Investigations to explore interactions in (polyhydroxy solute plus L-ascorbic acid + H2O) solutions at different temperatures: Calorimetric and viscometric approach

Isothermal titration micro-calorimeter has been used to measure the enthalpy change (q) of polyhydroxy solutes [(+)-D-xylose, xylitol, (+)-D-glucose, 2-deoxy-D-glucose, (+)-methyl-alpha-D glucopyranoside, and (+)-maltose monohydrate] in water and in (0.05, 0.15, and 0.25) ma kg 1 I. -ascorbic acid(aq) solutions at (288.15, 298.15, 308.15, and 318.15) K. Limiting enthalpies of dilution (Delta H-dil degrees) of these solutes were calculated from heat evolved/absorbed during calorimetric experiments. Further thermodynamic quantities such as limiting enthalpies of dilution of transfer (AtrAthill'), change in heat capacity (Delta dilC(p,2,m)(0)), and pair (h(AB)) and triplet (h(ABB)) enthalpic interaction coefficients were also calculated and used to explore the nature of interactions of solutes with cosolute (L -ascorbic acid). The Jones-Dole viscosity B-coefficients for (+)-D-xylose, xylitol, (+)-D-galactose, galactitol, (+)-D-glucose, 2-deoxy-D-glucose, (+)-methyl-alpha-D glucopyranoside, and (+)-maltose monohydrate in water and in (0.05, 0.15, 0.25, and 0.35) ma kg(1) t-ascorbic acid(aq) solutions have been determined from viscosity (II) data measured over temperature range (288.15-318.15) K and at pressure, P = 101.3 kPa. The temperature dependence of B-coefficients (dB/dT), and viscosity B-coefficients of transfer (AtrB) of solutes from water to cosolute have also been estimated. These parameters have been discussed in terms of structure -making (kosmotropic) or -breaking (chaotropic) behavior of solutes. (C) 2016 Elsevier Ltd.