An approach to the problem of the dependence of the dissociation constant of weak electrolytes on the temperature and on the solvent composition in the ethane-1,2-diol–2-methoxyethanol solvent system

1989 ◽  
Vol 85 (7) ◽  
pp. 1697 ◽  
Author(s):  
Giancarlo Franchini ◽  
Andrea Marchetti ◽  
Carlo Preti ◽  
Lorenzo Tassi ◽  
Giuseppe Tosi
Keyword(s):  
Dissociation Constant ◽  
Solvent System ◽  
Solvent Composition ◽  
Weak Electrolytes

Kinetic medium effects. III. Solvent effects on A1 and A2 Hydrolyses in water-dimethyl sulphoxide mixtures

1967 ◽  
Vol 20 (9) ◽  
pp. 1815 ◽  
Author(s):  
BG Cox ◽  
PT McTigue
Keyword(s):  
Ethyl Acetate ◽  
Solvent Effect ◽  
Activity Coefficients ◽  
Solvent Effects ◽  
Butyl Acetate ◽  
Solvent System ◽  
Solvent Composition ◽  
Dimethyl Sulphoxide ◽  
Medium Effects ◽  
System Activity

The relative rates of the concurrent A1 and A2 hydrolyses of t-butyl acetate have been measured as a function of solvent composition in water-dimethyl sulphoxide (DMSO) mixtures. A large difference in solvent effect is observed, which correlates well with observed solvent effects on ethyl acetate (A2) and acetal (Al) hydrolyses in the same solvent system. Activity coefficients have been measured for t-butyl acetate, ethyl acetate, and acetal in various water-DMSO mixtures.

Metal-Assisted Reactions. Part XXX. Control of Rates of Heterogeneously Catalyzed Transfer Hydrogenolysis through Changes in Solvent Composition

2003 ◽  
Vol 56 (5) ◽  
pp. 423 ◽  
Author(s):  
José A. C. Alves ◽  
Amadeu F. Brigas ◽  
Robert A. W. Johnstone
Keyword(s):  
Liquid Phase ◽  
Adsorption Isotherms ◽  
Mixed Solvent ◽  
Phase Transfer ◽  
Catalyst Surface ◽  
Solvent System ◽  
Solvent Composition ◽  
Phase Solubility ◽  
Mixed Solvent System ◽  
Rate Of Reaction

Adsorption isotherms in the liquid phase can be used to determine the relative strengths of adsorption of reactants and solvent at a catalyst surface. Such isotherms can then be used to indicate which type of solvent would be most suitable for a heterogeneously catalyzed reaction in the liquid-phase. Solubility in any chosen solvent is also important. As examples, rates of heterogeneously catalyzed liquid-phase transfer hydrogenolyzes of aryl tetrazolyl ethers (1) have been shown to be highly dependent on both the nature of the solvent and on the solution concentrations of the reactants. The rate of reaction can be varied from zero to a maximum and then back to zero simply by adjusting the solubility of the reductant through changes in the proportion of water in a mixed-solvent system.

Re-examination of the Kirkwood–Westheimer theory of electrostatic effects. III. Dissociation constants of cis-3- and trans-4-substituted cyclohexanecarboxylic acids in water–dimethyl sulfoxide mixtures

1978 ◽  
Vol 56 (8) ◽  
pp. 1130-1133 ◽  
Author(s):  
Jitka Kirchnerova ◽  
Patrick G. Farrell ◽  
John T. Edward ◽  
Jean-Claude Halle ◽  
Robert Schaal
Keyword(s):  
Dimethyl Sulfoxide ◽  
Dissociation Constant ◽  
Dissociation Constants ◽  
Solvent Composition ◽  
Potentiometric Method ◽  
Acid Dissociation ◽  
Electrostatic Effects ◽  
Acid Dissociation Constants ◽  
Cyclohexanecarboxylic Acid

Acid dissociation constants of two cis-3- and of four trans-4-substituted cyclohexanecarboxylic acids in water – dimethyl sulfoxide mixtures of varying composition were determined by a potentiometric method. Results have been analyzed according to the model of Kirkwood and Westheimer, and shown to differ from calculated values because of certain oversimplifications built into the model. Dissociation constant differences between cyclohexanecarboxylic acid and the compounds studied vary only slightly with changing solvent composition.

