Proton dissociation of aqueous organic acids studied by multivariate chemometrics

Abstract

Thermodynamic data of proton dissociation of 75 organic acids belonging to four classes (protonated amines, aliphatic carboxylic acids, benzoic acids, phenols) have been processed by multivariate chemometric techniques. The variables consist of conventional thermodynamic quantities (Gibbs function, enthalpy, entropy) and of partial components of these quantities (internal and external, electrostatic and nonelectrostatic components). The above data refer to the aqueous medium, at 25OC and I = 0 mol dm-3. The Gibbs function of deprotonation in the gas phase and the Hammett a constant have also been considered. Multivariate techniques include Principal Component Analysis, Factor Analysis, and feature selection. Factor Analysis and related concepts have proved to be useful in defining the causes of differences in acid strengths and their respective importance.

Solvatochromic Linear Solvation Energy Relationships (LSER) for Solubility of Gases in Various Solvents by Target Factor Analysis

“…The correct number of abstract factors was obtained by using three tests, namely Malinowski's indicator function (IND), real error in the data matrix (RE), and the percentage of significance level (%SL) associated with the successive F values evaluated for an increasing number of factors. 42 Once the number of factors was determined, TFA was applied for identification of the chemical nature of these factors. The target vectors were the Hildebrand solubility parameters and the solvatochromic parameters of the different solvents.…”