13C-n.m.r. studies of the acetylation sequences in partially N-deacetylated chitins (chitosans).

Chitosans obtained under homogeneous conditions of N-deacetylation, with degrees of N-deacetylation between 46% and 94%, were depolymerised and their 125-MHz 13C-n.m.r. spectra have been interpreted. The sequence of 2-acetamido-2-deoxy-beta-D-glucopyranose (GlcNAc) and 2-amino-2-deoxy-beta-D-glucopyranose (GlcN) residues influenced the chemical shifts, and the diad and triad frequencies have been calculated. Chitosans that were N-deacetylated under homogeneous and heterogeneous conditions gave values for the diad and triad frequencies that were consistent with a random arrangement of GlcN and GlcNAc residues.