Dielectric and thermodynamic studies on a binary mixture of anisole with butyric or caprylic acid

The molecular interaction of anisole with fatty acids, such as butyric acid and caprylic acid, has been studied using standard dielectric methods. The permittivity at static and optical frequency (the sodium D-line) of a mixture of anisole + butyric acid and anisole + caprylic acid were measured at three different temperatures. Kirkwood correlation parameters, the excess permittivity, the Bruggeman parameter and excess free-energy were determined for each concentration of the mixture. A positive value of excess permittivity was obtained for the mixture of anisole + butyric acid, whereas for most concentrations of the anisole + caprylic acid mixture, the excess permittivity was negative at all studied temperatures. Negative and positive values of the Bruggeman parameters were obtained for the anisole + butyric acid and anisole + caprylic acid mixtures, respectively. Parallel and anti-parallel alignments of dipoles in the mixtures were identified.