Determination of distribution of o-acetyl group in trihydric alcohol units of cellulose acetate by carbon-13 nuclear magnetic resonance analysis

Abstract

The total degree of substitution, DS(≡ ≪F≪), the distribution of DS and the distribution of the substituent group in a glucopyranose unit ≪fk≪ (the suffix k means the carbon position in the Cl chain conformation) are accurately defined for cellulose derivatives. ≪fk≪ of cellulose acetate (CA) was evaluated from the 1H nuclear magnetic resonance (NMR) chemical shift of the O-acetyl protons and the 13C NMR chemical shift of the O-acetyl carbons. 1H NMR method is applicable only to completely substituted cellulose acetate, but the 13C NMR method is proved applicable for the entire range of the DS (0-3). CA (DS=2.92)-trichloromethane, CA (DS=2.46)- acetone, and CA (Z)S=0.49)-dimethyl sulfoxide systems are employed successfully. ≪Fk≪ values determined by 13C NMR spectrum are in good agreement with those by the chemical analysis. The reactivity of the O-acetyl groups during the hydrolysis reaction process using hydrochloric acid as a catalyst decreases in the following order: C2>C6>C3. © 1981, The Society of Polymer Science, Japan. All rights reserved.