J.Serb.Chem.Soc.65(10)681–689(2000)
UDC 547.582.4:542.9:541.12.03
JSCS-2792
Original scientific paper
Synthesis of some bis- and mono-2-hydroxybenzoic acid
derivatives and the determination of their acidity constants
EVGENIJA A. DJURENDIC , GYÖNGYI GY. VASTAG#, TERÉZIA M. SURÁNYI#,
MIRJANA M. POPSAVIN# and KATARINA M. PENOV GASI#
Institute of Chemistry, Faculty of Sciences, University of Novi Sad,
Trg D. Obradovica 3, YU-21000 Novi Sad, Yugoslavia
(Received 21 March, revised 14 June 2000)
Several bis- and mono-2-hydroxybenzoic acid derivatives were
synthesized by the reaction of methyl 2-hydroxybenzoate with some
alcohols (diols, polyols and amino alcohols) and their acidity
constants were determined in 60 % aqueous ethanol by the potentiometric
titration method. It has been shown that the biochemical behaviour of
these compounds is greatly dependent on their acidity. It appears that
the ester derivatives are weaker acids than the amide derivatives and,
therefore, can be potentially more involved in the processes of metal
ions transport in plants, whereas the introduction of –OH and –CH3
groups has a very small effect on the biochemical properties.
Keywords: 2-hydroxybenzoic acid derivatives, synthesis, acidity
constants.
J.Serb.Chem.Soc.65(10)691–694(2000)
UDC 615.28/.281
JSCS–2793
Original scientific paper
An alternative synthesis of clindamycin
KEITH BOWDEN and GRAHAM P. STEVENS
Department of Biological and Chemical Sciences, Central Campus,
University of Essex, Wivenhoe Park, Colchester, Essex, UK, CO4 3SQ
(Received 7 June 2000)
A novel synthesis of clindamycin from lincomycin using Nchlorosuccinimide and triphenylphosphine is reported. This results in
high yields and avoids the use of tetrachloromethane employed in the
current manufacturing process.
Keywords: clindamycin, N-chlorosuccinmide.
J.Serb.Chem.Soc.65(10)695–708(2000)
UDC 547.462.3:539.172.3
JSCS–2794
Original scientific paper
Protonation of maleic and fumaric acid in aqueous
sulfuric acid solutions
KATICA JANKOVSKA1, LIDIJA SOPTRAJANOVA2 and ILINKA SPIREVSKA2
1Faculty of Metallurgy and Technology, Rudjer Boskovic bb, 91000
Skopje, Macedonia and
2Institute of Chemistry, Faculty of Natural Sciences and Mathematics,
P.O. Box 162, 91001 Skopje, Macedonia
(Received 26 January, revised 12 June 2000)
The protonations of maleic and fumaric acid in an acidic medium
(aqueous solutions of sulfuric acid) were followed
spectrophotometrically at room temperature. The acid-base equilibria
were characterised qualitatively and quantitatively. The pKBH+ values
were determined using the Hammett equation, employing several acid
functions in order to determine which of them describes best the
protonation process of the studied organic acids. The thermodynamic
pKBH+ values as well as those of the solvation parameters m, m* and f
and of the thermodynamic protonation constants (or, rather, the pKa,p
values) were also defermined. The method of characteristic vector
analysis (CVA) was used to reconstruct the experimental spectra.
Keywords: maleic acid, fumaric acid, protonation, spectrophotometry.
J.Serb.Chem.Soc.65(10)709–713(2000)
UDC 547.461.3:539.173:541.127
JSCS–2795
Original scientific paper
Belousov-Zhabotinsky oscillatory reaction. Kinetics of malonic acid
decomposition
SLAVICA BLAGOJEVIC,1 NATASA PEJIC,1 SLOBODAN ANIC2 and
LJILJANA KOLAR-ANIC2
1Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, YU11000 Belgrade and
2Faculty of Physical Chemistry, University of Belgrade, Studentski trg
12-16, P. O. Box 137, YU-11001 Belgrade, Yugoslavia
(Received 26 April 2000)
The kinetics of the Belousov-Zhabotinsky (BZ) oscillatory reaction was
analyzed. With this aim, the time evolution of a reaction mixture
composed of malonic acid, bromate, sulfuric acid and cerium(III) was
studied at 298 K. Pseudo-first order kinetics with respect to malonic
acid as the species undergoing decomposition with a corresponding rate
constant, k = 7.5´10-3 min-1, was found.
Keywords: kinetics, non-linear dynamics, oscillatory reaction,
Belousov-Zhabotinsky reaction.
J. Serb. Chem. Soc. 65(10)715–723(2000)
UDC 632.952:541.183:549.67:582.28
JSCS-2796
Original scientific paper
Kinetics of aflatoxin B1 and G2 adsorption on Ca-clinoptilolite
ALEKSANDRA DAKOVIC, MAGDALENA TOMASEVIC-CANOVIC, VERA DONDUR1,
ALEKSANDRA VUJAKOVIC and PREDRAG RADOSEVIC
Institute for Technology of Nuclear and Other Mineral Raw Materials, P.
O. Box 390, YU-11001, Belgrade, and 1Faculty of Physical Chemistry, P.
O. Box 137, YU-11001 Belgrade, Yugoslavia
(Received 26 March 2000)
The kinetics of aflatoxins B1 and G2 adsorption on Ca-clinoptilolite at
pH 2 and 7, in aqueous electrolyte at 37 ºC were studied. For both
aflatoxins, the adsorption process begins with a fast reaction whereby
most of the toxin is adsorbed in the first few minutes. This fast
process is followed by the significantly slower process of aflatoxin
bonding at active centers of mineral adsorbent. The initial rate method
showed that the fast adsorption process of aflatoxin B1 and G2, at both
pH values is a first order reaction, while the slow adsorption process
of these aflatoxins is a zero order reaction. The adsorption indexes
and adsorption rates for both examined toxins were pH dependent. In the
investigated initial toxins concentration ranges (500–3000 mg/dm3),
high adsorption indexes were achieved (> 80 %).
