Partitioning of solutes in different solvent systems: the contribution of hydrogen-bonding capacity and polarity.
Published partition coefficient values of 121 solutes in five solvent systems (1-octanol-water, n-heptane-water, chloroform-water, diethyl ether-water, and n-butyl acetate-water) were correlated with solute properties, namely intrinsic molecular volume (indicator of cavity formation) and the solvatochromic parameters pi* (dipolarity/polarizability), beta (H-bond acceptor basicity), and alpha (H-bond donor acidity). While the cavity term and the H-bond accepting capacity played a comparable role in all solvent systems, the H-bond donor acidity was significant only in the alkane-water and chloroform-water systems. Comparison of the regression coefficients of pi*, beta, and alpha demonstrated the important role that water content at saturation in the organic solvents plays in the partitioning of solutes. Analysis of the differences between 1-octanol-water and n-heptane-water partition coefficients (delta log Poct-hep) and between 1-octanol-water and chloroform-water partition coefficients (delta log Poct-chf) showed that these values mainly quantitate the capacity of solute to donate hydrogen bonds. In contrast, the differences between 1-octanol-water and diethyl ether-water or n-butylacetate-water partition coefficients, (delta log Poct-dee and delta log Poct-ba, respectively) contain no structural information.
el Tayar
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N
School of Pharmacy, University of Lausanne, Switzerland.
Tsai
R S
RS
Testa
B
B
Carrupt
P A
PA
Leo
A
A
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006860:Hydrogen Bonding; D012996:Solutions / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*
D012996:Solutions; D012997:Solvents