclopentenes, and hydrogen peroxide, when r. stands for C6H11, the allyl adduct. Hydrogen peroxide gives rise to a degenerate branching of chains. Based on the proposed scheme, a modeling of the reaction is shown to account fairly well for the concentration-time profiles. Rate constants of many steps are evaluated and discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 503-522, 1998
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  • 23
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    International Journal of Chemical Kinetics 30 (1998), S. 541-554 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Experiments have been carried out on the oxidation of CF3CFH2 (HFC-134a). Reaction was initiated by continuous photolysis of F2 in the near-ultraviolet. The F atoms produced abstracted a hydrogen atom from CF3CFH2 initiating oxidation in gas mixtures containing O2 and made up to a total pressure of 700 torr with N2. Product yields were measured using Fourier-transform infrared (FTIR) spectroscopy. Experiments were performed with several different partial pressures of O2 present, and at three temperatures; 298, 323, and 357 K. The major products were HC(O)F, CF3C(O)F, and CF3O3CF3, consistent with H atom abstraction by O2 and CC bond scission being the dominant loss processes for CF3CFHO radicals:\documentclass{article}\pagestyle{empty}\begin{document}$ CF3CFHO+O2 \rightarrow CF3C(O)F+HO2 (4a) $\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$ CF3CFHO+M \rightarrow CF3+HC(O)F+M (4b) $\end{document}The following expression was derived for the ratio of rate constants for these reactions:k4a/k4b=(3.8±1.6)×10-24 exp[(2400±500)/T]cm3 molecule-1 (viii)The main fate of the CF3 radicals was formation of CF3O3CF3 and small amounts of CF3OH were detected. The results of the present experiments in which F atoms were used to initiate reaction are in good agreement with those of previous studies in which Cl atoms were employed to initiate the oxidation of HFC-134a. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 541-554, 1998
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  • 24
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    International Journal of Chemical Kinetics 30 (1998), S. 683-697 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An experimental and theoretical study of the pyrolysis and oxidation of parabenzoquinone has been performed. The experiments were conducted in an isothermal quartz flow reactor at atmospheric pressure in the temperature range 600-1500 K. The main variables considered are temperature, oxygen concentration, and presence of CO. A detailed reaction mechanism for the pyrolysis and oxidation chemistry of parabenzoquinone is proposed, which provides a good description of the experimental results. Both the experimental work and the kinetic mechanism proposed for the pyrolysis and oxidation of parabenzoquinone represent the first systematic study carried out for this important aromatic compound.Our pyrolysis results confirm that the primary dissociation channel for p-benzoquinone leads to CO and a C5H4O isomer, presumably cyclopentadienone. However, significant formation of CO2 during the pyrolysis may indicate the existence of a secondary dissociation channel leading to CO2 and a C5H4 isomer. Under oxidizing conditions, consumption of p-benzoquinone occurs mainly by dissociation at lower temperatures. As the temperature increases interaction of OC6H4O with the radical pool becomes more significant, occurring primarily through hydrogen abstraction reactions followed by ring opening reactions of the OC6H3O radical. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 683-697, 1998
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  • 25
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    International Journal of Chemical Kinetics 30 (1998), S. 711-719 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photochemistry of IrCl62- complex in simple alcohols have been studied using laser-flash photolysis. Single electron transfer from the solvent molecule to the light-excited complex has been shown to be the primary photochemical process. Quantum yields of the photoreduction of IrCl62- complex and the rate constants of its reaction with hydroxyalkyl radicals were determined at 200-330 K. Deviations of the rate constants from Debye-Smoluchowski equation for diffusion-controlled reactions are discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 711-719, 1998
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  • 26
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    International Journal of Chemical Kinetics 30 (1998), S. 737-744 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of the mass transfer phenomena on the thermal decomposition of calcium carbonate powders under vacuum was investigated through a detailed kinetic analysis by the constant transformation rate thermal analysis (CRTA). Reliable kinetic curves, free from the mass transfer problems, can be obtained by CRTA under vacuum, but within a restricted range of small sample sizes, 〈10 mg. The influence of mass transfer phenomena on the apparent kinetic parameters is discussed in relation to the distribution of fractional reaction α of the individual particles in a sample assemblage. Only when the distribution of α is maintained constant among a series of experimental kinetic curves, can a reliable activation energy, E, be obtained by one of the isoconversion methods. In this respect, a single cyclic CRTA permits the α distribution to be maintained constant between the two adjacent data points with different decomposition rates. In the present study, an apparent E value of about 223 kJ mol-1 was obtained by the Friedman method from a series of CRTA curves with sample sizes less than 10 mg and by the rate jump method from a single cyclic CRTA curve with sample size of about 40 mg. The first-order (F1) law was determined to be the most appropriate kinetic model function, from a series of CRTA curves, instead of the ideal contracting geometry (R3) law formalized for the three-dimensional shrinkage of the reaction interface in the respective particles. The particle size distribution of the sample particles is suggested to be one possible reason for the apparent agreement with the F1 law. A kinetic exponent n of the nth-order law that deviated from unity was obtained from the CRTA curves with sample sizes larger than 10 mg, due to an additional distribution of α produced by mass transfer phenomena. Because the α distribution due to the mass and heat transfer phenomena cannot be expressed practically in an analytical function, a meaningful kinetic model and preexponential factor are difficult to estimate from kinetic data that are influenced by the transfer phenomena. © 1998 John Wiley & Sons, Inc. Int. J Chem Kinet: 30: 737-744, 1998
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  • 27
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    International Journal of Chemical Kinetics 30 (1998), S. 769-776 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants for the reaction of ozone with methylvinyl ketone (H2C(DOUBLEBOND)CHC(O)CH3), methacrolein (H2C(DOUBLEBOND)C(CH3)CHO), methacrylic acid (H2C(DOUBLEBOND)C(CH3)C(O)OH), and acrylic acid (H2C(DOUBLEBOND)CHC(O)OH) were measured at room temperature (296±2 K) in the presence of a sufficient amount of cyclohexane to scavenge OH-radicals. Results from pseudo-first-order experiments in the presence of excess ozone were found not to be consistent with relative rate measurements. It appeared that the formation of the so-called Criegee-intermediates leads to an enhanced decrease in the concentration of the two organic acids investigated. It is shown that the presence of formic acid, which is known to react efficiently with Criegee-intermediates, diminishes the observed removal rate of the organic acids. The rate constant for the reaction of ozone with the unsaturated carbonyl compounds methylvinyl ketone and methacrolein was found not to be influenced by the addition of formic acid. Rate constants for the reaction of ozone determined in the presence of excess formic acid are (in cm3 molecule-1 s-1): methylvinyl ketone (5.4±0.6)×10-18; methacrolein (1.3±0.14)×10-18; methacrylic acid (4.1±0.4)×10-18; and acrylic acid (0.65±0.13)×10-18. Results are found to be consistent with the Criegee mechanism of the gas-phase ozonolysis. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 769-776, 1998
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  • 28
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    International Journal of Chemical Kinetics 30 (1998), S. 785-797 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reduction of iodine by hydroxylamine within the [H+] range 3×10-1-3×10-4 mol.L-1 was first studied until completion of the reaction. In most cases, the concentration of iodine decreased monotonically. However, within a narrow range of reagent concentrations ([NH3OH+]0/[I2]0 ratio below 15, [H+] around 0.1 mol.L-1, and ionic strength around 0.1 mol.L-1), the [I2] and [I3-] vs. time curves showed 2 and 3 extrema, respectively. This peculiar phenomenon is discussed using a 4 reaction scheme (I2+I-⇔I3-, 2 I2+NH3OH++H2O→HNO2+4 I-+5 H+, NH3OH++HNO2→N2O+2 H2O+H+, and 2 HNO2+2 I-+2 H+→2 NO+I2+2 H2O). In a flow reactor, sustained oscillations in redox potential were recorded with an extremely long period (around 24 h).The kinetics of the reaction was then investigated in the starting conditions. The proposed rate equation points out a reinforcement of the inhibition by hydrogen ions when [H+] is above 4×10-2 mol.L-1 at 25°C. A mechanism based on ion-transfer reactions is postulated. It involves both NH2OH and NH3OH+ as the reducing reactive species. The additional rate suppression by H+ at low pH would be connected to the existence of H2OI+ in the reactive medium. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 785-797, 1998
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  • 29
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetic studies of the oxidation of the bis[1-hydroxy-2-(salicylideneamino)ethane]manganese(II) complex by hydrogen peroxide in acetonitrile solutions, at (30.0±0.2)°C, are described. A first-order dependence on the total manganese and the peroxide concentrations was verified, leading to the rapid formation of a Mn(III) intermediate, monitored by stopped-flow measurements, at 394 nm, with a rate constant kf=(1.15±0.03)×105 mol-1 dm3 s-1. The participation of hydroxyl radicals in the process was detected by spin-trapping EPR spectra. The final product was monitored both by EPR spectra, and spectrophotometrically by the slow decay of the intermediary Mn(III) species, with a rate constant kd=(2.60±0.09) s-1. It was identified as the corresponding mononuclear Mn(IV) complex, and characterized by different spectroscopic techniques. Comparative results of the reactivity of the starting complex versus molecular oxygen, leading to the same final product, were also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 889-897, 1998
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  • 30
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    International Journal of Chemical Kinetics 30 (1998), S. 903-912 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diffuse Interface Model (DIM) is introduced to describe the mechanism of high-temperature corrosion/internal oxidation. The zone has dissolved oxygen and metal atoms diffuse and react resulting in the inward movement of zone. The high-temperature oxidation data for cobalt, iron, and nickel, which are for metal deficit (p-type), have been analyzed using a nonlinear optimization method to obtain the optimal values for different parameters, diffusivity of metal atoms in metal oxide, diffiusivity of gaseous species in the corrosion product, diffusivity of oxidant in the unreacted solid (metal or alloy), the rate constant for the reaction and the fraction of the zone reacted. The expression for diffusivity in the reaction zone has been modified by relating diffusivities of the product layer and the core as function of fraction of zone reacted. The model was applied to the experimental data for the high-temperature oxidation of cobalt, iron, and nickel by pure oxygen at an atmospheric pressure. The model predicts the values of diffusion coefficients, preexponential factors, and activation energies for diffusion process, which are generally compared favorably with those reported in the literature. Linear relationship are derived relating the diffusion coefficient in the core and product layer to the parabolic rate constant which is valid for iron, cobalt, and nickel for high-temperature oxidation (900-1350°C) by oxygen at an atmospheric pressure according to the following equations:\scriptfont4=\seveni \scriptscriptfont4=\fivei $$D_{\rm P}=1.4\times 10^{-8}\ \it k_{g}$$ $$D_{\rm C}=6.9\times 10^{-9}\ \it k_{g}$$The results of the model have been successfully used to predict the experimentally determined parabolic rate constants for the oxidation of cobalt at high temperatures for two different investigators [6,7] under similar conditions. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 903-912, 1998
