Study of (solute + solute) and (solute + solvent) interactions of homologous series of some α-amino acids in aqueous-streptomycin sulfate solutions at different temperatures by using physicochemical methods

Abstract

Densities, ρ, ultrasonic speeds, u, and viscosities, η of solutions of glycine/l-alanine/l-valine/l-isoleucine in water and aqueous-streptomycin sulfate {1% (0.0069mol·kg−1) and 2% (0.0137mol·kg−1) streptomycin sulfate in water} mixed solvents were measured at T (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15)K and atmospheric pressure. From these experimental results, the apparent molar volume, Vϕ, limiting apparent molar volume, Vϕ° and the slope, Sv, apparent molar compressibility, Ks,ϕ, limiting apparent molar compressibility, Ks,ϕ° and the slope, Sk, transfer volume, Vϕ,tr°, transfer compressibility, Ks,ϕ,tr°, limiting apparent molar expansivity, Eϕ°, Falkenhagen Coefficient, A, Jones–Dole coefficient, B, hydration number, nH, and temperature derivative of B-coefficient, dB/dT were calculated. Also, the activation parameters such as the free energies of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, were calculated and discussed in terms of transition state theory. The results are interpreted in terms of (solute+solvent) and (solute+solute) interactions in these systems. It has been observed that all these amino acids act as structure-breaker in aqueous-streptomycin sulfate solvents. In addition to this, Vϕ°, Ks,ϕ°, B and Δμ2°# have been split into group contributions of the amino acids using linear correlation with number of carbon atoms in the alkyl chain of the amino acids.