JSCS Vol 72, No. 12

 

Issue dedicated to Dragutin M. Dražić on the occasion of his retirement as Editor-in-Chief and in recognition of his great effort and success in editing of the Journal of the Serbian Chemical Society

 

Whole issue - PDF (5.307 KB)

 

J. Serb. Chem. Soc. 72 (12) 1171 (2007)

 

EDITORIAL

 

This issue of the Journal of the Serbian Chemical Society was chosen by the members of the Presidency of the Society and of the Editorial Board from Serbia to mark the retirement of Dragutin M. Dražić as Editor-in-Chief of the Journal.

Dragutin Dražić succeeded Slobodan V. Ribnikar, who was Editor-in-Chief for 10 years, AMong others in the 77-year old history of the Journal and who introduced many improvements in editing and editing policy, including editing in English since 1985.

Dragutin Dražić was Editor-in Chief for more than 20 years. In addition to his immense impact as a scientist and university teacher to the field of Electrochemistry and Physical Chemistry and to the understanding of the importance of chemistry and of the natural science in general (see J. Serb. Chem Soc., 66 (2001) 731), his great effort in the editing of the Journal resulted in its pivotal position in the world of scientific journals in Serbia. With no intention to repeat Dragutin Dražić’s great contribution to the development of contemporary chemical minds in the former Yugoslavia, and lately in Serbia (see J. Serb. Chem. Soc., 72 (2007) 1), we simply say: THANK YOU! Saying this, we are aware that we express the gratitude of the chemistry community not only in Serbia, but also worldwide, where the nAMe Dragutin Dražić is recognized.

The papers in this issue were prepared by the authors from Serbia who aided Dragutin Dražić, JSCS Honorary Editor, in his editing efforts, by submitting theirs manuscripts, through sub-editing and revision of the submitted manuscripts, or some other way, to establish a journal with the reputation which Journal of the Serbian Chemical Society holds today on the international scene.

Branislav Nikolić, Editor-in-Chief

Bogdan Šolaja, President of the Serbian Chemical Society

Full Article  - PDF 82 KB

J. Serb. Chem. Soc. 72 (12) 1173–1179 (2007)

UDC 54.024+542.9:547.815:547.514, JSCS–3650, doi: 10.2298/JSC0712173E; Original scientific paper

 

Radical reactions of xanthates: annulation of the cyclopentene ring

AHMED MOHAMED ELHESHI*, VESELIN MASLAK*,** and RADOMIR N. SAICIC*,**

*Faculty of Chemistry, University of Belgrade, Studentski trg 16, P. O. Box 158, 11000 Belgrade, Serbia

**ICTM, Center for Chemistry, Njegoseva 12, Belgrade, Serbia

 

(Received 03 July 2007)

Homoallylic radicals, generated from the corresponding xanthates, react with terminal alkynes to give cyclopentene derivatives in moderate yields.

 

Keywords: radicals, annulation, cyclopentene, xanthates, alkynes.

Full Article  - PDF 138 KB

J. Serb. Chem. Soc. 72 (12) 1181–1190 (2007)

UDC 541.459:615.28, JSCS–3651, 10.2298/JSC0712181O; Original scientific paper

 

On peroxide antimalarials

IGOR OPSENICA, DEJAN OPSENICA, MILKA JADRANIN, KIRSTEN S. SMITH*, WILBUR K. MILHOUS*, MANOLIS STRATAKIS** and BOGDAN SOLAJA***

Institute of Chemistry, Technology and Metallurgy, Belgrade, Serbia

*Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA

**Department of Chemistry, University of Crete, Voutes, 71003 Iraklion, Greece

***Faculty of Chemistry, University of Belgrade, P.O. Box 158, 11001 Belgrade, Serbia

 

(Received 06 September 2007)

Several dicyclohexylidene tetraoxanes were prepared in order to gain a further insight into structure–activity relationship of this kind of antimalarials. The tetraoxanes 2–5, obtained as a cis/trans mixture, showed pronounced antimalarial activity against Plasmodium falciparum chloroquine susceptible D6, chloroquine resistant W2 and multidrug-resistant TM91C235 (Thailand) strains. They have better than or similar activity to the corresponding desmethyl dicyclohexylidene derivatives. Two chimeric endoperoxides with superior antimalarial activity to the natural product ascaridole were also synthesized.

 

Keywords: mixed tetraoxanes, endoperoxides, malaria, P. falciparum.

Full Article - PDF 218 KB

J. Serb. Chem. Soc. 72 (12) 1191–1200 (2007)

UDC 530.13:541.124:544.4:547.564.8:66.012, JSCS–3652, doi: 10.2298/JSC0712191J; Original scientific paper

 

Substituent and structural effects on the kinetics of the reaction of N-(substituted phenylmethylene)-m- and -p-AMinobenzoic acids with diazodiphenylmethane

BRATISLAV Z. JOVANOVIC, ALEKSANDAR D. MARINKOVIC, ŽELJKO VITNIK* and IVAN O. JURANIC*

Department of Organic Chemistry, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O. Box 35-03, 11120 Belgrade, Serbia

*Faculty of Chemistry, University of Belgrade, Studentski trg 12–16, 11001 Belgrade, Serbia

 

(Received 26 April 2007)

The rate constants for the reaction of twenty-two N-(substituted phenyl methylene)-m- and -p-AMinobenzoic acids with diazodiphenylmethane were determined in absolute ethanol at 30 °C. The effects of substituents on the reactivity of the investigated compounds were interpreted by correlation of the rate constants with LFER equations. The results of quantum mechanical calculations of the mole cular structure together with experimental results gave a better insight into the effects of structure on the transmission of electronic effects of the substituents. New σ constants for substituted benzylideneAMino group were calculated.

 

Keywords: rate constants; substituent and structural effects; geometry optimization.

Full Article - PDF 174 KB

J. Serb. Chem. Soc. 72 (12) 1201–1216 (2007)

UDC 546–32+547.53.024:541.121+544.35:543.4/.5, JSCS–3653, doi: 10.2298/JSC0712201V; Original scientific paper

 

An LFER study of the protolytic equilibria of 4-aryl-2,4-dioxobutanoic acids in aqueous solutions

TATJANA Z. VERBIC, BRANKO J. DRAKULIC*, MIRE F. ZLOH**, JOVANA R. PECELJ, GORDANA V. POPOVIC*** and IVAN O. JURANIC

Faculty of Chemistry, University of Belgrade, Studentski Trg 12–16, 11000 Belgrade, Serbia

*Department of Chemistry – Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Njegoseva 12, 11000 Belgrade, Serbia

**The School of Pharmacy, University of London, 29/39 Brunswick Square, London WC1N 1AX, United Kingdom

***Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, 11000 Belgrade, Serbia

 

(Received 29 May 2007)

