JSCS Vol 64, No. 4
J. Serb. Chem. Soc. 64(4) 235-243 (1999)
UDC 547.583.1/.4:546.65:541.124.7
JSCS-2644
Original scientific paper
Influence of substituent positions on the
spectral and thermal behaviours of 2-chloro-5-nitro- and 5-chloro-2-nitrobenzoates
of light lanthanides
WIESLAWA FERENCand BEATA BOCIAN
Department of Inorganic
and General Chemistry, Maria Curie-Sklodowska University, PI 20-031, Lublin,
Poland
(Received 8 July 1998,
revised 18 January 1999)
The physico-chemical properties and thermal
stability in air of light lanthanide 2-chloro-5-nitro- and
5-chloro-2-nitrobenzoates were compared and the influence of the position of Cl
and NO2 substituents on their spectral and thermal
stability was studied. The complexes of both series are crystalline, hydrated
or anhydrous salts with colours typical for Ln3+ ions. The carboxylate group in these complexes is a bidentate
chelating ligand. The NO2 group in the chloronitrobenzoates does not
undergo isomerization and does not coordinate with the central ions. The
thermal stability of the light lanthanide 2-chloro-5-nitro- and
5-chloro-2-nitrobenzoates was studied in the temperature range 273523 K because
above 523 K explosive decomposition occurs. The positions of the Cl and NO2 substituents in the benzene ring influence the degree of
hydration, but insignificantly influence the thermal properties and the
decomposition mechanism of these complexes or their solibilities. Differences
in the properties of the chloronitrobenzoates are probably connected with the
various influence of the inductive and mesomeric effect of the Cl and NO2 substituents on the electron density in the benzene ring.
Key words: 5-chloro-2-nitro- and 2-chloro-5-nitrobenzoates
of light lanthanides, thermal stability of complexes, spectrochemical
investigations, influence of Cl and NO2 substituents on the properties of chloronitrobenzoates,
solubility in water, complexes of light lanthanides, influence of substituents.
J.
Serb. Chem. Soc. 64(4) 245-257 (1999)
UDC 669.245/.275:543.251
JSCS-2665
Original scientific paper
Electrochemical deposition and phase structure
of electrodeposited NiW alloys
M. OBRADOVIC, J. STEVANOVIC, A. R. DESPIC and R. STEVANOVIC
ICTM - Institute of
Electrochemistry, Njegoseva 12, P.O.Box 815, YU-11001 Belgrade, Yugoslavia,
E-mail rade@elab.tmf.bg.ac.yu
(Received 30 December
1998)
The induced deposition of W in the presence or
iron-group metals has been known for a long time without a proper understanding
of the mechanism of the codepostion. Hints were made by several authors,
concerning primarily a similar case of codeposition of Mo, which were not
sufficiently substantiated by proper kinetic investigations, as the research
was oriented mainly toward practical aims. In the present investigation the
induced deposition of W with Ni was studied primarily from the viewpoint of the
composition and phase structure of the resulting NiW alloy. The method of
anodic linear sweep voltammetry was used to analyze the deposits obtained at a
rotating disc electrode, as this has proved to be a good tool for the analysis
of thin-layer deposits. The polarization diagram was found to exhibit a sharp
current maximum and a subsequent decay at potentials at which Ni deposition
starts. As some W oxide was found to deposit at less negative potential, the
sharp rise of current and the maximum are acribed to the catalytic effect of
the oxide on hydrogen evolution, larger than that of the depositing NiW alloy.
The deposit was found to exhibit two peaks upon anodic dissolution, both at
significantly more positive potentials than that of Ni dissolution. The first
peak is of a limited quantity of electricity, independent on the amount of the
deposit which is reflected in the second peak only. An aging effect was found,
rendering an alloy requiring much more positive potentials for dissolution than
those for dissolution of freshly deposited alloys.
Key words: nickelwolfram, induced
codeposition, phase structure.
J.
Serb. Chem. Soc. 64(4) 259-263 (1999)
UDC 546.59/541.182.65/:543.251
JSCS-2666
Original scientific paper
Effect of square wave pulse on the deposition
structure of gold nanoparticles
SHENGBIN LEI, SHIYONG ZHAO, SHENHAO CHEN, ZIPINGI AI* and SHUYUN WANG**
Chemistry Department of
Shandong University, Jinan, P.R. China, 250100,
*Experimental Center
of Shandong University, and
**Testing Center of
Shandong Teachers' University, Jinan, P.R. China, 250014
(Received 11 January
1999)
Electrophoretic deposition (EPD) of colloidal
particles is a newly developed method for the fabrication of colloidal particle
superlattices. By modifying the EPD procedure with square wave pulse,
multilayer formation of gold particles is reduced and a more orderly packed
monolayer can be prepared.
