Apparent Dipole Moments of 1-Alkanols in Cyclohexane and <Emphasis Type="Italic">n</Emphasis>-Heptane,and Excess Molar Volumes of (1-Alkanol + Cyclohexane or <Emphasis Type="Italic">n</Emphasis>-Heptane) at 298.15 K

Excess molar volumes and relative permittivities at a frequency of 30 kHz were determined precisely for the binary mixtures of 1-alkanols, C_nH_2n+1OH for n = 1 to 10, with cyclohexane or n-heptane to the mole fraction of 1-alkanol, x, to 0.1 at a temperature of 298.15 K. Apparent dipole moments, , of the 1-alkanols were calculated by using the Frohlich equation, and the limiting values, ₀, were determined by extrapolating to infinite dilution. The solvent effect on ₀ was very small. The value of ₀ was largest in methanol and decreased with increasing n. It was found that the alkanols were isolated up to x 0.003. The threshold of molecular interaction beyond this critical mole fraction was ascertained by means of FT-IR spectra. The dipole moments of the 1-alkanols for n = 1–4 were evaluated by ab initio calculations. The average values of ₀ for the rotational configurations calculated by assuming the Boltzmann distribution agreed excellently with the observed ones. The excess partial molar volumes of 1-alkanols determined at the infinite dilution depended on n as well as the solvent. These results are discussed from the viewpoint of the interactions between the solute and solvent molecules.