Abstract

The free energy of transfer from the bulk solution to the interface for several alkanols of different hydrophobicity and topology is obtained from the change in the surface tension of the solution with the alkanol concentration. Values of the free energy of transfer were obtained at total surface coverage of the alkanol both at zero surface pressure and at the surface pressure of saturation. The first values (?G0) were defined at constant surface area, while the latter values (?G0)'' were defined at constant surface pressure. Although both parameters are primarily determined by the hydrophobicity of the solute, they are significantly affected by the topology of the alkanol. Plots of both parameters versus the solute hydrophobicity show that, while displacing the hydroxyl group toward the center of the alkanol and branching decrease the value of (?G0), the opposite is observed regarding (?G0)'' values. The results are explained in terms of the tendency of the alkanols to cover the interface and their surface area.