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  • Physical Chemistry  (15)
  • Wiley-Blackwell  (15)
  • 1980-1984  (15)
  • 1970-1974
  • 1955-1959
  • 1940-1944
  • 1983  (15)
  • 1
    Electronic Resource
    Electronic Resource
    Thermal dehydration kinetics of disaccharides (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 141-149 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vacuum decomposition of sucrose and cellobiose has been observed in the 150-250°C temperature range. The predominant decomposition product of both sugars is H2O with less than 5% CO, CO2, CH2O, CH3CHO, CH3OH, and C2H5OH formed. The detailed rates and temperature dependences suggest that with the possible exception of C2H5OH, the minor products are formed in secondary reactions of the dehydration products. Further it is shown that the so-called “melting with decomposition” of a sugar is in reality a high-temperature dissolution of the disaccharide in the eliminated water.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150205
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  • 2
    Electronic Resource
    Electronic Resource
    Electron transfer to trans-dihydroxotetraoxoosmate(VIII). II. Kinetics of the oxidation of dimethylsulfoxide in aqueous alkaline media (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 881-890 
    Details
    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 dimethylsulfoxide by oxohydroxoosmate(VIII) complex ions in alkaline media follow pseudo-first-order disappearance in Os(VIII). The values of the observed pseudo-first-order rate constant are linearly dependent on initial dimethylsulfoxide concentrations in a fortyfold range, and increase with increasing [OH-], leveling off at higher relative [OH-]. The results are interpreted in terms of outer sphere interactions involving dimethylsulfoxide and various species of the Os(VIII) complex. The more nucleophilic dihydroxotetraoxoosmate(VIII) ion reacts about 50 times faster than the trihydroxotrioxoosmate(VIII) species.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150904
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  • 3
    Electronic Resource
    Electronic Resource
    Studies in nickel(IV) chemistry. Kinetics of electron transfer from dimethyl sulfoxide to oxohydroxonickel(IV) in aqueous acid medium (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 945-958 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of decomposition of “oxohydroxonickel(IV)” [Ni(IV)] with concomitant intramolecular electron transfer to produce hexaaquanickel(II) and dioxygen in aqueous acid solutions show pseudo-first-order dissappearance of the Ni(IV). The pseudo-first-order rate constants for the acid decomposition (kad) satisfy \documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm ad}} = k_{\rm d} {\rm K}_{{\rm MH}} [{\rm H}^ +]/(1 + {\rm K}_{{\rm MH}} [{\rm H}^ +])$$\end{document} where KMH and kd refer to the equilibrium protonation constant and the decomposition constant of the protonated species of the Ni(IV) respectively. The values of KMH and kd in aqueous medium at 45°C and μ = 2.0M are 25.5 ± 1M-1 and (1.7 ± 0.1) × 10-5 s-1, respectively.The kinetics of the intermolecular electron transfer from dimethyl sulfoxide (DMSO) to the Ni(IV), producing Ni(H2O)62+ and dimethyl sulfone as products, have been investigated by monitoring the formation of Ni(H2O)62+. The pseudo-first-order rate constants for the electron transfer kobs are linearly dependent on [DMSO]0 or [H+], attaining limiting values at higher relative [DMSO]0 or [H+], in accordance with \documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm obs}} = \frac{{[{\rm DMSO}]_0 }}{{1 + K_{{\rm MH}} [{\rm H}^ +]}}\left({\frac{{k_{1{\rm x}} K_{1{\rm c}} }}{{1 + K_{1{\rm c}} [{\rm DMSO}]_0 }} + \frac{{k_{2{\rm x}} K_{2{\rm c}} }}{{1 + K_{2{\rm c}} [{\rm DMSO}]_0 }}} \right)$$\end{document} where K1c and K2c represent the formation constants of the precursors involving DMSO and the unprotonated and one-protonated Ni(IV) species, respectively, and k1x and k2x are the corresponding decomposition rate constants of the precursors. The values of K2c and k2x are (2.3 ± 0.1) × 104M-1 and 19 ± 1 s-1, respectively, at 45°C and μ = 1.0M. Results are interpreted in terms of probable mechanisms involving (1) a rate-determining decomposition of the protonated Ni(IV) followed by rapid product formation steps, and (2) precursor complex formation between DMSO and the unprotonated or the protonated species of the Ni(IV) followed by rate-determining decomposition with electron transfer.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550151002
