JSCS Vol 66, No. 8

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J.Serb.Chem.Soc. 66(8) 499–505(2001)
UDC 547.918
Original scientific paper

The Ferrier rearrangement as the key step in the synthesis of C7–C16-alkyl 2,3-dideoxy glucosides from glucose and C7–C16-alkanols


Department of Chemistry, Faculty of Science, University of Kragujevac, P. O. Box 60, YU-34000 Kragujevac, E-mail: konstan@eunet.yu,
*Institute for Chemistry, Technology and Metallurgy, Njegoseva 12, YU-11000 Belgrade,
**Faculty of Chemistry, University of Belgrade, P. O. Box 158, YU-11001 Belgrade and
***Institute of Chemistry, Faculty of Science, University of Novi Sad, Trg Dositeja Obradovica 3, YU-21000 Novi Sad, Yugoslavia

(Received 8 March 2001)
The Ferrier rearrangment was used as the key step in the synthesis of C7–C16-alkyl 2,3-dideoxy glucosides from glucose and C7–C16-alkanols.
Keywords: synthesis of C7–C16-alkyl 2,3-dideoxy glucosides, Ferrier rearrangement.
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J.Serb.Chem.Soc.66 (8)507–516(2001)
UDC 547.554
JSCS – 2880
Original scientific paper

Synthesis and investigation of solvent effects on the ultraviolet absorption spectra of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones


Department of Organic Chemistry, Faculty of Technology and Metallurgy, University of Belgrade, P. O. Box 3503, YU–11001, Belgrade, Yugoslavia

(Received 5 April, revised 15 May 2001)
A number of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones from cyanoacetamide and the corresponding alkyl ethyl acetoacetates were synthesized according to modified literature procedures. The alkyl ethyl acetoacetates were obtained by the reaction of C-alkylation of ethyl acetoacetate. An investigation of the reaction conditions for the synthesis of 4-methyl-3-cyano-6-hydroxy-2-pyridone from cyanoacetamide and ethyl acetoacetate in eight different solvents was also performed. The ultraviolet absorption spectra of synthesized pyridones were measured in nine different solvents in the range 200–400 nm. The effects of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of linear solvation energy relationships using a general equation of the form n = n0 + sp* + aa + bb, where p* is a measure of the solvent polarity, a is the scale of the solvent hydrogen bond donor acidities and b is the scale of the solvent hydrogen bond acceptor basicities.
Keywords: alkylation, ethyl acetoacetate, alkyl ethyl acetoacetates synthesis, 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones, spectroscopy, cyclization, ultraviolet absorption spectra, solvent effects, linear solvation energy relationships.
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J.Chem.Soc.Soc. 66(8)517–521(2001)
UDC 546.271
JSCS – 2881
Original scientific paper

On the Klemm model for bistability of mixtures of interacting enantiomers


Faculty of Science, University of Kragujevac, P. O. Box 60, YU-34000 Kragujevac, Yugoslavia

(Received 19 April 2001)
The solution of the Klemm model for spontaneous chiral stereoselection has been obtained. It is shown that a system whose time-evolution is described by the Klemm model, independently of the initial value of the enantiomeric excess, always reaches a racemic terminal state. In a system described by the Klemm model bistability never occurs.
Keywords: chirality, homochirality, bistability, Klemm model, Frank model.
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J.Serb.Chem.Soc. 66(8)523–534(2001)
UDC 549.521.4
JSCS – 2882
Original scientific paper

Thermodynamical consideration of the synthesis of solid AlN from thermal plasma


Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, P. O. Box 137, YU-11001 Belgrade

(Received 30 March 2001)
The synthesis process of solid AlN in thermal plasmas was investigated theoretically by computing the equilibrium composition of the gas mixture involving nitrogen and various amounts of aluminum, oxygen and hydrogen for the temperature range between 1000 and 5500 K. The results obtained by treating the plasma as a single-gas system were combined with those which take into account the presence of solid AlN and liquid Al, to find the optimal conditions for the deposition of solid AlN. The factors determining the efficiency of this process are discussed.
Keywords: plasma synthesis, AlN synthesis, thermodynamics of AlN.
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J.Serb.Chem.Soc. 66(8)535–542(2001)
UDC 546.271
JSCS – 2883
Original scientific paper

