Preferential solvation of ions in mixed solvents. 6: Univalent anions in aqueous organic solvents according to the inverse Kirkwood–Buff integral (IKBI) approach

Abstract

The inverse Kirkwood–Buff integral (IKBI) approach is applied to the preferential solvation of F −, Cl −, Br −, I −, and ClO 4 - in aqueous mixtures of the co-solvents (S) methanol (MeOH), ethanol (EtOH), t-butanol ( t-BuOH), 1,2-ethanediol (EG), glycerol (Gly), acetone (Me 2CO), acetonitrile (MeCN), formamide (FA), N, N-dimethylformamide (DMF), N, N, N′, N′, N″, N″-hexamethyl phosphoric triamide (HMPT), and dimethylsulfoxide (DMSO), as far as the relevant data exist in the literature. Fluoride anions are selectively solvated by the water up to large mole fractions ( x S ⩾ 0.4) of S = EtOH, t-BuOH, Me 2CO, MeCN, and DMF, and up to lower contents ( x S ∼ 0.1) of MeOH, EG, FA, and DMSO. The other anions are preferentially solvated by water to diminishing extent as their sizes become larger, and the largest ones show some preference for S in water-rich mixtures of MeOH and FA, whereas in aqueous Gly even chloride is preferentially solvated by the Gly. The competition between the co-solvent and the anion for the hydrogen bonds that water molecules donate is the main cause for the observed preferential solvation behaviour.