[igr1]

Hello,
I already read the possibility to reduce molecular weight of chitosan by allowing to react with sodium nitrite.
I found that the reaction might give the following product:

the question is what is the chemical mechanism of this reaction?
I bet for a rearrangement of Tiffeneau-Demjanov to explain the transformation of the cycle of 6 elements to a cycle of 5 element. But this can not explain the separation of the sugar residues. How can this reaction reduce the molecular weight of chitosan?

thank you very much