Tohru Chiba

Determination of substituent distribution in cellulose ethers by 13C- and 1H-N.M.R. studies of their acetylated derivatives: O-(2-hydroxypropyl)cellulose

Abstract Structural characteristics of O-(2-hydroxypropyl)cellulose samples, namely the molar substitution (mol. subst.), the total degree of substitution (d.s.), and the individual degree of substitution of hydroxyl groups on the glucose residues for a wide mol. subst. range of samples were determined after peracetylation by 1H- and 13C-n.m.r. analyses. The mol. subst. value was determined by comparing the acetyl methyl proton signal with that of the 2-hydroxypropyl methyl group. The acetyl carbonyl carbon signal of acetylated O-(2-hydroxypropyl)cellulose samples was found to split into a quadruplet in Me2SO at 100°, reflecting the position of the substituent (2, 3, and 6) on the glucose residue and of the (oligo-)propylene oxide substituent end-group, and allowing determination of the substituent distribution as well as the total degree of substitution in a series of O-(2-hydroxypropyl)cellulose samples.

Determination of substituent distribution in cellulose ethers by means of a 13C nuclear magnetic resonance study on their acetylated derivatives: 3. Hydroxyethylcellulose

Abstract The distribution of substituent, i.e. oligo(ethylene oxide) groups, in hydroxyethylcelluloses having various values of molar substitution was determined by means of 13 C nuclear magnetic resonance after the acetylation of hydroxyl groups both at the unsubstituted position in the anhydroglucose unit and at the substituent end position of the parent hydroxyethylcellulose. The acetyl carbonyl signal of the acetylated hydroxyethylcellulose samples was found to split into a triplet in DMSO-d 6 at 100°C corresponding to the positions of acetyl groups (2, 3 or 6 overlapped with the substituent end) on the anhydroglucose unit. While in CDCl 3 at 40°C, the acetyl carbonyl signal for the substituent end position was observed to be separated from those on the anhydroglucose unit. By combining these results, the distribution of the substituent groups was determined for a series of hydroxyethylcellulose samples of a wide range of molar substitution values.