IONIZATION OF SOME NITROGEN-CONTAINING ORGANIC BASES IN WATER-ETHANOL AND WATER-ACETONE MEDIA

Abstract

In this paper, the ionization constants (pKa) of some nitrogen-containing organic bases (morfoline, piperidine and benzylamine) in water-ethanol and water-acetone media at various concentrations of organic solvent in the system has been determined by the potentiometric titration method. It was established that the value of pKa of nitrogen-containing organic bases in aqueous-organic media naturally decreases with increasing content of organic solvent in the system. It was shown that their nature (aromatic or heterocyclic) and the physico-chemical properties of the medium are significantly influenced by the nature and degree of change in the electron donor ability of the nitrogen-containing organic bases studied It should be noted that for the studied nitrogen-containing organic bases (morfoline, piperidine and benzylamine), when passing from an aqueous medium to an organic one (ethanol or acetone), the pKa values naturally decrease with an increase in the content of the organic solvent in the system. In general, in the transition from an aqueous medium to an organic one (ethanol or acetone), a change in pKa can reach 2.43 units. It was established that the dependence of the values of pKa of nitrogen-containing organic bases which were determinate via potentiometric titration method on the inverse of the dielectric constant of water-ethanol and water-acetone solutions tends to be linear, consistent with Izmailov’s theory. Thus, we can conclude that the change in the ratio of the mixed solvent components and, as a result, in general, dielectric permeability of the medium does not lead to a significant change in the solvation characteristics of the nitrogen-containing organic bases studied.