“…Both protonation constants; however, deviate from the values obtained by titrations (Table 4) The specific rotation of HGluc at T = 20-25 °C was reported to be between -6.9° and 5.80° [19,20,35,56,152,153] pointing to the uncertainty of the experimental data. Nevertheless, -6.7° [152] and -6.9° [153] were determined from freshly prepared HGluc, which is close to our value and to those reported previously [19,56]. Based on this agreement, the specific rotation found for HGul seems to be reliable.…”