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

The solvation of sugars in aqueous media matters in the understanding of biological systems and 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 studies. Presence of NaCl is known to perturb hydrogen bondings of sugar hydrates. However, direct evidence to elucidate mechanism at atom level is very rare even though the “NaCl Effect” was well known in biomass chemical transformations. Here we report 1H NMR elucidation evidences of mono/disaccharides hydrates in different concentrations of NaCl aqueous solutions. We here conclude two new findings: 1) under ideal usage of NaCl, different mono/disaccharides hydrates are likely to be converted into a stable sugar-NaCl-water form via a stepwise mechanism; 2) reactivity order (acidity difference) of different hydroxyls in mono/disaccharides has intangible influence on hydrate form change induced by NaCl. An ideal NaCl usage based on maximum of 1H NMR shift was proposed.