Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The densities, and speeds of sound, u of -aminobutyric acid (GABA) in water and in (0.005, 0.01, 0.02, 0.04 and 0.06) mol*kg-1 aqueous caffeine (CAF) solutions were measured at temperatures, T = (293.15 to 318.15) K and P = 0.01 MPa. Measured data have been used to calculate apparent molar volumes at infinitesimal concentration (Vo2,), and apparent molar isentropic compressibility (Ko2,), the corresponding transfer parameters and other derived properties. The negative transfer values suggest the dominance of hydrophobic interactions and structure-breaking tendency of caffeine molecules. UV-visible spectroscopic studies have been carried out and the shifts in absorption spectra signify the role of hydrogen bonding interactions. Structures of GABA and CAF have also been optimized at gas phase and solution phase by employing density functional theory (DFT) at B3LYP/6-31+G* theoretical level and the H-bond interactions between the two molecules have been studied. It is observed that there are strong Hbond interactions between GABA and CAF.