Investigation on solute-solvent interactions of glycine, L-alanine and L-valine in aqueous tetraethylammonium iodide solutions at different temperatures with reference to volumetric and acoustic measurements

The interactions of amino acids glycine, L-alanine and L-valine with tetraethylammonium iodide (TEAI) as a function of temperature have been investigated by a combination of volumetric and acoustic measurement. Densities (rho) and ultrasonic speeds (u) of amino acids in aqueous solutions of TEAI have been measured at T = (288.15, 293.15, 298.15, 303.15 and 308.15) K and p = 0.1 MPa. The apparent molar volume (V-empty set the partial molar volume (V-empty set(0)) and standard partial molar volumes of transfer (Delta V-empty set(0)) for amino acids from water to aqueous TEAI solutions have been calculated from density values. Apparent molar isentropic compressibility (K-empty set,K-s), partial molar isentropic compressibility (K-empty set,s(0)), partial molar isentropic compressibility of transfer (Delta K-empty set,s(0)) have been calculated from values of the ultrasonic speed. The pair and triplet interaction coefficients have been calculated from both properties. The linear variation of V-empty set(0); with the number of carbon atoms in the alkyl chain of amino acids has been utilized to calculate the contribution of the charged end groups (NH3+, COO-), (CH2) group and other alkyl chains of the amino acids to V-empty set(0). The results obtained are discussed in the light of various interactions operating in ternary systems of amino acids, water and TEAI. (C) 2015 Elsevier Ltd. All rights reserved.