Determination of substituent distribution in cellulose ethers by means of a 13C NMR study on their acetylated derivatives, 4. O-methyl-O-hydroxyalkylcelluloses

A structural study on O-methyl-O-hydroxypropylcellulose (MHPC) and on O-methyl-O-hydroxyethylcellulose (MHEC) was performed by means of a ¹³C NMR analysis after acetylation of the unsubstituted hydroxyl groups at the anhydroglucose ring and those at the end of the substituents. The carbonyl signal of the acetyl group in acetylated MHPC and MHPC samples was found to be resolved into four peaks according to the location of the acetyl function either at the 2-, 3- and 6-position of an anhydroglucose unit or at the end of an oligo(oxyalkylene) substituent, allowing to determine the distribution of methyl and oligo(oxyalkylene) substituent groups. The methyl signal of the methoxy group in MHPC was also found to be sensitive to its position either at the anhydroglucose unit or at the end of the oligo(oxypropylene) substituent.