Studies on chitin, 8. Modification reaction of chitin in highly swollen state with aromatic cyclic carboxylic acid anhydrides

Reaction of partially deacetylated chitin with aromatic cyclic carboxylic acid anhydrides such as phthalic anhydride, trimellitic anhydride, and pyromellitic dianhydride was successfully carried out under almost homogeneous conditions in organic aprotic solvents using highly swollen precipitates of water‐soluble chitin with about 50% deacetylation. The resulting amic acid‐chitins were converted into the corresponding imide‐chitins by heating. In addition to imidization, this heat treatment also promotes removal of acid anhydrides reacted at the hydroxyl group giving rise to the formation of selectively N‐substituted derivatives. These novel chitin derivatives exhibit a much improved solubility in organic solvents and aqueous alkaline solutions. As anticipated, the imide‐chitins, derived from trimellitic anhydride and pyromellitic dianhydride, showed reactivity toward amine under heterogeneous conditions, and the reaction capacities toward p‐chloroaniline were determined to be 4,2 · 10−4 and 4,6 · 10−4 mol · g−1, respectively.