Key words: gold, colloidal particles, electrophoretic
deposition, square wave pulse deposition.
J.
Serb. Chem. Soc. 64(4) 265-273 (1999)
UDC. 648.648/539.21/:543.251/546.48/
JSCS-2667
Original scientific paper
Investigation of the polyaniline film porosity
by the electrodeposition of cadmium on the film
V.D. JOVIC, B. M. JOVIC*, E. R. STOJILKOVIC**, T. TRISOVIC* and M.
VOJNOVIC***
Center for
Multidisciplinary Studies, University of Belgrade, P.O.Box 33, YU-11030
Belgrade,
*Institute of Technical
Science of the Serbian Academy of Sciences and Arts, P.O.Box 745,YU-11001
Belgrade,
**Faculty of
Agriculture, University of Belgrade, Nemanjina 6, YU-11080 Zemun-Belgrade and
***Faculty of Technology
and Metallurgy, University of Belgrade,Karnegijeva 4, YU-11000 Belgrade,
Yugoslavia
(Received
11 January 1999)
Electrochemical
deposition of cadmium on electropolymerized polyaniline films of different
morphology and thickness has been performed in order to obtain information
about the morphology (porosity) of the polymer films. Polyaniline films were
electropolymerized on glassy carbon electrodes by cyclic voltammetry. The
morphology and the thickness of the film were varied by changing the anodic
limit potential and the number of cycles during the film formation. It was
shown that the electrodeposition of cadmium takes place only on the glassy
carbon substrate, in the open pores of the polymer film. It was also shown that
by plotting the amount of electrodeposited cadmium on the film as a function of
the film thickness (expressed as the charge under the anodic peak of film
oxidation) qualitative data about the porosity of the film can be obtained,
while microscopic observation of the cadmium deposit yields quantitative data.
Key
words: cyclic voltammetry, electrodeposition of Cd, morphology (porosity),
polyaniline film.
J.
Serb. Chem. Soc. 64(4)275-284(1999)
UDK 541.138.2:546.82/661.56/
JSCS-2668
Original scientific paper
Electrochemical formation of oxide films on Ti
surfaces in nitric acid
NEDKA PETROVSKA, ABDURAUF PRUSI and LJUBOMIR ARSOV
Faculty of Technology
and Metallurgy, University "St. Cyril and Methodius", 91000 Skopje,
Macedonia
(Received 11 January
1999)
The electrochemical formation of oxide films on
Ti surfaces in various concentrations of aqueous nitric acid solutions was studied.
The influence of the nitric acid concentrations in the active/passive region
was investigated by cyclic voltammetry. The complex indices of refraction and
the thickness of generated films in the potential region between the
steady-state potential at open circuit and the limit anodic potentials were
determined by ellipsometry. The crystallinity of the anodic oxide films were
investigated by Raman spectroscopy. The amorphous structure at lower potentials
and the short- range crystalline order, with anatase structure, near the limit
anodic potential were shown.
Key words: Ti electrode, anodic oxide films,
cyclic voltammetry, ellipsometry, Raman spectroscopy.
J.
Serb. Chem. Soc. 64(4) 285-295 (1999)
UDC 546.28:446.171.11:621.762
JSCS-2669
Original scientific paper
Sol-gel derived silicon nitride powders
LJILJANA CEROVIC, SLOBODAN K. MILONJIC, SLAVICA ZEC and DJAMILA
BAHLOUL-HOURLIER*
Vinca Institute of
Nuclear Sciences, P.O.Box 522, YU-11001 Belgrade, Yugoslavia and
*Laboratoire de
Materiaux Ceramiques et Traitement de Surface, URA CNRS 320, Faculte des
Sciences, 87060 Limoges, France
(Received
15 December 1998)
The
sol-gel synthesis of silicon nitride powders has been studied. The precursor
gels were prepared from a colloidal dispersion of silicon dioxide and sucrose,
with mole ratios of reactants, C/SiO2, ranging
from 2 to 4. The carboreduction and nitridation processes were performed at
temperatures between 1400-1550 °C under a dynamic nitrogen atmosphere, with a 4
h hold. The optimum C/SiO2 ratio and temperature for
preparation of the Si3N4 powders were selected. For the SiO2CN2 system
examined, the boundary temperature between Si3N4 and SiC
formation was established, in relation to the amount of carbon introduced.
Key
words: sol-gel, silicon nitride powders, colloidal silica.
J.
