Any function that measures the thermodynamic @[email protected] or -accepting ability of a solvent system, or a closely related thermodynamic property, such as the tendency of the @[email protected] of the solvent system to form @[email protected] (The term 'basicity function' is not in common use in connection with basic solutions.) @[email protected] functions are not unique properties of the solvent system alone, but depend on the solute (or family of closely related solutes) with respect to which the thermodynamic tendency is measured. Commonly used @[email protected] functions refer to concentrated acidic or basic solutions. @[email protected] functions are usually established over a range of composition of such a system by UV/VIS spectrophotometric or NMR measurements of the degree of hydronation (protonation or @[email protected] formation) for the members of a series of structurally similar indicator bases (or acids) of different strength: the best known of these functions is the Hammett acidity function \(H_{0}\) (for uncharged indicator bases that are primary aromatic @[email protected]).
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1081 [Terms] [Paper]