Factor analysis applied to the correlation between dissociation constants and solvatochromic parameters in water-acetonitrile mixtures .1. Solvent effects on the dissociation of carboxylic acid groups in some diuretics, quinolones, buffers and peptides

The dissociation constants in several acetonitrile-water mixtures of the carboxylic acid groups of 19 substances, included into four different sets (diuretics, quinolones, buffers and peptides) were first submitted to factor analysis (FA) in order to find how many factors affect the variations in the data sets. Then target factor analysis (TFA) was performed in order to identify these factors. The influence of solvatochromic parameters in the interactions between carboxylic acid groups and the solvents studied was identified and quantified. The model Kamlet-Taft equation for each substance was established. The general effect of the preferential solvation of electrolytes in acetonitrile-water mixtures on the values of the protonation constants in these media is also described.