Dielectric relaxation of para polar liquids under high frequency electric field

The structural and associational aspects of nonspherical para polar liquids (j) in nonpolar solvents (i) are studied through high frequency conductivities sigma(ij)'s of solutions. The relaxation time tau of the respective liquids under 3cm. wavelength electric field at various experimental temperatures in degrees C are estimated from the slope of individual variations of real sigma'(ij) and imaginary sigma"(ij) parts of hf complex conductivity sigma*(ij) with weight fractions w(j)'s of polar liquid. The temperature variation of tau for comparatively larger nonspherical para molecules in dioxane are not strictly obeyed by the Debye model unlike other simpler para di- or tri-substituted benzene in benzene. Thermodynamic energy parameters Delta H-tau, Delta S-tau and Delta F-tau are obtained from Eyring's rate process equation with the estimated tau's in order to get information on the solvent environment around them. The higher values of gamma obtained from ln tau(j)T against In eta equation indicate the solid phase rotators for the liquids. The estimated Kalman and Debye factors tau(j)T/eta(gamma) and tau(j)T/eta establish the Debye relaxation mechanism for almost all the para-molecules. The obtained dipole moments mu(j)'S in terms of slope beta of sigma(ij)-w(j) curve and dimensionless parameter 'b' involved with estimated tau are then compared with the reported mu and mu(theo) obtained from bond angles and bond moments. The mu(j)'s of para liquids are often zero but at other temperatures they show net moments. The slight disagreement between the measured and theoretical mu's reveals the presence of the inductive and mesomeric moments of substituted polar groups in molecules at different temperatures. (C) 2000 Elsevier Science B.V. All rights reserved.