Dielectric Study of the Intermolecular Association of Alcohols in Solutions of Benzene

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Abstract
The relative permittivity at 1 MHz, the refractive index at the wavelength of sodium D-line and density of the nine alcohols, 1-propanol (A), 2-propanol (B), 1-butanol (C), 2-methyl-1-propanol (D), 1-pentanol (E), 1-hexanol (F), 1-heptanol (G), 3-methyl-2-hexanol (H), 3-methyl-3-hexanol (I), have been measured at 25 °C in benzene in the entire concentration range. The measurements for 1-dodecanol (J) have been made in dilute solutions only. The dipole moments of these molecules in dilute solutions, using Higasi’s equation, and the apparent dipole moment for various solute concentrations, using Kirkwood-Fröhlich equation, have been calculated. The results suggest that at low concentrations the alcohols associate to form weakly polar multimers. At high concentrations and in pure liquids, the isomers in which the hydroxyl group is relatively free, favour the formation of highly polar multimers, whereas the isomers in which the hydroxyl group is sterically blocked by the methyl group, favour the formation of closed or ring dimers having low dipole moment.