There is ambiguity in the literature as to the identity of chitobiose. Although chitin consists of b14 linked N-acetylglucosamine residues, chitobiose contains glucosamine residues instead. This convention derives from the fact that chitobiose was originally  isolated from acetolysis of chitin as its octaacetate, and the name chitobiose was given to the parent disaccharide by analogy with cellobiose, the repeating disaccharide from cellulose. Subsequent investigation of the linkage between the glucosamine residues of chitin  led to the convention that chitobiose is a dimer of glucosamine, so that the repeating unit of chitin is the N-acetylated derivative of chitobiose, i.e. N,N'-diacetylchitobiose. More precisely, chitobiose is the b(14) dimer of glucosamine, symbolized GlcNb-4GlcN in the short form recommended in the document on glycoproteins , and the corresponding N,N'-diacetyl derivative is N-acetyl-D-glucosaminyl-b(14)-N-acetyl-D-glucosamine (GlcNAcb-4GlcNAc) or N,N'-diacetylchitobiose. By analogy the higher homologue is N,N',N"-triacetylchitotriose (GlcNAcb-4GlcNAcb-4GlcNAc).
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