PROTON DISSOCIATION OF AQUEOUS-ORGANIC ACIDS STUDIED BY MULTIVARIATE CHEMOMETRICS

Thermodynamic data of proton dissociation of 75 organic acids belongin g to four classes (protonated amines, aliphatic carboxylic acids, benz oic acids, phenols) have been processed by multivariate chemometric te chniques. The variables consist of conventional thermodynamic quantiti es (Gibbs function, enthalpy, entropy) and of partial components of th ese quantities (internal and external, electrostatic and nonelectrosta tic components). The above data refer to the aqueous medium, at 25 deg rees C and I = 0 mol dm(-3). The Gibbs function of deprotonation in th e gas phase and the Hammett a constant have also been considered. Mult ivariate techniques include Principal Component Analysis, Factor Analy sis, and feature selection. Factor Analysis and related concepts have proved to be useful in defining the causes of differences in acid stre ngths and their respective importance.