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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of chemical information and modeling 35 (1995), S. 675-696 
    ISSN: 1520-5142
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-1111
    Keywords: conductivity ; ion–cryptand complexes ; thermodynamic formation constants in acetonitrile ; lithium ; sodium and potassium perchlorates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method is presented for the analysis of precise conductance data to obtain the true thermodynamic formation constants of macrocyclic–cation complexes. The method, based on the Lee–Wheaton theory on mixed electrolytes, takes into consideration the ion pair formation of both the uncomplexed and complexed cations and avoids the use of the simple additivity assumption of the conductances of two electrolytic species present in salt/ligand/solvent systems. The method has been applied to determine the thermodynamic complexation constants of lithium, sodium and potassium ions with the cryptands [221], [222] and their decyl derivatives [221D], [222D] in acetonitrile. The results show that the presence of an alkyl chain in the molecular structure of the cryptands decreases the macrocyclic–cation complexation constant with respect to the values obtained for the parent compounds by almost an order of magnitude. Such a finding has been explained in terms of the asymmetric position in the space of the oxyethylenic bridges of the macrocyclic ligand promoted by the presence of the linked hydrocarbon chain. The above explanation has been confirmed by the anomalous behavior of both the ion-pair association constants of complexed salts and their limiting molar conductivity.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 25 (1996), S. 541-553 
    ISSN: 1572-8927
    Keywords: Potassium ; cesium ; fluoride ; halide ions and perchlorate ; methanol ; water ; molar conductivities ; ion association ; Gibbs energies of transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electrolytic conductivities of KF and CsF in methanol solution have been determined at 25°C. The single ion molar conductivities of the fluoride ion, obtained from the two salts are in excellent agreement and indicate that the F− ion is highly solvated in methanol (MeOH). Combination of the present and literature data for related salts in both water and MeOH indicate that while the primary solvation of ions may be more extensive in H2O there is considerable enhancement of the secondary solvation sheath in MeOH. Recalculation of high precision literature conductivity data using a consistent mathematical approach indicates that ion pair formation constants for simple 1:1 electrolytes in MeOH are 1 or 2 orders of magnitude greater than in H2O. This is shown to be entirely due to the less favorable solvation of ions in MeOH, as the Gibbs energies of transfer of the neutral ion pairs MX from H2O to MeOH are also unfavorable. Calculations also show that ion association in MeOH is strongly influenced by coulombic interactions whereas in H2O short range interactions are generally more important.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-8927
    Keywords: Electrolytic conductance ; molar conductance ; ion pair formation ; complex formation ; 18-crown-6 ; calix[4]arene-bis-crown-6 ; lithium perchlorate ; sodium perchlorate ; potassium perchlorate ; rubidium perchlorate ; cesium perchlorate ; acetonitrile ; methanol ; propylene carbonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Résumé The interactions of Li+, Na+, K+, Rb+, and Cs+ with the “double-crown calix,” calix[4]arene-bis-crown-6, have been studied in methanol, acetonitrile, and propylene carbonate at 25°C using precise conductivity measurements. For Li+ and Na+ in solutions containing this calix[4]arene, only 1:1 cation:ligand complexes are formed which permit the determination of the thermodynamic complexation formation constants,K f. The conductivity data strongly suggest that 2:1 cationcalixarene complexes form with K+, Rb+, and Cs+. The existence of 2:1 complexes was experimentally confirmed for the potassium systems by a mass spectroscopic method.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We successfully observed clear K-series kaonic hydrogen X-rays for the first time taking advantage of two charged pions tagging technique and a gaseous hydrogen target. The strong-interaction energy shift and width of 1s state of K −p atom were determined to be ΔE 1s = -323 ± 63 (statistical) ± 11 (systematic) eV and Г1s = 407 ± 208 ± 100 eV. Our result means that the K −p strong interaction near threshold is repulsive and the long-standing kaonic hydrogen puzzle is solved.
    Type of Medium: Electronic Resource
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