Association of n-Alcohols in Non-polar Solvents. Part I. The Dielectric Polarisations, Apparent Dipole Moments, and Near-infrared Spectra of n-Alcohols in Carbon Tetrachloride and Cyclohexane By D. A. lbbitson and L. F. Moore,* Derby and District College of TechnologyDielectric constant, c, density, and near-infrared spectra of a series of solutions of graded concentration of n-alcohols in carbon tetrachloride and cyclohexane have been determined. Apparent dipole moments of the solutes have been calculated and solute polarisation, P,, evaluated as a function of alcohol weight fraction. Existence in solution of monomer only coincides with linear dependence of both t and P, on alcohol weight fraction. Positive and negative deviations of t and P, are explained by presence of effective amounts of linear dimer and trimer, and cyclic polymer, respectively.A N attempt has been made to resolve the controversy existing with regard to the mode of association of n-alcohols in non-polar solvents,l and to explain the nature of the solute polarisation (P,)-concentration plots for such solutions.2 That the latter plots are anomalous is well re~ognised,~ several workers reporting the occurrence of maxima or minima at relatively low concentrations,* and others finding the plots to be re~tilinear.~ In many cases, however, data are unavailable for solutions of sufficiently low concentration for monomer species only to exist. Although general agreement exists that the anomalous dielectric behaviour arises from solute association, discussion in terms of the structures of the species present is limited.6 Only Liebaert and Leroy 7 have attempted a quantitative interpretation in terms of a particular association model.In the present investigation dielectric constant, E, density, and neax-infrared spectra of a series of solutions of graded concentration of n-alcohols in carbon tetrachloride and cyclohexane have been determined. Solute polarisations have been calculated at each concentration and the plots of P, and c against alcohol weight fraction, w , examined and compared with the near-infrared spectra. Apparent dipole moments of the solutes have also been evaluated. I t is concluded that the lower polymers existing in solution are linear and the higher polymers, cyclic.
EXPERIMENTAL
Dipole Moments.-(a) Materials.The n-alcohols were dried over anhydrous magnesium sulphate for a t least 24 hr., and distilled from sodium immediately before use." Spectrosol " carbon tetrachloride and cyclohexane were dried as described previously.*