Dielectric relaxation studies of aqueous l-glutamine-ethanol mixtures in the microwave frequency range

Abstract

A study on the dielectric properties of various molar concentration levels of aqueous l-glutamine, ethanol mixtures at microwave frequency region (0.02 < ν/GHz < 20) is carried out in the temperature range of 298 K to 323 K. Dielectric parameters such as dielectric permittivity, dielectric loss of different molar concentrations of l-glutamine in water, ethanol medium are evaluated. It is noticed that the real and imaginary part of dielectric permittivity increases with increase in molar concentration levels of l-glutamine in water and ethanol medium and decreases with increase in temperature. From these parameters, average relaxation time (τ), excessive inverse relaxation time (1/τ)E, excessive dielectric permittivity (εE) are determined and their behavior is analyzed in terms of the distribution of hydrogen bond network in the liquid medium. The theoretical dipole moments of l-glutamine in both aqueous and ethanol medium are determined by using DFT-B3LYP method with different solvation models. Mean molecular polarizability (αM) of the system is calculated from the Lippincott δ function potential model and compared with the Lefevre method. The activation entropy (ΔS*), activation enthalpy (ΔH*), Helmholtz energy (ΔFE) parameters have also been evaluated and the results are correlated.