The protolytic equilibria of 13 4-aryl-2,4-dioxobutanoic acids (ADKs) were spectrophotometrically studied in aqueous solutions in the pH range 1–9 at 25±1 °C and an ionic strength of 0.1 mol l-1 (NaCl), with the exception of the 4-OH- derivative which was also potentiometrically studied in the pH range 7–10 at 25±1 °C and an ionic strength of 0.1 mol l-1 (NaCl). In solution, the compounds simultaneously exist in one diketo and two enolic forms; therefore, the determined acidity constants (pKa1 1.87–2.29, pKa2 6.63–8.13 and pKa3(4-OH-) 9.52) represent system macro constants. The 1H-NMR spectrum of the basic compound (4-phenyl-2,4-dioxobutanoic acid) (25 °C, pD 5.0) proved the existence of all tautomeric forms. Using the extended HAMmett relation, the determined pKa values were correlated with literature σ values. The predicted pKa values were in fair accordance with the experimentally observed ones. Molecular, monoanionic and dianionic forms of the basic compound were optimized by the semi-empirical molecular orbital PM6 method using the implicit water solvation model (COSMO). The obtained geometries were used to explain the quality of the LFER models.

 

Keywords: acidity constants, 4-aryl-2,4-dioxobutanoic acids (ADK), linear free energy relationship (LFER).

Full Article - PDF 259 KB

J. Serb. Chem. Soc. 72 (12) 1217–1227 (2007)

UDC 547.595+66.093.1+66.061:531.61, JSCS–3654, doi: 10.2298/JSC0712217N; Original scientific paper

 

A linear solvation energy relationship study for the reactivity of 2-substituted cyclohex-1-enecarboxylic and 2-substituted benzoic acids with diazodiphenylmethane in aprotic and protic solvents

JASMINA B. NIKOLIC and GORDANA S. USCUMLIC

Department of Organic Chemistry, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3505, 11120 Belgrade, Serbia

 

(Received 17 July 2007)

The rate constants for the reaction of 2-substituted cyclohex-1-enylcarboxylic acids and the corresponding 2-substituted benzoic acids with diazodiphenyl methane were determined in various aprotic solvents at 30 ºC. In order to explain the kinetic results through solvent effects, the second order rate constants of the reaction of the exAMined acids were correlated using the KAMlet–Taft solvatechromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and transition state. The signs of the equation coefficients support the proposed reaction mechanism. The quantitative relationship between the molecular structure and the chemical reactivity is discussed, as well as the effect of geometry on the reactivity of the exAMined molecules.

 

Keywords: carboxylic acids, linear solvation energy relationship, diazodiphenylmethane, aprotic solvents, protic solvents.

Full Article - PDF 174 KB

J. Serb. Chem. Soc. 72 (12) 1229–1236 (2007)

UDC 546.17'11+547.53.024:543.422.25, JSCS– 3655, doi: 10.2298/JSC0712229M; Original scientific paper

 

A study of substituent effects on the NH bond in alkyl and aryl 4,6-disubstituted-3-cyano-2-pyridones

MILICA MISIC–VUKOVIC, SLOBODANKA JOVANOVIC*, DUSAN MIJIN, JANOSZ CSANADI** and DEJAN DJOKOVIC***

Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Serbia

*Galenika a.d., R&AMp;D Institute, Batajnicki drum b.b., 11000 Belgrade, Serbia

**Faculty of Science, University of Novi Sad, 21000 Novi Sad, Serbia

***Faculty of Chemistry, University of Belgrade, 11000 Belgrade, Serbia

 

(Received 08 October 2007)

Substituent effects on the IR stretching frequencies and 1H-NMR chemical shifts of the pyridone NH group in 4- and 6-disubstituted alkyl and aryl 3-cyano-2-pyridones were investigated. The bands most sensitive to substituent effects from the broad and multiple IR NH band for each compound were selected by a computer calculation. The selected values of the IR frequencies and the determined 1H-NMR chemical shifts were subjected to LFER analysis, by correlations with the HAMett σm/p and Swain–Lupton F and R substituent constants.

 

Keywords: substituted 2-pyridones, LFER analysis, NH bond, IR and 1H-NMR spectra.

Full Article - PDF 138 KB

J. Serb. Chem. Soc. 72 (12) 1237–1254 (2007)

UDC 547.2–035.8+547.52:547.915(497.11), JSCS– 3656, doi: 10.2298/JSC0712237S; Original scientific paper

 

Evaluation of saturated and aromatic hydrocarbons oil–oil maturity correlation parAMeters (SE Pannonian Basin, Serbia)

KSENIJA STOJANOVIC*,**, BRANIMIR JOVANČIĆEVIĆ**,***, DRAGOMIR VITOROVIĆ**,***, YULIA GOLOVKO****, GALINA PEVNEVA**** and ANATOLY GOLOVKO****

*Department of Medicine, University of Belgrade, Visegradska 26, 11000 Belgrade, Serbia

**ICTM – Center of Chemistry, University of Belgrade, Njegoseva 12, 11000 Belgrade, Serbia

***Department of Chemistry, University of Belgrade, Studentski trg 12–16, 11000 Belgrade, Serbia

****Institute of Petroleum Chemistry, 3, Academichesky Ave., 634055 Tomsk, Russia

 

(Received 10 May 2007)

Twenty three crude oils from the Serbian part of the Pannonian Basin (14 from the Vojvodina Province and 9 from the Drmno Depression) were investigated, aimed at an evaluation of oil–oil maturity correlation parAMeters based on the distribution and abundance of saturated biomarkers and alkylarene constituents. Factor and cluster analyses were used for this purpose. Factor analyses using varimax rotation were first run separately, i.e., of maturity parAMeters based on the abundance of (a) n-alkanes and isoprenoids, (b) steranes and triterpanes, (c) alkylnaphthalenes, and (d) alkylphenanthrenes. These analyses yielded 9 important “maturity factors”. Eight of them, showing higher than 30 % of variance, were further involved in another factor analysis, as well as in cluster analysis using the Ward method. In this way, all maturity parAMeters based on saturated biomarkers and alkylarenes were evaluated and ranged, considering the fact that the observed factors represented their linear combinations. The results showed that in the correlation of crude oils from the Serbian part of the Pannonian Basin, the most important were maturity parAMeters based on isomerization reactions involving one methyl group in thermodynAMically less stable α-methylnaphthalenes, ethylnaphthalenes, dimethylnaphthalenes and methylphenanthrenes, and their change into more stable isomers with the methyl group in the β position in the aromatic ring. Processes constituting high loadings factor 2 and factor 3 parAMeters were also defined. Hierarchy between the “factors” and parAMeters were controlled, and approved, by cluster analysis using the Ward method. Finally, the investigated crude oils were correlated by factor and cluster analyses, using all the important “maturity factors”. Differences in maturity were observed between the Vojvodina and Drmno Depression crude oils, as well as between oils originating from South Banat, North Banat and the Velebit oil field (Vojvodina locality).

