Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 7, pp. 986−991.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © N.V. Dolgopyatova, V.Yu. Novikov, I.N. Konovalova, N.M. Putintsev, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86,
No. 7, pp. 1052−1058.
ORGANIC AND PETROCHEMICAL
Mechanism of Acid Hydrolysis of N-Acetyl-D-glucosamine
N. V. Dolgopyatova
, V. Yu. Novikov
, I. N. Konovalova
, and N. M. Putintsev
Murmansk State Technical University, Murmansk, Russia
Knipovich Polar Research Institute of Marine Fishery and Oceanography, Murmansk, Russia
Received May 16, 2013
Abstract—The hydrolysis kinetics of the chitin monomer, N-acetyl-D-glucosamine, in HCl, HClO
, and H
was studied in relation to the acid concentration. The rate constants of N-acetyl-D-glucosamine deacetylation and
D(+)-glucosamine formation in HClO
were determined for the ﬁ rst time. The rate of the acetamide
bond hydrolysis in N-acetyl-D-glucosamine depends on the concentrations of hydrogen ions and water. The nu-
cleophilicity of the acid residues does not affect the rate of N-acetyl-D-glucosamine hydrolysis.
mino saccharides D(+)-glucosamine and N-acetyl-
D-glucosamine widely occur in the nature, play an
important role in biology, and are used in medicine,
organic and bioorganic chemistry, in cosmetic and food
industry, and in other branches . The use of these
amino saccharides as antiarthritics is of most practical
interest [2, 3].
D(+)-Glucosamine is prepared by exhaustive
depolymerization and deacetylation of natural
polysaccharide chitin under the action of concentrated
HCl on heating .
Also, an enzymatic procedure for preparing
glucosamine from chitin  and enzymatic procedures
for chitin depolymerization under the action of various
chitinolytic enzymes  have been suggested.
N-Acetyl-D-glucosamine can be prepared from
chitin by mild acid hydrolysis [5, 6]. Partial hydrolysis
is usually performed with hydrochloric acid, and the
hydrolysis products contain, along with the monomer,
also small oligomers (chitooligosaccharides). Acid
hydrolysis of chitin and chitosan leads to cleavage of
both glycoside (degradation, depolymerization) and
acetamide (deacetylation) bonds. Therefore, products
of partial acid hydrolysis contain acetylated and
N-Acetyl-D-glucosamine can be prepared by
acetylation of D(+)-glucosamine. A simple procedure for
D(+)-glucosamine acetylation with various acetylating
agents such as acetic anhydride  or acetyl chloride
 is the most widely used.
As found in , deacetylation of chitin and N-acetyl-
D-glucosamine in hydrochloric acid is described by a
ﬁ rst-order rate equation, and the dependence of the
rate of this reaction on the acid concentration passes
through a maximum at the HCl concentration of 29.8%.
Gizatulina et al.  studied the inﬂ uence exerted on the
chitin degradation kinetics by the degree of ionization
and nucleophilicity of different acids.
Studies of the acid hydrolysis of chitin showed
that the glycoside bonds are cleaved ﬁ rst, and the
deacetylation mainly occurs at the step of N-acetyl-D-
glucosamine [7, 8]. The practical use of N-acetyl-D-
glucosamine requires either preservation of the acetyl
group or its removal by deacetylation.
We found no data in the literature on how the
hydrolysis kinetics of N-acetyl-D-glucosamine is
inﬂ uenced by the degree of ionization and by the
nucleophilicity of various acids.
To reﬁ ne the mechanism of acid deacetylation and
ﬁ nd the optimal conditions for practical use of chitin
monomers, we studied the speciﬁ c features of N-acetyl-