Gibbs energy of solvation of organic ions in aqueous and dimethyl sulfoxide solutions

Abstract

The Gibbs energy of solvation of several ions in water and dimethyl sulfoxide (DMSO) solutions was obtained through the use of thermodynamic equations relating ΔG_solv* of the ion with gas phase basicity, pK_a, ΔG_solv* of neutral species and the Gibbs energy of solvation of the proton. We have used the most accurate and recent values for these properties, and this report provides 56 Gibbs energy of solvation values in aqueous solution and 30 in DMSO solution. Our results support the general view that anions are much better solvated in aqueous solution than in DMSO. An important example is the hydroxide ion for which the Gibbs energy of transfer from water to DMSO is 26 kcal mol⁻¹. The majority of anions have a Gibbs energy of transfer in the range 10 to 15 kcal mol⁻¹. In the case of cations, DMSO has a larger solvation ability but the difference in the Gibbs energy of solvation between water and DMSO is not greater than 5 kcal mol⁻¹. The present data can be very useful for the development of continuum solvation models.