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1989 (1)
1976 (2)
1974 (1)
1Author    G. AndereggRequires cookie*
 Title    Komplexone, XLVII Die Thermodynamik der Komplexbildung von einigen ein-und zweiwertigen Metallionen mit Aethylendiamintetraacetat-und Uramildiacetat-Ion Complexone, XLVII Thermodynamics of Complex Formation of Some Univalent and Bivalent Metal Ions with Ethylenediaminetetraacetate and Uramildiacetate Anions  
 Abstract    The enthalpies of complex formation of EDTA and uramildiacetate (UDA) with univalent cations (H+, Li+, Na+, K + , Ag+ and T1+) have been obtained by direct calori-metric measurements at ionic strength 0.1 (or 1) and 20 °C. For comparison data for the formation of 1:1 UDA complexes with Mg 2+ , Ca 2+ , Ba 2+ and Sr 2+ have also been obtained. From these values and the stability constants the thermodynamic functions A G and A S are calculated. The results are compared with those of similar systems. 
  Reference    (Z. Naturforsch. 31b, 786—789 [1976]; eingegangen am 15. März 1976) 
  Published    1976 
  Keywords    EDTA Complexes, Uramildiacetate Complexes, Stability Constants, Enthalpy, Entropy 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0786.pdf 
 Identifier    ZNB-1976-31b-0786 
 Volume    31 
2Author    B. S. Sekhon, S. L. ChopraRequires cookie*
 Title    Stabilities of Vanadyl Complexes with Methionine, Phenylalanine, and Threonine  
 Abstract    Stepwise formation constants corresponding to 1:1 vanadyl complexes with methionine, phenyl­ alanine and threonine have been determined at 25 °C, and at various ionic concentrations, viz. 0.01, 0.1 and 0.3 M , maintained by the addition of potassium chloride solution. Thermodynamic stability constants have been obtained by extrapolation of log K values to zero ionic strength. Logarithms of the overall stability constants (lo g £ (u = 0)) are 7.72 for methionine, 7.70 for phenyl­ alanine and 7.44 for threonine complexes. The corresponding free energy changes (AG°) are — 10.53, — 10.51, — 10.15 kcal-mol-1 respectively. 
  Reference    (Z. Naturforsch. 29c, 336 [1974]; received November 30 1973/April 9 1974) 
  Published    1974 
  Keywords    Amino Acid Complexes, Vanadyl Complexes, Stability Constant 
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 TEI-XML for    default:Reihe_C/29/ZNC-1974-29c-0336.pdf 
 Identifier    ZNC-1974-29c-0336 
 Volume    29 
3Author    Jürgen PolsterRequires cookie*
 Title    Ein neues Verfahren zur spektrometrischen Analyse von Metallkomplex-Lösungen A New Method for Spectrometric Analysis of Complex Metal Solutions  
 Abstract    A new simple method is given to analyse potentiometrically titrated and spectrophoto-metrically measured complex-solutions of the system AH ^ A -j-H3Ü+ and n • A + M^MA n . The absorbance coefficients of the metal complex MA n and the stability constants can be determined for each titration step by construction of the "extinction triangle" in the (two-dimensional) absorbance (E) diagram. It is not necessary to know the absolute pH value of the solution. The titration of 2-nitroso-l-naphthol-4-sulfonic acid/zinc sulfate in water is shown as an example. 
  Reference    (Z. Naturforsch. 31b, 1621—1625 [1976]; eingegangen am 15. September 1976) 
  Published    1976 
  Keywords    Spectrophotometry Titrations, Absorbance Diagrams, Complex, Stability Constants, Absorbance Coefficients 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1621.pdf 
 Identifier    ZNB-1976-31b-1621 
 Volume    31 
4Author    Guogang Liang, NicolasA. Corfù, Helmut SigelRequires cookie*
 Title    Influence of Decreasing Solvent Polarity (Dioxane-Water Mixtures) on the Stability of Metal Ion Complexes Formed with Phosphate Monoesters  
 Abstract    The acidity constants o f H (R —M P)~, where R —M P: = 4-nitrophenyl phosphate (N PhP2). phenyl phosphate (PhP2) and D -ribose 5'-m onophosphate (R ibM P2). and the stability constants of the binary C u (R -M P) com plexes w'ere determ ined by potentiom etric pH titrations in aqueous solution and in 20. 30, 40 and 50% (v/v) dioxane-water mixtures. The solvent influence on the corresponding equilibrium constants is com pared with the same influence on previously studied systems containing uridine 5'-triphosphate. formate or acetate. The influence o f the solvent com position on the various ligand (L) system s was evaluated by constructing log Km(L) versus pK[j(L) plots; in all cases straight lines are obtained with slopes close to 1. This indicates that in all these system s, despite the different negative charges o f the involved ligands, the solvent effect on proton binding and on metal ion binding is approxim ately o f the same size: A decreasing solvent polarity resulting from the addition o f increasing am ounts o f organic solvent to the aqueous solutions favors the affinity o f the negatively charged ligands for protons and metal ions as well. Information o f this type is considered important because the 'effective' or 'equivalent solution' dielectric constants in active-site cavities o f enzym es are reduced com pared with the dielectric constant o f bulk water; i. e., in protein cavities also a decreased 'solvent polarity' is occurring and this is expected to affect the stability o f metal ion-ligand bonds. 
  Reference    Z. Naturforsch. 44b, 538 (1989); received N ovem ber 28 1988 
  Published    1989 
  Keywords    Phosphate M onoester, Metal Ion C om plexes, Solvent Influence, Stability Constants, A ctive-Site Cavities o f Enzymes 
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 TEI-XML for    default:Reihe_B/44/ZNB-1989-44b-0538.pdf 
 Identifier    ZNB-1989-44b-0538 
 Volume    44