Microwave Absorption and Molecular Structure in Liquids. LXXIX. Dielectric Behavior and Association of Some Normal Alcohols in n-Heptane Solution

Abstract

Dielectric constants and losses at 25°C of 1-butanol, 1-hexanol, 1-heptanol, and 1-decanol, each at six concentrations from 0.03 to 0.3 mole fraction in n-heptane, have been measured at wavelengths from 2 mm to 600 m. At the lower concentrations, the dielectric absorption may be resolved into two dispersion regions, characterized by relaxation times τ3 (≈ 3 psec and almost concentration independent) and τ2 (ranging from 25 to 100 psec and concentration dependent). The latter dispersion increases its contribution relative to the former with increasing alcohol concentration. At the higher concentrations a final process with a long relaxation time, τ1 (strongly concentration dependent), appears. This third process corresponds to the principal low-frequency dispersion already well characterized in pure primary normal aliphatic alcohols. The high-frequency process, because of its very short relaxation time, is attributed to rotation of the hydroxyl group about its C–O bond, the intermediate process is related to the reorientation of the monomer and possibly small multimers or a polymer chain segment, such as an -OR group rotating about its bond, while the low-frequency process involves hydrogen-bonded structures of some considerable size.