Studies on chitin, 4. Evidence for formation of block and random copolymers of N‐acetyl‐D‐glucosamine and D‐glucosamine by hetero‐ and homogeneous hydrolyses

Abstract

Chitin was deacetylated by heterogeneous and homogeneous alkaline hydrolyses. In the heterogeneous hydrolysis, upper limits in the degree of deacetylation were found to exist at low reaction temperatures. The products obtained were all insoluble in water and those with a degree of deacetylation up to 80% retained some crystallinity. These results seemed to indicate that the deacetylation under the heterogeneous conditions proceeded preferentially in the amorphous region to give block‐type copolymers of N‐acetyle‐D‐glucosamine and D‐glucosamine units. In the homogeneous hydrolysis, on the other hand, all the products with a degree of deacetylation of ca. 50% were found to be soluble in water independent of the hydrolysis temperature. The crystallinity of the products decreased much more rapidly and samples with a degree of deacetylation >40% were amorphous. These results suggested that the deacetylation under homogeneous conditions proceeded randomly to give the random‐type copolymers of the two units. This randomness was concluded to have brought about the interesting water‐solubility of products with a degree of deacetylation of ca. 50%.