The Critical Increment of Ionic Reactions. II. The Influence of Dielectric Constant and Ionic Strength

1938 ◽  
Vol 60 (2) ◽  
pp. 330-334 ◽  
Author(s):  
W. J. Svirbely ◽  
Arthur Schramm
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Ionic Reactions

scholarly journals Speciation Studies of L-Histidine Complexes of Pb(II), Cd(II), and Hg(II) in DMSO-Water Mixtures

2012 ◽  
Vol 2012 ◽  
pp. 1-9
Author(s):  
K. Bharath Kumar Naik ◽  
B. Ananda Kumar ◽  
S. Raju ◽  
G. Nageswara Rao
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Complex Formation ◽  
Species Distribution ◽  
Statistical Parameters ◽  
Experimental Conditions ◽  
Equilibrium Study ◽  
Predominant Species ◽  
Chemical Models ◽  
Best Fit

Equilibrium study on complex formation of L-histidine with Pb(II), Cd(II), and Hg(II) has been investigated pH metrically in DMSO-water mixtures (0–60% v/v) at 303 K and 0.16 mol L−1 ionic strength. The predominant species detected for Pb(II) and Cd(II) are ML2H4, ML2H3, ML2H2, ML2H, and ML2 and those for Hg(II) are ML2H4, ML2H3, ML2, and ML. The appropriateness of experimental conditions is verified by introducing errors intentionally in the concentrations of ingredients. The models containing different numbers of species were refined by using the computer program MINIQUAD75. The best-fit chemical models were arrived at based on statistical parameters. The trend in variation of stability constants of the complexes with dielectric constant of the medium is attributed to the electrostatic and nonelectrostatic forces. The species distribution and the plausible equilibria for the formation of the species are also presented.

ÉTUDE DES EFFETS ÉLECTROSTATIQUES SUR LE MÉCANISME D'ACTION CATALYTIQUE DE LA PHOSPHATASE ALCALINE INTESTINALE DE VEAU

1965 ◽  
Vol 43 (8) ◽  
pp. 2222-2235 ◽  
Author(s):  
Michel Lazdunski ◽  
Jacques Brouillard ◽  
Ludovic Ouellet
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Maximum Activity ◽  
Enzyme Molecule ◽  
High Substrate Concentration ◽  
Nitrophenyl Phosphate ◽  
Phosphatase Alcaline ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Activated Complex

The influence of dioxane and ethanol on the rate of hydrolysis of p-nitrophenyl phosphate in the presence of an intestinal alcaline phosphatase can be interpreted as a dielectric constant effect, at high substrate concentration. The dielectric constant effect is a function of the pH of the medium and is maximum around pH 9.4 at 25 °C and pH 9.0 at 15 °C. An interpretation suggesting that the change in diameter of the enzyme molecule becoming an activated complex is minimum at a pH of maximum activity is proposed. The same model can take into account the influence of the ionic strength on the same reaction.

scholarly journals Effect of Solvent on Protonation Equilibria ofL-Proline andL-Valine in 1, 2-Propanediol-Water Mixtures

2012 ◽  
Vol 9 (2) ◽  
pp. 517-524 ◽  
Author(s):  
P. Bhushanavathi ◽  
B. Veeraswamy ◽  
G. Nageswara Rao ◽  
U. Viplavaprasad
Keyword(s):  
Dielectric Constant ◽  
Sodium Chloride ◽  
Ionic Strength ◽  
Protonation Constants ◽  
Protonation Equilibria ◽  
Effect Of Solvent ◽  
R Factor ◽  
Chemical Models ◽  
Best Fit ◽  
Skewness And Kurtosis

Protonation equilibria ofL-proline and L-valine in varying compositions (0.0-60.0% v/v) of 1, 2-Propanediol-water mixtures were investigated pH-metrically. Titrations were performed at 303.0 K and the ionic strength of the medium was maintained at 0.16 mol L-1using sodium chloride. The best fit chemical models of the protonation equilibria were based on crystallographic R-factor, Χ2, skewness, and kurtosis. All the protonation constants of proline and valine increased with increasing propanediol content. This is attributed to the dielectric constant of the medium.

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