JSCS Vol 61, No. 7
J.
Serb. Chem. Soc. 61(7)517-522(1996)
UDC 547/.9:541.183.12
JSCS-2258
Original scientific paper
GLYCIDYL
ESTERS SYNTHESIS CATALYSED BY ION-EXCHANGE RESINS
DUSAN Z. MIJIN, IVANA D.
OSTRIC and MILICA M. MISIC-VUKOVIC
Faculty
of Technology and Metallurgy, University of Belgrade
Karnegijeva 4, P.O.Box 494Belgrade , Yugoslavia
(Received 14 November 1995)
Ion-exchange resins not
previously used for this purpose were employed to study the synthesis of glycidyl esters. The reaction was carried out both with
free acids and their sodium salts. The model reaction was the synthesis of glycidyl stearate. Crude glycidyl stearate was afforded in
yields greater than 90% in a nonaquous, but not
anhydrous system with GC purity above 99%. The phase-transfer catalytic (PTC)
mechanism is proposed for the investigated reaction.
Key words: Glycidyl stearate, phase transfer catalysis, ion-exchange resins
J.
Serb. Chem. Soc. 61(7)523-528(1996)
UDC 547.743/.745
JSCS-2259
Original scientific paper
CYCLOADDITION
REACTIONS OF AZOMETHINE YLIDES GENERATED BY
1,2 PROTOTROPY FROM IMINES
SUREN HUSINEC*, LJILJANA
MILOVANOVIC** and
*Institute of Chemistry Belgrade
**Faculty of Pharmacy, Department of Organic Chemisty,
Vojvode Stepe 450, YU-11000
Belgrade , Yugoslavia
(Received
7 December 1995)
The in situ formation
of azomethine ylides by
condensing an amino ester and an aldehyde followed by
cycloaddition to the activated double bond was
investigated. Different types of substituted pyrrolidines
were synthesised by this methodology.
Key words: cycloaddition
reaction, azomethine ylides,
1,2 prototropy, 1,3 dipolar cycloaddtion, imines, amino ester, pyrrolidine
J.
Serb. Chem. Soc. 61(7)529-533(1996)
UDC 543.866.002.2
JSCS-2260
Original scintific paper
PRODUCTION,
PURIFICATION AND SOME PROPERTIES OF EXTRACELLULAR BACTERIOLYTIC ENZYMES
PRODUCED BY STREPTOMYCES HYGROSCOPICUS
IVANKA KARADZIC*, GORDANA
GOJGIC-CVIJOVIC** and JOVAN VUCETIC***
*Faculty
of Medicine, Institute of Chemistry, Visegradska 26,
YU-11000 Belgrade,
** Institute of Chemistry, Technology and Metallurgy, Department of Chemistry, Njegoseva 12, P.O.Box 815,
YU-11001 Belgrade and
***Faculty of Chemistry, Akademski trg 16, YU-11000 Belgrade, Yugoslavia
(Received
17 August 1995)
A strain Streptomyces hygroscopicus
was isolated from a soil sample from
Key words: Streptomyces,
proteolytic, bacteriolytic,
extracellular, enzyme
J.
Serb. Chem. Soc. 61(7)535-538(1996)
UDC 547.953:547.963.4
JSCS-2261
Original scientific paper
COVALENT GLYCOPHOSPHOLIPID BINDING TO HEMOGLOBIN. A NEW POST-TRANSLATIONAL MODIFICATION OCCURRING IN
ERYTHROCYTES EXPOSED TO INSULIN
VESNA NIKETIC*, NENAD
TOMASEVIC*, VLATKA VAJS** and ZANKA BOJIC*
*Department
of Chemistry, University of Belgrade P.O. Box 158Belgrade
**Center for Chemistry, ICTM, Belgrade , Yugoslavia
(Received,
7 August 1995)
In this work a novel
hitherto unrecognised hemoglobin (Hb)
fraction, HbA1x, which we detected previously in hemolysates
of erythrocytes exposed to high concentration of insulin under hypoglycemic
conditions, both in vivo and in vitro, was analysed.
Both 
chains of Hb in HbA1x
were found to be modified by covalent binding of a substance containing sugar,
phosphate and fatty acid residues. HbA1x was therefore termed glycophospholipid (GPL) adduct (Hb-GPL).
To our knowledge, this is the first demonstration of such modification of Hb, as well as the first demonstration of
post-translational GPL binding to proteins in response to insulin binding to a
cell. The mechanism proposed for Hb-GPL formation is
briefly described.
Key words: hemoglobin, glycophospholipid,
insulin
J.