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  • 31
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    International Journal of Chemical Kinetics 30 (1998), S. 923-932 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 1-butanethiol with hydrogen atoms was investigated at room temperature under pressures of 133, 266, 532, 2660, and 5320 Pa, using two types of fast-flow discharge reactors; the main products were n-butane and 1-butene with total yields of more than 90%. In the reaction of 1-butanethiol and deuterium atoms, monodeuterated 1-butanethiol was observed by a photo-ionizing mass spectrometer. The relative rate of the two initial reactions of 1-butanethiol with hydrogen atoms was 0.272 (k1/k2). The n-butane and 1-butene are considered to be produced via chemically activated 1-butanethiol on the basis of the pressure dependence of the two main products.\scriptfont4=\seveni \scriptscriptfont4=\fivei \halign{\hfill $#$&$#$\hfill &$#$\hfill &\hfill\qquad\qquad #\cr\rm 1\hbox{-}C_{4}H_{9}S&\rm H&\rm +H\longrightarrow 1\hbox{-}C_{4}H_{9}\cdot +H_{2}S& (1)\cr \rm 1\hbox{-}C_{4}H_{9}S&\rm H&\rm +H\longrightarrow 1\hbox{-}C_{4}H_{9}S\cdot +H_{2}& (2)\cr\rm 1\hbox{-}C_{4}H_{9}S&\rm \cdot &\rm +H\longrightarrow 1\hbox{-}C_{4}H_{9}SH\ast & (3)\cr } \bigskip\rm{}Relative rates of molecular elimination of hydrogen sulfide and C—S bond fission for the chemically activated 1-butanethiol, k5/k4 and k6/k4, were 0.114 and 0.0552 under 532 Pa of pressure at room temperature. Activation energies of the two reactions were calculated to be 228 [kJ/mol] and 297 [kJ/mol], respectively, by use of RRKM on the base of estimated A factors.\scriptfont4=\seveni \scriptscriptfont4=\fivei \halign{\hfill $#$&$#$\hfill &$#$\hfill &\hfill\qquad\qquad #\cr\rm 1\hbox{-}C_{4}H_{9}SH\ast +M&\rm \longrightarrow &\rm 1\hbox{-}C_{4}H_{9}SH& (4)\cr \rm 1\hbox{-}C_{4}H_{9}SH\ast &\rm \longrightarrow &\rm 1\hbox{-}C_{4}H_{8}+H_{2}S& (5)\cr\rm 1\hbox{-}C_{4}H_{9}SH\ast &\rm \longrightarrow &\rm 1\hbox{-}C_{4}H_{9}\cdot +HS\cdot & (6)\cr } \bigskip\rm{}© 1998 John Wiley & Sons, Inc. Int. J. Chem Kinet 30: 923-932, 1998
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  • 32
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    International Journal of Chemical Kinetics 30 (1998), S. 7-19 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Manganese(III) solutions were prepared by known electrochemical methods in sulfuric acid, acetic acid, and pyrophosphate media. The nature of the oxidizing species present in manganese(III) solutions was characterized by spectrophotometric and redox potential measurements. Kinetics of oxidation of L-glutamine by manganese(III) in sulfuric acid (1.5 M), acetic acid (60% v/v), and pyrophosphate (pH=1.3) media at 313 K, 323 K, and 328 K, respectively, have been studied. Three different rate laws have been obtained for the three media. Effects of varying ionic strength, solvent composition, and added anions, such as fluoride, chloride, perchlorate, pyrophosphate, and bisulfate, have been investigated. There is evidence for the existence of free radicals as transient species. Activation parameters have been evaluated using Arrhenius and Eyring plots. Mechanisms consistent with the observed kinetic data have been proposed and discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 7-19, 1998.
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  • 33
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have examined the kinetics and mechanism of the dediazoniation reaction of p-methylbenzenediazonium tetrafluoroborate in the presence and absence of CuCl2 using a methodology developed by us that allows, simultaneously, and within the same experiment to identify, to quantify, and to obtain the rate constants for the formation of all dediazoniation products, and, indirectly, the rate constant for the diazonium salt decomposition. The methodology developed combines the use of coupling reactions, to form a stable azo dye, followed by analysis by HPLC. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 31-39, 1998.
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  • 34
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    International Journal of Chemical Kinetics 30 (1998), S. 63-67 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of reagent concentration and the pH in the kinetic behavior of the dissociation of Fe(II)-fulvic acid complexes were studied using a spectrophotometric technique. The results show that this behavior is not strongly affected by the concentration of fulvic acid, the concentration of the metal cation on the ratio of these concentrations and that variations in pH are more important in the dissociation process. A possible explanation based in the relative influence of proton concentration on the stability of the complexes is proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 63-67,1998.
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  • 35
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    International Journal of Chemical Kinetics 30 (1998), S. 89-97 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Data relative to methane trapping of SiCl2 and a rate constant for the SiCl2 into C(SINGLEBOND)H bond insertion process of k-1=13.4 M-1s-1 at 921 K are reported. Results on the decomposition of the trapping product, methyldichlorosilane, are also reported. This decomposition follows first-order kinetics with a rate constant of k=1.5±0.2×10-3 s-1 at 905 K and produces methane, trichlorosilane, methyltrichlorosilane, and tetrachlorosilane. It is argued that the decomposition involves silylene intermediates, is nonchain, and is initiated primarily by the molecular methane elimination process MeSiHCl2(SINGLEBOND)1→ CH4+SiCl2. Free radicals and Si(SINGLEBOND)C bond fission may also contribute to the decomposition but are not dominant. The kinetics of MeSiHCl2 decomposition are shown to be consistent with the kinetics of the reverse SiCl2/CH4 trapping reaction and with the overall reaction thermochemistry. Reaction modeling gives product yields, reactant conversions, and rates in reasonable agreement with the data. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 89-97, 1998.
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  • 36
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    International Journal of Chemical Kinetics 30 (1998), S. 151-159 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article is concerned with the application of a new method to recover the rate constants in chemical reactions. The method is based on treating the unknown parameters as time dependent. With appropriate experimental data the unknown rate constants are guided from an arbitrary initial condition to their true value at a final time. An explicit equation describing the time evolution of the parameters is obtained by minimizing the error along the trajectory. The method leads to an iterative algorithm which is described in detail. Numerical results with the method indicate that accurate estimates of the rate constants can be obtained directly from experimental data. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 151-159, 1998.
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  • 37
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    International Journal of Chemical Kinetics 30 (1998), S. 145-150 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants were determined for the nitrosation reactions of the following substrates: Methyl (MU), Ethyl (EU),Propyl (PU)Butyl (BU), and Allylurea (AU). The rate equation found at a constant pH was: v=k[HNO2] [Urea]. The reactions were carried out in predominantly organic media(dioxane-acetic acid-water) with differing polarities. The proposed reaction mechanism involves the proton transfer from the protonated N-alkyl-N-nitrosourea to the acetate anion. As the polarity of the medium decreased, an approximation of the rate constants of the nitrosation of the different substrates was observed. This approximation can be interpreted as a function of the impediment generated by the R alkyl radical in the rate controlling step. Accordingly, the substrate reactivity will be associated with the ease in which the protonated N-alkyl-N nitrosurea can transfer the proton to the acetate anion. The results achieved in this study are in accordance with there activities observed in the nitrosation of these substrates in aqueous media MU≫(EU≈PU≈BU)〉AU. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 145-150, 1998.
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  • 38
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    International Journal of Chemical Kinetics 30 (1998), S. 179-184 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations have been used to characterize the transition states for halogen abstraction by CH3 in reactions with CF4, CF3Cl, CF3Br, and CF3I (1-4). Geometries and frequencies were obtained at the HF/6-31G(d) and MP2=full/6-31G(d) levels of theory. Energy barriers were computed via the Gaussian-2 methodology, and the results were employed in transition state theory analyses to obtain the rate constants over 298-2500 K. There is good accord with literature measurements in the approximate temperature range 360-500 K for reactions (2-4), and the computed activation energies are accurate to within ±6 kJ mol-1. Recommended rate constant expressions for use in combustion modeling are k;1=1.6×10-19 (T/K)2.41 exp(-13150 K/T), k2=8.4×10-20(T/K)2.34 exp(-5000 K/T), k3=4.6×10-19 (T/K)2.05 exp(-3990 K/T), and k4=8.3×10-19 (T/K)2.18 exp(-1870 K/T) cm3 molecule-1 s-1. The results are discussed in the context of flame suppression chemistry. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 179-184, 1998.
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  • 39
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    International Journal of Chemical Kinetics 30 (1998), S. 185-191 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of decomposition of azetidine {(CH2)3N(SINGLEBOND)H)} was measured using single-pulse shock-tube techniques, over the temperature range 855-1100 K, in high argon dilution. These data confirm and extend an earlier investigation that utilized the very low-pressure pyrolysis method. A brief survey of many reports regarding the interesting features of azetidine is presented. In two appendices the thermodynamic and kinetic data on trimethylene sulfide, oxide, and immine are intercompared. New ab-initio calculations are cited for the parent species and their fragmentation products. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 185-191, 1998.
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  • 40
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    International Journal of Chemical Kinetics 30 (1998), S. 201-206 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dual-phase oscillations are observed in Belousov-Zhabotinsky system with 4-hydroxy-3-methoxybenzaldehyde (vanillin) as the substrate and manganous sulphate or ammonium Ce(IV) sulphate as the catalyst. The nonoscillatory period of time between the two phases decreases with increase in the concentration of the catalyst and the substrate. Under uncatalyzed and ferroin catalyzed conditions the system exhibits single-phase oscillations. The first-phase oscillations are due to vanillin whereas the second-phase oscillations are brought about by 4-hydroxy-3-methoxybenzoic acid (vanillic acid) formed during the course of the first-phase reactions. The reactions are explained with relevant steps of the FKN mechanism. © 1998 John Wiley & Sons, Inc. Int J. Chem. Kinet 30: 201-206, 1998.
