The hydrolysis of the O-glycosidic linkages (depolymerization) and
the N-acetyl linkage (de-N-acetylation) of partially N-acetylated
chitosans were studied in dilute and concentrated HCl. The rate of
hydrolysis of the glycosidic linkages was found to be equal to the
rate of de-N-acetylation in dilute acid, while the glycosidic linkages
was hydrolysed more than 10 times faster than the N-acetyl linkage
in concentrated HCl. This can be explained by assuming that the hydrolysis
of the N-acetyl Linkage is a S(N)2 reaction Gate-Limiting step: addition
of water to the carbonium ion) while the hydrolysis of the glycosidic
linkages is a S(N)1 reaction where the rate-limiting step is the
formation of the carbonium ion. The specificity of the acid-catalysed
cleavage of the different chitosan glycosidic linkages in concentrated
HCl was such that the linkages between two acetylated units (A-A)
and between an acetylated and a deacetylated unit (A-D) was cleaved
with about equal rate and three orders of magnitude faster than the
other two linkages (D-A and D-D). The activation energies for acid
hydrolysis of two almost fully de-N-acetylated chitosans (F-A = 0.002
and F-A < 0.0003) were determined to be 152.2 +/- 8.1 and 158.1 +/-
9.8 kJ mol(-1), respectively, representing the activation energy
for hydrolysis of the D-D glycosidic linkage in chitosans. The activation
energies for acid hydrolysis of two partially N-acetylated chitosans
(F-A = 0.47 and F-A = 0.62) were determined to be 130.4 +/- 2.5 and
134.3 +/- 3.1 kJ mol(-1), respectively, representing the activation
energy for hydrolysis of the A-A and A-D glycosidic linkage in chitosans.
(C) 2001 Elsevier Science Ltd. All rights reserved.
%0 Journal Article
%1 Varum2001
%A Varum, K. M.
%A Ottoy, M. H.
%A Smidsrod, O.
%C THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND
%D 2001
%I ELSEVIER SCI LTD
%J Carbohydr. Polym.
%K ; ;; [ISI:] activation chitins chitosan; chitosans; de-N-acetylation; deacetylated degradation; depolymerization; energies field lysozyme mechanisms; n-acetylated nmr-spectroscopy; reaction specificity;
%N 1
%P 89 -- 98
%T Acid hydrolysis of chitosans
%V 46
%X The hydrolysis of the O-glycosidic linkages (depolymerization) and
the N-acetyl linkage (de-N-acetylation) of partially N-acetylated
chitosans were studied in dilute and concentrated HCl. The rate of
hydrolysis of the glycosidic linkages was found to be equal to the
rate of de-N-acetylation in dilute acid, while the glycosidic linkages
was hydrolysed more than 10 times faster than the N-acetyl linkage
in concentrated HCl. This can be explained by assuming that the hydrolysis
of the N-acetyl Linkage is a S(N)2 reaction Gate-Limiting step: addition
of water to the carbonium ion) while the hydrolysis of the glycosidic
linkages is a S(N)1 reaction where the rate-limiting step is the
formation of the carbonium ion. The specificity of the acid-catalysed
cleavage of the different chitosan glycosidic linkages in concentrated
HCl was such that the linkages between two acetylated units (A-A)
and between an acetylated and a deacetylated unit (A-D) was cleaved
with about equal rate and three orders of magnitude faster than the
other two linkages (D-A and D-D). The activation energies for acid
hydrolysis of two almost fully de-N-acetylated chitosans (F-A = 0.002
and F-A < 0.0003) were determined to be 152.2 +/- 8.1 and 158.1 +/-
9.8 kJ mol(-1), respectively, representing the activation energy
for hydrolysis of the D-D glycosidic linkage in chitosans. The activation
energies for acid hydrolysis of two partially N-acetylated chitosans
(F-A = 0.47 and F-A = 0.62) were determined to be 130.4 +/- 2.5 and
134.3 +/- 3.1 kJ mol(-1), respectively, representing the activation
energy for hydrolysis of the A-A and A-D glycosidic linkage in chitosans.
(C) 2001 Elsevier Science Ltd. All rights reserved.
