The Effect of Solvent Structure on the Mobility of Symmetrical Ions in Aqueous Solution

The solubilities of 18 decanones have been measured in H 2 0 and D 2 0 at 25°C from their U.V. absorption spectra. The data were used to calculate AG,O, the standard free energy of transfer of these solutes from H 2 0 to D,O. AG,O was found negative for the saturated ketones, but positive for most of the unsaturated and polycyclic isomers. A rough correlation was observed between AG,O and the degree of branching in the hydrocarbon chains of the ketones: AG,O increases with the degree of branching. From the temperature dependence of AG,D obtained at 10, 25, and 40 "C, heats of transfer AH? were determined for typical ketones, namely 2-decanone and adamantanone. AH? was found as -2.1 kcal mol-' for 2-decanone and -0 + 0.5 kcal mol-' for adamantanone.The results are discussed in terms of two main contributions: (I) an isotope effect in the free energy of cavity formation and (2) L'interpretation des resultats est donnee selon deux contributions principales aux fonctions de transfert: (1) difference dans I'tnergitique de la formation d'une cavite dans les deux solvants et (2) difference dans les effets que les solutes exercent sur la structure des solvants. La premiere contribution est evaluee a I'aide de la theorie "scaled-particle", et la specificit6 observee dans le AGP des differents solutes est attribuee i la partie structurale de la fonction de transfert.

Section: Introductionsupporting

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Thermodynamic Properties of Aqueous Organic Solutes in Relation to Their Structure. Part I. Free Energy of Transfer from H₂O to D₂O for a Series of Isomeric Ketones

Jolicoeur¹,

Lacroix²

1973

“…Thus, the behaviour in ED of the selected sodium salts appears perfectly consistent with measurements in other simple alcohols (17) where K decreases with the increasing anion size.…”

Section: Discussionsupporting

confidence: 85%

Thermodynamic behaviour of some electrolytes in ethane-1,2-diol from −10 to +80 °C

Corradini¹,

Marcheselli²,

Tassi³

et al. 1993

ethane-1,2-diol were determined in the -10 5 t 5 +80°C temperature range. The experimental data were analyzed by the Fuoss-Hsia equation, which provides further informative parameters such as the dissociation constant ( K ) of the ion pairs formed in solution, the limiting equivalent conductivity (A,), and the ion-size parameter ( 0 ) . Therrnodynamic behaviour of these electrolytes was derived from analysis of the K values. Single-ion conductivities were evaluated on the basis of the assumption of Ph,PBPh, as reference electrolyte.

“…(Tables 2 and 3) A (S cm2 mol-') and molar concentrations, C (mol dmp3), ofMeaBr, E t a B r , Pr$\lBr, Bu4NBr, and Bu4PBr in 2-PrOH-H20 mixtures at 25°C mixtures, i.e., A. decreases with increasing size of the tetraalkylammonium ions in the order Me4N+ > Et4N+ > Pr4N+ > Bu4N+ = Bu4P+ and with decreasing dielectric constant of the solvent mixtures. This is in agreement with the earlier findings (1)(2)(3)(4)(5)(6)(7)(8)(11)(12)(13)(14) in several pure and mixed solvents. However, the decrease in A. values with increasing proportion of 2-PrOH can also be explained on the basis of ion-solvent interactions, which increase with the increase in ionic size and hydrophobic solvation of cations following the order Me4N+ < Et4N+ < Pr4N+ < Bu4N+ …”

Section: Limiting Equivalent Conductancesupporting

confidence: 93%

Conductimetric studies of ionic association of tetraalkylammonium halides in iso-propanol + water mixtures at 25 °C. Part II.

Ansari¹,

Islam²

1988

AIJAZ AHMAD ANSARI and M. R. ISLAM. Can. J. Chem. 66, 1720Chem. 66, (1988.Electrical conductivities of Me4NBr, Et4NBr, Pr4NBr, Bu4NBr, and Bu4PBr have been measured in isopropanol + water KA, and the distance of ion-size parameter (R or a;) are computed from these data. A better fit of the conductance data was provided by the F78 equation. Ion-solvent interactions and effective sizes of tetraalkylarnmonium ions are also discussed in order to understand the magnitude of the ionic association. The overall association behaviour of these salts has been found to increase with decrease in dielectric constant of the medium.