On the effect of temperature on the dielectric relaxation time of some benzene derivatives and certain of their binary mixtures

• Published in: Physics and chemistry of liquids 2006-10, Vol.44 (5), p.513-519
• Main Authors: Vasan, S. T., Ayachit, Narasimha. H., Deshpande, D. K.
• Format: Article
• Language: English
• Subjects: Activation energy; Dielectric relaxation; Enthalpy; Entropy; Microwave; PACS CODE: 77.22 Gm; Substituted benzenes
• ISSN: 0031-9104; 1029-0451
• DOI: 10.1080/00319100600643823

Dielectric relaxation behaviour of polar molecules in a non-polar solvent, or mixtures of these substances at different microwave frequencies and over a range of temperatures and concentrations give an idea about inter- and intra-molecular forces. Also such studies enable one to calculate thermodynamic parameters such as, the change of activation energy for dipole orientation (Δ G*), the enthalpy (Δ H*) and entropy (Δ S*) of activation. Such studies in the case of binary, ternary, etc. mixtures of polar molecules in pure liquid phase or in dilute solution phase of them in a non-polar solvent help in drawing certain quantitative conclusions regarding their relaxation behaviour as to whether a single component is responsible for observed microwave absorption, or a cooperative phenomenon (average) by all the dipoles of the mixture contribute to it. An experimental investigation is here performed on typical systems. With this in view, systematic dielectric measurements in a range of temperatures are carried out at a single microwave frequency on a single weight fraction in benzene of the four substituted phenols, namely, p-fluorophenylacetonitrile, p-bromonitrobenzene, m-bromonitrobenzene and 2-chloro-6-fluoro-benzaldehyde and on binary (1 : 1) mixtures of [p-2-chloro-6-fluoro-benzaldehyde + o-ethylphenol] and [p-fluorophenylacetonitrile + 2-n-butyl phenol] in benzene as solvent at different temperatures. The results are presented and discussed.