@article{Varum2001,
__markedentry = {[phpts:6]},
abstract = {The hydrolysis of the O-glycosidic linkages (depolymerization) and
the N-acetyl linkage (de-N-acetylation) of partially N-acetylated
chitosans were studied in dilute and concentrated HCl. The rate of
hydrolysis of the glycosidic linkages was found to be equal to the
rate of de-N-acetylation in dilute acid, while the glycosidic linkages
was hydrolysed more than 10 times faster than the N-acetyl linkage
in concentrated HCl. This can be explained by assuming that the hydrolysis
of the N-acetyl Linkage is a S(N)2 reaction Gate-Limiting step: addition
of water to the carbonium ion) while the hydrolysis of the glycosidic
linkages is a S(N)1 reaction where the rate-limiting step is the
formation of the carbonium ion. The specificity of the acid-catalysed
cleavage of the different chitosan glycosidic linkages in concentrated
HCl was such that the linkages between two acetylated units (A-A)
and between an acetylated and a deacetylated unit (A-D) was cleaved
with about equal rate and three orders of magnitude faster than the
other two linkages (D-A and D-D). The activation energies for acid
hydrolysis of two almost fully de-N-acetylated chitosans (F-A = 0.002
and F-A < 0.0003) were determined to be 152.2 +/- 8.1 and 158.1 +/-
9.8 kJ mol(-1), respectively, representing the activation energy
for hydrolysis of the D-D glycosidic linkage in chitosans. The activation
energies for acid hydrolysis of two partially N-acetylated chitosans
(F-A = 0.47 and F-A = 0.62) were determined to be 130.4 +/- 2.5 and
134.3 +/- 3.1 kJ mol(-1), respectively, representing the activation
energy for hydrolysis of the A-A and A-D glycosidic linkage in chitosans.
(C) 2001 Elsevier Science Ltd. All rights reserved.},
added-at = {2011-11-04T13:47:04.000+0100},
address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND},
author = {Varum, K. M. and Ottoy, M. H. and Smidsrod, O.},
authoraddress = {Norwegian Univ Sci & Technol, Dept Biotechnol, NOBIPOL, Norwegian
Biopolymer Lab, N-7491 Trondheim, Norway. ; Norsk Hydro AS, Res Ctr,
Div Biotechnol, N-3901 Porsgrunn, Norway.},
biburl = {https://www.bibsonomy.org/bibtex/26f484d8c801c1f044e799a82340a2da6/pawelsikorski},
citedref = {ANTHONSEN MW, 1993, CARBOHYD POLYM, V22, P193 ; DRAGET KI, 1992, BIOMATERIALS,
V13, P635 ; HOLME HK, 2000, IN PRESS THERMAL DEP ; ISHIGURO K, 1992,
CARBOHYD RES, V237, P333 ; MEYER KH, 1937, HELV CHIM ACTA, V20, P353
; MOGGRIDGE RCG, 1938, J CHEM SOC 1, P745 ; NORDTVEIT RJ, 1994, CARBOHYD
POLYM, V23, P253 ; RUPLEY JA, 1964, BIOCHIM BIOPHYS ACTA, V83, P245
; SANNAN T, 1976, MAKROMOL CHEM, V177, P3589 ; TANFORD C, 1961, PHYSICAL
CHEM MACROM ; TSUKADA S, 1981, CARBOHYD RES, V88, P19 ; VARUM KM,
1991, CARBOHYD RES, V211, P17 ; VARUM KM, 1991, CARBOHYD RES, V217,
P19 ; VARUM KM, 1996, ADV CHITIN SCI, V1, P173 ; VARUM KM, 1996,
BBA-GEN SUBJECTS, V1291, P5 ; VARUM KM, 1997, ADV CHITIN SCI, V2,
P168},
interhash = {4fa8a83e015e6e0921f32f0b60689620},
intrahash = {6f484d8c801c1f044e799a82340a2da6},
isifile-dt = {Article},
isifile-ga = {444HZ},
isifile-j9 = {CARBOHYD POLYM},
isifile-nr = {16},
isifile-pi = {OXFORD},
isifile-rp = {Varum, KM, Norwegian Univ Sci & Technol, Dept Biotechnol, NOBIPOL,
; Norwegian Biopolymer Lab, N-7491 Trondheim, Norway.},
isifile-sc = {Chemistry, Applied; Chemistry, Organic; Polymer Science},
isifile-tc = {27},
issn = {0144-8617},
journal = {Carbohydr. Polym.},
keywords = {; ;; [ISI:] activation chitins chitosan; chitosans; de-N-acetylation; deacetylated degradation; depolymerization; energies field lysozyme mechanisms; n-acetylated nmr-spectroscopy; reaction specificity;},
language = {English},
month = SEP,
number = 1,
owner = {phpts},
pages = {89 -- 98},
publisher = {ELSEVIER SCI LTD},
size = {10 p.},
sourceid = {ISI:000169395200010},
timestamp = {2011-11-04T13:47:27.000+0100},
title = {Acid hydrolysis of chitosans},
volume = 46,
year = 2001
}