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  • 41
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    International Journal of Chemical Kinetics 30 (1998), S. 277-283 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of Zn(II), Cd(II), and Hg(II) incorporation into meso tetrameta-tolueneporphyri n (H2T(m-CH3)PP) in acetone have been studied by means of stopped-flow method. A unified reaction mechanism was proposed and the kinetic parameters were obtained by nonlinear least-square methods. The effect of ionic strength (I) on Cd(II)/H2T(m-CH3)PP was investigated. It has been found that there is a negative kinetic salt effect and the relationship of rate constants with ionic strength was obtained. Some solvent effects have also been investigated in this article. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 277-283, 1998.
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  • 42
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    International Journal of Chemical Kinetics 30 (1998), S. 249-255 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A discharge flow reactor coupled to a laser-induced fluorescence (LIF) detector and a mass spectrometer was used to study the kinetics of the reactions CH3O+Br→products (1) and CH3O+BrO→products (2). From the kinetic analysis of CH3O by LIF in the presence of an excess of Br or BrO, the following rate constants were obtained at 298 K: k1=(7.0±0.4)×10-11 cm3 molecule-1 s-1 and k2=(3.8±0.4)×10-11 cm3 molecule-1 s-1. The data obtained are useful for the interpretation of other laboratory studies of the reactions of CH3O2 with Br and BrO. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 249-255, 1998.
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  • 43
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    International Journal of Chemical Kinetics 30 (1998), S. 267-272 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title reactions are subjected to a kinetic analysis in 44 wt% ethanol-water, at 25.0°C, ionic strength 0.2 (KCl). With a large excess of amine over the substrate, pseudo-first-order rate coefficients (kobs) are obtained, which are linearly dependent on the amine concentration. The nucleophilic rate constants (kN) are determined from plots of kobs vs. amine concentration. The Brönsted-type plot obtained with the kN values is linear, with slope β=0.63. The magnitude of this slope suggests that the mechanism is concerted, as opposed to a stepwise process with rate-determining breakdown of a zwitterionic tetrahedral intermediate (T±), in which the value of β is usually 0.8-1.0. The pyridinolysis of the same substrate in the same solvent is stepwise with the breakdown of T± as the rate-determining step. The change to a concerted mechanism for the title reactions is attributed to the superior nucleofugality of the alicyclic amines, compared to the isobasic pyridines, which destabilizes kinetically the “intermediate” T± in such a way that it does not exist, and the mechanism becomes enforced concerted. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 267-272, 1998.
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  • 44
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    International Journal of Chemical Kinetics 30 (1998), S. 311-311 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 45
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    International Journal of Chemical Kinetics 30 (1998), S. 335-340 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics and mechanism of the reaction of Cr(VI) with oxalic acid have been studied in presence and absence of H2SO4, HClO4, and CH3COOH by monitoring the formation of Cr(III)-oxalic acid complex at 560 nm. The effect of total [oxalic acid], [Cr(VI)], [H2SO4], [HClO4], and [CH3COOH] on the reaction rate was determined at 30°C. Formation of carbon dioxide was also confirmed. The oxidation rate increases with [oxalic acid] and [CH3COOH] while it decreases with [H2SO4], [HClO4], and pH. The rate law governing the oxidation of oxalic acid over a wide range of conditions is rate=k1 Kes1 [oxalic acid]T [Cr(VI)]T 1+Kes1 [oxalic acid]T, where only undissociated oxalic acid is kinetically active. Kinetic evidence for the formation of a Cr(VI)(SINGLEBOND)oxalic acid 1:1 complex has been obtained and the equilibrium constant for their formation has been determined. The 1:1 complex exists most likely in an open chain form. The rate-limiting step of the oxidation reaction involves the breaking of the C(SINGLEBOND)C bond in the 1:2 complex. Oxidizing ability of Cr(VI) species have been discussed. Mechanism with the associated reaction kinetics is assigned. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 335-340, 1998
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  • 46
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of trans-[Cr(Salen)(OH2)2]+ with aqueous sulfite yields trans-[Cr(Salen)(OH2)(OSO2(SINGLEBOND)O)]- (O-bonded isomer). The rate and activation parameter data for the formation of the sulfito complex are consistent with a mechanism involving rate-limiting addition of SO2 to the CrIII(SINGLEBOND)OH bond. The complex ions, trans-[(OH2)Cr(Salen)(OSO2(SINGLEBOND)O)]-, and trans-[(OH)Cr(Salen)(OSO2(SINGLEBOND)O)]2-, undergo reversible anation by NCS-, N3-, imidazole, and pyridine resulting in the formation of trans-[XCr(Salen)(OSO2(SINGLEBOND)O)](N+1)-(n=1 for X=N3-,NCS-, and 0 for X=imidazole and pyridine) predominantly via dissociative interchange mechanism. The labilizing action of the coordinated sulfite on the trans-CrIII-X bond in trans-[XCr(Salen)(OSO2)](n+1)- follows the sequence: NCS-pyridine ca. N3- ca. imidazole. Data analysis indicated that the coordinated sulfite has little trans activating influence. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 373-384, 1998
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  • 47
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    International Journal of Chemical Kinetics 30 (1998), S. 471-474 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate method, rate constants have been measured for the gas-phase reactions of the OH radical with the dibasic esters dimethyl succinate [CH3OC(O)CH2CH2C(O)OCH3], dimethyl glutarate [CH3OC(O)CH2CH2CH2C(O)OCH3], and dimethyl adipate [CH3OC(O)CH2CH2CH2CH2C(O)OCH3] at 298±3 K. The rate constants obtained were (in units of 10-12 cm3 molecule-1 s-1): dimethyl succinate, 1.4±0.6; dimethyl glutarate, 3.3±1.1; and dimethyl adipate, 8.4±2.5, where the indicated errors include the estimated overall uncertainty of ±25% in the rate constant for cyclohexane, the reference compound. The calculated tropospheric lifetimes of these dibasic esters due to gas-phase reaction with the OH radical range from 1.4 days for dimethyl adipate to 8.3 days for dimethyl succinate for a 24 h average OH radical concentration of 1.0×106 molecule cm-3. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 471-474, 1998
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  • 48
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six analogues and derivatives (1-6) of 3-phenylhydrazonopentane-2,4-dione (7) were subjected to gas-phase thermolysis. The Arrhenius log A (s-1) and Ea (kJ mol-1) of the analogues (1-5) are, respectively: 10.42 and 140.8 for 1-cyano-1-phenyl-hydrazonopropanone (1), 11.19 and 135.4 for 1-cyano-1-(\documentclass{article}\pagestyle{empty}\begin{document}$ \underline{\rm{p}} $\end{document}-nitrophenylhydrazono)-propanone (2) , 10.68 and 144.9 for 1-cyano-1-(\documentclass{article}\pagestyle{empty}\begin{document}$ \underline{\rm{p}} $\end{document}-methoxyphenylhydrazono)propanone (3), 11.76 and 137.8 for 1-cyano-3-phenyl-1-phenylhydrazonopropanone (4), and 11.29 and 145.9 for 1-cyano-1-phenylhydrazonobutanone (5). The corresponding values for ethyl 3-oxo-2-phenylhydrazonobutanoate (6) are 11.90 s-1 and 143.3 kJ mol-1. The rates of reaction at 600 K are compared with those of the title diketone (7) and of pentane-2,4-dione (8) and rationalized in terms of a plausible elimination pathway involving a semiconcerted six-membered transition state. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 457-462, 1998
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  • 49
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pulse radiolysis was used to study the kinetics of the reactions of CH3C(O)CH2O2 radicals with NO and NO2 at 295 K. By monitoring the rate of formation and decay of NO2 using its absorption at 400 and 450 nm the rate constants k(CH3C(O)CH2O2+NO)=(8±2)×10-12 and k(CH3C(O)CH2O2+NO2)=(6.4±0.6)×10-12 cm3 molecule-1 s-1 were determined. Long path length Fourier transform infrared spectrometers were used to investigate the IR spectrum and thermal stability of the peroxynitrate, CH3C(O)CH2O2NO2. A value of k-6≈3 s-1 was determined for the rate of thermal decomposition of CH3C(O)CH2O2NO2 in 700 torr total pressure of O2 diluent at 295 K. When combined with lower temperature studies (250-275 K) a decomposition rate of k-6=1.9×1016 exp (-10830/T) s-1 is determined. Density functional theory was used to calculate the IR spectrum of CH3C(O)CH2O2NO2. Finally, the rate constants for reactions of the CH3C(O)CH2 radical with NO and NO2 were determined to be k(CH3C(O)CH2+NO)=(2.6±0.3)×10-11 and k(CH3C(O)CH2+NO2)=(1.6±0.4)×10-11 cm3 molecule-1 s-1. The results are discussed in the context of the atmospheric chemistry of acetone and the long range atmospheric transport of NOx. © John Wiley & Sons, Inc. Int J Chem Kinet: 30: 475-489, 1998
