Dielectric Constants of Aliphatic Ketones

Abstract

The dielectric constants and densities of eight aliphatic ketones were determined over nearly the entire temperature range of the liquid phase. The results lead to the conclusion that dipole‐dipole coupling is the important factor in determining the dielectric constants of these liquids. The data show definite departures from Onsager's theory. Use of the Onsager formula to calculate dipole moments from dielectric constant data on the pure polar liquids, as suggested by Böttcher, is not justified in the case of the ketones and is to be undertaken with caution in other cases. It is not possible to attribute the departures for the ketones to proton bonding. The results are, however, consistent with Kirkwood's more detailed theory. It is further shown that dielectric constants of normal aliphatic alcohols are consistent with Kirkwood's theory as applied to a crude model of the liquid ``structure'' of these alcohols.