The Thermodynamics of Ionization of Polycarboxylic Acids

Thermodynamic parameters for the successive ionizations of a number of monomeric polycarboxylic acids have been determined from a temperature-dependence study of the ionization constants calculated from potentiometric data obtained using cells without liquid junction. Specifically the acids are: 1,2,3-propanetri-; 1,2,3,4-butanetetra-; 1,3-benzenedi-; 1,2,3-, 1,2,4-, and 1,3,5-benzenetri-; 1,2,4,5-benzenetetra-; and 1,2,3,4,5,6-benzenehexacarboxylic acids. The data are critically discussed in terms of the common models of ionization and of reactivity effects of substituents on ionization for monomeric and polymeric polybasic acids.