Solubilization of n-alkylbenzenes into 1-dodecanesulfonic acid micelles

The solubilization of benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-peptylbenzene into 1-dodecanesulfonic acid was measured. Concentrations of all the substrates in equilibrium were determined spectrophotometrically at 293.15, 298.15, 303.15, and 308.15 K. The first stepwise association constants ((K) over bar(1)) between solubilizate monomer and vacant micelle were evaluated from the equilibrium concentration and were found to increase with hydrophobicity of the solubilizate molecules. They were 1.31 x 10(3), 3.28 x 10(3), 9.64 x 10(3), 2.96 x 10(4), 9.52 x 10(4), and 3.95 x 10(5) mol(-1) dm(3) at 298.15 K for benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-pentylbenzene, respectively. The standard Gibbs energy, enthalpy, and entropy changes in this system were compared with those for solubilizations of polycyclic aromatic compounds and of p-n-alkylbenzoic acids to thermodynamically study the solubilized state of the solubilizates.