An Alternative Explanation of the Influence of Medium Basicity in the Acid-Base Concept

Abstract

A model of influencing chemical and physical properties (equilibria and spectral parameters) of HBD (Hydrogen Bond Donor) acids by HBA (Hydrogen Bond Acceptor) bases, based on the influence of of HBD-HBA complexes by nonspecific interactions with the medium, is proposed. The model interprets also current difficulties associated with evaluation of basicity effects, namely (i) the problem of the number of characteristics of bases necessary for interpretation of experiment, (ii) the problem of the effect of base as solvent and solute, (iii) problematic effects of some bases such as trialkylamines and pyridines and (iv) LFER dependences observed only for chemically related bases. The model is applied to evaluation of the basicity effect on the HDB-HBA equilibrium between bases and 4-fluorophenol and on the wavenumbers of OH stretching vibration of complexes of phenol with eleven bases. Relationships are given between basicity factors F¹, F² and decadic logarithms of equilibrium constants of association of 4-fluorophenol with the bases in the gas state (log K^g) and sensitivity of the latter parameter to nonspecific interactions with the medium (p).