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the decomposition of N-brominated alanine in aqueous solution (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 1321-1328 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aqueous bromine reacts with alkyl-sidechain amino acids through a series of steps resulting in the formation of the corresponding alkyl aldelydes and nitriles. The kinetics and the mechanism of the interaction of bromine with alanine are examined. The products and the rates of this reaction are dependent in a complex way on the initial reactant concentration and pH. Acetaldeyde production is favored at low bromine-to-alanine ratios, low bromine concentrations, and pH values above 6. The first-order rate constant for the formation of acetaldelyde from alanine under these conditions is k4 = 1.98 × 1015 e-22,500/RT min-1. At higher concentration the nitrile is formed through a bromoimine intermediate. Under most conditions the nitrile appears to form from a catalyzed decomposition of the bromoimine which is too fast to be followed by the methods used in this study. However, residual amounts of the bromoimine decay by a slower first-order mechanism. The rate constant for this slower reaction in the case of alanine at pH 6.8-6.9 and alanine concentrations of 1 × 10-4M is k6 = 1.75 × 105 e-10,400/RT min-1.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550151207
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  • 5
    Electronic Resource
    Electronic Resource
    The kinetics and mechanisms of elementary NF2 reactions with O and N atoms (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 399-415 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A combined EPR-LMR spectrometer with a fast-flow system has been used to investigate the kinetics and mechanisms of NF2 reactions with O and N atoms at 298 K. The overall rate constants of these reactions are: k0 = (2.8 ± 0.4) × 10-11 cm3/s and kN = (5.7 ± 0.8) × 10-11 cm3/s. The stoichiometry of the reactions with respect to O, N, NF2, F, and NO has been determined. The statistical theory of bimolecular reactions has been used for interpretation of the results obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150502
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  • 6
    Electronic Resource
    Electronic Resource
    Studies in nickel(IV) chemistry. Kinetics of the Cu(II) ion-mediated acid decomposition of tris(dimethylglyoximato) nickelate(IV) in aqueous acidic medium (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 521-536 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of the Cu(II) ion-mediated acid decomposition of tris (dimethylglyoximato)nickelate(IV), Ni(dmg)32- (dmg2- = dimethylglyoximate dianion), are reported in aqueous medium in the range of 3.6 ≤ pH ≤ 6.6 at 35°C and μ = 0.57 M. The pseudo-first-order rate constants of the disappearance of Ni(IV) kobs(M) satisfy the equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{{\rm obs(M)}} = k_{ad} + k_{dec(M)} $$\end{document} where kad refers to the pseudo-first-order rate constants for the proton-assisted decomposition of the Ni(IV) complex determined independently and is a function of [H+], and kdec(M) to that for the Cu(II) ion-mediated route and is a function of [H+] and [Cu2+]. Both kobs(M) and kdec(M) are found to increase with increasing [Cu(II)]0, tending to attain limiting values at higher relative [Cu(II)]0. At low [Cu(II)]0 the kdec(M) is found to register a decrease with increasing pH in the pH range of 3.6-4.4, then an increase in the range of 4.4-5.76, and again a decrease in the range of 5.76-6.6. Results on the Cu(II) ion-mediated acid decomposition are interpreted in terms of a probable mechanism involving pH-dependent adduct formation equilibria involving the one-protonated and the two-protonated species of Ni(IV) and the various species of Cu(II) ion in the media, followed by rate-determining acid decomposition of the adduct(s) to give Ni(II) aq. and Cu(dmgH)2. While the two-protonated Ni(IV) complex apparently reacts about five orders of magnitude faster than the one-protonated species, the aquacopper(II) reacts about two orders of magnitude slower than the hydroxoaquacopper(II).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150603
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  • 7
    Electronic Resource
    Electronic Resource
