Thermal Conversion Pathways for Simple Sugars

As temperature increases, two stages of decomposition occur during pyrolysis of many simple sugars, but the different chemical pathways have not been established. Pyrolysis of a set of saccharides and saccharide-like model compounds with simple structural variations was measured with simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC):  five D-aldohexoses (D-allose, D-altrose, D-galactose, D-glucose, and D-mannose), two D-aldohexitols (D-glucitol and D-mannitol), two deoxy-aldohexoses (2-deoxy-D-glucose and 6-deoxy-L-galactose), three aldopentoses (D-arabinose, L-arabinose, and D-xylose), two ketohexoses (D-fructose and D-tagatose), and two D-glucose dimers (D-cellobiose and D-trehalose dihydrate). Observing the effects of these structural variations indicate that the two-stage mass loss is not due to the combination of 1,6-bicyclic formation or to simple dehydration activity being favored at different temperatures. Additionally, comparisons among the model compounds revealed that a single maximum occurs for reactants described as a hydrogenated acyclic sugar alcohol, the dimer of D-glucose with an α(1-1) glycosydic bond, or a β(1-4) glycosydic polymer of D-glucose.