Dissociation equilibria of picric acid in the binary N, N-dimethylformamide/2-methoxyethanol solvent system

1991 ◽  
Vol 69 (3) ◽  
pp. 509-517 ◽  
Author(s):  
Andrea Marchetti ◽  
Carlo Preti ◽  
Mara Tagliazucchi ◽  
Lorenzo Tassi ◽  
Giuseppe Tosi
Keyword(s):  
Dissociation Constant ◽  
Picric Acid ◽  
Solvent System ◽  
Solvent Mixture ◽  
Statistical Weight ◽  
Nonaqueous Solvent ◽  
Solvent Mixtures ◽  
Best Fitting ◽  
Complete Form ◽  
Experimental Values

Three empirical equations are proposed to fit the experimental values of the dissociation constant for picric acid, chosen as guide-solute working in the N, N-dimethylformamide/2-methoxyethanol solvent system. The work was performed operating at 19 temperatures ranging from − 10 to + 80 °C in the pure solvents and in their nine mixtures, identified by the mole fraction (X) of one component. This empirical treatment, which describes the dependence of the dissociation constant on temperature and composition of the solvent mixture, is represented by functions of the type K = K(T), K = K(X), and K = K(T, X). The K = K(T, X) equation in its complete form is composed of 20 terms, some of which can be eliminated because of small statistical weight; the number and type of these terms vary on passing from one solvent system to another and the best-fitting form is suggested. A comparison among various K = K(T, X) equations proposed in the present and in previous works has been made. Key words: dissociation equilibria, binary nonaqueous solvent mixtures, picric acid, N,N-dimethylformamide, 2-methoxyethanol.

THE SULPHURIC ACID SOLVENT SYSTEM: PART II. CONDUCTIVITY MEASUREMENTS ON SOLUTIONS OF SOME ACIDS

1961 ◽  
Vol 39 (6) ◽  
pp. 1266-1273 ◽  
Author(s):  
J. Barr ◽  
R. J. Gillespie ◽  
E. A. Robinson
Keyword(s):  
Dissociation Constant ◽  
Sulphuric Acid ◽  
Dissociation Constants ◽  
Solvent System ◽  
Acid Dissociation ◽  
Acid System ◽  
Conductivity Measurements ◽  
Acid Dissociation Constants ◽  
Strong Base ◽  
System Part

Conductivity measurements have been made on solutions of the following substances in sulphuric acid: HClO4, HSO3F, HSO3Cl, HPO2F2, HAs(HSO4)4, CH3SO3H, and CF3CO2H. Of these substances HSO3F, HSO3Cl, HAs(HSO4)4, and probably HClO4, behave as acids, CF3CO2H is a non-electrolyte, and HPO2F2, and probably CH3SO3H, are bases of the sulphuric acid system. Acid dissociation constants for HSO3F, HSO3Cl, and HAs(HSO4)4 have been determined by comparing the conductivities of their solutions with those of H2S2O7, whose dissociation constant is known from other measurements, and also by conductimetric titration with a strong base, e.g. KHSO4. These acids of the sulphuric acid system decrease in strength in the order HSO3F > HAs(HSO4)4 > HSO3Cl > HClO4.

scholarly journals CONSTANTS OF ELECTROLYTIC DISSOCIATION OF THE LITHIUM, SODIUM AND POTASSIUM SULFATES IN AQUEOUS ISOPROPANOL SOLUTIONS

2020 ◽  
Vol 63 (3) ◽  
pp. 16-22
Author(s):  
Ivan M. Borisov ◽  
Azamdzhon A. Nabiev
Keyword(s):  
Alkali Metal ◽  
Aqueous Solutions ◽  
Dissociation Constant ◽  
Salt Concentration ◽  
Volume Content ◽  
Molar Conductivity ◽  
Electrolytic Dissociation ◽  
Weak Electrolytes ◽  
Sodium And Potassium ◽  
Aqueous Isopropanol

