Studies on Chitin. 14. N-Acetylation Behavior of Chitosan with Acetyl Chloride and Acetic Anhydride in a Highly Swelled State

Abstract N-Acetylation on chitosan has been studied in a highly swelled state with acetyl chloride in comparison with that with acetic anhydride under various conditions to establish the general possibility and scope of the acylation reactions on chitosan and other polysaccharides. A highly swelled chitosan precipitate prepared by pouring a chitosan solution in aqueous acetic acid/methanol into pyridine is quite suitable for efficient modifications, and the reaction with either acylating reagent proceeded smoothly and reproducibly under mild conditions. Although acetic anhydride is generally more appropriate in protic solvens, acetyl chloride is effective and advantageous especially in pyridine containing only small amounts of protic solvents.