Dependence of enthalpic pairwise self-interactions on ionic strength: Some 2-deoxy and N-acetyl monosaccharides in aqueous NaCl solutions at T = 298.15 K

Abstract

The dilution enthalpies of four derivatives of monosaccharides, namely 2-deoxy-d-glucose (2-DGlu), N-acetyl-d-glucosamine (GluNAc), 2-deoxy-d-galactose (2-DGal) and N-acetyl-d-galactosamine (GalNAc), in aqueous NaCl solutions of various molalities (b=0–3.0mol·kg−1) have been determined respectively at T=298.15K by isothermal titration calorimetry (MicroCal ITC200). The corresponding values of enthalpic pairwise self-interaction coefficients (h2) have been calculated according to the McMillan–Mayer theory. It was found that across the range studied of ionic strength (I) or molality (b=I), the h2 coefficients are all positive, in the order h2 (GluNAc)>h2 (GalNAc)>h2 (2-DGlu)>h2 (2-DGal), and decrease gradually after increasing first up to a maximum at b≈1.5mol·kg−1. The effects of ionic strength (I) on the trends of h2 have been discussed from the point of view of complex (solute+solute) and (solute+solvent) interactions in solutions.