JSCS Vol 64, No. 4
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.
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 email@example.com
(Received 30 December
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.
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
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.
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
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.
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
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.
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
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.
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
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.
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.
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
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.
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Last Updated April 13, 1999
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