MOLECULAR-WEIGHT MANIPULATION OF CHITOSAN .1. KINETICS OF DEPOLYMERIZATION BY NITROUS-ACID

The kinetics of the depolymerization of chitosan in dilute aqueous HCl solutions by nitrous acid were studied. The rate of depolymerization is independent of the molecular weight of chitosan, first order with r espect to the concentrations of both nitrous acid and glucosamine moie ties, not catalysed by either hydrogen or chloride ions, and Arrhenius temperature dependent. Chitosan exhibits significantly decreased reac tivity as the degree of deacetylation of the polymer increases. These results are consistent with a depolymerization reaction mechanism in w hich the rate-limiting step is nitrosation of the unprotonated amine b y nitrous acidium ion.