 

Keywords: crude oils, SE Pannonian Basin, saturated biomarkers, alkylarenes, maturity, factor and cluster analyses.

Full Article - PDF 312 KB

J. Serb. Chem. Soc. 72 (12) 1255–1263 (2007)

UDC 547.458.2+54.05:664.642:582.282.23, JSCS– 3657, 10.2298/JSC0712255A; Original scientific paper

 

Preparation and studies on immobilized α-glucosidase from baker’s yeast Saccharomyces cerevisiae

KHALED S. O. H. AHMED, NENAD B. MILOSAVIC*, MILICA M. POPOVIC, RADIVOJE M. PRODANOVIC, ZORICA D. KNEZEVIC** and RATKO M. JANKOV

Department of Biochemistry, Faculty of Chemistry, Studentski trg 12–16, 11000 Belgrade, Serbia

*Department of Chemistry, Institute of Chemistry, Technology and Metallurgy, Njegoseva 12, 11001 Belgrade, Serbia

**Department of Biochemical Engineering, Faculty of Technology and Metallurgy, Karnegijeva 4, 11000 Belgrade, Serbia

 

(Received 10 July 2007)

α-Glucosidase from S. cerevisiae was covalently immobilized onto Sepabeads EC–EA by the glutaraldehyde method. An analysis of the variables controlling the immobilization process is first presented and it is shown that the highest coupling of α-glucosidase occurred within 24 h. Also, a loading of 30 mg/g support proved to be effective, resulting in a rather high activity of around 45 U g–1 with a satisfactory degree of enzyme fixed. Both free and immobilized enzymes were then characterized by determining the activity profile as a function of pH, temperature and thermal stability. The obtained immobilized preparation showed the sAMe optimum pH, but a higher optimum temperature compared with the soluble one. In addition, the immobilized enzyme treated at 45 ºC for 1 h still retained an activity of around 20 %, whereas the free enzyme completely lost its original activity under this condition. In conclusion, the developed immobilization procedure is quite simple, easily reproducible and provides a promising solution for the application of immobilized α-glucosidase.

 

Keywords: maltase, Sepabeads EC–EA, immobilization, stabilization.

Full Article - PDF 218 KB

J. Serb. Chem. Soc. 72 (12) 1265–1269 (2007)

UDC 547.913.2/.5+547.565.2+537.363:615.277, JSCS–3658, 10.2298/JSC0712265V; Original scientific paper

 

Interactions of the anti-tumor sesquiterpene hydroquinone avarol with DNA in vitro

MIROSLAVA VUJCIC, SRDJAN TUFEGDZIC, ZORAN VUJCIC*, MIROSLAV J. GASIC and DUSAN SLADIC*

Institute of Chemistry, Technology and Metallurgy, Department of Chemistry, Njegoševa 12, 11000 Belgrade, Serbia

*Faculty of Chemistry, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia

 

(Received 06 August 2007)

Changes in electrophoresis pattern after interaction of supercoiled plasmid pBR322 DNA with avarol was studied at a micromolar concentration of reactants under mild reaction conditions. Interactions of avarol with linear high-molecular CT-DNA at millimolar concentrations were analyzed by electrophoresis and UV spectrophotometry. It was observed that avarol is capable of quenching ethidium bromide fluorescence in DNA bands. An increase in the absorbance of DNA was detected. The results indicate the binding of avarol to DNA and/or modification of nucleotide bases.

 

Keywords: avarol, hydroquinone, anti-tumor activity, pBR322 DNA, calf thymus DNA.

Full Article - PDF 233 KB

J. Serb. Chem. Soc. 72 (12) 1271–1274 (2007)

UDC *Gerardia savaglia:639.61/.62:547.567:547.96, JSCS–3659, 10.2298/JSC0712271P; Short communication

 

Short communication

Chemical modification of the lectin of the marine coral Gerardia savaglia by marine quinone avarone

IVANA PAJIC, ZORAN VUJCIC, MIROSLAVA VUJCIC*, IRENA NOVAKOVIC*, DUSAN SLADIC and MIROSLAV J. GASIC*

Faculty of Chemistry, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia

*Center for Chemistry – ICTM, Njegoseva 12, 11000 Belgrade, Serbia

 

(Received 03 August 2007)

The quinone avarone, isolated from the marine sponge Dysidea avara, possesses the ability to chemically modify proteins. In this work, modification of lectin isolated from the coral Gerardia savaglia by avarone was exAMined. The techniques used for studying the modification were: SDS PAGE, isoelectric focusing and hemagglutination testing. The results of the SDS PAGE indicate dimerization of the protein. A shift of the pI toward lower value occurs upon modification. The change of the hemagglutination activity of the protein confirms that chemical modification of G. savaglia lectin by avarone changes its ability to interact with the membrane of erythrocytes.

 

Keywords: avarone, quinone, Gerardia savaglia lectin, covalent modification.

Full Article - PDF 264 KB

J. Serb. Chem. Soc. 72 (12) 1275–1280 (2007)

UDC 547.913.2/.5+547.473:543.062:543.422.25, JSCS–3660, 10.2298/JSC0712275T; Short communication

 

Short communication

Quantitative analysis of sesquiterpene lactone cnicin in seven Centaurea species wild-growing in Serbia and Montenegro using 1H-NMR spectroscopy

VELE TESEVIC, SLOBODAN MILOSAVLJEVIC, VLATKA VAJS*, PEDJA JANACKOVIC**, IRIS DJORDJEVIC***, MILKA JADRANIN* and IVAN VUCKOVIC*

Faculty of Chemistry, Studentski trg 12–16, P.O. Box 158, 11001 Belgrade, Serbia

*Institute of Chemistry, Technology and Metallurgy, Njegoseva 12, 11001 Belgrade, Serbia

**Faculty of Biology, Studentski trg 12–16, 11001 Belgrade, Serbia

***Faculty for Veterinary Medicine, University of Belgrade, Bulevar Oslobođenja 18, 11000 Belgrade, Serbia 

 

(Received 02 March 2007)

1H-NMR spectroscopy was applied for the quantitative analysis of cnicin, a bioactive germacranolide type sesquiterpene lactone, in the aerial parts of seven wild-growing Centaurea species collected in Serbia and Montenegro. The analysis was performed by comparison of the integral of the one-proton signal of cnicin (H-13, δ 5.75) with that of the two-proton singlet (δ 6.98) of 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT), used as the internal standard. Cnicin, within concentration the range 1.06–6.12 mg/g, calculated per weight of the fresh plant material was detected in six species, the exception being C. salonitana. This method allows the rapid and simple quantification of cnicin without any pre-purification step.

 

Keywords: 1H-NMR, Centaurea, cnicin, BHT.

