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

Abstract

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 (ρ) 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=0.1MPa. The apparent molar volume (V∅), the partial molar volume (V∅0) and standard partial molar volumes of transfer (ΔV∅0) for amino acids from water to aqueous TEAI solutions have been calculated from density values. Apparent molar isentropic compressibility (K∅,s), partial molar isentropic compressibility (K∅,s0), partial molar isentropic compressibility of transfer (ΔK∅,s0) 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∅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∅0. The results obtained are discussed in the light of various interactions operating in ternary systems of amino acids, water and TEAI.