SOLUBILIZATION OF ARENES AND N-ALKYLBENZENES INTO IONIC SURFACTANT MICELLES

Citation
Y. Moroi et al., SOLUBILIZATION OF ARENES AND N-ALKYLBENZENES INTO IONIC SURFACTANT MICELLES, Colloids and surfaces. A, Physicochemical and engineering aspects, 109, 1996, pp. 201-208
Citations number
33
Categorie Soggetti
Chemistry Physical
ISSN journal
09277757
Volume
109
Year of publication
1996
Pages
201 - 208
Database
ISI
SICI code
0927-7757(1996)109:<201:SOAANI>2.0.ZU;2-S
Abstract
The solubilization of benzene, naphthalene, anthracene and pyrene in a queous micellar dodecylammonium trifluoroacetate solution (DAPA) and o f n-alkylbenzenes (benzene to n-pentylbenzene) in 1-dodecanesulfonic a cid (DSA) solution were measured. The maximum additive concentrations (MAC) of naphthalene, anthracene, and pyrene and the equilibrium conce ntrations of the benzenes were determined spectrophotometrically at 29 8.2, 303.2 and 208.2 K for DAPA and at an additional temperature of 29 3.2 K for DSA. The first stepwise association constants ((K) over bar( 1)) between solubilizate monomer and vacant micelle were evaluated fro m the MAC and the equilibrium concentration, and were found to increas e with the hydrophobicity of the solubilizate molecules. Standard enth alpy and entropy changes of the solubilization were obtained from the temperature dependence of the (K) over bar(1) values, and the location of these solubilizates in the micelle was discussed thermodynamically , with the spectra of the solubilizates in solvents of varying dielect ric constants also being used to compare with the spectra in their sol ubilized state. The standard entropy changes are negative for the poly cyclic aromatic compounds, and positive for the n-alkylbenzenes. This fact indicates that structured water molecules around the alkyl chains play an important role in their solubilization into micelles, althoug h quite the same association takes place between micelle and solubiliz ate for both kinds of solubilizates.