Study of Dielectric and Thermodynamic properties of Aqueous Glycine

Abstract

Abstract Dielectric and thermodynamic properties of aqueous glycine having molecular weight 75.07 g/mol have been studied at different concentrations in the range 0.459 to 1.480 mol/kg in the temperature range of 298.15–278.15 K. Time Domain Reflectometery technique was used in the frequency range of 10 MHz to 30 GHz. Havriliak-Nigami equation was used to analyze the frequency dependence of the complex permittivity spectra. Two relaxation processes have been detected for studied system which requires two Debye relaxation model to describe the complex permittivity spectra 𝛆*(v). The low frequency relaxation process is associated with glycine molecules called β-relaxation while the high frequency relaxation process is associated with water molecules called γ-relaxation. For β –process, relaxation time was observed to be increasing towards lower temperature and higher concentration, which is associated with the rotational motion of glycine molecules in the surrounding of water. Relaxation strength was also observed to be increasing towards low temperature and high concentration, relaxation time and relaxation strength for γ- process was found almost independent of temperature. The study also covers solvation dynamics of glycine through the observed hydration number (Nhyd) and the effective hydration number (Zib). The effective dipole moment has been obtained using Cavell equation in order to see the effect of temperature and concentrations on the dipole moment and ultimately the dielectric constant of the solute molecules. The nature of the molecular interactions in pure liquid and liquid mixtures can be well understood in terms of thermodynamic functions. Thermo dynamical parameters such as molal entropy (∆S), molal enthalpy (∆H) and molal free energy (∆F) in addition to activation entropy, enthalpy and free energies have also been calculated in order to support the obtained dielectric parameters.