Thermal behaviour of anhydrous, dihydrate and (2/1) ethanol forms of 1-O-α--glucopyranosyl--mannitol

The melting points of anhydrous 1-O-α--glucopyranosyl--mannitol, 1-O-α--glucopyranosyl--mannitol dihydrate and a new compound, 1-O-α--glucopyranosyl--mannitol-ethanol (2/1) were determined using differential scanning calorimetry. The melting onset values were 169.2 (3), 104.3 (18) and 158.7 (9), respectively, and the melting peak values were 171.4 (5), 107.9 (15) and 160.1 (6), respectively. 1-O-α--glucopyranosyl--mannitol dihydrate and 1-O-α--glucopyranosyl--mannitol-ethanol (2/1) decompose to anhydrous form when heated at slow heating rates.According to TG-FTIR measurements, 1-O-α--glucopyranosyl--mannitol-ethanol (2/1) lost its ethanol in the 110–190°C range, and 1-O-α--glucopyranosyl--mannitol dihydrate lost its crystal water in the 60–210°C range. After removal of ethanol and crystal water, both decomposed in air totally as carbohydrates usually do, forming lower hydrocarbons with OH-groups, CO₂ and H₂O.