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Thermochemical investigations of associated solutions: 5. Calculation of solute-solvent equilibrium constants from solubility in mixtures containing two complexing solvents.

Journal of pharmaceutical sciences (1987-07-01)
W E Acree, J W McCargar
ABSTRACT

Solubilities are reported for carbazole in binary dibutyl ether plus 1-chlorohexane mixtures at 25 degrees C. Results of these measurements are compared with solution models developed for solubility in systems containing specific solute-solvent interactions. A simple stoichiometric complexation model based on a 1:1 carbazole:dibutyl ether complex could describe the measured solubility to within an average absolute deviation of 1.7%. The calculated equilibrium constant, though, was about one-half of values previously determined from carbazole solubilities in several binary dibutyl ether plus alkane mixtures. A more sophisticated solution model, derived by assuming both 1:1 carbazole: dibutyl ether and carbazole:chlorohexane complexes, could describe the solubilities to within 2.4%. This latter model enables the carbazole-chlorohexane association constant to be calculated from experimental carbazole solubilities and a priori knowledge of the carbazole-dibutyl ether equilibrium constant.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Dibutyl ether, anhydrous, 99.3%
Sigma-Aldrich
1-Chlorohexane, 99%
Sigma-Aldrich
Dibutyl ether, ReagentPlus®, ≥99%