Use of scaled-particle theory in the assessment of the Ph4As+/Ph4B− assumption for single ions

• Published in: Canadian journal of chemistry 1979-01, Vol.57 (1), p.71-76
• Main Authors: Abraham, Michael H, Nasehzadeh, Asadollah
• Format: Article
• Language: English
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/v79-012

A novel method for the assessment of the Ph 4 As + /Ph 4 B − assumption for free energies of transfer of single ions has recently been suggested by Treiner, and used by him to deduce that the assumption is not valid for transfers between water, propylene carbonate, sulpholane, dimethylsulphoxide, N-methyl-2-pyrrolidone, and perhaps also dimethylformamide. The basis of the method is the estimation of the free energy of cavity formation by scaled-particle theory, together with the hypothesis that the free energy of interaction of Ph 4 As + (or Ph 4 B − ) with solvent molecules is the same in all solvents, ΔG t 0 (int) = 0. It is shown in the present paper that (a) whether or not the Ph 4 As + /Ph 4 B − assumption applies to transfer to a given solvent depends on which other solvent is taken as the reference solvent in Treiner's method, (b) the calculation of the cavity free energy term by scaled-particle theory and by the theory of Sinanoglu - Reisse - Moura Ramos (SRMR) yields values so different that the method cannot be considered reliable, (c) the calculation of cavity enthalpies and entropies for Ph 4 As + or Ph 4 B − by scaled-particle theory yields results that are chemically not reasonable, (d) the hypothesis that ΔG t 0 (int) = 0 conflicts with SRMR theory, and (e) the conclusions reached by Treiner are not in accord with recent work that in general supports the Ph 4 As + /Ph 4 B − assumption for solvents that are rejected by Treiner.