JSCS Vol 62, No 2
J. Serb. Chem. Soc. 62(2) 81-97
Nucleation and growth of diamond in oxyacetylene flame chemical vapour deposition
SLOBODAN N. MARINKOVIC
The Vinca Institute of Nuclear Sciences, P. O. Box 522, YU-11001 Belgrade, Yugoslavia
(Received 10 October 1996)
2. Flame structure
3. Nucleation of diamond
3.1. Dependence of nucleation density on various parameters
4. Mechanism of diamond
5. Polycrystalline diamond growth-influence of deposition conditions
Dependence of oriented growth and crystalline order of diamond coatings on the
linear velocity of combustion flame
5.2. Formation of large crystals
6. Conclusion Key words: diamond, nucleation, growth, oxyacetylene flame.
Poly(ethylene oxide) homologs: from oligomers to polymer networks
CHRISTO B. TSVETANOV, RAYNA STAMENOVA, DOBRINKA DOTCHEVA, MARIA DOYCHEVA and ALEXANDER ORAHOVATS
Institute of Polymers, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria
(Received 8 May 1996)
2. Poly(ethylene glycols)
3. Poly(ethylene oxide) resins
4. Poly(ethylene oxide) networks
Key words:ethylene oxide polymers, methods for the synthesis, UV crosslinking of PEO composites.
The regiochemistry of the cycloaddition of 1-methylphthalazinium ylides to non-symmetrically substituted olefins
STEFAN DIMA, IONEL MANGALAGIU*, MARIA CAPROSU*, MIRCEA CONSTANTINESCU*, ION HUMELNICU* and MAGDA PETROVANU*
DE JOS" University Galati, Faculty of Science, Chemistry Department, Str.
Domneasca, Nr. 47, Galati - 6200, Romania and
*The "Al I. Cuza" University, Iasi, Faculty of Chemistry, Organic Chemistry Department, B-dul Copou, Nr. 11, Iasi - 6600, Romania
(Received 20 September 1996)
For the first time in series of 1-methylphthalazine we have accomplished a theoretical and experimental study of the regiochemistry of the 3+2 dipolar cycloaddition of 1-methylphthalazinium ylides to ethyl acrylate and acrylonitrile. Eight new pyrrolo-1-methylphthal-azine heterocycles have been obtained. A possible mechanism of the reactions is presented.
Key words: 3+2 dipolar cycloaddition, new pyrrolophtalazines, theoretical study of
Some new constituents from domestic plant species of Artemisia monogyna W. & K. and Artemisia annua L.
MIODRAG ĐERMANOVIC, MILUTIN STEFANOVIC, VERICA ĐERMANOVIC* and MIRJANA MILOVANOVIC**
Chemistry, University of Belgrade, Studentski trg 16, P.O.Box 158, YU-11001
*Institute of Chemistry, Technology and Metallurgy, Njegoševa 12, YU-11000 Belgrade and
**Faculty of Agriculture, Department of Food Technology, University of Belgrade, Nemanjina 6, YU-11081 Zemun, Yugoslavia
(Received 10 October 1996)
Investigation of the constituents of Artemisia monogyna (family Asteraceae) afforded the sesquiterpene lactone ß-santonin (1) and a derivative of acetophenone, brevifolin (2), which was isolated for the first time from this plant species. The chemical identification of a new coumarin derivative, scopoletin (3), isolated from Artemisia annua (family Asteraceae), is also described. The isolation was achieved by column chromatography and the structures were established mainly by interpretation of their physical and spectral data.
Key words: Asteraceae, traditional medicine.
Reduction of thiazolidine sulphones with methyltrichlorosilane/sodium iodide
MIROSLAV J. GAŠIC and BOGDAN PUTNIKOVIC*
Faculty of Chemistry, University of Belgrade, Studentski trg 16, PO Box 158, YU-11001 Belgrade, Yugoslavia
(Received 10 October 1996)
A simple and efficient reduction of thiazolidine sulphones under mild reaction conditions was developed using a mixture of methyltrichlorosilane/sodium iodide as a reducing agent. The yields are good and the products were isolated without racemisation or deprotection of the secondary amine.
Key words: tiazolidine sulphones reduction of, methyltrichlorosilane/sodium iodide.
*Present address: School of Chemistry, University of Leeds, United Kingdom
Complexation behaviour of copper(II) ion with thiuram disulphide in non-aqueous solvents
ALEKSANDRA LABAN, SLOBODAN GRUJIC*, DRAGAN VESELINOVIC** and PREDRAG DJURDJEVIC*
Pharmacy of Serbia, V. Stepe 452, YU-11221 Belgrade,
*Institute of Chemistry, Faculty of Science, P.O.Box 60, 34000 Kragujevac and
**Faculty of Physical Chemistry, P.O.Box 137, YU-11001 Belgrade, Yugoslavia
(Received 17 June, revised 11 November 1996)
The complexation equlibria between copper(II)-nitrate and tetramethylthiuram disulphide (tmtd) in dioxane and acetone solutions were studied by UV-vis. spectrophotometry. Applying the non-linear least squares method, the following complexes with their respective stability constants, log b ‘+s), were found to give the best fit to the experimental data:
Copper(II)-chloride and tmtd in dioxane solutions form the complex [Cu4(tmtd)2]4+ with the stability constant 19.1+0.1. The copper(II)-tmtd complexes were characterized by elemental analysis, TLC and IR spectroscopy. The structures of the complexes are discussed.
