Dielectric relaxation phenomena and high frequency conductivity of rigid polar liquids in different solvents.

The double relaxation phenomena in apparently rigid aliphatic polar liquids (j) like chloral and ethyltrichloroacetate in nonpolar solvents (i) benzene, n-hexane and n-heptane under 4.2, 9.8 and 24.6 GHz electric fields at 30 degreesC have been studied. Only five systems of polar-nonpolar liquid mixtures show the double relaxation times tau (1) and tau (2) due to rotation of their flexible parts and the whole molecules. The probability of showing the double relaxation phenomena is greater in aliphatic solvents at 9.8 and 24.6 GHz electric fields indicating their nonrigidity. This is also supported by the symmetric and asymmetric distribution parameters gamma and delta estimated From values of x and y at w(j) --> 0 involved with dimensionless dielectric constants k(ij)' k(ij)", k(oij) and k(ooij) of solutions. The variation of x and y with weight fractions w(j)'s of solutes are found to be unusual predicting their probable solute-solvent and solute-solute molecular association under high frequency (hf) electric fields. The dipole moments mu (1) and mu (2) of the flexible parts and the whole molecules from the slopes beta 's of hf conductivities sigma (ij)'s with w(j)'s and the estimated tau (1) and tau (2) reveal their solute-solute associations in the aliphatic solvents. The theoretical dipole moments mu (theo)'s in terms of available bond angles and bond moments conform the estimated mu (j)'s only to establish the existence of mesomeric, inductive and electromeric effects in them. (C) 2000 Elsevier Science B.V. All rights reserved.