Description:
AbstractCelluloses of different origin are hydrolyzed at different rates in acid medium both in fiber form (heterogeneous process) and in solution (homogeneous process). On the basis of measurements for well purified samples of commercial wood and cotton celluloses, molecularly dissolved in concentrated phosphoric acid, it was recently proposed that the fact that initial rates of hydrolysis are higher for wood cellulose than for cotton cellulose is largely related to inductive effects from modified (electrophilic) groups, e.g., carboxyls and carbonyls. Some of these groups are no doubt introduced during purification processes involving oxidative bleaching. It is possible that some of the modified groups are of native origin, but they are few (less than one modified group for 400 glucose units). The probable mechanisms for the influence on the rate of hydrolysis of modified groups, e.g., inductive and steric effects, rearrangements of the ring structure, are discussed in relation to the present knowledge of polysaccharide reactions. The concepts of inductive effects are supported by evidence from the hydrolysis of hemicelluloses and other polysaccharides containing uronic acid groups.