Anion solvation properties of protic solvents. 2. Salt distribution study

Y. Marcus, E. Pross, J. Hormadaly

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25 Scopus citations

Abstract

Standard Gibbs free energies of transfer of chloride anions from water to organic solvents ΔG°tr(Cl-,H2O→S), based on the tetraphenylarsonium tetraphenylborate extrathermodynamic assumption, have been selected from the data in the literature, and correlated with the solvent index ET. The expression ΔG°tr(Cl-,H2O→S)/(RT ln 10) = (29.5 ± 1.4) - (0.116 ± 0.007)(ET/kJ mol-1) is found to express the data sufficiently well, so that ΔG°tr could be calculated for a large group of protic solvents for which ET data were recently obtained. Also, the distribution of potassium chloride between dilute solution of crown ethers in these solvents and aqueous solutions was measured, and the standard Gibbs free energies of distribution, ΔG°distr, were obtained. These are related to the former quantities by ΔG°tr(Cl-,H2O→S)/kJ mol-1 = ΔG°distr/kJ mol-1 + (116/∈S) + (29 ± 3) where ∈S is the dielectric constant of the solvent. This semiempirical expression is rationalized in terms of the interactions leading to the distribution equilibrium. Distribution measurements as described here are proposed as a general method for obtaining individual standard Gibbs energies of transfer of anions from water to immiscible solvents.

Original languageEnglish
Pages (from-to)2708-2715
Number of pages8
JournalJournal of Physical Chemistry
Volume84
Issue number21
DOIs
StatePublished - 1 Jan 1980
Externally publishedYes

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