Ultrasonic speed, densities and viscosities of xylitol in water and in aqueous tyrosine and phenylalanine solutions at different temperatures

Abstract

Ultrasonic speed u, densities ρ and viscosities η of xylitol in water and in 0.001 m aqueous l-tyrosine (Tyr) and l-phenylalanine (Phe) have been measured at different temperatures. From the density and ultrasonic speed measurements apparent molar isentropic compression $$ \kappa_{{S,{\kern 1pt} \phi }} $$ , apparent molar isentropic compressions at infinite dilution $$ \kappa_{{S,{\kern 1pt} \phi }}^{0} $$ , experimental slope S K , hydration number n H , transfer partial molar isentropic compressibility $$ \Delta_{tr} \kappa_{{S{\kern 1pt} ,\phi }}^{0} $$ of xylitol from water to aqueous Tyr and Phe have been obtained. From the viscosity data, B-coefficient and B-coefficient of transfer Δ tr B of xylitol from water to aqueous Phe and Tyr at different temperatures have also been estimated. Gibbs free energies of activation of viscous flow per mole of solvent Δμ 1 0# and per mole of solute Δμ 2 0# have been calculated by using Feakins transition state theory for the studied systems. The calculated parameters have been interpreted in terms of solute–solute and solute–solvent interactions and hydration behavior of xylitol.