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  • Physical Chemistry  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Complexes of TRI- and tetraprotonated forms of 1,4,7,10,13-pentaazacyclopentadecane with various mono- and divalent anions in aqueous media (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 443-450 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acid dissociation and anion complexation properties of 3+ and 4+ forms of 1,4,7,10,13-pentaazacyclopentadecane were investigated by pH potentiometry, conductometric titration and 13C NMR experiments. The 3+ and 4+ species form complexes with a variety of mono- and divalent anions, and their complexation constants can be determined by pH potentiometric methods. However, no iodide complexes are detected and neither is a pentaprotonated species. Enthalpy and entropy changes for the acid dissociation of the 3+ ligand and for its complexation with chloride are estimated. The complexation and acid dissociation properties of the ligand are discussed in terms of internal hydrogen bonding interactions and solvation effects.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610050804
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  • 2
    Electronic Resource
    Electronic Resource
    Compensation effects in the complexation reactions of α- and β-cyclodextrin (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 825-832 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Analysis of temperature dependent equilibrium constant data for the complexation of α-cyclodextrin with approximately 70 different substrates demonstrates the existence of a general compensation effect. Enthalpies (kJ mol-1) and entropies (J K-1 mol-1) of complexation are related by ΔH = -5·70(±0·05) + [421·1(±1·2)]ΔS. A few substrates deviate from the general effect, possibly owing to reorganization of internal hydrogen bonding interactions. Complexation reactions involving β-cyclodextrin are found to divide into two groups. Eleven small molecule or ion substrates undergo isoentropic complexations with ΔS = -5·7±2 J K-1 mol-1. Fourteen larger substrate species exhibit a compensation effect with ΔH = -23·5(±0·2) + [634(±26)]ΔS. The compensation behavior of the two cyclodextrins is discussed in terms of bonding mechanisms and cavity size.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610081209
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of the existence, value and uncertainty of the compensation or isokinetic temperature (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 273-280 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The demonstration of the existence of a compensation effect, the linear dependence of the enthalphy on the entropy for a series of chemical reactions, is often complicated by an apparent linear dependence arising solely from experimental errors. A non-linear least squares method has been developed for establishing the existence or non-existence of a compensation effect and for determining the value of the compensation temperature if the effect exists. The uncertainty in the value of the compensation temperature can be determined by means of a Monte Carlo procedure. If a compensation effect does not exist, three cases can be distinguished: (1) the relationship between the enthalpy and entropy is linear, but the compensation temperature is 0 K; (2) the various reactions cannot be distinguished from each other because of experimental errors; and (3) the reactions do differ, but the relationship (if one exists) between the enthalpy and entropy is not linear. The method is illustrated using both hypothetical and experimental examples.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060504
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    Paper (German National Licenses)
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