Keywords: clinoptilolite, adsorption, aflatoxin B1, aflatoxin G2.
J.Serb.Chem.Soc.65(10)725–731(2000)
UDC 543.544.4/.7:547.261/546.212
JSCS–2797
Original scientific paper
Influence of the stationary and mobile phase composition in ideal
chromatographic systems on the log k values in column chromatography.
I. ODS/methanol–water system
T. J. JANJIC, G. VUCKOVIC# and M. B. CELAP#
Faculty of Chemistry, University of Belgrade, P. O. Box 158, YU-11001
Belgrade, Yugoslavia
(Received 18 May 2000)
On the basis of the literature data it was established that in the case
of ODS column chromatography with methanol as modifier the value log
xs/x1 (where xs and x1 denote methanol mole fractions in the stationary
and the mobile phase, respecitvely) is a linear function of the
corresponding Bosch’s PmN parameter as well as of the log k value of
the investigated substances. It was also found that the phase
equilibrium in the system ODS/methanol-water is in accordance with the
Everett’s equation for ideal systems (K = 10.88). Finally, a linear
relationship between the log xs/x1 values and the volume fraction of
methanol (j) was found in the range of 0.5–1.0, which corresponds to
the linear part of the function log k = f(j), established
experimentally by other authors.
Keywords: C18 liquid chromatography, stationary phase composition,
mobile phase composition, capacity factors, PmN parameter, log k pair
linearity rule, proportionality rule, RPP scale.
J.Serb.Chem.Soc.65(10)733–742(2000)
UDC 543.544.42:661.183.7:547.261:547.722/.728
JSCS–2798
Original scientific paper
Application of the Log k pair linearity rule and Proportionality rule
to the RPP mobile phase scales estimation on diol-silica
column
TOMISLAV J. JANJIC, GORDANA VUCKOVIC# and MILENKO B. CELAP#
Faculty of Chemistry, University of Belgrade, P. O. Box 158, YU-11001
Belgrade, Yugoslavia
(Received 12 May 2000)
By the application of the Log k pair linearity rule and the
Proportionality rule to the previously published log k values for 27
compounds, obtained on diol-silica columns with acetonitrile, methanol
and tetrahydrofuran as modifiers, the existence of common RPP scales
was established. The obtained correlation coefficients of the linear
function log k = f(RPP) were better than 0.9900 for 26 compounds in the
first, 21 in the second and 20 in the third case. In addition, in the
case of the two first modifiers a linear correlation between the
obtained RPP values and mol % of modifier in the mobile phase was
found. On the basis of this, the following simple linear function: log
k = f(mol % of modifier) was proposed as a criterion for log k values
judgement in practical work. A linear correlation was also established
between intercept and slope of the function, in spite of the fact that
the investigated compounds essentially differ in their descriptors.
Keywords: column chromatography, diol-silica sorbent, log k pair
linearity rule, proportinality rule, RPP scale.
J.Serb.Chem.Soc.65(10)743–754(2000)
UDC 546.65/654:546.226 33:534.24
JSCS–2799
Original scientific paper
Lanthanide doped alkaline metal sulphates as candidates for EPR
dosimetry
JELENA PETKOVIC, IVANA MLADENOVIC, NIKOLA VUKELIC, MILOS MOJOVIC
and GORAN BACIC
Faculty of Physical Chemistry, University of Belgrade, Studentski trg
12, YU-11001 Belgrade,
Yugoslavia
(Received 2 June 2000)
The applicability of lanthanide doped alkaline metal sulphates as a new
type of dosimeters for EPR dosimetery of ionizing radiation has been
investigated in an attempt to obtain a dosimeter with better
characteristics than the commonly used alanine dosimeter. Irradiation
of samples doped with different lanthanides (Y, Ln, Gd) showed that the
best sensitivity is obtained using dosimeters doped with Y2(SO4)3.
Different procedures for manufacturing dosimeters were studied and an
optimum procedure was established. The time stability of the EPR signal
of the irradiated Y2(SO4)3 dosimeter was investigated using a 15N-PDT
standard and no fading of the EPR signal was observed over at least two
weeks. The dose dependence of alanine and Y2(SO4)3 doped K3Na(SO4)2
dosimeters irradiated in the range 20 Gy – 200 kGy was analysed using a
combination of 1-hit and 2-hit mechanisms of free radicals creation.
Keywords: lanthanide doped K3Na(SO4)2, electron paramagnetic resonance,
dosimetry.
J.Serb.Chem.Soc. 65(10)000-000(2000)
UDC 542.4/.47::541.124
JSCS-2800
Original scientific paper
An experimental study of the drying of granular materials in a packed bed passed by
hot air the local humidity of the material
ANCA MOISE and RADU Z. TUDOSE
Department of Chemical Engineering, Iasi Technical University, Mangeron nr. 71,
Iasi-6600, Romania
(Received 26 July 1999, revised 14 June 2000)
With the purpose of establishing the mechanism resposible for the drying of
granular materials in a packed bed passed by a gaseous thermic agent, experimental
kinetic study was perormed. In a pilot plant, the axial and radial distributions of
the solid local humidity were determined in the nonsteady regime. The results show
it is possible for three zones, each at a different state of dryness, to exist in
the bed: one zone with initial humidity, one zone with variable humidity and one
zone with dried material.
Keywords: drying, packed bed, kinetics of drying.