Serb. Chem. Soc. 61 (7)539-543(1996)
UDC 539.143.3:547.538
JSCS-2262
Original scientific paper
THE
DEPENDENCE OF THE TOTAL P-ELECTRON ENERGY OF ISOMETRIC UNBRANCHED CATACONDENSED
BENZENOID HYDROCARBONS WITH A FIXED NUMBER OF BAY REGIONS ON THE NUMBER OF
KEKULÉ STRUCTURES
SVETLANA MARKOVIC, IVAN GUTMAN and JELENA SUKOVIC
Faculty
of Scince, University of Kragujevac P.O. Box 60Kragujevac , Yugoslavia
(Received
11 December 1995)
The dependence of the
total 
-electron energy of large unbranched catacondensed benzenoid
hydrocarbons on the number of Kekulé structures is
examined in families of isomers possessing a fixed number of bay regions (b).
For small values of b this dependence is found to be curvilinear,
whereas for larger values of b the dependence is essentially linear.
These findings are in harmony with, and provide a further extension of, the
results of previous studies in which the effect of bay regions was not taken
into account.
Key words: total p-electron energy, number of Kekulé structures, number of bay regions
J.
Serb. Chem. Soc. 61(7)545-549(1995)
UDC 547.963.3:543.51:537.533.1
JSCS-2263
Original scientific paper
SOME
ASPECTS OF THE QUANTITATIVE ANALYSIS OF CYCLIC NUCLEOTIDES BY FAST-ATOM
BOMBARDMENT MASS SPECTROMETRY
ALEKSANDRA A. PERIC*, MILA
D. LAUSEVIC*, RUSSELL P. NEWTON** and GARETH A. BRENTON**
*Faculty
of Technology and Metallurgy, University of Belgrade, Karnegijeva
4, P.O.Box 494, YU-11000 Belgrade, Yugoslavia
and
**University College of Swansea, Swansea SA2 8PP, United Kingdom
(Received
27 September 1995, revised 28 January 1996)
The possibilities of
the quantitative analysis of cyclic nucleotides by fast-atom bombardment are
examined. Aspects such as the amount of matrix, the formation of protonated ion species and the presence of more than one
cyclic nucleotide in the sample are discussed and the conclusion has been
reached that these aspects are in direct relation with the quantification of
the data obtained from the mass spectra. Consideration of these aspects
suggests that fast-atom bombardment does not seem to be a convenient ionisation technique for the quantitative analysis of
cyclic nucleotides.
Key words: cyclic nucleotides, mass spectrometry,
fast-atom bombardment
J.
Serb. Chem. Soc. 61(7)551-556(1996)
UDC 547.771:661.78
JSCS-2264
Original scientific paper
METAL COMPLEXES WITH PYRAZOLE-DERIVED LIGANDS.
PART 3. COBALT(II) COMPLEXES
WITH 3(5)-AMINO-4-ACETYL-5(3)-METHYLPYRAZOLE
VUKADIN M. LEOVAC*, ERIKA Z.
IVEGES*, VALERIJA
*Institute
of Chemistry, Faculty of Science, Trg D. Obradovica 3, YU-21000 Novi Sad, Yugoslavia,
**Institute of Physics, Faculty of Science, Trg D. Obradovica 4, YU-21000 Novi Sad, Yugoslavia,
***Department of General and Inorganic Chemistry, Faculty of Technology and
Metallurgy, P. O. Box 494, YU-11001 Belgrade, Yugoslavia
(Received
6 October 1995)
Several tetrahedral
cobalt(II) complexes with 3(5)-amino-4-acetyl-5(3)-methylpyrazole
(HL) of the general formula [CoX2(HL)2] (X = Cl, Br, I, NCO, NCS), as well as the octahedral [Co(H2O)4(HL)2]
(NO3)2 and [Co{m-N(CN)}2)2(HL)2]
complexes were synthesized and characterized by elemental analysis, molar
conductivity, magnetic susceptibility measurements. IR,
reflectance and absorption electronic spectra.
Key words: cobalt(II)-complexes,
3(5)-amino-4-acetyl-5(3)-methylpyrazole, physico-chemical characterization
J.
