pK Values of carboxylic acids have been measured in mixtures water-organic solvent and confronted with the Born equation. Solubilities of benzoic acid have been measured. From the pK and solubilities found the ΔGt0(C6H5COO-) values have been calculated for various two-component solvents. The results agree with the idea that the ion transfer into another medium is affected not only by electrostatic, but also by non-electrostatic forces.
The autoprotolysis constants were determined potentiometrically for water-ethanol, water-1-propanol, water-2-propanol, and water-2-methyl-2-propanol mixtures containing alcohol in concentrations of 60% (m/m) and more. Three methods were employed for the calculation of the activity ratios of the lyate ions in the systems: an empirical method based on the autoprotolysis constant and the activities of the solvent constituents, a method based on thermodynamic data, particularly the Gibbs energies of ion transfer from water to the mixed solvent, and a method based on 1H NMR data. The results of the three methods are mutually compared and discussed. The known heats of ionization for the water-ethanol system and the ionization constants of the components enabled the entropy of ionization of a mixture of water with ethanol to be calculated.
A new method for calculating the activity ratio of lyate ions in the water-alcohol mixtures is proposed on the basis of utilizing the linear relations between the Gibbs energies of ion transfer. The results for the water-methanol, -ethanol, and -2-propanol systems are compared with literature data. At the same time, the individual ionic products of water and alcohol in their mixtures were calculated. The accuracy of the method depends on the accuracy of experimental determination of the Gibbs energies of electrolyte transfer and of ionic products in mixed solvents.
Kinetic method for the evaluation of Iyate ions activities in two-component protogenic solvents has been discussed. Spectral methods for the measurement of equilibria between alkoxide and hydroxide ions have been compared. A correlation between dissociation constants of water and of weak organic acids in solvent mixtures has been found. By means of this correlation, ratios of Iyate ions activities in water-ethanol and water-2-propanol mixtures have been calculated. These activity ratios, together with the known composition of reaction products, have been used to evaluate the selectivity of the neutral and alkaline solvolysis of phthalic anhydride and benzyl chloride in solvent mixtures quoted above.
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