Full Article - PDF 140 KB

J. Serb. Chem. Soc. 72 (12) 1281–1293 (2007)

UDC 546.732.004.12:548.7:547.772:548.73, JSCS–3661, doi: 10.2298/JSC0712281L; Original scientific paper

 

Transition metal complexes with pyrazole based ligands.
Part 27. Structural and thermal characterization of cobalt(II) halide and pseudohalide complexes with 4-acetyl-3-AMino-5-methylpyrazole

VUKADIN M. LEOVAC, ZORAN D. TOMIC*, KATALIN MÉSZÁROS SZÉCSÉNYI, LJILJANA S. JOVANOVIC and MILAN D. JOKSOVIC**

University of Novi Sad, Faculty of Sciences, Department of Chemistry, Trg D. Obradovica 3, 21000 Novi Sad, Serbia

*"Vinca" Institute of Nuclear Sciences, Laboratory of Theoretical Physics and Condensed Matter Physics, P.O. Box 522, 11001 Belgrade, Serbia

**Faculty of Sciences, University of Kragujevac, R. Domanovica 12, 34000 Kragujevac, Serbia

 

(Received 02 August 2007)

The crystal and molecular structures of four tetrahedral structurally similar [Co(aAMp)2X2] complexes (aAMp = 4-acetyl-3-AMino-5-methylpyrazole, X = Cl, Br, I and NCS) were determined by X-ray diffraction analysis and are discussed in detail. It was found that the different capacity of the ligand X (NCS vs. Cl, Br, I) for the formation of non-bonding cntacts influence the mode of molecular association in the solid state. The complexes were characterized by UV–Vis spectroscopy. The first step of the thermal decomposition of the compounds was checked and is discussed in the view of the IR spectrum of the intermediate isolated from [Co(aAMp)2Br2] by the quasi-isothermal technique.

 

Keywords: Cobalt(II) complexes, 4-acetyl-3-AMino-5-methylpyrazole, crystal structure, electronic spectra, quasi-isothermal TA.

Full Article - PDF 356 KB

J. Serb. Chem. Soc. 72 (12) 1295–1308 (2007)

UDC 546.732+547.64:66.087.3, JSCS–3662, doi: 10.2298/JSC0712295V; Original scientific paper

 

High-spin binuclear Co(II) complexes with a pendant octaazAMaclocycle and carboxylates

G. VUCKOVIC, S. B. TANASKOVIC*, Z .M. MIODRAGOVIC and V. STANIC

Faculty of Chemistry, University of Belgrade, P.O. Box 158, 11001 Belgrade, Serbia

*Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, 11001 Belgrade, Serbia

 

(Received 24 September 2007)

Three new binuclear Co(II) mixed-ligand complexes with N,N′,N′′,N′′′-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) and mono- or dicarboxylate ligands were prepared and some of their physical properties were determined. The general formulas: [Co2(HCOO)2tpmc](ClO4)2·4H2O, [Co2(CH3COO)2tpmc](ClO4)2 and [Co2(tpht)tpmc](ClO4)2·4H2O (tphtH2 = terephthalic acid) were proposed on the basis of elemental analyses (C,H,N) and molar conductivity. UV/Vis absorption and IR spectra, magnetic and CV measurements were used to study their geometries and properties. For the monocarboxylate complexes, an exo coordination of Co(II) with four nitrogens from tpmc and bis-bidentate bonded HCOO-/CH3COO- in the trans position is assumed. Tpmc adopts the chair conformation. For the dicarboxylate complex, it is supposed that a terephthalate dianion, as well as methylene chains from cyclAM bridged two Co(II) atoms, while tpmc is in the boat conformation. The complexes were stable against chemical and electrochemical oxidation of Co(II) to Co(III). The data are compared with those for the previously published Cu(II) complexes containing the corresponding ligands and mutual similarities or differences were considered. Finally, some antibacterial activity of the complexes was found.

 

Keywords: Co(II) mixed-ligand complexes, N,N′,N′′,N′′′- tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane, acetate, formate, terephthalate.

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J. Serb. Chem. Soc. 72 (12) 1309–1319 (2007)

UDC 546.39+546.141:544.4:54–44:66.092–977, JSCS–3663, doi: 10.2298/JSC0712309S; Original scientific paper

 

A kinetic study of the thermal degradation of cetyltrimethylAMmonium bromide inside the mesoporous SBA-3 molecular sieve

DJORDJE STOJAKOVIC, NEVENKA RAJIC, MAJA MRAK* and VENCESLAV KAUCIC**

Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Serbia

*Jozef Stefan Institute, JAMova 39, 1000 Ljubljana, Slovenia

**National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia

 

(Received 12 June 2007)

The thermal degradation of cetyltrimethylAMmonium bromide (CTMAB) inside the mesoporous SBA-3 was studied under non-isothermal conditions. There are two distinct and complex kinetic processes which partly overlap, each consisting of one dominant and three minor individual processes. The two dominant processes can be described by the Sestak–Berggren model. The main decomposition step (the first dominant process) involves the overcoming of weak interactions between CTMAB and the silica network and proceeds with a lower Ea value (116±2 kJ mol‑1) than the second dominant process (153±5 kJ mol-1), which can be explained by the size reduction of the pore openings due to the contraction of the SBA-3 unit cell caused by the removal of CTMAB.

 

Keywords: NPK method, non-isothermal kinetics, open-frAMework, SBA-3, cetyltrimethylAMmonium bromide (CTMAB).

Full Article - PDF 303 KB

J. Serb. Chem. Soc. 72 (12) 1321–1327 (2007)

UDC 519.17–124+519.177:577.11, JSCS–3664, doi: 10.2298/JSC0712321G; Original scientific paper

 

Relating Estrada index with spectral radius

IVAN GUTMAN, SLAVKO RADENKOVIC, BORIS FURTULA, TOUFIK MANSOUR* and MATTHIAS SCHORK**

Faculty of Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac, Serbia

*Department of Mathematics, University of Haifa, 31905 Haifa, Israel

**CAMillo–Sitte–Weg 25, 60488 Frankfurt, Germany

 

(Received 3 July 2007)

The Estrada index EE is a recently proposed molecular structure-descriptor, used in the modeling of certain features of the 3D structure of organic molecules, in particular of the degree of folding of proteins and other long-chain biopolymers. The Estrada index is computed from the spectrum of the molecular graph. Therefore, finding its relation with the spectral radius r (= the greatest graph eigenvalue) is of interest, especially because the structure-dependency of r is relatively well understood. In this work, the basic characteristics of the relation between EE and r, which turned out to be much more complicated than initially anticipated, was determined.

 

Keywords: molecular graph, Estrada index, spectral radius, graph spectrum.

Full Article - PDF 194 KB

J. Serb. Chem. Soc. 72 (12) 1329–1341 (2007)

UDC 532.74+519.6+519.218.7:541.124.7+537.872, JSCS–3665, doi: 10.2298/JSC0712329M; Original scientific paper

 

Are the progrAM packages for molecular structure calculations really black boxes?

