abstract
Density (rho) and ultrasonic velocity (u) values of amino acids L-alanine, L-proline, L-valine, and L-leucine in 2M aqueous KCl and 2M aqueous KNO(3) solutions have been measured as a function of amino acid concentration at different temperatures (298.15 K, 303.15 K, 308.15 K, 313.15 K, 318.15 K, and 323.15 K). Using the. and u data, partial molal volume (phi(o)(v)) and partial molal isentropic compressibility (phi(o)(k)) values have been computed. The increase in partial molal volume with temperature has been attributed to the volume expansion of hydrated zwitterions. The phi(o)(v) and phi(o)(k) values of L-alanine, L-proline, L-valine, and L-leucine in 2M aqueous KCl and KNO3 solutions have been found to be larger than the corresponding values in water. The larger partial molal volumes of L-alanine, L-proline, L-valine, and L-leucine in 2 M aqueous KCl and KNO(3) solutions have been ascribed to the formation of 'zwitterionK(+)/Cl(-)/NO(3)(-)' and 'K(+)/Cl(-)/NO(3)(-)- water dipole' aggregates in solutions. The formation of these entities in solutions causes the release of water associated with zwitterions to the bulk water. The larger partial molal compressibilities of L-alanine/L-proline-/L-valine-/L-leucine-2M aqueous KCl/KNO(3) solutions than the corresponding values in water have been attributed to the formation of 'zwitterion-ion' and 'ion-water dipole' incompressible entities in solutions.
keywords
DILUTE AQUEOUS-SOLUTIONS; ADIABATIC COMPRESSIBILITIES; CHLORIDE SOLUTIONS; HEAT-CAPACITIES; ALPHA-AMINO; L-ALANINE; MODEL COMPOUNDS; T=298.15 K; ISENTROPIC COMPRESSIBILITY; CALCIUM-CHLORIDE
subject category
Thermodynamics; Chemistry; Mechanics; Physics
authors
Riyazuddeen; Khan, I
our authors
Imran Khan
Post-Doc FellowshipGroups
acknowledgements
The authors are thankful to the Chairman, Department of Chemistry, A. M. U. Aligarh, for providing the necessary facility required in this research project. One of the authors ( I. K.) thanks UGC for awarding the UGC fellowship.