Serb. Chem. Soc. 61(7)557-565(1996)
UDC 547.261:541.138:66.094.3
JSCS-2265
Original scientific paper
STRUCTURAL
EFFECTS IN ELECTROCATALYSIS: OXIDATION OF METHANOL ON SINGLE CRYSTAL PLATINUM ELECTRODES IN ALKALINE SOLUTION
A.V. TRIPKOVIC and K.Dj. POPOVIC
Institute of Electrochemistry University of Belgrade
P.O.Box 815Belgrade , Yugoslavia
(Received 3
November 1995, revised 13 March 1996)
The effect of structure
on the oxidation of methanol has been studied by investigating the reaction on
three platinum low index planes, and ten stepped surfaces from all three zones
of the stereographic triangle in 0.1 M NaOH. A
pronounced structural dependence of the reaction has been shown. The most active
plane from the low index surfaces was the (100). The highest current peak was
obtained on the (111) plane but at a more positive potential then on the (100)
plane. The most active of the stepped surfaces appeared to be the (322). The
activity of the stepped surfaces was influenced by the step orientation and the
step density. The origin of the surface activity was associated with the
presence of OH species and the degree of OH coverage on the low index planes
and on the different sites (terraces and steps) on the stepped surfaces.
Key words: methanol oxidation; structural effects; single
crystal platinum electrodes; alkaline solution.
J.
Serb. Chem. Soc. 61(7)567-575(1996)
UDC 543.251:546.11' 74'' 98'''
JSCS-2226
Original scientific paper
VOLTAMMETRIC
STUDIES OF ELECTRODEPOSITED HYDROGEN AT ELECTROCHEMICALLY DEPOSITED
PD-NI-ELECTRODES
LJ. VRACAR* and M. STOJANOVIC**
*
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4,
P.O. Box 494, YU-11001 Belgrade and
**Military-Technical Institute, Kataniceva 15,
YU-11000 Belegrade, Yugoslavia
(Received
10 November 1995, revised 12 March 1996)
Potentiodynamic studies of H accommodation at a
Pd-Ni electrodeposited alloy show that the hydrogen deposition-absorption or H
oxidation processes can be distinguished from possible spontaneous oxidation,
over somewhat overlapping potential regions. Some process which involves
diffusion is indicated in experiments at various sweep rates where a linearity
between jp,a
and 
1/2 is observed. It is suggested that this process
can be diffusion of absorbed H into the electrode surface. Electrocatalytic
behaviour of this alloy for any process occuring in the "hydrogen region" of potential
must take into account the changed surface properties due to the presence of sorbed H.
Key words: Pd-Ni alloy, hydrogen adsorption, hydrogen
absorption, hydrogen evolution, cyclic voltammetry
J.
Serb. Chem. Soc. 61(7)577-582(1996
UDC 546.59:548.51/.55
JSCS-2267
Original scientific paper
THE
INITIAL STAGES OF THE NUCLEATION AND GROWTH OF AU ON AU(111)
OBSERVED BY STM
SVETLANA STRBAC* and ZLATKO
RAKOCEVIC**
*Institute of Electrochemistry P.O.Box 815Belgrade
**Vinca Inastitute of
Nuclear Sciences, P.O.Box 522Belgrade , Yugoslavia
(Received
13 December 1995)
Tne initial stages of the nucleation
and growth of Au on the Au(111) single crystal
substrate have been observed by scanning tunneling microscopy (STM) in air with
the surface coverage by deposited gold atoms ranging from 0.006 monolayer (ML)
to 0.04 ML. The creation of two types of clusters was observed. The first type
were two-dimensional (2D)-3SQRT3 clusters with vacancies in various positions
having mainly seven atoms and tending to a hexagonal structure. We suppose that
such clusters nucleate at point defects of flat terraces. With an increase in
coverage these clusters grew up into (2D) terraces with the arrangement of gold
atoms consistent with the symmetry of the (111) plane of the substrate
indicating that growth occurs in a layer-by-layer mode. The second type of clusters were lined clusters whose creation begins
at step edges. In the initial stages, they nucleate as 1D clusters.
Their further growth is characterized by the formation of quazi-hexagonal
strings. The coalescence of those strings leads to the growth of the second
layer before the first one is completely filled in.
Key words: nucleation, gold, single crystal, scanning
tunneling microscopy
J.
Serb. Chem. Soc. 61(7)583-590(1996)
UDC 41.134.4:41.138:621.316:541.135.6/.61
JSCS-2268
Original scientific paper
THE CURRENT DISTRIBUTION IN AN ELECTROCHEMICAL CELL.
PART II. QUALITATIVE CONSIDERATIONS ON THE BASIS OF
POLARIZATION CURVE SHAPE
KONSTANTIN I. POPOV,
STRAHINJA K. ZECEVIC and SLAVISA M. PESIC
Faculty
of Technology and Metallurgy, University of Belgrade
P.O.Box 494Belgrade , Yugoslavia
(Received
14 November 1995, revised 11 March 1996)
The current
density-cell voltage curves of the system (-)Cu/CuSO4, H2SO4,
H2O/Cu(+) were recorded in cell with a parallel plate electrodes for
different parameters such as inter-electrode distance, distance between the
edges of the electrodes and the side walls of the cell, CuSO4 and H2SO4
concentrations, temperature and the agitation of the electrolyte. The current
distribution is qualitatively discussed on the basis of polarization curve
shape and current line propagation depth outsides the space between the eleectrodes.