ANA MRAKOVIC, MILICA DRVENDZIJA, ALEKSANDRA SAMOLOV, MILENA PETKOVIC and MILJENKO PERIC

Faculty of Physical Chemistry, University of Belgrade, P. O. Box 137, 11000 Belgrade, Serbia

 

(Received 26 September 2007)

In this communication it is shown that the widely held opinion that compact progrAM packages for quantum–mechanical calculations of molecular structure can safely be used as black boxes is completely wrong. In order to illustrate this, the results of computations of equilibrium bond lengths, vibrational frequencies and dissociation energies for all homonuclear diatomic molecules involving the atoms from the first two rows of the Periodic Table, performed using the Gaussian progrAM package are presented. It is demonstrated that the sensible use of the progrAM requires a solid knowledge of quantum chemistry.

 

Keywords: molecular structure calculations, Gaussian, dissociation energy.

Full Article - PDF 181 KB

J. Serb. Chem. Soc. 72 (12) 1343–1350 (2007)

UDC 519.17–124+539.124+537.872, JSCS–3666, doi: 10.2298/JSC0712343R; Original scientific paper

 

Total π-electron energy and Laplacian energy: How far the analogy goes?

SLAVKO RADENKOVIC and IVAN GUTMAN

Faculty of Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac, Serbia

 

(Received 23 July 2007)

The Laplacian energy LE is a newly introduced molecular-graph-based analog of the total π-electron energy E. It is shown that LE and E have a similar structure-dependency only when molecules of different sizes are compared, when a good linear correlation between them exists. Within classes of isomers, LE and E are either not correlated at all or (as in the case of acyclic systems) are inversely proportional. The acyclic graphs and molecular graphs having the greatest and smallest LE values (determined in this work) differ significantly from those (previously known) having the greatest and smallest E values.

 

Keywords: Laplacian energy, graph energy, total π-electron energy.

Full Article - PDF 201 KB

J. Serb. Chem. Soc. 72 (12) 1351–1362 (2007)

UDC 661.183.6:544.354–128.4:549.632:544.344, JSCS–3667, doi: 10.2298/JSC0712351D; Original scientific paper

 

Thermally induced conversion of Mg2+ cation exchanged LTA, FAU, GIS and SOD zeolites: syntheses and characterization of γ-cordierite, a new Mg2Al4Si5O18 polymorph

RADOVAN DIMITRIJEVIC and VERA DONDUR*

Faculty of Mining and Geology, Department of Crystallography, University of Belgrade, Djusina 7, 11000 Belgrade, Serbia

*Faculty of Physical Chemistry, Akademski trg 16, University of Belgrade, Serbia

 

(Received 26 September 2007)

The thermal behaviours of fully Mg2+ cation exchanged LTA, FAU (X and Y species), GIS and SOD zeolites were investigated in the temperature range from AMbient to 1400 °C. The initial zeolite frAMeworks collapsed into AMorphous intermediate substances after air heating between 800–850 °C. Prolonged annealing of these products above 850 °C induced recrystallization into sapphirine-like phases (Mg–LTA and Mg–FAUx zeolites) and μ-cordierite (Mg–FAUy and Mg–GIS zeolites) phases. These phases were unstable during further temperature/time treatment and between 1000–1100 °C, they polymorphously transformed into γ-cordierite, a new Mg2Al4Si5O18 polymorph. γ-Cordierite was formed as a transformation product from the investigated zeolite precursors, except for the Mg–SOD zeolite. Structurally the γ-cordierite phase is a modulated, Mg-stuffed derivative of cristobalite with the approximate composition Mg2Al4Si5O18, which precedes the appearance of α-cordierite. The orthorhombic unit cell dimensions calculated from X-ray powder diffraction pattern are: a = 16.387(7) Å, b = 8.835(4) Å, c = 7.853(3) Å. γ-Cordierite has a narrow range of temperature stability (1100–1200 °C) and during prolonged temperature/time treatment, it is polymorphously transformed to the α-cordierite phase.

 

Keywords: Mg2+ cation exchanged zeolites, thermal conversion, γ-cordierite new polymorph, phase stability.

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J. Serb. Chem. Soc. 72 (12) 1363–1367 (2007)

UDC 661.183.6:544.354–128.4:549.632:544.344, JSCS–3668, doi: 10.2298/JSC0712363M; Short communication

 

Short communication

A consideration of the correct calculation of thermodynAMic parAMeters of adsorption

SLOBODAN K. MILONJIC

The Vinca Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia

 

(Received 09 October 2007)

The Langmuir and Freundlich isotherm equations have been widely used for interpreting various adsorption processes. There are, however, many serious mistakes in the literature in determination or calculation of thermodynAMic parAMeters, especially in the determination of the change in the free energy of adsorption using Langmuir, Freundlich and Henry constants. Many authors used these constants for the determination of ΔG expressed instead of dimensionless in some concentration units (for exAMple: l mol-1, l g-1, ml mg-1, etc.).

 

Keywords: adsorption, thermodynAMic parAMeters, correct calculation.

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J. Serb. Chem. Soc. 72 (12) 1369–1381 (2007)

UDC 546.56:536.5+66.087+532.612, JSCS–3669, doi: 10.2298/JSC0712369N; Original scientific paper

 

Effect of temperature on the electrodeposition of disperse copper deposits

NEBOJSA D. NIKOLIC*, LJUBICA J. PAVLOVIC*, MIOMIR G. PAVLOVIC* and KONSTANTIN I. POPOV*,**

*ICTM – Institute of Electrochemistry, University of Belgrade, Njegoseva 12, P. O. Box 473, 11001 Belgrade, Serbia

**Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3503, 11001 Belgrade, Serbia

 

(Received 23 July 2007)

The effect of temperature on the electrodeposition of copper at overpotentials belonging to the plateau of the limiting diffusion current density and higher was exAMined by the determination of the average current efficiency of hydrogen evolution and by scanning electron microscopic (SEM) analysis of the morphology of the formed copper deposits. Increasing the temperature of the solution led to a shift of both the beginning and the end of the plateau of the limiting diffusion current density towards lower electrodeposition overpotentials. Also, higher temperatures led to the formation of morphological forms of copper deposits characteristic for electrodeposition of copper at some higher overpotentials. The unexpected trend in the development of copper structures electrodeposited at an overpotential of 800 mV is discussed in terms of the effect of temperature on the viscosity and surface tension of the electroplating solution.

 

Keywords: electrodeposition, copper, hydrogen evolution, temperature, viscosity, surface tension.