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  • 50
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    International Journal of Chemical Kinetics 30 (1998), S. 533-540 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate method, rate constants have been measured for the gas-phase reactions of the OH radical with 1-hexanol, 1-methoxy-2-propanol, 2-butoxyethanol, 1,2-ethanediol, and 1,2-propanediol at 296±2 K, of (in units of 10-12 cm3 molecule-1 s-1): 15.8±3.5; 20.9±3.1; 29.4±4.3; 14.7±2.6; and 21.5±4.0, respectively, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. These OH radical reaction rate constants are higher than certain of the literature values, by up to a factor of 2. Rate constants were also measured for the reactions of 1-methoxy-2-propanol and 2-butoxyethanol with NO3 radicals and O3, with respective NO3 radical and O3 reaction rate constants (in cm3 molecule-1 s-1 units) of: 1-methoxy-2-propanol, (1.7±0.7)×10-15, and 〈1.1×10-19; and 2-butoxyethanol, (3.0±1.2)×10-15, and 〈1.1×10-19. The dominant tropospheric loss process for the alcohols, glycols, and glycol ethers studied here is calculated to be by reaction with the OH radical, with lifetimes of 0.4-0.8 day for a 24 h average OH radical concentration of 1.0×106 molecule cm-3. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 533-540, 1998
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  • 51
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    International Journal of Chemical Kinetics 30 (1998), S. 523-532 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ligand substitution kinetics for the reaction [PtIVMe3(X)(NN)]+NaY=[PtIVMe3(Y)(NN)]+NaX, where NN=bipy or phen, X=MeO-, CH3COO-, or HCOO-, and Y=SCN- or N3-, has been studied in methanol at various temperatures. The kinetic parameters for the reaction are as follows. The reaction of [PtMe3(OMe)(phen)] with NaSCN: k1=36.1±10.0 s-1; ΔH1≠=65.9±14.2 kJ mol-1; ΔS1≠=6±47 J mol-1 K-1; k-2=0.0355±0.0034 s-1; ΔH-2≠=63.8±1.1 kJ mol-1; ΔS-2≠=-58.8±3.6 J mol-1 K-1; and k-1/k2=148±19. The reaction of [PtMe3(OAc)(bipy)] with NaN3: k1=26.2±0.1 s-1; ΔH1≠=60.5±6.6 kJ mol-1; ΔS1≠=-14±22 J mol-1K-1; k-2=0.134±0.081 s-1; ΔH-2≠=74.1±24.3 kJ mol-1; ΔS-2≠=-10±82 J mol-1K-1; and k-1/k2=0.479±0.012. The reaction of [PtMe3(OAc)(bipy)] with NaSCN: k1=26.4±0.3 s-1; ΔH1≠=59.6±6.7 kJ mol-1; ΔS1≠=-17±23 J mol-1K-1; k-2=0.174±0.200 s-1; ΔH-2≠=62.7±10.3 kJ mol-1; ΔS-2≠=-48±35 J mol-1K-1; and k-1/k2=1.01±0.08. The reaction of [PtMe3(OOCH)(bipy)] with NaN3: k1=36.8±0.3 s-1; ΔH1≠=66.4±4.7 kJ mol-1; ΔS1≠=7±16 J mol-1K-1; k-2=0.164±0.076 s-1; ΔH-2≠=47.0±18.1 kJ mol-1; ΔS-2≠=-101±61 J mol-1 K-1; and k-1/k2=5.90±0.18. The reaction of [PtMe3(OOCH)(bipy)] with NaSCN: k1 =33.5±0.2 s-1; ΔH1≠=58.0±0.4 kJ mol-1; ΔS1≠=-20.5±1.6 J mol-1 K-1; k-2=0.222±0.083 s-1; ΔH-2≠=54.9±6.3 kJ mol-1; ΔS-2≠=-73.0±21.3 J mol-1 K-1; and k-1/k2=12.0±0.3. Conditional pseudo-first-order rate constant k0 increased linearly with the concentration of NaY, while it decreased drastically with the concentration of NaX. Some plausible mechanisms were examined, and the following mechanism was proposed. [Note to reader: Please see article pdf to view this scheme.] © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 523-532, 1998
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  • 52
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    International Journal of Chemical Kinetics 30 (1998), S. 555-563 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser-flash photolysis of RBr/O3/SF6/He mixtures at 248 nm has been coupled with BrO detection by time-resolved UV absorption spectroscopy to measure BrO product yields from O(1D) reactions with HBr, CF3Br, CH3Br, CF2ClBr, and CF2HBr at 298±3 K. The measured yields are: HBr, 0.20±0.04; CF3Br, 0.49±0.07; CH3Br, 0.44±0.05; CF2ClBr, 0.31±0.06; and CF2HBr, 0.39±0.07 (uncertainties are 2σ and include estimates of both random and systematic errors). The results are discussed in light of other available information or O(1D)+RBr reactions. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 555-563, 1998
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  • 53
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    International Journal of Chemical Kinetics 30 (1998), S. 243-247 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nine amino acids, aspartic acid, glycine, serine, tyrosine, alanine, glutamic acid, threonine, cystine, phenylalanine, and two peptides, and two peptides, glycine-glycine peptide, glutamic acid-cystine-glycine peptide, give rise to damped oscillations of the Belousov-Zhabotinskii(BZ) type in a batch reactor. Both Mn2+ and Fe(phen)32 are essential for most of those oscillations; and the oscillations in [Mn3+] and [Fe(phen)33+] are also observed. The role of two metallic ions played in the oscillations are analyzed, showing that Mn2+ catalyzes the oxidation of the amino acids or peptides by BrO3- to produce some intermediates which effectively reduce Br2 to Br- catalyzed by Fe(phen)32+. © 1998 John Wiley & Sons, Inc. Int. J. Chem Kinet 30: 243-247, 1998.
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  • 54
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    International Journal of Chemical Kinetics 30 (1998), S. 215-221 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lifetime of the ferryl ion FeO2+, (minutes at pH below 1) is reduced by a factor of 50 at pH above 3. This is rationalized in terms of an acid-base equilibrium between two different hydrolytic forms of this species (Fe(OH)++2 and Fe(OH)+3) with a pKa=2.0. The rate constants for reactions between FeO2+ and selected compounds found in cloud water were measured in acid solutions by stopped-flow technique. For inorganic reactants: kHNO2=1.1×104 M-1 s-1, kNO2-≤105 M-1 s-1, kCl-=1.0×102 M-1 s-1, kHSO3-=2.5×105 M-1 s-1, kSO2=4.5×105 M-1 s-1, and kMn(II)=1.0×104 M-1 s-1 were obtained and for the organic reactants: kHCOOH=160 M-1 s-1, kHCOO-=3×105 M-1, kCH3COOH=3.1 M-1 s-1, kCH2(OH)2=400 M-1 s-1, kCH3COCH3=16 M-1 s-1, kCH3CH20H=2.5×103 M-1 s-1, kC6H5OH=4.0×103 M-1 s-1, and kC6H5COOH=80 M-1 s-1 were obtained. A good correlation between log(k) and the standard one electron reduction potential (E°) indicates that the reactions of inorganic compounds proceed by electron transfer. The reaction mechanisms in case of organic compounds are very similar to the reactions of the OH radical, i.e., H-abstraction, and a fairly good correlation between log(k) and the bond dissociation energy BDE was obtained. Activation parameters were measured for the reaction of FeO2+ with HNO2 (Ea=34.5 kJ/mol); Mn2+ (Ea=21.3 kJ/mol); HCOOH (Ea=22.3 kJ/mol); CH2(OH)2 (Ea=44.5 kJ/mol); and C6H5OH (Ea=28.1 kJ/mol). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 215-221, 1998.
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  • 55
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    International Journal of Chemical Kinetics 30 (1998), S. 229-241 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions. Experimental results obtained in a jet-stirred reactor (JSR) at 1 and 10 atm, 0.2≤φ≤2.5, and 800≤T≤1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, φ=1.0 and 650≤T≤1300 K. The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates, and products pertinent to the oxidation of DME. These data test the kinetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process. Additionally, the shock-tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior. This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (e.g., the primary reference fuels, n-heptane and iso-octane) under similar conditions. The numerical model consists of 78 chemical species and 336 chemical reactions. The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 229-241, 1998.
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  • 56
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    International Journal of Chemical Kinetics 30 (1998), S. 223-228 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using stationary-point information from a BAC-MP4 potential-energy surface and statistical-dynamical methods, we have calculated the total rate coefficient for the two-channel reaction,\documentclass{article}\pagestyle{empty}\begin{document}$ CH3+NO\rightarrow HCN+H2O\quad (R1) $\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$ \rightarrow H2CN+OH,\quad (R2) $\end{document}in the temperature range 1000 K≥T≥2500 K. The result obtained,\documentclass{article}\pagestyle{empty}\begin{document}$ kT=3.0 \times 10-1T3.52exp(-3950/RT) cm3/mole s, $\end{document}is in excellent agreement with recent shock-tube measurements of kT by Braun-Unkhoff, et al. and Hennig and Wagner. Qualitative considerations suggest that the radical channel (R2) is dominant in this temperature range. The analysis and the results are discussed in some detail. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 223-228, 1998.
