Transfer Free Energies of Fluoride Ion in Aqueous Mixtures of Some Organic Solvents

Abstract

Standard free energies of transfer, ΔGt°, of potassium fluoride (KF) from water to aqueous mixtures of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetonitrile (ACN), 1,2-dimethoxyethane (DME), and 2-methoxyethanol (ME) have been determined at 25 °C from emf measurements performed on the double cell: Pb(Hg)–PbF2/KF(m), solvent/K(Hg)/KF(m), water/PbF2–Pb(Hg). ΔGt° values of F− were obtained from these values using the corresponding values of K+, as obtained earlier by use of tetraphenylarsonium tetraphenylborate reference electrolyte assumption. In each solvent system ΔGt°(F−) values are found to be increasingly positive with cosolvent composition reflecting the pronounced destabilization of F− and their relative order : DME>DMSO≥DMF>>ACN≈ME conforms to what is expected from the relative ‘aproticity’ of the dipolar aprotic cosolvents and that induced in the protic ME by the possible intramolecular H-bonding. The observed larger destabilization of F− compared to OH− in ME–water system has been attributed to the H-bonding effect of the protic cosolvent ME and the reverse behaviour in DME–water and DMSO–water systems to the absence of such effect of these cosolvents. Moreover, tests of Feakins-type extrapolation for assigning individual ion contribution using ΔGt°(KF) values along with those of other potassium halides, provided some important reflections on the inadequacy of such plots made without the data points of F−.

Gibbs Energies of Transfer of Anions from Water to Mixed Aqueous Organic Solvents

“…Note that the values of Δ t G °(F - ) reported by Hefter were in terms of integral kJ mol -1 numbers, so that the averages for the three cations (only two at each solvent composition) should not convey the impression of better precision. As far as the Δ t G °(F - ) values from Bhattacharya et al go, they are in agreement with the former set, and it is noteworthy that the Δ t G °(OH - ) values from Bhattacharya et al are similar to these too. The lower values for Δ t G °(OH - ) from the other two sources appear to be inconsistent with this.…”

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

“…For the other halide [35], n Cl À from [33], , Br À from [34], j I À , h I À from [36], and ¤ ClO À anions data from [25] exist for F À up to x DMF = 0.3 and from [26] for Br À and I À up to x DMF = 0.5, but also for the neat DMF. The value of V F,DMF had to be estimated, there being no value for it in [12].…”

Solvent Extraction Study of Nd3+-F- , Eu3+-F- , and Tm3+-F- Interaction in Mixed System of Dimethyl Sulfoxide and Water

“…Because the AGa(F~) has been obtained experimentally by Bhattacharya et al [5], the Δ g/RT may be calculated with Eq. (10) from the values of In /^(mix) and In /^(HjO) and are shown in Fig.…”