1H NMR Elucidation of Observed Stable Sugar-NaCl-water Complexes in Aqueous Solution

The solvation of sugars in aqueous media matters in understanding of biological system and in carbohydrate transformations. Generally, 2 – 4 water units were proposed to interact with each hydroxyl group in monosaccharides via different types of hydrogen bondings at room temperature in previous study. Presence of NaCl was known to perturb hydrogen bondings of sugar hydrates, however direct evidence to elucidate mechanism at atom level is very rare even though “NaCl Effect” was well known in biomass chemical transformations. Here we reported 1H NMR elucidation evidences of mono/disaccharides hydrates in different concentration of NaCl aqueous solutions. We here conclude two new findings: 1) under ideal usage of NaCl, different mono/disaccharides hydrates were likely converted into a stable sugar-NaCl-water form; 2) pKa value of different hydroxyls in mono/disaccharides has intangible influence on hydrate form change induced by NaCl. A proposed ideal NaCl usage based on maximum of 1H NMR shift is consistent with optimized condition in reported literature.