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  • 1
    Electronic Resource
    Electronic Resource
    A spectrophotometric determination of the formation constants of the inclusion complexes ofα- andβ-cyclodextrins with the azonium and ammonium tautomers of methyl orange and methyl yellow (1991)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 11 (1991), S. 29-40 
    Details
    ISSN: 1573-1111
    Keywords: Methyl orange ; methyl yellow ; α-cyclodextrin ; β-cyclodextrin ; formation constants ; inclusion complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The color fading caused by the addition ofα-cyclodextrin orβ-cyclodextrin to an aqueous solution of a tautomeric mixture of methyl orange or methyl yellow is studied spectrophotometrically at pH 1.1 and 25.0°C. A model involving 1 : 1 stoichiometry has been used to analyze the spectrophotometric data. The addition of a cyclodextrin shifts the tautomeric mixture towards the side of the ammonium tautomer. An expression allowing the calculation of the tautomeric equilibrium constant of the inclusion complexes is derived. The formation constants of the inclusion complexes of the individual tautomers are determined. Bothα- andβ-cyclodextrins bind the ammonium tautomer stronger than the azonium tautomer. The inclusion complexes ofα-cyclodextrin are more stable than the corresponding ones ofβ-cyclodextrin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01073681
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  • 2
    Electronic Resource
    Electronic Resource
    Conductance Study of the Binding of K+ by Dibenzo-pyridino-18-crown-6 and 1,10-N,N′-didecyl-diaza-18-crown-6 in Acetonitrile (1997)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 29 (1997), S. 15-22 
    Details
    ISSN: 1573-1111
    Keywords: Inclusion complexes ; stability constants ; crown ethers ; aza crown ethers ; potassium ion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The binding of K+ by dibenzo-pyridino-18-crown-6 (B2-py-18-C-6) and1,10-N,N′-didecyl-diaza-18-crown-6 (22-DD) has been studiedconductometrically at 10, 15, 20 and 25 °C in acetonitrile. Thecomplexes formed were assumed to have 1 : 1 stoichiometry. The complexes ofK+ with 18-crown-6 (18-C-6) and dibenzo-18-crown-6 (B2-18-C-6) were alsostudied for comparison purposes. The stability constant, K, of a givencomplex and its molar conductance, Λ c, were obtained by subjectingthe conductance data to a non-linear least-squares curve fitting procedure.The values of the enthalpy change, ΔH, the entropy change, ΔSand the Gibbs free energy, ΔG, associated with the formation of the 1: 1 complexes were derived and compared with relevant literature data. Thevalues of ΔG at 25 °C indicate that the binding capacity of thefour macrocycles follows the order 18-C-6 〉 22-DD 〉 B2-18-C-6 〉B2-py-18-C-6. The difference between the molar ionic conductance of the freeK+ cation and that of the bound cation, KL+, was estimated and the trend insuch differences correlates with the molecular size of the macrocycle, L.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007923632191
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  • 3
    Electronic Resource
    Electronic Resource
    A thermodynamic study of the association of alkali metal cations with dicyclohexano-18-crown-6 (1988)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 6 (1988), S. 555-564 
    Details
    ISSN: 1573-1111
    Keywords: Dicyclohexano-18-crown-6 ; alkali cations ; thermodynamic study ; crown ethers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A thermodynamic study of the association of Na+, K+, Rb+, and Cs+ with dicyclohexano-18-crown-6 in acetonitrile has been carried out at 308, 303, 298, 293, and 288 K using a conductometric technique. The observed molar conductivities, A, were found to decrease significantly for mole ratios less than unity. A model involving 1∶1 stoichiometry has been used to analyze the conductivity data. The stability constant,K, and the limiting molar conductivity, A c , for each 1∶1 complex were determined from the conductivity data by using a nonlinear least squares curve fitting procedure. The binding sequence, based on the value of logK at 298 K, as derived from this study is K+〉Na+〉Rb+〉Cs+. Values of ΔH o and ΔS o are reported and their significance is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656336
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  • 4
    Electronic Resource
    Electronic Resource
    A conductance study of the binding of benzo-15-crown-5 with alkali cations in acetonitrile (1988)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 6 (1988), S. 583-591 
    Details
    ISSN: 1573-1111
    Keywords: Benzo-15-crown-5 ; alkali cations ; electrolytic conductance ; crown ethers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The decrease in the molar electrolytic conductance of Na+, K+, Rb+, and Cs+ tetraphenylborates, caused by the addition of benzo-15-crown-5 in acetonitrile at constant ionic strength, is analyzed according to a model involving 1:1 stoichiometry. The stability constant,K, and the limiting molar conductivity, Λ c , for each 1:1 complex are determined from the conductance measurements by using a nonlinear least squares curve fitting procedure. The stability sequence of the 1:1 complexes, as deduced from data at 288, 293, 298, 303, and 308 K, has the order Na+〉K+〉Rb+〉Cs+. Values of ΔH 0, ΔS 0, and Λ c at 298 K are reported and their significance is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656339
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  • 5
    Electronic Resource
    Electronic Resource
    A thermodynamic study of the inclusion processes of α- andβ-cyclodextrins with the acid forms of methyl orange and methyl yellow (1992)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 14 (1992), S. 195-204 
    Details
    ISSN: 1573-1111
    Keywords: Inclusion complexes ; stability constants ; cyclodextrins ; methyl orange ; methyl yellow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of temperature on the UV-visible spectra of the acid forms of methyl orange and methyl yellow in the presence of α- andβ-cyclodextrins was analysed in terms of 1 : 1 inclusion processes. Three inclusion processes were considered for each azo dye/cyclodextrin system. The processes are the apparent inclusion process, the ammonium inclusion process, and the azonium inclusion process. The values of ΔH 0 and ΔS 0 are reported for each process. The inclusion complexes of the ammonium tautomer are more stable than those of the azonium tautomer and α-cyclodextrin inclusion complexes are more stable than those ofβ-cyclodextrin. The inclusion processes resulted in a shift in the position of the tautomeric equilibrium of an azo dye. A significant color fading was observed in α-cyclodextrin/methyl yellow solutions. No measurable changes in the absorbances were observed in the case of azo dye solutions containing γ-cyclodextrin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01045980
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the photolytic CO-substitutions of cyclopentadienyl(dicarbonyl)iron thiocarboxylate complexes, Cp′Fe(CO)2SCOR (Cp′ = C5H5, ButC5H4,1,3-Bu2tC5H3; R = alkyl, aryl) (2000)
    Springer
    Transition metal chemistry 25 (2000), S. 659-663 
    Details
    ISSN: 1572-901X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the photolytic CO-substitution of Cp′Fe(CO)2SCOR [Cp′ = C5H5, Bu t C5H4, 1,3-Bu2 t C5H3; R = Me, Bu t , Ph, 2-(O2N)C6H4, 3-(O2N)C6H4, 4-(O2N)C6H4, 3,5-(O2N)2C6H3] with PPh3 were studied in CH2Cl2 at 0 °C by i.r. spectroscopy. The reactions yielded exclusively the mono-CO-substituted derivatives, Cp′Fe-(CO)(PPh3) SCOR, and were found to follow second order kinetics with first order dependence on the concentration of each reactant. The differences in rates are discussed in terms of current knowledge pertaining to such reactions. An associative mechanism is proposed to account for the kinetic data of the reactions described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007004619353
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