Ultrasonic Velocity and Absorption Studies on Some Amino Acids in Water-Aprotic Solvent Mixtures

Ultrasonic velocity and absorption studies have been carried out in the amino acids namely glycine and β-alanine in Water-dioxane, Water-tetrahydrofuran and Water-dimethylformamide mixed solvents. These studies are carried out in the amino acid concentration range of 0.1 to 0.8 molar at a fixed frequency of 5 MHz and at a fixed temperature of 303 K. The ultrasonic velocity in aqueous solutions of amino acids containing 10% V/V of dioxane, tetrahydrofuran and dimethylformamide increases non-linearly with increase of concentration of amino acids. The non-linear increase in ultrasonic velocity is explained on the basis of ionic hydration, hydrogen bonding and the structure breaking power of various aprotic solvents used. The observed absorption has been explained as due to ionic hydration, weakening of hydrogen bonds and proton transfer reactions occurring in these solutions.