Enthalpies of transfer for conjugate-base anions of weak acids in acetonitrile–methanol mixtures. An approach to molecular thermodynamics of ionization for weak acids in the aqueous phase

Abstract

A group-dependent correlation is observed between the Gibbs energies of ionization for weak acids in the aqueous phase, ΔG0, and the specific interaction enthalpies for the conjugate-base anions of weak acids and for uncharged amines, ΔtHSI(AN → MeOH). A group-independent correlation is observed between the entropies of ionization for weak acids in the aqueous phase, ΔSo, and the specific interaction enthalpies for the conjugate bases. The weak acid ionization in the aqueous phases is rationalized thermodynamically by the low endoergicity of ionization and entropy-controlled substituent effects.