Homogeneous esterification mechanism of bagasse modified with phthalic anhydride in ionic liquid. Part 2: Reactive behavior of hemicelluloses.

The phthalation of bagasse was comparatively investigated with the isolated three main components in 1-allyl-3-methylidazium chloride (AmimCl) to reveal the reaction behavior of bagasse. In the present study, the reaction behavior of hemicelluloses during the homogeneous phthalation was extensively explored. The phthalation degree of hemicellulosic samples ranged from 16.37% to 52.14%. The reaction priority on the main and side chains of hemicelluloses were revealed by the changes of monosaccharide contents upon phthalation. The results indicated that side-chains of hemicelluloses were more easily phthalated than main-chains, and the phthalation of secondary hydroxyl groups on uronic acids was more difficult than that on neutral sugars. 13C NMR and HSQC analyses suggested the similar reactivity of the secondary hydroxyls at C-2 and C-3 positions in anhydroxylose units. These results provide more detailed understanding of the homogenous modification of lignocellulose.