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  • 57
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    International Journal of Chemical Kinetics 30 (1998), S. 407-414 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the oxidation of aspirin (ASP) by bromamine-T (BAT), N-bromosuccinimide (NBS), and N-bromophthalimide (NBP) has been studied in aqueous perchloric acid at 303 K. The oxidation reaction follows identical kinetics with first-order in [oxidant], fractional-order in [ASP], and inverse fractional-order in [H+]. Under identical experimental conditions the extent of oxidation with different oxidizing agents is in the order: NBS 〉 BAT 〉 NBP. The rate decreased with decreasing dielectric constant of the medium. The variation of ionic strength and the addition of the reaction products and halide ions had no significant effect on the reaction rate. The solvent isotope effect was studied using D2O. Kinetic parameters were evaluated by studying the reaction at different temperatures. The reaction products were identified by GC-MS. The proposed reaction mechanism and the derived rate law are consistent with the observed kinetic data. Formation and decomposition constants for ASP-oxidant complexes have been evaluated. Decarboxylation, bromination, and loss of acetic acid gave 2,4,6-tribromophenol. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 407-414, 1998
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  • 58
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    International Journal of Chemical Kinetics 30 (1998), S. 451-456 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-cyanomethyl-N-ethyl aniline (CEAN) and N-cyanomethyl-N-ethyl-p-anisidine (CEPA) have been thermolyzed in a stirred-flow reactor, in the range of 510-560 °C, pressures of 7-11 torr and residence times of 0.5-0.9 s, using toluene as carrier gas. N-cyanomethyl-N-ethyl-p-nitroaniline (ECNA) was thermolyzed at 640°C and 13% conversion. Ethylene and HCN formed in 43% yield each as products from all three starting materials. Phenyl methanaldimine and p-anisidyl methanaldimine were also products of CEAN and CEPA, respectively. The consumption of CEAN and CEPA showed first-order kinetics for a three-fold increase of reactant inflow and initial conversions of up to 40 percent. The following Arrhenius equations were obtained from the rate coefficients for the production of ethylene: CEAN: k=1015.10±0.74 exp(-238±11 kJ/mol·RT); CEPA: k=1015.61±0.29 exp(-246±4 kJ/mol·RT). The results are explained by means of radical, nonchain thermolysis mechanisms. The thermochemistry of relevant reaction steps has been estimated from thermochemical parameters calculated by using the semiempirical AM1 method. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 451-456, 1998
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  • 59
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    International Journal of Chemical Kinetics 30 (1998), S. 497-502 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase reaction of bornyl acetate (bicyclo[2,2,1]-heptan-2-ol-1,7,7-trimethyl-acetate) with hydroxyl radical has been studied. A relative method was used to determine the rate constant for this reaction, with n-octane as reference compound.Methyl nitrite photolysis experiments were carried out in an environmental smog chamber at atmospheric pressure and (294±2) K. The rate constant determined for bornyl acetate is k=(13.9±2.2)×10-12 cm3 molecule-1 s-1.The experimental rate constant has been compared with the rate constants calculated with the structure-activity relationship (SAR) and with the evolution trend of the acetate rate constants. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 497-502, 1998
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  • 60
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    International Journal of Chemical Kinetics 30 (1998), S. 565-570 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tert-Butyl hydroperoxide and hydrogen peroxide readily react with the radical cation derived from 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The reaction is inhibited by ABTS and protons, and can be interpreted in terms of a mechanism comprising a partially reversible electron transferROOH+ABTS•+↔ ROO · + ABTS + H+ (1)followed by the self-reactions of the hydroperoxide derived radicals and reactions between them and another ABTS derived radical. A complete kinetic analysis allows an evaluation of the rate constant for reaction (1). A value of 0.2 M-1 s-1 was obtained for both compounds. The back reaction of process (1) is more relevant when tert-butyl hydroperoxide is employed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 565-570, 1998
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  • 61
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    International Journal of Chemical Kinetics 30 (1998), S. 589-594 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate method, rate constants for the gas-phase reactions of 2-methyl-3-buten-2-ol (MBO) with OH radicals, ozone, NO3 radicals, and Cl atoms have been investigated using FTIR. The measured values for MBO at 298±2 K and 740±5 torr total pressure are: kOH=(3.9±1.2)×10-11 cm3 molecule-1 s-1, kO3=(8.6±2.9)×10-18 cm3 molecule-1 s-1, kNO3=(8.6±2.9)×10-15 cm3 molecule-1 s-1, and kCl=(4.7±1.0)×10-10 cm3 molecule-1 s-1. Atmospheric lifetimes have been estimated with respect to the reactions with OH, O3, NO3, and Cl. The atmospheric relevance of this compound as a precursor for acetone is, also, briefly discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 589-594, 1998
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  • 62
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    International Journal of Chemical Kinetics 30 (1998), S. 621-628 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,1,1-Trifluoroethane has been decomposed in comparative rate single-pulse shock-tube experiments. The rate expression for elimination at ca. 2.5 bar and in the temperature range of 1050 to 1200 K has been found to be\documentclass{article}\pagestyle{empty}\begin{document}$ \it k\rm (CF_{3}\joinrel{\relbar\!\!\relbar}CH_{3}\relbar\!\!\rightarrow HF+CF_{2}=CH_{2})=7.0\times 10^{14}\ exp(-37260/T)s^{-1} $\end{document}The experimental conditions appear to be such that the unimolecular reaction is at the beginning of the fall-off region and we find that for step sizes down between 500 and 1000 cm-1 the high-pressure rate expression is in the range\documentclass{article}\pagestyle{empty}\begin{document}$ \it k\rm (CF_{3}\joinrel{\relbar\!\!\relbar}CH_{3}\relbar\!\!\rightarrow HF+CF_{2}=CH_{2})=2.0\times 10^{15}\ exp(-38300/T)\ to\ 4\ \times\ 10^{15}\ exp(-39000/T)s^{-1} $\end{document}where the smaller rate parameters refer to the larger step size down. The results are compared with those from an earlier study and the anomalously high A-factor is noted. It is suggested that the existing rate expressions for the fluorinated ethanes may need to be reevaluated. © 1998 John Wiley & Sons, Inc., Int J Chem Kinet: 30: 621-628, 1998
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  • 63
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of the thermal decomposition of smithsonite has been determined from a comparison of the results obtained from isothermal, linear heating rate (TG), and Constant Rate Thermal Analysis (CRTA) experiments. Two important precautions have been taken in this work. Firstly, the chemical composition of the sample has been checked in order to be sure that pure anhydrous zinc carbonate has been used. Secondly, the experimental conditions have been selected in such a way to avoid the influence of heat and mass transfer phenomena on the forward reaction. It has been shown that the mechanism for the thermal decomposition of smithsonite depends upon temperature. Thus, at temperatures lower than 650 K, approximately, an A0.5 kinetic model describes the reaction, whereas, at temperatures roughly higher than 690 K the above reaction obeys a F1 kinetic law. An interpretation of this behavior is given. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 647-655, 1998
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  • 64
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    International Journal of Chemical Kinetics 30 (1998), S. 571-576 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The room temperature rate coefficient for the reaction Br+Br2O→Br2+BrO (3) has been measured using the technique of pulse-laser photolysis with long-path transient absorption detection of the BrO reaction product. A value of k3=(2.0±0.5)×10-10 cm3 molecule-1 s-1 was determined. The photolysis products of Br2O at 308 nm were also examined. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 571-576, 1998
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  • 65
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    International Journal of Chemical Kinetics 30 (1998), S. 577-587 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The products of the gas-phase reaction of the OH radical with 3-methyl-1-butene in the presence of NO have been investigated at room temperature and 740 torr total pressure of air by gas chromatography with flame ionization detection, in situ Fourier transform infrared absorption spectroscopy, and direct air sampling atmospheric pressure ionization tandem mass spectrometry. The products identified and quantified by GC-FID and in situ FT-IR absorption spectroscopy were HCHO, 2-methylpropanal, acetone, glycolaldehyde, and methacrolein, with formation yields of 0.70±0.06, 0.58±0.08, 0.17±0.02, 0.18±0.03, and 0.033±0.007, respectively. In addition, IR absorption bands due to organic nitrates were observed, consistent with API-MS observations of product ion peaks attributed to the β-hydroxynitrates (CH3)2CHCH(ONO2)CH2OH and/or (CH3)2CHCH(OH)CH2ONO2 formed from the reactions of the corresponding β-hydroxyalkyl peroxy radicals with NO. A formation yield of ca. 0.15 for these nitrates was estimated using IR absorption band intensities for known organic nitrates. These products account for essentially all of the reacted 3-methyl-1-butene. Analysis of the potential reaction pathways involved shows that H-atom abstraction from the allylic C(SINGLEBOND)H bond in 3-methyl-1-butene is a minor pathway which accounts for 5-10% of the overall OH radical reaction. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 577-587, 1998
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  • 66
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    International Journal of Chemical Kinetics 30 (1998), S. 595-604 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a stirred batch reactor, the Ce(III)- or Mn(II)-catalyzed Belousov-Zhabotinsky reaction with mixed organic acid/ketone substrates exhibits oscillatory behavior. The organic acids studied here are: dl-mandelic acid (MDA), dl-4-bromomandelic acid (BMDA), and dl-4-hydroxymandelic acid (HMDA), and the ketones are: acetone (Me2CO), methyl ethyl ketone (MeCOEt), diethyl ketone (Et2CO), acetophenone (MeCOPh), and cyclohexanone ((CH2)5CO). The effects of bromate ion, organic acid, ketone, metal-ion catalyst, and sulfuric acid concentrations on the oscillatory patterns are investigated. Both conventional and stopped-flow methods are applied to study the kinetics of the oxidation reactions of the above organic acids by Ce(IV) or Mn(III) ion. The order of relative reactivities of the oxidation reactions of organic acids in 1 M H2SO4 is Mn(III)(SINGLEBOND)HMDA reaction 〉 Ce(IV)(SINGLEBOND)HMDA reaction 〉 Mn(III)(SINGLEBOND)BMDA, reaction 〉 Mn(III)(SINGLEBOND)MDA reaction 〉 Ce(IV)(SINGLEBOND)BMDA reaction 〉 Ce(IV)(SINGLEBOND)MDA reaction. Spectrophotometric study of the bromination reactions of the above ketones shows that these reactions are zero-order with respect to bromine and first-order with respect to ketone and that ketone enolization is the rate-determining step. The order of relative rates of bromination or enolization reactions of ketones in 1 M H2SO4 is (CH2)5CO≫(MeCOEt, Et2CO, Me2CO)〉MeCOPh. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet:30: 595-604, 1998
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  • 67
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    International Journal of Chemical Kinetics 30 (1998), S. 641-646 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of bromide ions to the component solutions of the Briggs- Rauscher oscillating system produces a variety of phenomena, depending on the sequence of the addition and on the initial bromide concentration. If the addition is made some minutes after the mixing of H2O2 and acidic IO3- and before adding malonic acid and Mn2+ ions, the oscillations last for five or six cycles, then suddenly ceases. If the addition is made immediately after the mixing of H2O2 and acidic IO3- and before adding malonic acid and Mn2+ ions, the oscillations do not start at all. The addition of bromide ions to an actively oscillating BR reaction causes a rapid suppression of the oscillations. Our observations may be accounted for by a mechanism involving the IBr species. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 641-646, 1998
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  • 68
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    International Journal of Chemical Kinetics 30 (1998), S. 673-681 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The authors present a critical analysis of the use of an overall single reaction rate equation instead of the true rate equations corresponding to the decomposition of a substance according to two parallel reactions. Isothermal as well as nonisothermal decomposition are considered. An apparent compensation effect has been evidenced in both cases. It has been assigned to the dependence of the kinetic parameters on temperature (for the isothermal case), conversion, and heating rate (for nonisothermal one). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 673-681, 1998
