Associating behaviour of pure polar liquids : dielectric properties of caprylic acid

(Received 24 March 1993, accepted in final form 7 May 1993)

Abstract
The associating behaviour of liquid caprylic acid has been studied by the determination of its dielectric properties. Experimental results of measurements of dielectric permittivity are reported. The molecular correlation factor was obtained with reference to the Kirkwood-Fröhlich theory and compared with the Abbott-Bolton model for non spherical molecules from above the MP to 392 K. On going from low to high temperature, the correlation factor increases from 0.2 to 0.5 and this, together with the increase of the static permittivity, suggests that the number of dimers in the liquid phase decreases with increasing temperature. A discussion of the associating behaviour of caprylic acid is reported, in view of a recent model for treating molecular systems in which dimerization occurs. According to this model a further correlation factor is introduced, besides that prescribed by the Kirkwood-Fröhlich theory, to account for correlation among dipole moments carried by monomers. This correlation factor for monomers calculated at room temperature, indicates the existence of a prevailing antiparallel order among monomers.