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J. Serb. Chem. Soc. 72 (12) 1383–1392 (2007)

UDC 539.61:547–311+667.6:669.5–034:620.193, JSCS–3670, doi: 10.2298/JSC0712383B; Original scientific paper

 

Adhesion of epoxy cataphoretic coatings on Zn alloys

JELENA B. BAJAT, VESNA B. MISKOVIC–STANKOVIC and DRAGUTIN M. DRAZIC*

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O. Box 35-03, 11120 Belgrade, Serbia

*ICTM – IEC, P.O. Box 815, 11001 Belgrade, Serbia

 

(Received 21 September 2006)

One of the most important factors in corrosion prevention by protective coatings is the loss of coating adhesion under environmental influence. In this work, the adhesion of epoxy cataphoretic coatings was exAMined on steel and steel modified by Zn–Fe and Zn–Co alloys. The dry and wet adhesions of epoxy primers were measured by the direct pull-off standardized procedure, as well as indirectly by the NMP test. The corrosion stability of the coated sAMples was investigated by electrochemical impedance spectroscopy. It was shown that under dry testing conditions all the sAMples exhibited very good adhesion. However, different trends of adhesion loss of different protective systems during exposure to a corrosive agent (3 % NaCl solution) were observed. The lowest adhesion values were obtained for epoxy coating on the steel substrate. The change in adhesion of the epoxy coating on steel modified by Zn–Co alloy during immersion in 3 % NaCl solution for 24 days was the smallest of all the investigated sAMples. Electrochemical impedance measurements in 3 % NaCl solution confirmed the good protective properties of this protective system, i.e., greater values of pore resistance were obtained.

 

Keywords: adhesion, Zn–Fe alloy, Zn–Co alloy, epoxy coating, electrochemical impedance spectroscopy.

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J. Serb. Chem. Soc. 72 (12) 1393–1402 (2007)

UDC 544.773.42+546.82–31:620.197.5, JSCS–3671, doi: 10.2298/JSC0712393P; Original scientific paper

 

Sol-gel prepared active ternary oxide coating on titanium in cathodic protection

VLADIMIR V. PANIC and BRANISLAV Z. NIKOLIC*

ICTM – Center for Electrochemistry, Njegoseva 12, 11000 Belgrade, Serbia

*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O.Box 3503, 11120, Belgrade, Serbia

 

(Received 24 July 2007)

The characteristics of a ternary oxide coating, on titanium, which consisted of TiO2, RuO2 and IrO2 in the molar ratio 0.6:0.3:0.1, calculated on the metal atom, were investigated for potential application for cathodic protection in a seawater environment. The oxide coatings on titanium were prepared by the sol gel procedure from a mixture of inorganic oxide sols, which were obtained by forced hydrolysis of metal chlorides. The morphology of the coating was exAMined by scanning electron microscopy. The electrochemical properties of activated titanium anodes were investigated by cyclic voltAMmetry and polarization measurements in a H2SO4- and NaCl-containing electrolyte, as well as in seawater sAMpled on the Adriatic coast in Tivat, Montenegro. The anode stability during operation in seawater was investigated by the galvanostatic accelerated corrosion stability test. The morphology and electrochemical characteristics of the ternary coating are compared to that of a sol-gel-prepared binary Ti0.6Ru0.4O2 coating. The activity of the ternary coating was similar to that of the binary Ti0.6Ru0.4O2 coating in the investigated solutions. However, the corrosion stability in seawater is found to be considerably greater for the ternary coating.

 

Keywords: ruthenium-oxide-based coatings, sol-gel procedure, iridium oxide, cathodic protection, stability.

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J. Serb. Chem. Soc. 72 (12) 1403–1418 (2007)

UDC 546.57'82–31+544.4.004.12:66.094.1:66.087+546.57, JSCS–3672, doi: 10.2298/JSC0712403M; Original scientific paper

 

Tailoring the morphology and electrocatalytic properties of electrochemically formed Ag/TiO2 composite deposits on titanium surfaces

S. V. MENTUS, I. BOSKOVIC*, J. M. PJESCIC*, V. GRUDIC* and Z. BOGDANOV**

Faculty of Physical Chemistry, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia

*Faculty of Metallurgy and Technology, Podgorica University, 81000 Podgorica, Montenegro

**Vinca Institute of Nuclear Sciences, 11001 Belgrade, Serbia

 

(Received 14 August 2007)

Three different forms of Ag/TiO2 composite layers, which have whisker-, dot- and island-like distribution of silver were obtained on a mechanically polished titanium surface by adjusting the conditions of silver deposition from an aqueous AgNO3 solution. The deposit morphology was the result of both the progrAM of electrode polarization and the template action of the simultaneously formed TiO2 layer. The catalytic activity of the composite layers toward the oxygen reduction reaction was studied in aqueous 0.1 M NaOH solutions and found to be a function of both the surface loading of silver and the type of silver distribution within the Ag/TiO2 composite layers. The reaction path of oxygen reduction on the composite layers was found to be always a 4e- one, characteristic otherwise of polycrystalline silver electrodes.

 

Keywords: metal/oxide composite electrocatalysts, oxygen reduction reaction, rotating disc electrode, silver electrodeposition, titanium dioxide film.

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J. Serb. Chem. Soc. 72 (12) 1419–1425 (2007)

UDC 66.094.3+544.6:547.261+547.263+544.478:621.352, JSCS–3673, doi: 10.2298/JSC0712419G; Short communication

 

Short communication

Mixtures of methanol and 2-propanol as a potential fuel for direct alcohol fuel cells

S. LJ. GOJKOVIC, A. V. TRIPKOVIC* and R. M. STEVANOVIC*

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O. Box 3503, 11120 Belgrade, Serbia

*ICTM-Institute of Electrochemistry, University of Belgrade, Njegoseva 12, P.O.Box 473, 11000 Belgrade, Serbia

 

(Received 29 March 2007)

The electrochemical oxidation of methanol, 2-propanol, and their mixtures was investigated on a Pt/C thin film electrode in acid solution. It was confirmed that the oxidation of 2-propanol commences at less positive potentials than that of methanol and exhibits significantly higher oxidation current densities at low potentials. When both methanol and 2-propanol were present in the solution, the onset of the oxidation current was the sAMe as for the oxidation of pure 2-propanol. Although both alcohols inhibit the oxidation reaction of each other to a certain extent, steady-state polarization measurements showed that their mixture provides higher current densities than single alcohols over the entire potential region from the hydrogen region to oxide formation on the Pt surface. This implies that the addition of 2-propanol into the fuel may extend the operational range of direct methanol fuel cells.

 

Keywords: electrochemical oxidation, 2-propanol, methanol, platinum supported catalyst, fuel cell.

