Molecular interaction studies of Gamma-aminobutyric acid (GABA) in an aqueous medium at various temperatures: A comprehensive analysis using volumetric, thermoacoustic and DFT methods

The interaction of Gamma-aminobutyric acid (GABA) in an aqueous medium at various concentrations (0.101–1.086) mol·kg⁻¹ as a function of temperature is being studied using volumetric, viscosity and acoustic analysis. The calculation of apparent molar volume ($V_{\Phi }$), partial molar volume ($V_{\varnothing }^o$), apparent molar isentropic compression ($K_{\varphi }$) and partial molar isentropic compression ($K_{\varphi }^0$) of GABA in an aqueous medium has been done by measuring the densities and speed of the sound in the temperature range of 298.15–323.15 K. The thermo-acoustic parameters like adiabatic compressibility (${\beta }_s$), acoustic impedance ($Z$), intermolecular free length ($L_f$), relative association ($\mathrm{RA}$), relaxation time ($\tau$), internal pressure (${\pi }_i$), enthalpy ($\Delta H$), Gibbs free energy ($\Delta G$), and change in entropy ($\Delta S$) are also computed. The strength of the hydrogen bond interaction of GABA in an aqueous medium and its dipole moment are calculated using single-point energy calculations. These calculations employ IEFPCM and PCM solvation models using DFT/B3LYP and MP2 methods with the 6-311G++ (d, p) basis set. The outcomes are interpreted in terms of hydrogen bond interactions that exist in the mixture.