1070-4272/05/7805-0791+2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 5, 2005, pp. 791!793. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5,
2005, pp. 807!809.
Original Russian Text Copyright + 2005 by Gizatulina, Chebotok, Novikov, Konovalova.
AND INDUSTRIAL ORGANIC CHEMISTRY
Kinetics of Acid Hydrolysis of Acetylglucosamine
G. A. Gizatulina, E. N. Chebotok, V. Yu. Novikov, and I. N. Konovalova
Murmansk State Technical University, Murmansk, Russia
Knipovich Arctic Research Institute of Marine Fishery and Oceanography, Murmansk, Russia
Received January 26, 2005
Abstract-The kinetics of acid hydrolysis of N-acetylglucosamine at different temperatures and reagent con-
centrations was studied. A mathematical model of the hydrolysis was proposed. The rate constant and activa-
tion energy of deacetylation were calculated.
Utilization of large volumes of chitin-containing
waste of crustaceans involves usually chemical hy-
drolysis of chitin and chitosan. Under these condi-
tions, chitin is hydrolyzed to its monomers: glucos-
amine (GA) and acetylglucosamine (AGA). Complete
depolymerization of chitin and chitosan is usually per-
formed in an acidic solution at elevated temperatures
. Under these conditions, the glucoside bonds in the
polysaccharide are ruptured to form the monomers.
Deacetylation occurs in parallel with depolymeriza-
tion. The deacetylated monomer is usually isolated in
the form of its salt of the acid used for hydrolysis. The
study of the mechanisms of acid hydrolysis of chitin
and chitosan as influenced by the degree of deacetyla-
tion and molecular weight of the initial polysaccharide
and hydrolysis conditions (temperature and acid con-
centration) is of both practical and theoretical interest.
Acid hydrolysis of chitin and chitosan was exten-
sively studied . However, the kinetics of this
process was not understood and the rate constants of
its elementary steps were not determined. Previously
we suggested a mathematical model of acid deacetyla-
tion of chitin [6, 7]. We found that the chitin deace-
tylation is described by the first-order kinetic equation
and the dependence of the reaction rate passes through
a maximum at the hydrochloric acid concentration
The aim of this study was to estimate the rate con-
stant and activation energy of AGA deacetylation and
to determine the hydrolysis rate of the acetamide bond
as influenced by the degree of polymerization of the
We used N-acetylglucosamine (AGA) prepared by
acetylation of D-glucosamine with acetic anhydride
by the reaction 
O $ C
Acetylation was performed as follows. A 900-ml
portion of AV-17-8 anion exchanger converted into
form by treatment with 10% aqueous solu-
tion of sodium carbonate was placed into a flask
equipped with a stirrer. A 900-ml portion of 0.38 M
aqueous solution of D-glucosamine hydrochloride
[75 g (0.46 mol) GA. HCl] and 90 ml of ethanol
(w = 96%) were added at 035oC. Acetic anhydride
(45 ml, 0.64 mol, w = 99%) was added in small por-
tions at 035oC. The reaction mixture was stirred for
3hat035oC. The resin was filtered off, washed with
500 ml of distilled water, and regenerated.
The filtrate and wash waters were evaporated under
reduced pressure (10320 mm Hg) at 50360oCtoa
viscous syrup containing crystals. Ethanol (75 ml,
w = 96%) was added, and the resulting mixture was
left to crystallize at 035oC for 12315 h.
The crystals were filtered off, washed with 300 ml
of acetone (chemically pure grade) to remove water,
and dried in a vacuum. The N-acetylglucosamine yield
was 73.5% of the theoretical yield corresponding
to Eq. (1).
N-Acetylglucosamine was hydrolyzed in hydro-
chloric acid with a concentration from 10 to 37.2%
at 40, 60, and 80oC. The hydrolyzate was neutralized
first with 2.7 M NaOH and then with 0.1 M NaOH to
pH 7.0, filtered through a Schott filter (pore diameter
no larger than 10 mm, POR 10), and analyzed for
AGA and GA content (M).
The AGA content was determined by the procedure
described in ; the total AGA + GA content, by the
procedure from . The GA amount was calculated