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J. Serb. Chem. Soc. 72 (12) 1427–1436 (2007)

UDC 544.6:615.33:541.135.5–034.21+541.135, JSCS–3674, doi: 10.2298/JSC0712427A; Original scientific paper

 

A study of the electrochemical activity of some macrolide antibiotics on a gold electrode in a neutral electrolyte

M. L. AVRAMOV IVIC, S. D. PETROVIC*,** and D. Z. MIJIN*

ICTM – Institute of Electrochemistry, University of Belgrade, Njegoseva 12, Belgrade, , Serbia

*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia

**Hemofarm Group, Pharmaceutical and Chemical Industry, Vrsac, Serbia

 

(Received 08 October 2007)

The aim of the present study is to present the different reactivity of azithromycin and clarithromycin (pure and commercial) at a gold electrode in neutral electrolyte using cyclic linear sweep voltAMmetry under the sAMe experimental conditions. A gold electrode was successfully used for the electrochemical qualitative and quantitative determination of azithromycin dihydrate and azithromycin from capsules (Hemomycin®) and for the separation of azithromycin from one of the excipients, lactose monohydrate. The good catalytically activity of the gold electrode was employed only for the qualitative electrochemical determination of pure clarithromycin by appearance of one cathodic and four anodic reactions, which enabled structural changes in this molecule during electrochemical reactions to be studied. Commercial clarithromycin, Clathrocyn® was qualitative determined by one reproducible anodic reaction. The activity of one of the excipients, Avicel, observed as a cathodic peak at different potential from the cathodic peak obtained with pure clarithromicin was used for the determination of its presence in Clathrocyn® tablets. FTIR Analysis showed the apparent changes in structure of pure clarithromycin, as well as in the molecule of clarithromycin in Clathrocyn® tablets. HPLC Analysis showed a significant decrease in the concentration of azithromycin, Hemomycin® clarithromycin and Clathrocyn® after the electrochemical reactions.

 

Keywords: azithromycin, clarithromycin, gold electrode, cyclic voltAMmetry.

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J. Serb. Chem. Soc. 72 (12) 1437–1463 (2007)

UDC 544.344+536.7.004.12:681.3.042/.043:536.658, JSCS–3675, 10.2298/JSC0712437D; Review paper

 

Review paper

Modelling of volumetric properties of binary and ternary mixtures by CEOS, CEOS/GE and empirical models

BOJAN D. DJORDJEVIC, SLOBODAN P. SERBANOVIC, IVONA R. RADOVIC, ALEKSANDAR Z. TASIC and MIRJANA LJ. KIJEVCANIN

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O. Box 35-03, 11120 Belgrade, Serbia

 

(Received 15 August 2007)

Although many cubic equations of state coupled with van der Waals-one fluid mixing rules including temperature dependent interaction parAMeters are sufficient for representing phase equilibria and excess properties (excess molar enthalpy HE, excess molar volume VE, etc.), difficulties appear in the correlation and prediction of thermodynAMic properties of complex mixtures at various temperature and pressure ranges. Great progress has been made by a new approach based on CEOS/GE models. This paper reviews the last six-year of progress achieved in modelling of the volumetric properties for complex binary and ternary systems of non-electrolytes by the CEOS and CEOS/GE approaches. In addition, the vdW1 and TCBT models were used to estimate the excess molar volume VE of ternary systems methanol + chloroform + benzene and 1-propanol + chloroform + benzene, as well as the corresponding binaries methanol + chloroform, chloroform + benzene, 1-propanol + chloroform and 1-propanol + benzene at 288.15–313.15 K and atmospheric pressure. Also, prediction of VE for both ternaries by empirical models (Radojković, Kohler, Jackob–Fitzner, Colinet, Tsao–Smith, Toop, Scatchard, Rastogi) was performed.

 

Keywords: correlation, prediction, volumetric properties, cubic EOS mixing rules, empirical models, non-electrolyte multicomponent systems.

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J. Serb. Chem. Soc. 72 (12) 1465–1475 (2007)

UDC 543:615.285+615.45:541.135.5–.39.26, JSCS–3676, doi: 10.2298/JSC0712465G; Original scientific paper

 

Determination of various insecticides and pharmaceuticals using differently modified glassy carbon electrodes

FERENC F. GAÁL*,**, VALÉRIA J. GUZSVÁNY* and LUKA J. BJELICA*

*Faculty of Sciences, Department of Chemistry, Trg D. Obradovića 3, 21000 Novi Sad, Serbia

**Academy of Sciences and Arts of Vojvodina, Dunavska 37, 21000 Novi Sad, Serbia

 

(Received 31 July 2007)

The applicability of differently modified glassy carbon (GC) electrodes for direct or indirect determinations of various physiologically active compounds (insecticides and pharmaceuticals) in different formulations and some real sAMples was investigated. SAMples of selected insecticides from the group of neonicotinoids with nitroguanidine (thiAMethoxAM and imidacloprid), cyanoimine (acetAMiprid) and nitromethilene (nitenpyrAM) fragments, prepared in an appropriate manner, were determined by voltAMmetry on bare and surface-modified GC electrodes, while in the case of pharmaceuticals such as Trodon and Akineton, the chloride anion titration was followed using bare GC and phosphorus doped (P–GC) electrodes. The P–GC was also used to monitor the chloride content in the photocatalytic degradation of the (4-chloro-2-methylphenoxy)acetic acid herbicide. It was found that apart from the nature of the electrode material, the analyte and supporting electrolyte, as well as the pretreatment of the electrode surface essentially influences the applicability of the employed sensors.

 

Keywords: bismuth film electrode, tetradecan film electrode, phosphorus-doped glassy carbon, insecticides, pharmaceuticals, electroanalytical determinations.

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J. Serb. Chem. Soc. 72 (12) 72 (12) 1477–1486 (2007)

UDC 544.4+541.14+66.092.094:632.954+628, JSCS–3677, doi: 10.2298/JSC0712477A; Original scientific paper

 

Photocatalytic removal of the herbicide clopyralid from water

BILJANA F. ABRAMOVIC*, VESNA B. ANDERLUH*, DANIELA V. SOJIC* and FERENC F. GAÁL*,**

*Faculty of Sciences, Department of Chemistry, Trg D. Obradovića 3, 21000 Novi Sad, Serbia

**Academy of Sciences and Arts of Vojvodina, Dunavska 37, 21000 Novi Sad, Serbia

 

(Received 20 July 2007)

The stability of the herbicide clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) was studied under different experimental conditions of pH, illumination and initial substrate concentration. It was found that in the pH interval from 1.0 to 9.0 in the presence/absence of daylight, clopyralid solutions were stable for at least a period of two months. The kinetics of the photocatalytic degradation of clopyralid in aqueous suspensions of TiO2 (Degussa P25) under UV and visible light, as well as of direct photolysis using the sAMe radiation sources, were also investigated. It was found that the rate of photocatalytic degradation in the presence of UV light was more than five times higher compared to direct photolysis, whereas in the presence of visible light, the corresponding rates of photocatalytic/photolytic degradation were much lower (more than 15 times). The reaction in the investigation concentration range is zero-order with respect to the degradation of the clopyralid pyridine moiety, with a reaction rate of 3.4×10−6 mol dm-3 min-1 and an adsorption coefficient of the substrate of 2.5×104 dm3 mol‑1.

 

Keywords: clopyralid, photocatalytic degradation, TiO2 Degussa P25, photolysis, water treatment.