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  • 69
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    International Journal of Chemical Kinetics 30 (1998), S. 707-709 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upper limits of 4×10-20 and 7×10-20 cm3 molecule-1 s-1 were established for the gas-phase reactions of H2O2 with O3 and NO, respectively. These reactions are too slow to explain features observed in the atmospheric vertical profile of H2O2. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 707-709, 1998
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  • 70
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    International Journal of Chemical Kinetics 30 (1998), S. 699-705 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pulse-radiolysis technique has been employed to produce and study the kinetics of hydrated electrons (eaq-) in a quaternary micro emulsion (Sodium Lauryl Sulfate (NaLS)/water/cyclohexane/1-pentanol) system. Two orders of magnitude higher life time (20 μs) of the eaq- has been obtained as compared to that in reverse micelles reported earlier. Several probes including a biomolecule have been used to determine the water pool concentrations and quenching constants (kq). The observed yield and half life (t1/2) of the hydrated electrons vary smoothly as the water droplet sizes are changed. The bimolecular rate constants for the reaction of eaq- with different solutes have been determined. It has been observed that the measured bimolecular rate constants for the reaction of hydrated electrons with different solutes are indicative of the solubilization sites, the water core sizes, and the surrounding environment. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 699-705, 1998
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  • 71
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    International Journal of Chemical Kinetics 30 (1998), S. 721-727 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficients for the reactions of hydrogen atoms with n-C3H7Br, s-C3H7Br, n-C4H9Br, and s-C4H9Br were determined in a discharge flow-reactor at 298 K and a pressure of 4 mbar. Molecular-beam sampling and subsequent mass-spectrometric detection with electron-impact ionisation was used for the measurement of the bromo-hydrocarbon concentration. The rate coefficients obtained are (in 1010 cm3 mol-1 s-1): 2.3±1.2 for n-C3H7Br, 2.3±1.2 for s-C3H7Br, 2.4±1.2 for n-C4H9Br, and 2.8±1.4 for s-C4H9Br. The results are compared with predictions from bond-energy bond-order (BEBO) calculations, where a reasonable agreement is found. Furthermore, also by BEBO calculations, the relative importance of bromine abstraction as compared to hydrogen abstraction is estimated. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 721-727, 1998
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  • 72
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    International Journal of Chemical Kinetics 30 (1998), S. 745-752 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of +2-butanol (2BU, CH3CH2CH(OH)CH3) and 2-pentanol (2PE, CH3CH2CH2CH(OH)CH3). 2BU and 2PE react with OH yielding bimolecular rate constants of (8.1±2.0)×10-12 cm3molecule-1s-1 and (11.9±3.0)×10-12 cm3molecule-1s-1, respectively, at 297±3 K and 1 atmosphere total pressure. Both 2BU and 2PE OH rate constants reported here are in agreement with previously reported values [1-4]. In order to more clearly define these alcohols' atmospheric reaction mechanisms, an investigation into the OH+alcohol reaction products was also conducted. The OH+2BU reaction products and yields observed were: methyl ethyl ketone (MEK, (60±2)%, CH3CH2C((DOUBLEBOND)O)CH3) and acetaldehyde ((29±4)% HC((DOUBLEBOND)O)CH3). The OH+2PE reaction products and yields observed were: 2-pentanone (2PO, (41±4)%, CH3C((DOUBLEBOND)O)CH2CH2CH3), propionaldehyde ((14±2)% HC((DOUBLEBOND)O)CH2CH3), and acetaldehyde ((40±4)%, HC((DOUBLEBOND)O)CH3). The alcohols' reaction mechanisms are discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. Labeled (18O) 2BU/OH reactions were conducted to investigate 2BU's atmospheric transformation mechanism details. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground level ozone-forming potential calculations (incremental reactivity) [5]. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 745-752, 1998
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  • 73
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    International Journal of Chemical Kinetics 30 (1998), S. 777-783 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 2-phenoxyquinoxaline (1) with hydroxide ion is accelerated by reactive counter-ion micelles of cetyltrialkylammonium hydroxides (alkyl=Me, Et, n-Pr, and n-Bu), cetylmethylpiperidinium hydroxide, and cetylquinuclidinium hydroxide containing bulky head groups. First-order rate constants for reaction of (1) with OH- increase with increasing bulk of the head group and are associated with an increase in nucleophile reactivity as water is squeezed away from the micelle surface. Micellar effects upon the alkaline hydrolysis of compound (1) were analyzed by using a model that describes micelle-ion interactions in terms of Langmuir isotherms. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 777-783, 1998
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  • 74
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    International Journal of Chemical Kinetics 30 (1998), S. 849-857 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aminolyses of the title substrates with anilines and benzylamines are investigated in acetonitrile. A clean second-order kinetics is obtained with a first-order rate law in the amine concentration, which is uncomplicated by the fast proton transfer step. The large magnitude of ρZ (ρ1g) as well as ρX (ρnuc) together with relatively large positive ρXZ values is consistent with a stepwise mechanism in which thiophenolate ion expulsion from the intermediate is rate limiting. For the reactions of aryl dithio-2-thiophenates with benzylamines the magnitude of ρX and ρZ values is relatively smaller suggesting that both the addition and expulsion of thiophenolate are partially rate determining. Relatively large secondary kinetic isotope effects, kH/kD≥1.7, with deuterated nucleophiles, support involvement a concurrent proton transfer to the departing thiophenolate ion in the transition state. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 849-857, 1998
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  • 75
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    International Journal of Chemical Kinetics 30 (1998), S. 869-874 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction between BrO3- and sulfite was studied by measuring the concentrations of [Br-] and [H+] both in buffered and in unbuffered solutions. A mechanism was applied for simulation of the experimental observations. Rate constants k1=(0.027±0.004) M-1s-1 and k2=(85±5) M-1s-1 were determined for the following reactions:\halign{\hfill $#$\hfill &\hfill\qquad\qquad #\cr 3\ \rm HSO_{3}\!^{-}+BrO_{3}\!^{-}\longrightarrow 3\ SO_{4}\!^{2-}+Br^{-}+3\ H^{+}& (1)\cr 3\ \rm H_{2}SO_{3}(\hbox{or}\ SO_{2.}\hbox{aq})+BrO_{3}\!^{-}\longrightarrow 3\ SO_{4}\!^{2-}+Br^{-}+6\ H^{+}& (2)\cr }Rate constant k1 was obtained directly from the experimental results on unbuffered reactions, where Reaction (1) was predominant. Rate constant k2 was obtained by computer fitting of [Br-] to the experimental values for buffered reactions, where the rate of Reaction (2) was about four times higher than that of Reaction (1). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 869-874, 1998
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  • 76
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    International Journal of Chemical Kinetics 30 (1998), S. 859-867 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Br-atom atomic resonance absorption spectrometry (ARAS) has been developed and applied to measure thermal decomposition rate constants for CF3Br (+ Kr)→CF3+Br (+ Kr) over the temperature range, 1222-1624 K. The Br-atom curve-of-growth (145〈λ〈163 nm) was determined using this reaction. For [Br]≤1×1012 molecules cm-3, absorbance, (ABS)=1.410×10-13 [Br], yielding σ=1.419×10-14 cm2. The curve-of-growth was then used to convert (ABS) to Br-atom profiles which were then analyzed to give measured rate constants. These can be expressed in second-order by k1=8.147×10-9 exp(-24488 K/T) cm3 molecule-1 s-1 (±33%, 1222≤T≤1624 K). A unimolecular theoretical approach was used to rationalize the data. Theory indicates that the dissociation rates are closer to second- than to first-order, i.e., the magnitudes are 30-53% of the low-pressure-limit rate constants over 1222-1624 K and 123-757 torr. With the known, E0=ΔH00=70.1 kcal mole-1, the optimized theoretical fit to the ARAS data requires 〈ΔE〉down=550 cm-1. These conclusions are consistent with recently published data and theory from Kiefer and Sathyanarayana. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 859-867, 1998
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  • 77
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    International Journal of Chemical Kinetics 30 (1998), S. 899-902 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stoichiometry of CO2 production during the ceric oxidation of various organic acids is measured under conditions with organic acid excess. Measurements utilize a photometric methodology. For anaerobic conditions stoichiometries [CO2]produced:[Ce(IV)]reduced of about 0 (malonic acid), 0.5 (e.g., glyoxylic acid), and 1.0 (oxalic acid) are found. Oxalic acid showed an oxygen-induced decrease of CO2 production, while other compounds such as malonic acid increased the amount of produced CO2 or showed no changes (e.g., tartronic acid). In the case of mesoxalic acid the stoichiometry is increased from about 0.5 to 2.0 due to the presence of molecular oxygen. The results are discussed on the basis of simple reaction mechanisms demonstrating that useful information on reaction pathways and intermediates can be extracted from these simple measurements. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 899-902, 1998
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  • 78
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a pulse-radiolysis transient UV-VIS absorption system, rate constants for the reactions of F atoms with CH3CHO (1) and CH3CO radicals with O2 (2) and NO (3) at 295 K and 1000 mbar total pressure of SF6 was determined to be k1=(1.4±0.2)×10-10, k2=(4.4±0.7)×10-12, and k3=(2.4±0.7)×10-11 cm3 molecule-1 s-1. By monitoring the formation of CH3C(O)O2 radicals (λ〉250nm) and NO2 (λ=400.5nm) following radiolysis of SF6/CH3CHO/O2 and SF6/CH3CHO/O2/NO mixtures, respectively, it was deduced that reaction of F atoms with CH3CHO gives (65±9)% CH3CO and (35±9)% HC(O)CH2 radicals. Finally, the data obtained here suggest that decomposition of HC(O)CH2O radicals via C—C bond scission occurs at a rate of 〈4.7×105 s-1. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 913-921, 1998
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  • 79
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    International Journal of Chemical Kinetics 30 (1998), S. 941-948 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ascorbic acid present in natural products is often analyzed by its reducing effect on 2,6-dichlorophenolindophenol (DCPI). In case of coexistence of Fe(II) in natural samples and if oxalic acid is used for their extraction and stabilization, a significant interference is observed. The reaction of Fe2+ with 2,6-dichlorophenolindophenol (DCPI) in acidic solutions in the presence or absence of oxalate ions was investigated. The reaction was studied with a Stopped-Flow Spectrophotometer (S.F.S) equiped with a data acquisition system, which allows the determination of initial rates and reaction rate constants. Results for the effect of the concentrations of all the reagents of the reaction are presented. During the experimental work all concentrations of the reagents were kept in such levels to make the reaction first-order in respect of DCPI. An interesting finding is, that, although Fe2+ and C2O42- ions do not react separately with DCPI (or react very slowly), they react very rapidly in mixtures and show a strong synergetic effect. The experimental data fit with the mechanism of the formation of intermediates FeC2O4 and [Fe(C2O4)2]2-. The proposed rate law agrees with the above mechanism and the experimental results. The value kc=(1.6±0.2)×105 M-1·s-1 was calculated for the second-order rate constant of the reaction of FeC2O4 and DCPI. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 941-948, 1998
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  • 80
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    International Journal of Chemical Kinetics 30 (1998), S. 41-45 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heats of formation of BrONO2, BrONO, BrOOH, FOOH, FOOCl, CF3C(O)OOH, HC(O)OOH, CH3C(O)OOH, and [CH3C(O)O]2 are estimated from bond contributions taken from J. Phys. Chem.,100, 10150 (1996). They agree within ±2 kcal/mol with recent experimental or ab initio data. The resulting BDE(O(SINGLEBOND)O)=36 kcal/mol value in diacetyl peroxide requires the concerted assistance of exothermic C(SINGLEBOND)C(O) weakening in the transition state of its decomposition into free radicals. It also implies the existence of a previously unrecognized 12 kcal/mol nonbonded repulsion in acyl anhydrides. The formation of chloryl chlorate with ΔHf(O2ClOClO2)=50 kcal/mol, a marginally stable species toward dissociation into (ClO3+OClO), may account for observations made in the [O(3P+OClO] system at low temperatures. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 41-45, 1998.
