N-acetylated Chitosan

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

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