Key words: copper(II)-complexes, complexation, thiuram disulphide
Influence of Zn2+ ions in a ZSM-5 catalyst on the C3-C4 hydrocarbons aromatization process
MIROSLAVA DOJCINOVIC, BORIVOJ ADNADJEVIC* and NENAD ANDREJIC
Institute of General
and Physical Chemistry, P.O. Box 551 YU-11000 Belgrade and
*Faculty of Physical Chemistry, University of Belgrade, Studentski trg 16, YU-11000 Belgrade, Yugoslavia
(Received 16 May, revised 13 November 1996)
Catalysts, based on zeolite ZSM-5 modified by Zn2+ ions, are suitable for aromatization of C3-C4 hydrocarbons. Zn2+ ions change the acidity of the catalysts by blocking the strong Br"nsted acid centers. The most probable aromatization mechanism is presented. The catalyst, based on a zeolite ZSM-5, with a module 50 and with a Zn content of 2.4%, was laboratory produced and applied to the aromatisation of a propane-butane mixture. In the temperature interval of 673-873 K propane was not converted, so it was supposed that the catalyst has Bronsted acid centers of medium strength, as well as Lewis acid centers, since the concentration of Zn2+ ions, concerning the zeolite module, was rather high.
Key words: Zn, ZSM-5 catalyst, catalysts acidity, C3-C4 hydrocarbons, aromatization process.
Stabilization of Tc-99m - pyrophosphate
JURIJ L. VUCINA
Laboratory for Radioisotopes, Vinča Institute of Nuclear Sciences, P.O.Box 522, YU-11001 Belgrade, Yugoslavia
(Received 11 April 1996)
In vitro stability of 99mTc(Sn)-PyP was examined under different experimental conditions. Hydrogen peroxide was added to accelerrate the re-oxidation of reduced technetium. The complex was protected by different methods. Nitrogen purging of the reactant solutions was found to be effective in the samples without hydrogen peroxide. The product was stable for six hours and the content of pertechnetate was about 5%. This method of protection was not efficient in the presence of hydrogen peroxide. The protecting capacity of ascorbic acid, 2,5-dihydroxybenzoic (gentisic) acid and N,N'-diphenyl-p-phenylendiamine (DPPD) was investigated. Ascorbic acid had a high protecting efficiency. In the presence of 5 µg of ascorbic acid per ml of the kit, the content of free pertechnetate was about 1% six hours after labelling. The presence of 10 µg of ascorbic acid was enough to eliminate the influence of 6 µg of exogenous hydrogen peroxide. The same effect was observed when gentisic acid was used. However its content must be ten times higher than ascorbic acid. The poorest stabilizing property performed DPPD. Some effect was observed only in samples without peroxide.
Key words: pyrophosphate, chemical stabilization, technetium-99m.
dsorption properties of poly-trimethylol propane triacrylate investigaged by gas-solid chromatography
RADMILA LUCIC, MILAN I. TRTANJ and JOZEF J. COMOR
Vinča Institute of Nuclear Sciences, P.O. Box 522, YU-11001 Belgrade, Yugoslavia
(Received 11 November 1996)
Trimethylol propane triacrylate is a candidate starting material for the preparation of molecularly imprinted polymers (MIP). A macroporous polymer adsorbent was prepared from this cross-linking monomer, using g-radiation induced polymerisation. This adsorbent is subjected to thorough characterisation in order to test its applicability for the synthesis of MIPs. As a part of this campaign, the adsorption properties of this material were investigated, using gas-solid chromatography with 16 different adsorbates on three temperatures. Its applicability for the successful preparation of highly selective MIPs is discussed, in the sense of the materials' adsorption characteristics.
Key words: gas-solid chromatography, adsorption properties, molecularly imprinted polymer materials.
Effect of viscosity on the potentiostatic current oscillations at Fe/H2SO4 interface
CHAO WANG and SHENHAO CHEN
Department of Chemistry, Shandong University, Jinan 250100, P. R. China
(Received 20 September 1996)
The periodic current oscillations of the stationary iron electrode under potentiostatic conditions are studied in 0.5 mol dm-3 H2SO4 solutions with or without glycerol. This oscillatory phenomenon appears quite sensitive to the viscosity of solution as well as the potentials applied. The influence of viscosity on the current oscillations is discussed on the basis of the mechanism previously obtained by the holographic microphotographic technique.
Key words: iron electrodissolution, potentiostatic current oscillations, viscosity of solution.
