Dielectric Dispersion and Intermolecular Association for 28 Pure Liquid Alcohols. The Position Dependence of Hydroxyl Group in the Hydrocarbon Chain

Abstract

Abstract The dielectric constants and losses of 28 linear alcohols, 1-alkanol (n=3–10), 2-alkanol (n=3–10), 3-alkanol (n=5–10), 4-alkanol (n=7–10), and 5-alkanol (n=9 and 10), have been measured at the frequencies from 1.35 to 4500 MHz at 15, 25, and 35 °C. The Kirkwood–Fröhlich equation was modified so that it could be applied to each dispersion region calculated. The concentration C1 of linear hydrogen-bonded chain polymers, which primary dispersion originates, was evaluated by means of this modified equation. The C1 decreases as the hydroxyl group approaches the center of a molecule, except for propanols and butanols, and also decreases with increasing temperature. For isomeric decanols, for example, the percentages of C1 (C1×100⁄C0) against alcohol gross stoichiometric concentration C0 at 15, 25, and 35 °C are about 71, 63, and 53% for 1-decanol, 52, 40, and 29% for 2-decanol, 22, 17, and 12% for 3-decanol, 11, 7, and 6% for 4-decanol, and 8, 6, and 5% for 5-decanol, respectively. The thermodynamic parameters, ΔF\eweq, ΔH\eweq, and ΔS\eweq, were obtained for dipole relaxation and viscous flow . The ΔFτ\eweq decreases, although the ΔHτ\eweq and ΔSτ\eweq increase, as the hydroxyl group approaches the center of a molecule. The ΔFη\eweq increases linealy with the molecular volume, irrespective of the position of the hydroxyl group.