Serb. Chem .Soc. 64(4) 297-302 (1999)
UDK 546.74/549.73/:66.091
JSCS-2670
Original scientific paper
Method for the preparation of Ni-ferrites from
b-diketonato complex compounds
A. S. NIKOLIC, Z.B. MARICIC*, T. J. SABO, M. KURAICA**, S. DJURIC*** and N.
JURANIC****
Faculty of Chemistry,
University of Belgrade, P. O. Box 158, YU-11001 Belgrade,
*RHBNC,Department of
Physics, University of London, UK,
**Faculty of Physics,
University of Belgrade,
***Faculty of Geology
and Mining, University of Belgrade, Yugoslavia and
****Mayo Foundation,
Rochester, MN 55905, USA
(Received 19 August
1998)
The thermal decomposition of Fe(III) and Ni(II)
complex compounds with b-diketonato ligands i.e., acetylacetone (AA),
benzoylacetone (BA) and dibenzoylmethane (DBM), were investigated. The goal was
to produce ultrafine metalic oxide powders (NiO×Fe2O3) as precursors for the preparation of
nickel-ferrite (NiFe2O4). The thermal
decomposition of these materials was carried out by simultaneous TG/DTG/DTA
analysis. The materials produced by this method were characterized by X-ray
powder diffraction and transmission electron microscopy (TEM). Within the
interpretation of results, the formation of nickel-ferrite (NiFe2O4) in comparison to the production of single
oxides (NiO and Fe2O3) was especially
interesting. At low temperatures (below 600 °C), the ultrafine ferrite
materials were obtained from complex compounds as precursors. The ferritization
rate increases in the series from DBM, BA to AA. The materials formed by the
thermal decomposition of the complex compoounds mixtures, with AA as the
ligand, with average particle size of 18 nm show favorable physico-chemical properties.
Key words: Ni-ferrites, preparation, b-diketonates,
complexes, characterization.
J.
Serb. Chem. Soc. 64(4) 303-310 (1999)
UDK 547.593.26:547.963.2:633.3
JSCS-2671
Original scientific paper
A modification of a method for phytic acid
determination
DRAGUTIN VELICKOVIC, BILJANA VUCELIC-RADOVIC, SRDJAN BLAGOJEVIC, MIROLJUB
BARAC, SLADjANA STANOJEVIC and MAJA LJUBICIC
Faculty of Agriculture,
University of Belgrade, P.O.Box 127, YU-11081 Belgrade, Yugoslavia
(Received 28 September
1998)
Several different methods for the determination
of phytic acid which do not require sophisticated equipment are currently in
use. These methods have been developed to measure the phytic acid content of a
variety of materials, such as plant tissues, food stuffs and soils. The aim of
the work was to modify the supernatant difference, macro-method developed by
Erdman and Thompson1 for the determination of the phytic acid
content in soybeans and soybean protein products. A micro-method was developed
for easier and faster phytic acid determination. The advantages of the
micro-method over the macro-method are the smaller amounts of sample and
smaller amount of the necessary reagents required, as well as the duration of
the analysis. By replacing the long filtration procedure with short
centrifugation step the duration of the analysis is reduced from 14 to 8 h. The
phytic acid content in Hodgson var. soybeans was determined using both methods.
The obtained results showed a high degree of compliance. Due to its advantages,
the micro-method appeared to be more successful. The micro-method was also
tested and found suitable for the determination of the phytic acid content of soy
protein isolates.
Key words: phytic acid, macro-method,
micro-method, soybeans, soy protein isolate.
J.
Serb. Chem. Soc. 64(4) 311-314 (1999)
UDK 547.787/.789.542.9
JSCS-2672
Short communication
SHORT COMMUNICATION
Synthesis of 4-oxothiazolidine derivatives
containing two exocyclic C=C bonds
RADE MARKOVIC and MARIJA BARANAC*
Faculty of Chemistry,
University of Belgrade, Studentski trg 16, P.O.Box 158, 11001 Belgrade,and
Center for Chemistry ICTM, P.O.Box 815, Belgrade, and
*Faculty of Pharmacy,
Department of Organic Chemistry, University of Belgrade, P.O.Box 146, YU-11224
Belgrade, Yugoslavia
(Received 22 October
1998)
Stereodefined thiazolidine derivatives bearing
two exocyclic C=C bonds were under mild reaction conditions synthesized from
5-substituted 4-oxothiazolidine precursors via the efficient
bromination-dehydrobromination pathway.
Key words: thiazolidines, halogenation,
diastereoselection.
Society Home Page
Contents of this Vol. Journal
Home Page
Copyright & copy; SHD 1999.
Last
Updated April 13, 1999
For
more information contact: SHD@elab.tmf.bg.ac.yu