Tricaprylin−Water Partition Coefficients and Their Temperature Dependence for Selected Chlorobenzenes

Abstract

Measurements of partition coefficients between tricaprylin (glyceryl tri-n-octanoate) and water are reported for seven chlorobenzenes (1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,3,5-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3,5-tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene) between 5 °C and 45 °C. The values are compared with reported data on octanol−water and triolein−water partition coefficients. The van't Hoff plots of log KOW versus T-1 exhibit linearity with values of KOW increasing by 5%−8% over this temperature range, and the enthalpy of phase change varies from 9.7 to 16 kJ/mol. Several reasons are suggested why tricaprylin−water partition coefficients may be preferable to octanol−water and triolein−water partition coefficients when quantifying a substance's hydrophobicity. The mutual solubilities of tricaprylin and water are less than that of octanol and water. Tricaprylin is less volatile than octanol and, being a triglyceride, is structurally more similar to lipids. Tri...