Preparations of regioselectively methylated cellulose acetates and their 1H and 13C NMR spectroscopic analyses

Seven possible regioselectively methylated cellulose acetates (RS-MCAs)-2,3,6-tri-O-methyl cellulose acetate, 3,6-di-O-methyl cellulose acetate, 2,6-di-O-methyl cellulose acetate, 2,3-di-O-methyl cellulose acetate, 6-O-methyl cellulose acetate, 3-O-methyl cellulose acetate, and 2-O-methyl cellulose acetate-were prepared for the first time from chemically synthesized cellulose derivatives obtained by cationic ring-opening polymerization and then were analyzed by H-1 and C-13 NMR spectroscopy. The chemical shifts of ring protons and carbons were influenced by substituent groups (methyl or acetyl) and clearly reflected the pattern of substituent distribution in anhydroglucose units. These data may conveniently be used for the determination of the substituent distribution of methyl cellulose. The synthesized RS-MCAs also may be used for the elucidation of the structure-property relationship. (C) 2002 Wiley Periodicals, Inc.