MECHANISMS OF PYROLYSIS OF POLYSACCHARIDES .6. INFLUENCE OF LINKAGE POSITION AND ORIENTATION IN PYROLYSIS OF POLYSACCHARIDES - A STUDY OF SEVERAL GLUCANS

Six naturally occurring and three synthetic glucans have been studied. The natural glucans contain 1,3-, 1,4- and 1,6- linkages with alpha- and beta-orientations, while the synthetic glucans contain all possible linkage positions and orientations and also varying proportions of pyranose and furanose forms. The volatile products of pyrolysis are very dependent on the presence of trace amounts of inorganic-contaminants, which were detected as metal ions in all of the natural glucans. For most glucans these contaminants were effectively removed by washing with dilute acid. This removal of contaminants was, however, incomplete in the cases of amylose and of laminaran. The glucans, after purification in this way, all gave very similar pyrolytic yields of levoglucosan (LG), showing that LG formation is not dependent on polysaccharide linkage position or orientation, and thus confirming a recent hypothesis for mechanism of LG formation. The presence during pyrolysis of inorganic compounds (either indigenous or added), always led to decrease in LG and increase in yield of formic and acetic acids, glycolaldehyde, hydroxyacetone and phenols, thus indicating that the mechanism of formation of such compounds is also not dependent on polysaccharide linkage position or orientation.