Thermodynamics of (solute + solute) and (solute + solvent) interactions of homologous series of amino acids with thiamine hydrochloride in aqueous medium at T = (305.15, 310.15, 315.15) K: A volumetric and acoustic approach

• Densities and speeds of sound of amino acids in thiamine-HCl.
• Positive apparent molar volumes predict dominance of solute-solvent interactions.
• Positive transfer volumes indicate ion-ion interactions in the mixtures.
• Pair and triplet interaction coefficients predict pair wise interactions in mixtures.
• Amino acids act as structure maker in aqueous thiamine-HCl solutions.

Apparent molar volumes (VϕVϕ) and apparent molar isentropic compression (Kϕ,sKϕ,s) of glycine, l-alanine, l-valine and l-leucine in (0.05, 0.10, 0.15, 0.20) mol·kg−1 aqueous solution of thiamine hydrochloride (thiamine-HCl) have been determined at T = (305.15, 310.15 and 315.15) K and experimental pressure p = 0.1 MPa, from the density and speed of sound measurements. The partial molar volume Vϕo, standard partial molar volumes of transfer ΔVϕo for amino acids from water to aqueous thiamine-HCl, partial molar isentropic compression Kϕ,sKϕ,s and partial molar isentropic compression of transfer ΔKϕ,so have been calculated from the corresponding data. Group contributions of amino acids to partial molar volume are also determined. The pair and triplet interaction coefficients are obtained from partial molar volumes of transfer and partial molar isentropic compression of transfer. The partial molar expansibility (∂Vϕo/∂T)p, second order derivative (∂2Vϕo/∂T2)p have also been calculated. The parameters obtained have been used to explain the results in terms of (solute-solute)/(ion-ion), (solute-solvent) interactions, structure making and structure breaking behaviour of amino acids in aqueous thiamine-HCl solutions.