NMR Studies of Lignins. 5. Investigation of Non-derivatized Spruce and Birch Lignin by 1H NMR Spectroscopy.

Abstract

Non-derivatized rnilled wood lignins frorn spruce (Picea abies) and birch (Betula verrucosa) have been examined by 1H NMR spectroscopy, using a 270 MHz instrurnent. The results confirrn and complement structural inforrnation obtained in previous 1H NMR studies with acetylated lignins. The lignins were found to contain only a few units with a noncyclic benzyl aryl ether linkage (spruce, <3 %; birch, ~5 %). The number of cinnarnyl alcohol units was srnall (< 1 %). Signals frorn b-1 structures could not be detected, and it is suggested that such structures exist in a rnasked form in the lignins. Support was obtained for the occurrence of units with a rnethylene group.