Editing N-acetylated Chitosan

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Chitosan 10B (0.6 g) was suspended<br>in distilled water (0.05 dm 3 ) and 20% aqueous acetic acid<br>(0.05 dm 3 ) was added gradually to the suspension with vig-<br>orous mixing. The suspension was mixed with magnetic<br>stirrer for over 1 day until it became a viscous, transpar-<br>ent and homogeneous solution. Subsequently, the required<br>amount of acetic anhydride (0.38–9.50 g) was poured gen-<br>tly into the solution with mixing at ambient temperature.<br>After stirring for 5 h, the reaction mixture was adjusted to<br>pH 9 with 5 mol dm −3 aqueous KOH solution and poured<br>into acetone (0.3 dm 3 ) in order to obtain the resulting NAC<br>as precipitate. The precipitate was filtered and suspended<br>in 1 mol dm −3 methanolic KOH solution. After stirring for<br>6 h, the resulting precipitate was filtered and rinsed with<br>methanol until the filtrate became neutral. Finally, the pre-<br>cipitate was lyophilized.<br>

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mixture of chitosan (5 g) and aqueous acetic<br>acid (600 ml, 0.12 M) was stirred for 24 h to ensure<br>total solubility. The pH was adjusted to 7.2 by slow<br>addition of 0.1 M NaOH with strong agitation,<br>yielding a gel slurry, the volume of which was<br>adjusted to about 900 ml. Palmitoyl chloride (20<br>ml,<br>d<br>=0.907 g/ml) was then added and the reaction<br>volume diluted to 1 l with distilled water. Similarly,<br>different volumes (10–60 ml) of palmitoyl chloride<br>were used to obtain various degrees of substitution.<br>Other derivatives were obtained using the same<br>conditions, substituting 20 ml of caproyl, octanoyl,<br>or myristoyl chloride. After 4–6 h, each preparation<br>was neutralized (pH 6.8–7.0) and precipitated with<br>acetone. The precipitate, collected by filtration, was<br>washed at 50–60 C with an excess of methanol and<br>decanted. The washing was repeated three times to<br>eliminate free fatty acids<br>





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