Key words: metal deposition, electrochemical cell,
current distribution
J.
Serb. Chem. Soc. 61(7)591-600(1996)
UDC 678.674/.743:691.7:620.193
JSCS-2269
Original scientific paper
CORROSION
BEHAVIOUR OF POLYESTER AND FLUOROPOLYMER COATINGS ON
COIL COATED STAINLESS STEEL
V. B. MISKOVIC-STANKOVIC*,
F. DEFLORIAN**, P. L. BONORA** and L. FEDRIZZI**
*Faculty
of Technology and Metallurgy, University of Belgrade, Karnegijeva
4, P.O.Box 494, YU-11001 Belgrade, Yugoslavia
and
**Material Engineering Department, University of Trento,
Trento, Italy
(Received
12 December 1995)
Coil coated stainless
steel is a new material for applications in civil and industrial fields with
the purpose of reducing maintenance costs and increasing the service life of
the products. The corrosion behaviour of different
types of stainless steel coated with both polyester and fluoropolymer
films of different thickness has been studied by means of AC impedance spectroscopy
(EIS), the break-point frequency method and scanning electron microscopy
analysis (SEM). The charge-transfer resistance and double-layer capacitance for
both polyester and fluoropolymer coatings on
stainless steel reveal no reactivity, corrosion or disbonding
on the substrate. The changes of pore resistance, coating capacitance and
break-point frequency over time indicate the different corrosion behaviour of polyester and fluoropolymer
coatings due to their different chemical structure and film thickness. On the
other hand, the polyester coatings on phosphatized
galvanized steel exhibit quite different behaviour in
regard to the same coatings on stainless steel. Different types of stainless
steel as substrate cause the different corrosion behaviour
of the investigated polyester and fluoropolymer
coatings. It has been observed that stainless steel which contains more nickel
and molybdenum shows higher resistance to corrosion attack in chloride
environments.
Key words: corrosion, electrochemical impedance
spectroscopy, protective properties, polyester coatings, fluoropolymer
coatings.
J.
Serb. Chem. Soc. 61(7)601-607(1996
UDC 576.45:535.37:620.193
JSCS-2270
Original scientific paper
THE
LUMINESCENT METHOD OF DETERMINING BERYLLIUM IN ENVIRONMENTAL SPECIMENS
L. E.
ZELTSER*, M. B. BASTIC**, XILOLA Y. USMALOVA* and LJ. V. BASTIC***
*Tachkent State University Tashkent , Uzbekistan
**Faculty of Technology and Metallurgy, University of Belgrade Belgrade , Yugoslavia
***Yugoslav Institute of Meat Hygiene and Technology, YU-11000 Belgrade , Yugoslavia
(Received
17 July 1995, revised 27 February 1996)
The paper deals with a
study of the formation of a complex of a new liminescence
reagent, calconcarbonic acid, with beryllium and the
development of a liminescent method for the
determination of Be in environmental specimens in the usual way or by applying
an immobilized reagent, which indicates the positive influence of
immobilization on the analytical parameters of the Be determination method. The
developed methods allow the determination of 2.0-8.0 ng
Be with a detection limit of 0.7 ng.
Key words: luminescence, beryllium ion determination.
J.
Serb. Chem. Soc. 61(7)609-614(1996)
UCC 669.292.5:621.7.016.2
JSCS-2271
Original scientific paper
APPARENT
ENERGY OF ACTIVATION FOR HOT WORKING OF VANADIUM MICROALLOYED STEEL
DJORDJE DROBNJAK*, ANKICA
KOPRIVICA**, NENAD RADOVIC* and MILOJICA ANDJELIC**
*Department
of Physical Metallurgy, Faculty of Technology and Metallurgy, University of
Belgrade, P.O.Box 494, YU-11001 Belgrade, Yugoslavia
and
**Institue for Ferrous Metallurgy, YU-43400 Niksic, Yugoslavia
(Received
24 October 1995)
Two-stage linear ln [sinh(as)] vs.1/T plots, based on isothermal continuous
and anisothermal multipass
torsion curves, indicate the double QHW behaviour
of a V-steel. Above Tnr, QHW is
independent of all variables but strain. Below Tnr
(which is interpass time dependent), i.e., in
a temperature range in which interpass recrystallization is supressed, QHW
is not only increased but that based on multipass
curves also interpass time dependent, and only valid
for multipass working operations.
Key words: microalloyed steel,
hot working, energy of activation, simulation torsion test, recrystallization
and precipitation interaction.