C-13-NMR ANALYSIS OF ACETYL GROUPS IN ACETYLATED WOOD .1. ACETYL GROUPS IN CELLULOSE AND HEMICELLULOSE

The acetyl groups in cellulose and hemicellulose within acetylated woo d was analyzed by C-13-NMR (carbon 13 nuclear magnetic resonance) spec troscopy. Before the analysis, the acetylated wood was delignified lig htly with a sodium chlorite procedure (Wise method) to dissolve in a M MNO/DMSO-d(6) mixture. The degree of delignification ranged from 40 to 70%, depending on the WPG (weight percent gain). It was indicated tha t the delignification caused no changes in the acetyl distributions in the xylan and cellulose. The X-ray diffraction analysis of the acetyl ated wood indicated that the crystalline region of the cellulose start ed to be reacted above the WPG of about 20%. The xylan in the wood was reactive during the acetylation, producing the mono- and the disubsti tutions of hydroxyl groups at small WPGs. The increase in WPG increase d the di-substitution in the xylan. All the hydroxyl groups in xylan w ere not substituted for at the WPG of about 20%. The cellulose in the wood was less reactive than the xylan, although the mono-, the di-, an d the tri-substitutions were produced at small WPGs. The increasing WP G increased the di- and the tri-substitutions in the cellulose. The fr ee hydroxyl groups in the non-crystalline region of the cellulose rema ined at the WPG of about 20%, at which point the crystalline region of the cellulose started to be reacted. The greater increase in WPG incr eased the di- and the tri-substitutions in cellulose.