Apparent dipole moments of 1-alkanols in cyclohexane and n-heptane, and excess molar volumes of (1-alkanol plus cyclohexane or n-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, CnH2n+1 OH 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, mu, of the 1-alkanols were calculated by using the Frohlich equation, and the limiting values, mu(0), were determined by extrapolating to infinite dilution. The solvent effect on mu(0) was very small. The value of mu(0) was largest in methanol and decreased with increasing n. It was found that the alkanols were isolated up to x approximate to 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 mu(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.