Dielectric dispersion and relaxation mechanism in some substituted anilines at microwave frequencies

The permittivity and dielectric loss of 2-chloro-6-methyl aniline, 3-chloro-2-methyl aniline, 3-chloro-4-methyl aniline, 4-chloro-2-methyl aniline and 5-chloro-2-methyl aniline have been measured at four microwave frequencies viz., 33.45, 18.98, 9.945 and 1.80 GHz and also at 300 KHz and optical frequency at 35°C in benzene solution. Ther permittivity and dielectric loss at different frequencies have been plotted against concentration (wt. fraction). The slopes of these straight lines have been used for the complex plane plots (a″ Vs. a′). The complex plane plots for these compounds are Cole-Cole arc's. The most probable relaxation time (τ_o) and distribution parameter (α) have been evaluated from these plots. The values of these parameters are found to be in agreement with those obtained from Higasi's single frequency method. Data have also been analysed in terms of two relaxation processes i.e., corresponding to overall rotation and group rotation. Nearly equal values of τ₂, the relaxation time for intramolecular rotation, for these substituted anilines suggest that the amino-group relaxes by an inversion mechanism. The dipole moments, evaluated by the microwave method, are also reported.