Limit of concentration constant of protolytic equilibrium

Lysova, S. S.; Starikova, T. A.; Zevatskii, Yu. É.

doi:10.1134/s1070363214080325

Cited by 4 publications

(2 citation statements)

References 5 publications

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“…Previously, in our paper, 12 we determined the thermodynamic dissociation constants of weak monobasic organic acids in the binary electrolyte−solvent systems through the application of concentration spectrophotometric measurements in combination with the numerical extrapolation methods.…”

Section: ■ Introductionmentioning

confidence: 99%

Determination of the Dissociation Constants of 5-Substituted 1H-Tetrazoles and Amino Acids by the Concentration Spectrophotometric Method: A New Approach

2017

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A new theoretical and experimental approach to determination of the thermodynamic dissociation constants of a number of active pharmaceutical compounds, such as 5-substituted-1H-tetrazoles and amino acids, has been proposed. We obtained our experimental data from A (absorbance) to C/mol•dm −3 (concentration of weak electrolyte) without either measuring pH during the experiment or using buffer solutions with a constant ionic strength. Thermodynamic dissociation constants were obtained by extrapolating the calculated dissociation constants to zero concentration of the investigated compound. We determined the previously unknown values of thermodynamic dissociation constants of three 5-substituted-1H-tetrazoles with poorly resolved spectra of the protonated and unprotonated forms.

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Section: ■ Introductionmentioning

confidence: 99%

Determination of the Dissociation Constants of 5-Substituted 1H-Tetrazoles and Amino Acids by the Concentration Spectrophotometric Method: A New Approach

2017

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“…Previously, we showed that the thermodynamic equilibrium constant K T could be measured by extrapolation of pK C to infinite dilution [3]:…”

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Protolytic Equilibrium Constant and Colligative Properties of Mono- and Polyelectrolyte Solutions

2015

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Proteolytic equilibria of weak mono-and polyelectrolytes in binary aqueous solutions were investigated using spectrophotometry. It was shown that concentration dissociation constants of weak mono-and polyelectrolytes in the concentration range 10 -5 -10 -2 M depended more on the electrolyte acidity or basicity and less on their structures.Colligative properties of electrolyte solutions are responsible for boiling-point elevation and freezing-point depression compared with the values for the pure solvent and reduction of the vapor pressure above the solution and the osmotic pressure. All these properties depend on not only the number of molecules of dissolved electrolyte but also their nature [1,2].Previously, we showed that the thermodynamic equilibrium constant K T could be measured by extrapolation of pK C to infinite dilution [3]:where pK C = -logK C ; K C , the concentration constant of proteolytic equilibrium for a weak electrolyte of solution molarity C; and b, an empirical coefficient. Obviously, the explicit form of K C as a function of concentration is linear, analogously to the colligative properties of electrolyte solutions.Therefore, it was hypothesized that proteolytic equilibria of weak electrolytes in binary aqueous solutions could be regarded as colligative properties. Then, coefficient b in Eq. (1) would be independent of the electrolyte structure.The theoretical justification of this hypothesis follows. The reduction of the free energy G(s) of a limiting diluted binary solution relative to that of the pure solvent G(sol) is [1]:where x is the mole fraction of dissolved compound. If the compound is a weak electrolyte with a prototropic or protophilic center, then it can dissociate as followswhere AH is an acid; B, a base.

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