title: Dependence of the distribution constant in liquid-liquid partition equilibria on the van der Waals molecular surface area.
abstract: The direct calculation of free energy of interactions between a solute j and two immiscible liquids shows a linear dependence between the (logarithm of) the distribution constant in liquid-liquid partition equilibrium log K(j) and the van der Waals surface area of the solute. The study provides a thermodynamic proof for the formula log K(BA,j) = c1 log K(BC,j) + c2 that describes the linear dependence between (the logarithm of) the distribution constant for a solute j in a solvent system (B/A) and (the logarithm of) the distribution constant for the same solute in a different solvent system (B/C). This relation has been well proven by various experimental studies and it is frequently used in liquid chromatographic separations as well as in liquid-liquid extractions, but was not explained previously based on thermodynamic results. The theory was verified using the prediction of octanol/water distribution constants log K(ow) for a wide range of molecules, including hydrocarbons and compounds with a variety of functional groups. The results have also been verified for the distribution constants in other solvent systems. The expression for the distribution constant obtained in this study also gives a theoretical base for the additive fragment methodology used for the prediction of log K(ow).
authors.affiliation: R. J. Reynolds Tobacco Co, Winston-Salem, NC, USA.
authors.forename: Serban C
authors.initials: SC
authors.lastname: Moldoveanu
authors.forename: Victor
authors.initials: V
authors.lastname: David
mesh_terms: D002853:Chromatography, Liquid; D057927:Hydrophobic and Hydrophilic Interactions; D059625:Liquid-Liquid Extraction; D000442:Octanols / Q000737:chemistry* / Q000302:isolation & purification; D012997:Solvents / Q000302:isolation & purification; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000032:analysis / Q000737:chemistry*
chemical_list: D000442:Octanols; D012997:Solvents; D014867:Water
keywords: Distribution constants; Liquid-liquid partition equilibria; Solvophobic interactions; Van der Waals molecular surface