Empirical analysis on the constituent terms of transfer enthalpies. Quarternary ammonium ions in acetonitrile–methanol mixtures

Abstract

Through an empirical analysis of transfer enthalpies in acetonitrile–methanol mixtures using ten quaternary ammonium ions, an equation which expresses the behaviour of the transfer enthalpy as a function of solvent composition has been derived: ΔH^AN→mix_t(RR′₃N⁺)=ΔH^AN→mix_t[(Buⁿ)₄N⁺]+δ_RΔH^AN→MeOH_t(RR′₃N⁺)x_MeOH+A(RR′₃N⁺)x_MeOHx_AN. On the basis of this equation it is suggested that the transfer enthalpy includes at least three types of interaction, a protophobic interaction, an electrostatic interaction and another interaction, presumably a specific interaction such as dipole–dipole or acid–base association.