    Couloamperometry. A fast kinetic technique for halogenations. I. Bromination rate constants of highly reactive enol ethers (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 855-866 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new couloamperometric apparatus has been designed to extend the range of this kinetic technique to the measurement of very high rate constants, 108M-1s-1, by using TFCR-EXSEL conditions (TFCR - very low reactant concentration; EXSEL - salt excess), which give half-lives of a few seconds for very fast second-order reactions. Very low faradaic currents, in the nanoampere range for halogens, corresponding to very low reactant concentrations of 10-8-10-9M, are measured selectively by compensating the eddy currents, principally the residual and the induced currents. When the electroactive species is bromine, the concentration is demonstrated to be linearly related to the limiting reduction current in the very low concentration range. The upper limit of this technique for bromination is at present 3 × 108M-1s-1. The method is applied to the kinetic study of highly reactive enol ethers EtO-C(R) = CH-R′, where R and R′ are H or Me. A value of 2.2 × 108M-1s-1 is obtained for kBr2, the rate constant for free bromine addition to EtO-CH = CH2, by extrapolating the kinetic bromide ion effects to [Br-] = 0. An α-methyl effect (kα-Me/kH)EtO of 15 is found; this is a small decrease in the methyl effect compared to the marked increase in the double bond reactivity. For the enol acetate MeCOO-CH = CH2, whose rate constant is 6 × 102M-1s-1, (kα-Me/kH)OCOMe is 21. The dependence of substituent effects on reactivity is discussed in terms of the Hammond effect on the transition state position and of charge delocalization by group G of olefins G-CH = CH2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150902
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  • 8
    Electronic Resource
    Electronic Resource
    Stopped-flow determination of carbon dioxide-diethanolamine reaction mechanism: Kinetics of carbamate formation (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 1147-1160 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction mechanism of carbon dioxide with diethanolamine (DEA) is investigated using the stopped-flow method with optical detection in the ranges of concentration [DEA] = 0.111-8.4 × 10-2M and [CO2] = 2.94-5.6 × 10-3M. The comparison of the fast time-dependent light transmission change of a pH indicator with theoretical simulations of integrated rate equations requires a kinetic model in which a simple carbamate formation takes place simultaneously with hydration reactions, whose contributions are far from being negligible. A first-order reaction relative to DEA is thus found with a rate constant for carbamate formation smaller than usually predicted (110 ± 15M-1s-1 at 25°C). The equilibrium constant for the same reaction is also determined giving pKR = 5.3 at 25°C, in satisfactory agreement with values assumed so far.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550151104
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  • 9
    Electronic Resource
    Electronic Resource
    Laser-induced kinetics: Arrhenius parameters for t-C4H9 + XI → i-C4H9X + I (X = H,D) and the Heat of Formation of the t-butyl radical (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 1283-1300 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metathesis reaction of DI with t-C4H9 generated by 351-nm photolysis of 2,2′-azoisopropane was studied in a low-pressure reactor (VLPφ Knudsen cell) in the temperature range of 302-411 K. The data obeyed the following Arrhenius relation when combined with recent data by Rossi and Golden gathered by the same technique (t-C4H9 by thermal decomposition of 2,2′-azoisobutane): log k2D(M-1s-1) = 9.60 - 1.90/θ, where θ = 2.303RT kcal/mol for 302 K 〈 T 〉 722 K. The metathesis reaction of HI with t-C4H9 was studied at 301 K and resulted in k2H(M-1·s-1) = (3.20 ± 0.62) × 108. An analogous Arrhenius relation was calculated for the protiated system if the small primary isotope effect k2H/k2D was assumed to be √2 at 700 K. It was of the following form: log k2H(M-1·s-1) = 9.73 - 1.68/θ.Preliminary data of Bracey and Walsh indicate that earlier Arrhenius parameters determined for the reverse reaction are somewhat in error. Their value of log k1(M-1·s-1) = 11.5 - 23.8/θ yields 7delta;Hf,3000(t-butyl) = 9.2 kcal/mol and S3000(t-butyl) = 74.2 cal/mol7°K when taken in conjuction with this study.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550151204
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetics of dialin thermolysis (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 219-233 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The liquid-phase thermolysis of 1,2-dihydronaphthalene was studied in a batch reactor in the range of 350-400°C. The measured product distributions were in good agreement with calculations based on a free-radical scheme with rate constants estimated by thermochemical methods. The kinetic calculations were carried out by numerical integration and by the long-chain approximation (LCA), which yielded a closed-form solution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150303
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