SOLUBILIZATION OF BENZENE, NAPHTHALENE, ANTHRACENE, AND PYRENE IN DODECYLAMMONIUM TRIFLUOROACETATE MICELLES

The solubilization of benzene, naphthalene, anthracene, and pyrene in aqueous micellar solution of dodecylammonium trifluoroacetate (DAPA) was measured. The maximum additive concentrations (MACs) of naphthalene, anthracene, and pyrene and benzene concentrations in equilibrium were determined spectrophotometrically at 298.2, 303.2, and 308.2 K. The first stepwise association constants (($) over bar K-1) between solubilizate monomer and vacant micelle were evaluated from the MAC and the equilibrium concentration and found to increase with hydrophobicity of solubilizate molecules. Standard enthalpy and entropy changes of the solubilization were obtained from the temperature dependence of the ($) over bar K-1 values, and the locus of these solubilizates in the micelle was thermodynamically discussed, where spectra of the solubilizates in solvents of varying dielectric constants were also used to compare with the ones in their solubilized state.