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    International Journal of Chemical Kinetics 30 (1998), S. 55-61 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tartaric acid oxidation by vanadium(V) in sulfuric acid medium was investigated spectrophotometrically at 760 nm and 30°C by appearance of the vanadium(IV), as vanadyl. The reaction rate was determined under pseudo-first-order conditions with an excess of hydroxyacid over the oxidant concentration. The oxidation showed a first-order dependence with respect to vanadium(V) concentration and fractional orders with respect to tartaric acid and sulfuric acid concentrations, with no control and with constant ionic strength. The reaction rate is enhanced by an increase of ionic strength, and slightly reduced by a decrease of the dielectric constant of the medium. The activation parameters were calculated based on the rate constants determined in the 293 to 313 K interval. The proposed oxidation mechanisms and the derived rate laws are consistent with the experimental rate laws. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 55-61, 1998.
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    International Journal of Chemical Kinetics 30 (1998), S. 99-110 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of silane thermal decomposition is investigated in a flow reactor. The time dependencies of silane consumption and disilane formation were compared with those parameters of solid product (aerosol particles) such as concentration, total hydrogen content in solid product, and fraction of hydrogen contained in solid product as polyhydride groups (SiH2)n. Silane loss and gaseous product formation were analyzed using a mass spectrometer. The hydrogen content in solid product was analyzed by the methods of IR-spectroscopy and hydrogen evolution. Based on a simple kinetic scheme we qualitatively explained the experimental dependencies of silane conversion and disilane formation, the effective activation energy of the decomposition process, and the amount of polyhydride groups in the solid product on reaction time and initial silane concentration. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 99-110, 1998.
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  • 83
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of 3-azabicyclo[3,3,0]oct-2-ene in the course of the synthesis of N-amino-3-azabicyclo[3,3,0]octane using the Raschig process results from the following two consecutive reactions: chlorine transfer between the monochloramine and the 3-azabicyclo[3,3,0]octane followed by a dehydrohalogenation of the substituted haloamine. The kinetics of the reaction were studied by HPLC and UV as a function of temperature (15 to 44°C), and the concentrations of NaOH (0.1 to 1 M) and the chlorinated derivative (1 to 4×10-3 M). The reaction is bimolecular (k=103×10-6 M-1 s-1; ΔH0#=89 kJ mol-1; and ΔS0#=-33.6 J mol-1 K-1) and has an E2 mechanism. The spectral data of 3-azabicyclo[3,3,0]oct-2-ene were determined. IR, NMR, and ES/MS analysis show dimerization of the water-soluble monomer into a white insoluble dimer. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 129-136, 1998.
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  • 84
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    International Journal of Chemical Kinetics 30 (1998), S. 121-127 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From a study of the complexation of FeIII with 2,6-dimethyl-3,5-heptanedione in aqueous solution, thermodynamic and kinetic parameters have been obtained. Results obtained for this system and a series of structurally similar iron(III) diketonates at different temperatures, establishes isokinetic behaviors of these kinds of reactions.Analytical correlations obtained may be useful to predict, for analogous ligands in similar experimental conditions, an essential mechanism, that pathways involving reaction of metal-hydrolyzed species with the enol tautomer are faster than pathways involving hexa-aqua species. Additionally, thermodynamic parameters associated with the monochelated complexations may be predicted. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 121-127, 1998.
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  • 85
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    International Journal of Chemical Kinetics 30 (1998), S. 193-200 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transient absorption spectra of 1-naphthylseleno (1-NaphSe·), and 2-naphthylseleno (2-NaphSe·) radicals, which are generated by laser-flash photolysis of the corresponding diselenides, were observed. The reactions of 1-NaphSe·, and 2-NaphSe· with 2-methyl-1,3-butadiene and α-methylstyrene were investigated by following the decay rates of these seleno radicals. By both steady-state and laser-flash photolysis, it is proved that these seleno radicals add to alkenes in a reversible manner. The reaction rate constants for such reversible addition reactions were determined by conducting the reaction in the presence of O2, which traps selectively the carbon-centered radicals formed by the addition reaction of the seleno radicals to the alkenes. The reactivity of 2-NaphSe· is higher than that of 1-NaphSe·, both of which are less reactive than PhSe·. These reactivities were interpreted with the properties of SOMO calculated by MO method. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 193-200, 1998.
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  • 86
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    International Journal of Chemical Kinetics 30 (1998), S. 257-266 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics and mechanisms of the reactions of aluminium(III) with pentane-2,4-dione (Hpd), 1,1,1-trifluoro pentane-2,4-dione (Htfpd) and heptane-3,5-dione (Hhptd) have been investigated in aqueous solution at 25°C and ionic strength 0.5 mol dm-3 sodium perchlorate. The kinetic data are consistent with a mechanism in which aluminium(III) reacts with the β-diketones by two pathways, one of which is acid independent while the second exhibits a second-order inverse-acid dependence. The acid-independent pathway is ascribed to a mechanism in which [Al(H2O)6]3+ reacts with the enol tautomers of Hpd, Htfpd, and Hhptd with rate constants of 1.7(±1.3)×10-2, 0.79(±0.21), and 7.5(±1.6)×10-3 dm3 mol-1 s-1, respectively. The inverse acid pathway is consistent with a mechanism in which [Al(H2O)5(OH)]2+ reacts with the enolate ions of Hpd, Htfpd, and Hhptd with rate constants of 4.32(±0.18)×106, 5.84(±0.24)×103, and 1.67(±0.05)×107 dm3 mol-1 s-1, respectively. An alternative formulation involves a pathway in which [Al(H2O)4(OH)2]+ reacts with the protonated enol tautomers of the ligands. This gives rate constants of 2.79(±0.12)×104, 3.86(±0.16)×105, and 8.98(±0.25)×103 dm3 mol-1 s-1 for reaction with Hpd, Htfpd, and Hhptd, respectively. Consideration of the kinetic data reported here together with data from the literature, suggest that [Al(H2O)5(OH)]2+ reacts by an associative or associative-interchange mechanism. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 257-266, 1998.
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  • 87
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of mixed CH3CN(SINGLEBOND)H2O solvents on rates of aminolysis of ionized phenyl salicylate, PS-, reveal a nonlinear decrease in the nucleophilic second-order rate constants, knms, (for aminolysis) with increase in the content of CH3CN until it becomes ∼50%, v/v. The values of knms remain almost unchanged with change in the CH3CN content within 50 to 70 or 80%, v/v. The effects of mixed CH3CN(SINGLEBOND)H2O solvents on pKa of leaving group, phenol, and protonated amine nucleophile have been concluded to be the major source for the observed mixed solvent effects on knms. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 301-307, 1998.
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  • 88
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    International Journal of Chemical Kinetics 30 (1998), S. 313-327 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By surveying the most used methods for evaluating the kinetic parameters from nonisothermal experiments, a new classification scheme of the methods is proposed. For each method the number of principles and theoretical approximations required to derive the equation which grounds it, is considered as a comparison criterion. The methods are, finally, classified into classes of equivalence.As a result of the analysis it is also suggested that the activation energy, as calculated from nonisothermal data, should be given as a range of values instead of a unique value. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 313-327, 1998.