Redox properties of an electrochemically activated (oxidized) carbon fibre electrode
T. P. GRCEV, M. V. CVETKOVSKA and T. B. OBRADOVIC
St. Cyril and Methodius University, Faculty of Technology and Metallurgy, Ruđer Boskovic 16, 91000 Skopje, R. of Macedonia
(Received 26 June, revised 4 November 1996)
The processes of electrochemical (constant current) oxidation of carbon fibre (CF)-electrode in 0.5 M H2SO4, and the redox behavior of the obtained surface product (oxygen containing groups) were studied using cyclic voltammetry and impedance spectroscopy. It was shown that the charge density of the obtained "oxide" layer is approx. 300 Ah kg-1 (superior battery active material). As far as the mechanism of the redox processes of the electrochemically oxidized CF-electrode is concerned it was found that the RC-charging process is dominant (over 90%), and that the capacitance is proportional to the quantity and/or thickness of the "oxide" layer (pseudo capacitance in origin).
Key words: carbon fibre, electrochemical activation, oxygen containing groups, redox charge, impedance spectroscopy.
formation and reduction of Cu(III) in oxide layers on Cu and Cu-Bi alloys in
Part. III. Distribution of the Cu(III) species in the oxide
R. M. STEVANOVIC, A. R. DESPIC and M. D. MAKSIMOVIC*
Electrochemistry ICTM, University of Belgrade, Njegoševa 12, P.O. Box 815,
YU-11000 Belgrade, and
*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O.Box 494, YU-11001 Belgrade, Yugoslavia
(Received 20 September 1996)
In a voltammetric investigation, the process of Cu(III) formation was studied indirectly by analyzing the peak of Cu(III) reduction upon the return of the potential sweep from the anodic limit. The charges pertaining to the reversible formation of Cu(III) species were obtained by integration of the cathodic branches of the voltammograms. The sweep rate dependence of the charge is discussed in terms of the different accessibility of the active sites at the surface and in the bulk of the oxide. The data were analyzed in a manner similar to those in some earlier investigations of some thermally prepared oxides. The total charge, Qtot as well as the surface, Q’s and the bulk, Qb charges were determined for pure Cu and Cu-Bi alloys of different composition. An increase of the Bi content in the alloy leads to a decrease in the total quantity of the obtainable Cu(III) species. However, if one assumes the same content of Cu oxide in the oxide film is in the Cu-Bi eutectic alloy substrate and considers the content of the Cu(III) relative to the Cu in the oxide, a different result is obtained. The relative quantity, Qtot, reaches a minimum value at a Bi content of about 20 at.%, after which it continually rises with increasing Bi content in the alloy, exceeding that at pure Cu. This implies that, upon increasing the Bi content above a critical value of 20 at.%, an increasing part of the CuO is further oxidized to Cu(III). The spontaneous degradation of Cu(III) after the anodic oxidation is interrupted is reflected in the fact that the open-circuit potential decays with time towards the values characteristic of a Cu2O/CuO interface. A theoretical interpretation of the decay can be obtained if it is assumed that degradation occurs by reaction of Cu(III) with the Cu2O species.
Key words: Cu-Bi alloy, anodic linear sweep voltammetry (ALSV), electrochemical oxidation of Cu alloys, Cu(III) species, kinetic formation and degradation.
High performance liquid chromatographic determination of clindamycin in pharmaceutical formulations
SOTE VLADIMIROV, LJILJANA MARKOVIC*, DANICA AGBABA, DOBRILA ŽIVANOV-STAKIC and JASMINA BRBORIC
Pharmaceutical Chemistry, Faculty of Pharmacy, P.O.box 146, Vojvode Stepe 450,
YU-11152 Belgrade and
*Department of Pharmacy, Vojvode Stepe 458, YU-11152 Belgrade, Yugoslavia
(Received 5 June, revised 13 November 1996)
A specific and simple HPLC procedure was developed, suitable for the determination of clindamycin hydrochloride monohydrate (CLHC) and clindamycin 2-dihydrogenphosphate (CLPH) in pharmaceutical formulations. Rp-HPLC analysis was performed with a LCD-Analytical Consta Metric 3000 system, equipped with a Spectro Monitor 3100 UV/VIS detector. Lincosamides assay procedures were carried out on a Supelcosil® LC-18-DB (250×4,6 mm, 5 µm particles) column in an acetonitrile-potassium dihydrogenphosphate buffer (0.1 M; pH 2.50) (225:775 v/v) as mobile phase. Column effluents were monitored at 206 nm for clindamycin. The calibration curves in concentration ranges from 200 to 1800 µg ml-1 were established for the investigated clindamycins. The HPLC method was applied for the determination of clindamycin in pharmaceutical formulations. The obtained results and statistical parameters for both the investigated clindamycins in pharmaceutical formulations, were satisfactory and ranged from 99.99% to 104.18% (R.S.D. was ranged from 0.79% to 0.99%).
Key words: HPLC determination, clindamycin, pharmaceutical formulations.
Palladium Reagents and Catalysts. Innovations in Organic Synthesis
by JIRO TSUJI
John Wiley & Sons Ltd., New York 1995, 560 pp., hard cover, Ł 20.00