Excess permittivity behaviour of some mixtures n-alcohol + alkane: an interpretation of the underlying molecular mechanism

Abstract

A molecular mechanism is proposed that underlies the macroscopic behaviour of excess dielectric permittivity of some mixtures {n-alcohol + alkane} at low (100 kHz) and microwave frequencies (1 GHz). This behaviour has been determined experimentally at 298 K, as a function of molar fraction, for the mixtures {n-hexane + (pentan-1-ol, hexan-1-ol or heptan-1-ol)} and {cyclohexane + (pentan-1-ol, hexan-1-ol or heptan-1-ol)}. From the magnitudes inherent to the process of dielectric relaxation the results obtained have been explained in terms of the behaviour of thermodynamic magnitudes such as the excess molar enthalpy and the excess molar volume, as well as the consideration that the total dipole moment of a multimere is greater than the sum of all dipole moments of the monomeres in which it can be decomposed (when hydrogen bonds are broken), in agreement with the linear association model of Malecki (LAM). Measurements of the relaxation times for the mixtures under study at various molar fractions using time-domain reflectometry (TDR) (DC–5 GHz) at ambient temperature confirm the considerations that support the proposed interpretation.

Acknowledgement

We are grateful to XUNTA DE GALICIA (PGIDIT02PXIB30102PR) for the financial help provided to us in the development of this work.