Factor analysis applied to correlation between acidity constants of series of diuretics, quinolones and buffers, with solvatochromic parameters in water-acetonitrile mixtures

The dissociation constants of series of compounds, diuretics, quinolones and buffers in several acetonitrile water mixtures were subjected to factor analysis. Two or three factors emerged depending on the group of substances. Target factor analysis results showed that the Kamlet and Taft equation was reduced in these mixtures: the independent term and π∗ solvatochromic parameter of polarity-polarizability appear in all cases whereas, in those cases in which a third factor was involved, this was the hydrogen bond basicity β solvatochromic parameter. An excellent correlation was found between the logarithm of the dissociation constant values of each acid in the binary mixtures and their corresponding π∗ and β values. The relationships obtained allow the pK values of the studied substances in any acetonitrile-water mixtures up to 70% (w/w) to be calculated as well as the most important solvent properties that affect electrolyte dissociation to be evaluated.