Ethylbenzene, solubilization

In a study of the solubilization of ethylbenzene in a series of potassium carbox-ylates ranging from Cg to Cig, it was found that as the concentration of surfactant increased, the amount of ethylbenzene solubilized increased, and that as the length of the carbon chain increased, the quantity of material incorporated per mole of surfactant increased with the carbon chain length. Such results have been criticized because of the assumption that the activity of the monomeric surfactant remained... 

One of the important properties of surfactants that is directly related to micelle formation is solubilization. Solubilization may be defined as the spontaneous dissolving of a substance (solid, liquid, or gas) by reversible interaction with the micelles of a surfactant in a solvent to form a thermodynamically stable isotropic solution with reduced thermodynamic activity of the solubilized material. Although both solvent-soluble and solvent-insoluble materials may be dissolved by the solubilization mechanism, the importance of the phenomenon from the practical point of view is that it makes possible the dissolving of substances in solvents in which they are normally insoluble. For example, although ethylbenzene is normally insoluble in water, almost 5 g of it may be dissolved in 100 mL of a 0.3 M aqueous solution of potassium hexadecanoate to yield a clear solution. 

Riegelmann et al. [93] studied various aromatic compounds solubilized in aqueous solutions of potassium laurate, dodecylamine hydrochloride, and a polyoxyethylene ether of dodecanol (Brij 35). The ultraviolet spectra of ethylbenzene in these micellar solutions were very similar to those in non-polar solvents (see Fig. 5.10) and it was concluded that this solubilizate resided completely in the micellar core. Some regions of the spectra of solubilized naphthalene, anthracene and azobenzene, on the other hand, showed similarities with the spectra of these compounds in water, whilst other regions resembled the spectra in non-polar solvents. The suggestion was made that these compounds were solubilized in such a way as to be in partial contact with both the polar micellar surface and the non-polar micellar core, i.e. a position of deep penetration. By similar reasoning it was concluded that o-nitroaniline was located at a position of short penetration whereas dimethylphthalate, whose spectrum closely resembled the spectrum in water, was thought to be adsorbed on the micellar surface. 

Table 5.6 Solubilization of ethylbenzene in soap solutions (25° C) (values corrected for water solubility) (from Klevens [2])...

Molar volume has been studied widely [2, 128, 148, 149] but no simple relationship has been shown between molar volume and the amount of solubilizate dissolved. Stearns et al. [148], studying hexane, heptane, and octane, and benzene, toluene, ethylbenzene, propylbenzene, and butylbcnzene concluded that there was inverse proportionality between the volume of hydrocarbon solubilized and molar volume. The slope of the plots of ml hydrocarbon dissolved per 100 g solution against molar volume of hydrocarbon are different for the aliphatic and aromatic series. Klevens [16], with polycyclic compounds in sodium laurate, found linear relationships between the log volume solubilized and molar volume, the slope of plots for linear polycyclics varying from that for the nonlinear polycyclics. Schwuger [149] reported that the amount of naphthalene, anthracene, pyrene, perylene and dibenzanthracene solubilized by micelles of dodecylpentaglycol ether was inversely related to the molecular size of these solubilizates. 

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