At introduction of isopropyl alcohol in saturated aqueous solutions of sulfates of lithium, sodium and potassium at 25 °C physico-chemical properties of the studied systems Li2SO4-H2O-C3H7OH, Na2SO4-H2O-C3H7OH and K2SO4-H2O-C3H7OH are changed. This reduces the density of solutions and salt content in aqueous isopropanol solutions due to a decrease in solubility of salts. It is shown that the variation of the volume content of alcohol from 0% to 90% results in the decrease of Li2SO4 solubility 1280 times, Na2SO4 – 548 times, K2SO4 – in 278 times. Alcohol additives also affect the degree of electrolytic dissociation of salt in aqueous isopropanol solutions. To study the electrochemical properties of salts we used conductometric method based on the measurement of the molar conductivity of solutions depending on salt concentration. In aqueous solutions, alkali metal sulfates exhibit the properties of strong electrolytes and almost completely dissociate into ions. When the volume content of isopropanol in the solution is more than 30%, alkali metal sulfates begin to show the properties of weak electrolytes, as evidenced by the correlation of the molar conductivity of the diluted solution with the salt concentration under the equation describing the state of weak electrolytes. From the transformations of experimental data in the coordinates of this equation, the values of the electrolytic dissociation constants of the studied salts were determined, which vary (8.30 ± 0.01)·10-5 to (4,35 ± 0,01)·10-8 (mol/l)2 when varying the alcohol content from 30 to 90% volume. It is shown that isopropanol additives reduce the constant (and hence the degree) of electrolytic dissociation of alkali metal sulfates: the higher the alcohol concentration in the solution, the weaker the salt becomes as an electrolyte. The value of the electrolytic dissociation constant depends on the nature of the salt: with an increase in the size of the sulfate cation, the electrolytic dissociation constant decreases.

Effect of Solvent Composition on Aflatoxin Fluorescence

1984 ◽  
Vol 67 (2) ◽  
pp. 306-308
Author(s):  
Ivan Chang-Yen ◽  
Valerie A Stoute ◽  
Jane B Felmine
Keyword(s):  
Excited State ◽  
Fluorescence Intensity ◽  
Solvent System ◽  
Solvent Composition ◽  
Effect Of Solvent ◽  
Chloroform Methanol

Abstract The influence of the chloroform-methanol solvent system on the fluorescence of aflatoxins Bi, B2, Gj, and G2 was investigated. Fluorescence intensity is markedly affected by solvent composition. The formation of excited state dimers and ionization are proposed to explain the effects observed.

Plasminogen-Plasmin System IX. Specific Binding of Tranexamic Acid to Plasmin

1975 ◽  
Vol 33 (03) ◽  
pp. 573-585 ◽  
Author(s):  
Masahiro Iwamoto
Keyword(s):  
Tranexamic Acid ◽  
Affinity Chromatography ◽  
Dissociation Constant ◽  
Factor Xiii ◽  
Specific Binding ◽  
The Other ◽  
Inhibitory Mechanism ◽  
Binding Studies ◽  
Similar Affinity ◽  
Fibrin Structure

SummaryInteractions between tranexamic acid and protein were studied in respect of the antifibrinolytic actions of tranexamic acid. Tranexamic acid did neither show any interaction with fibrinogen or fibrin, nor was incorporated into cross-linked fibrin structure by the action of factor XIII. On the other hand, tranexamic acid bound to human plasmin with a dissociation constant of 3.5 × 10−5 M, which was very close to the inhibition constant (3.6 × 10−5 M) for this compound in inhibiting plasmin-induced fibrinolysis. The binding site of tranexamic acid on plasmin was not the catalytic site of plasmin, because TLCK-blocked plasmin also showed a similar affinity to tranexamic acid (the dissociation constant, 2.9–4.8 × 10−5 M).In the binding studies with the highly purified plasminogen and TLCK-plasmin preparations which were obtained by affinity chromatography on lysine-substituted Sepharose, the molar binding ratio was shown to be 1.5–1.6 moles tranexamic acid per one mole protein.On the basis of these and other findings, a model for the inhibitory mechanism of tranexamic acid is presented.

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