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  • 89
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    International Journal of Chemical Kinetics 30 (1998), S. 341-347 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of acetonitrile in the temperature range 1350-1950 K is modeled with a reaction scheme containing 23 species and 43 elementary reactions. Values of {[product]t/[CH3CN]0}/t, which were reported in a previous investigation are computed with this scheme at 50 K intervals and are compared with the values reported in the literature. Except for acrylonitrile and propyl nitrile at the high-temperature end of the study, very good agreement between the calculation and the experiment is obtained. A sensitivity spectrum of the kinetic scheme is shown and a discussion of the overall mechanism is presented. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 341-347, 1998
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  • 90
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    International Journal of Chemical Kinetics 30 (1998), S. 359-366 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal dehydrochlorination CF2ClCH3→CF2(DOUBLEBOND)CH2+HCl has been studied in a static system between 597 and 664 K in the presence of CCl4, C2Cl6, CF2(DOUBLEBOND)CH2, HCl, and CF3CH3. A kinetic radical and molecular reaction model has been developed. In addition to describing earlier results on the acceleration of the pyrolysis by CCl4 and the further acceleration by HCl, this model describes quantitatively up to conversions of 20% (i) the dependence of the catalytic effect of CCl4 at low concentrations, (ii) the stronger catalytic effect of C2Cl6, and (iii) the inhibitory effect of added CF2CH2 and CF3CH3 when CCl4 is used as a catalyst. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 359-366, 1998
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  • 91
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    International Journal of Chemical Kinetics 30 (1998), S. 415-418 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the substitution reactions of Fe(CN)5H2O3- ion with a series of nitrogen and sulfur containing heterocycles were studied in aqueous media. In the presence of excess ligand, varied over a large range of concentrations, second-order rate constants were calculated at μ = 0.100 M NaClO4. Activation parameters for the formation reactions were found, ΔH*ast; and ΔS*, 28 ± 6 kJ/mol and 135±20 J/mol, respectively. The results are interpreted as being consistent with dissociative, SN1 mechanism. The kinetics of formation and dissociation were studied by stopped-flow technique at several temperatures. An investigation of the kinetics of exchange of coordinated heterocycles for 1,3,5-triazine, yielded rate saturation that is typical of a limiting SN1 mechanism. Activation parameters of the limiting first-order specific rate of dissociations were found with ΔH* and ΔS* 53±2 kJ/mol and 105±5 J/mol, respectively. From the specific rates of formation and dissociation reactions the equilibrium constants were calculated. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 415-418, 1998
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  • 92
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isobutane pyrolysis has been studied at 20-200 torr initial pressures and 773-793 K, in a packed reactor treated with PbO and in a reactor packed with platinum foils. These packings strongly inhibit product formation and this effect is explained by the occurrence of the heterogeneous termination step:\documentclass{article}\pagestyle{empty}\begin{document}$ \rm H\cdot\mathrel{\mathop{\relbar\joinrel\longrightarrow}^{walls}} product $\end{document}at the reactor walls. The reaction has been modeled in the temperature and pressure range on the basis of a kinetic scheme which has been proposed for the homogeneous reaction and step (w) with the following values of kw:$$\eqalign{(k_{_{w}})_{_{\rm{PbO}}}&=3.7\ 10^{8}\ \rm{exp} \left[-{9000\over \rm{T}}\right]\rm{S}^{-1}\cr(k_{_{w}})_{_{\rm{Pt}}}&=15000\ \rm{S}^{-1}\ \rm{at\ any\ temperature}\cr}$$for both types of packing. The corresponding sticking coefficients of hydrogen atoms are:$$\eqalign{\gamma _{_{\rm{PbO}}} &=160\ \rm{exp} \left[-{9000\over \rm{T}}\right]\cr\gamma _{_{\rm{Pt}}} &=0.03\cr}$$© 1998 John Wiley & Sons, Inc. Int J Chem. Kinet 30: 439-450,1998
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  • 93
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    International Journal of Chemical Kinetics 30 (1998), S. 605-611 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the oxidation of diazepam (DZ) by Chloramine-B (CAB) has been studied in aqueous hydrochloric acid medium. The oxidation reaction follows the rate law:\documentclass{article}\pagestyle{empty}\begin{document}$ \it{-d[\rm{CAB}]\over\it dt_{\ .}}=k\rm{[CAB][DZ]^{0.6}[HCl]^{0.6}} $\end{document}The dependence of the reaction rate on temperature is studied and activation parameters for the rate-determining step are evaluated. The dielectric constant of the medium has a small effect on the rate. Ionic strength and the reaction product benzenesulfonamide have no effect on the reaction rate. The solvent isotope effect is studied. A probable mechanism for the observed kinetic data is proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 605-611, 1998
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  • 94
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    International Journal of Chemical Kinetics 30 (1998), S. 613-619 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction between glycolaldehyde (GA) and tetrachloroaurate(III) in acetic acid-sodium acetate buffer has been studied. The reaction is first-order with respect to [AuIII] as well as [GA]. Both H+ and Cl- ions retard the rate of reaction. AuCl4-, AuCl3(OH2), and AuCl3(OH)- are the reactive species of gold(III) with gradually increasing reactivity. A reaction mechanism involving two-electron transfer rate determining steps has been proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 613-619, 1998
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  • 95
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    International Journal of Chemical Kinetics 30 (1998), S. 629-640 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes an experimental and modeling study of the oxidation of isobutene. The low-temperature oxidation was studied in a continuous-flow stirred-tank reactor operated at constant temperature (from 833 to 913 K) and pressure (1 atm), with fuel equivalence ratios from 3 to 6 and space times ranging from 1 to 10 s corresponding to isobutene conversion yields from 1 to 50%. The main carbon containing products were analyzed by gas chromatography. The ignition delays of isobutene-oxygen-argon mixtures with fuel equivalence ratios from 1 to 3 were measured behind shock waves. Reflected shock waves permitted to obtain temperatures from 1230 to 1930 K and pressures from 9.5 to 10.5 atm.A mechanism has been proposed to reproduce the profiles obtained for the reactants consumption and the products formation during the slow oxidation and to compute the ignition delays in the shock tube. Simulations were performed using CHEMKIN II. A correct agreement between the simulated values and the experimental data has been obtained in both apparatuses. The main reaction paths have been determined for both series of measurements by a sensitivity and rate of production analysis. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 629-640, 1998
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  • 96
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isobutane pyrolysis has been studied in the presence of oxygen at about 773 K in unpacked and in PbO-coated packed Pyrex reactors. The reaction is shown to be accelerated by oxygen in reactors of low surface-to-volume ratio and strongly inhibited in packed PbO-coated reactors. These oxygen effects are explained in terms of interaction between two radical chain systems, one of pyrolysis, the other of oxidation. Oxygen introduces additional chain initiations and a degenerate chain branching step due to H2O2 while oxygenated radicals are efficiently removed at the reactor wall. All experimental results have been modeled and many rate constants of elementary steps were evaluated. The collision efficiency of HO2 radicals on a PbO-coated Pyrex surface has been determined in the temperature range of this study. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 657-671, 1998
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  • 97
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    International Journal of Chemical Kinetics 30 (1998), S. 729-736 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Potential-energy surfaces for various channels of the HNO+NO2 reaction have been studied at the G2M(RCC,MP2) level. The calculations show that direct hydrogen abstraction leading to the NO+cis-HONO products should be the most significant reaction mechanism. Based on TST calculations of the rate constant, this channel is predicted to have an activation energy of 6-7 kcal/mol and an A factor of ca. 10-11 cm3 molecule-1 s-1 at ambient temperature. Direct H-abstraction giving NO+trans-HONO has a high barrier on PES and the formation of trans-HONO would rather occur by the addition/1,3-H shift mechanism via the HN(O)NO2 intermediate or by the secondary isomerization of cis-HONO. The formation of NO+HNO2 can take place by direct hydrogen transfer with the barrier of ca. 3 kcal/mol higher than that for the NO+cis-HONO channel. The formation of HNO2 by oxygen abstraction is predicted to be the least significant reaction channel. The rate constant calculated in the temperature range 300-5000 K for the lowest energy path producing NO+cis-HONO gave rise to\documentclass{article}\pagestyle{empty}\begin{document}$ k_{a}=7.34\cdot 10^{-20}\ \rm{T}^{2.64}\ \rm{exp}(-2034/T)\ \rm{cm}^{3}\ \rm{molecule}^{-1}\ \rm{s}^{-1}. $\end{document}© 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 729-736, 1998
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  • 98
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extension to the rotating-sector method, which is usually applied to determine propagation and termination rate constants, is presented. The analytical treatment developed accounts for the simultaneous presence of a thermal initiation and of a first-order termination process. The applicability of the rotating-sector method is thus extended to situations where the rate in dark is higher than 5% of the rate in the presence of light, and more accurate estimates of the rate constants are obtained than before for any values of the “dark” rate. A previously published experiment on the application of the rotating-sector method to the autoxidation of styrene was reanalyzed. The estimates obtained for the propagation and the termination rate constants were 11% and 19% higher than the previous estimates, respectively. Finally, the improved rotating-sector method was also applied to the experimental determination of propagation (kp) and termination rate constants (2×kt) for both 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC) and 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) liposomes. The following results were obtained at 37°C: for PLPC kp =16.6 M-1s-1, and 2×kt=1.27×105 M-1s-1; for DLPC kp(intermolecular)=(13.3-13.9) M-1s-1, kp(intramolecular)=(4.7-5.4) s-1, and 2×kt=(0.99-1.05)×105 M-1s-1. The separation of the intermolecular and intramolecular propagation rate constants for DLPC was made possible both by a special adaptation of the rotating-sector equations to substrates with two oxidizable moieties, and by the experimental determination of the ratio between partially oxidized DLPC molecules (only one acyl is oxidized) and fully oxidized DLPC molecules (both acyls are oxidized). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 753-767, 1998
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  • 99
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    International Journal of Chemical Kinetics 30 (1998), S. 805-830 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comprehensive detailed chemical kinetic mechanism for methanol oxidation has been developed and validated against multiple experimental data sets. The data are from static-reactor, flow-reactor, shock-tube, and laminar-flame experiments, and cover conditions of temperature from 633-2050 K, pressure from 0.26-20 atm, and equivalence ratio from 0.05-2.6. Methanol oxidation is found to be highly sensitive to the kinetics of the hydroperoxyl radical through a chain-branching reaction sequence involving hydrogen peroxide at low temperatures, and a chain-terminating path at high temperatures. The sensitivity persists at unusually high temperatures due to the fast reaction of CH2OH+O2=CH2O+HO2 compared to CH2OH+M=CH2O+H+M. The branching ratio of CH3OH+OH=CH2OH/CH3O+H2O was found to be a more important parameter under the higher temperature conditions, due to the rate-controlling nature of the branching reaction of the H-atom formed through CH3O thermal decomposition. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 805-830, 1998
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  • 100
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    International Journal of Chemical Kinetics 30 (1998), S. 799-803 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collisional deactivation of I(2P1/2) by the title compounds was investigated through the use of the time-resolved atomic absorption of excited iodine atoms at 206.2 nm. Rate constants for atomic spin-orbit relaxation by CH3Cl, CH2Cl2, CHCl3, CCl3F, and CCl4 are 3.1±0.3×10-13, 1.28±0.08×10-13, 5.7±0.3×10-14, 3.9±0.4×10-15, and 2.3±0.3×10-15cm3 molecule-1 s-1, respectively, at room temperature (298 K).The higher efficiency observed for relaxation by CH3Cl, CH2Cl2, and CHCl3 reveals a contribution in the deactivation process of the first overtone corresponding to the C(SINGLEBOND)H stretching of the deactivating molecule (which lies close to 7603 cm-1) as well as the number of the contributing modes and certain molecular properties such as the dipole moment. It is believed that, for these molecules, a quasi-resonant (E-v,r,t) energy transfer mechanism operates. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 799-803, 1998
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