Solubility Parameters and the Distribution of Ions to Nonaqueous Solvents

Abstract

Provided a singly charged, spherically symmetrical ion has a radius greater than ca. 0.2 nm, its distribution to a nonaqueous solvent from water can be accounted for by assigning to it a Hildebrand solubility parameter estimated for an uncharged atom or molecule, regardless of the model assumed for the Gibbs energy of charging the ionthat of Born, Abraham, and Liszi (J. Chem. Soc., Faraday Trans. 1 1978, 74, 1604, 2858) or Abe (J. Phys. Chem. 1986, 90, 713)in the nonaqueous phase. For smaller ions, however, no choice of solubility parameter or ion size can alone account for their extractability. The extensive data available for the Gibbs energy of transfer of monovalent ions from water to a variety of solvents can be accounted for by assigning to the ion, in addition to a plausible solubility parameter, an effective radius rs = (ri3 + Δrs3)1/3, wherein ri is the radius of the ion and Δrs is an adjustable distance characteristic of the solvent. Separate sets of Δrs values are needed for cations and anions....