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J. Serb. Chem. Soc. 72 (12) 1487–1492 (2007)

UDC 54.06+663.251:546.3:543.41, JSCS–3678, doi: 10.2298/JSC0712487R; Original scientific paper

 

Multivariate data visualization methods based on elemental analysis of wines by atomic absorption spectrometry

SLAVICA RAZIC, DJURO COKESA* and SNEZANA SREMAC*

*Faculty of Pharmacy, Institute of Analytical Chemistry, Vojvode Stepe 450, 11211 Belgrade, Serbia

**The Vinca Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia

 

(Received 3 July 2007)

The contents of five metals (Cu, Mn, Fe, Cd, and Pb) in several red and white wines originating from different regions of Serbia were determined by flAMe and graphite furnace atomic absorption spectrometry. The data were processed using chemometric techniques. Principal component and factor analysis were applied in order to highlight the relations between the elements and, after data reduction, three main factors controlling variability were identified. Application of hierarchical cluster analysis to the studied wines indicated differentiation of the sAMples belonging to different origins. No discrimination between red and white wines was found.

 

Keywords: principal component analysis, factor analysis, cluster analysis, metals, wines, classification.

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J. Serb. Chem. Soc. 72 (12) 1493–1506 (2007)

UDC 678.741.004.12:541.135.21:542.913, JSCS–3679, doi: 10.2298/JSC0712493V; Original scientific paper

 

Properties of aliphatic hyperbranched polyesters in dilute solutions

JASNA VUKOVIC, MANFRED D. LECHNER and SLOBODAN JOVANOVIC*

Institute for Chemistry, University of Osnabrueck, Barbarastraße 7, 49069 Osnabrueck, Germany

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia

 

(Received 20 August 2007)

The results of an investigation of the influence of the synthesis procedure, number of pseudo generations and degree of branching of hydroxy-functional aliphatic hyperbranched polyesters (AHBP) on the values of limiting viscosity number, [η], hydrodynAMic radius, Rη, molar mass and polydispersity index, Q, are presented in this paper. Two series of AHBP, synthesized from 2,2-bis(hydroxylmethyl)propionic acid and di-trimethylolpropane using a pseudo-one-step and a one-step procedure were investigated. The obtained results show that the values of [η] and Rη for all exAMined sAMples are the highest in a 0.7 mass % solution of LiCl in N,N-dimethylacetAMide (LiCl/DMAc), which indicates that this solvent is the best from the investigated ones. The values of [η] in N-methyl-2-pyrrolidinone (NMP) increased up to the sixth pseudo generation, after which a slight decrease occurred as the consequence of the presence of side-reaction products, formed during the synthesis. The appearance of these side-reaction products was also confirmed from the characteristic the GPC chromatogrAMs. For the sAMples of AHBP synthesized using the pseudo-one-step procedure, a good linear dependence between log [η] and log Mw was obtained up to the fifth pseudo generation, when LiCl/DMAc, NMP and DMAc were used as solvents. The values of the “shrinking” factor, g’, were calculated for all investigated AHBPs.

 

Keywords: aliphatic hyperbranched polyesters, dilute solutions, limiting viscosity number, GPC.

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J. Serb. Chem. Soc. 72 (12) 1507–1514 (2007)

UDC 678–13+66–96+544.35:543.422.25, JSCS–3680, doi: 10.2298/JSC0712507M; Original scientific paper

 

Preparation and modification of itaconic anhydride–methyl methacrylate copolymers

MILOS B. MILOVANOVIC, SNEZANA S. TRIFUNOVIC*, LYNNE KATSIKAS** and IVANKA G. POPOVIC**

Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Njegoseva 12, Belgrade, Serbia

*Faculty of Chemistry, University of Belgrade, Studentski trg 12–16, Belgrade, Serbia

**Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia

 

(Received 02 August 2007)

The free radical copolymerisation of itaconic anhydride and methyl methacrylate in solution was studied at 60 °C. The copolymer composition was determined by 1H-NMR spectroscopy and the obtained monomer reactivity ratios were calculated, rITA = 1.35±0.11; rMMA = 0.22±0.22 (by the Fineman–Ross method) and rITA = 1.27±0.38; rMMA = 0.10±0.05 (by the Mayo–Lewis method). The synthesised copolymers were modified by reaction with di-n-butyl AMine. The copolymer composition after AMidation was determined by elemental analysis via the nitrogen content. Amidation of the anhydride units in the copolymers with di-n-butyl AMine resulted in complete conversion to itaconAMic acid.

 

Keywords: copolymerisation, itaconic anhydride, methyl methacrylate, AMidation, itaconAMic acid.

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J. Serb. Chem. Soc. 72 (12) 1515–1531 (2007)

UDC 678.048:542.913:678.742.004.12, JSCS–3681, doi: 10.2298/JSC0712515P; Original scientific paper

 

The influence of antioxidant and post-synthetic treatment on the properties of biodegradable poly(butylene succinate)s modified with poly(propylene oxide)

DRAGANA PEPIC, MARIJA RADOICIC, MARIJA S. NIKOLIC and JASNA DJONLAGIC

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia

 

(Received 31 July 2007)

Novel poly(ester–ether)s based on poly(butylene succinate) (PBS) as the hard segments and 30 mass % of poly(propylene oxide) (PPO) as the soft segments were synthesized with varying AMount of the antioxidant (N,N'-diphenyl-p-phenylenediAMine, DPPD). The influences of the addition of DPPD and the impact of post-synthetic treatment by precipitation on the molecular structure, thermal and physical properties, as well as on the storage stability of the biodegradable aliphatic copolyesters, were investigated. The structure and composition of the copolymers were determined by means of 1H-NMR spectroscopy. The molecular weight and polydispersity of the poly(ester–ether)s were evaluated from solution viscosity and GPC measurements. The thermal properties and stability were evaluated, respecttively, by means of DSC and non-isothermal thermogravimetry in an inert nitrogen atmosphere. The biodegradability potential of the polymers was studied in hydrolytic and enzymatic degradation tests with Candida cylindracea lipase by monitoring the weight loss of polymer films after incubation. The weight losses of the sAMples increased with time and were in the range from 1 to 5 mass % after 4 weeks. GPC analysis confirmed that there were changes in the molecular weight of the copolyesters during both hydrolytic and enzymatic degradation tests, leading to the conclusion that the degradation mechanism of poly(butylenes succinate) modified with PPO occurred through surface erosion and bulk degradation.

 

Keywords: poly(ester–ether), poly(butylene succinate), poly(propylene oxide), biodegradable, antioxidant, enzymatic degradation.

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J. Serb. Chem. Soc. 72 (12) 1533–1543 (2007)

 

Contents of Volume 72

Full Article - PDF 134 KB

J. Serb. Chem. Soc. 72 (12) 1545–1548 (2007)

 

Subject index

Full Article - PDF 85 KB

J. Serb. Chem. Soc. 72 (12) 1549–1554 (2007)

 

Author index

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End of Vol 72

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November 25, 2007.
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