Some problems connected with boron determination by atomic absorption spectroscopy and the sensitivity improvement


Vinca Instititute of Nuclear Sciences, Laboratory of Physical Chemistry, P.O. Box 522, YU-11001 Belgrade, Yugoslavia

(Received 13 March 2001)
Two atomizers were compared: an N2O–C2H2 flame and a stabilized U-shaped DC arc with aerosol supply. Both the high plasma temperature and the reducing atmosphere obtained by acetylene addition to the argon stream substantially increase the sensitivity of boron determination by atomic absorption spectroscopy (AAS) when the arc atomizer is used. The results were compared with those for silicon as a control element. The experimental characteristic concentrations for both elements were compared with the computed values. The experimentally obtained characteristic concentration for boron when using the arc atomizer was in better agreement with the calculated value. It was estimated that the influence of stable monoxide formation on the sensitivity for both elements was about the same, but reduction of analyte and formation of non-volatile carbide particles was more important for boron, which is the main reason for the low sensitivity of boron determination using a flame atomizer. The use of an arc atomizer suppresses this interference and significantly improves the sensitivity of the determination.
Keywords: boron, atomic absorption spectroscopy, characteristic concentration, DC arc plasma.
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J.Serb.Chem.Soc. 66(8)543–553(2001)
UDC 546.634
JSCS – 2884
Original scientific paper

Complexes of light lanthanides with 2,3-dimethoxybenzoic acid


Faculty of Chemistry, Maria Curie-Sklodowska University, Pl. 20-031 Lublin, Poland

(Received 7 February, revised 5 May 2001)
The complexes of light lanthanides with 2,3-dimethoxybenzoic acid of the formula: Ln(C9H9O4)3, where Ln = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric studies, as well as X-ray and magnetic measurements. The complexes have colours typical for Ln3+ ions (La, Ce, Eu, Gd–white, Sm–cream, Pr–green, Nd–violet). The carboxylate group in these complexes is a bidentate, chelating ligand or a tridentate chelating and bridging one. They are crystalline compounds characterized by low symmetry. On heating in air to 1173 K, the 2,3-dimethoxybenzoates of the light lanthanides decompose in various ways. The complexes of Ce(III), Pr(III), Sm(III), Eu(III) and Gd(III) decompose directly to oxides of the respective metals while those of La(III) and Nd(III) via the intermediate formation of La2O2CO3 and Nd2O2CO3. The solubilities of the 2,3-dimethoxybenzoates of the light lanthanides in water at 293 K are in the orders of 10-3 – 10-2 mol dm-3. The magnetic moments were determined in the range 4.2–298 K and the complexes are found to obey the Curie-Weiss law.
Keywords: 2,3-dimethoxybenzoates, light lanthanides, thermal stability, magnetic moments.
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J.Serb.Chem.Soc. 66(8)555–561(2001)
UDC 541.183.1:553.67:632.4 aflatoxin B1
JSCS – 2885
Original scientific paper

The effect of exchangeable cations in clinoptilolite and montmorillonite on the adsorption of aflatoxin B1


Institute for Technology of Nuclear and Other Mineral Raw Materials, P. O. Box 390, YU-11001, Belgrade and
*VMA - Institute for Hygiene, YU-11000, Belgrade, Yugoslavia

(Received 25 January 2001)
The adsorption of aflatoxin B1 (AFB1) by cation-exchanged clinoptilolite zeolitic tuff and montmorillonite was investigated at 37°C and pH 3.8 from an aqueous electrolyte having a composition similar to that of gastric juices of animals. Both minerals were exchanged from the natural form to the sodium form and then to the Cu2+, Zn2+ and Co2+-rich forms. The cation exchange was different for the different cations, but in all cases the exchanges were larger on montmorillonite than on clinoptilolite. The degree of exchange on montmorillonite was 76 % for copper (from a total of CEC 0.95 meq/g, Cu2+ –0.73 meq/g) and 85 % for zinc and cobalt. Under the same conditions (concentration, temperature, pH, contact time), the degree of exchange on zeolitic tuff was 12 % for Cu2+ (from a total CEC of 1.46 meq/g, Cu2+ –0.17 meq/g), 8 % for Zn2+ and 10 % for Co2+. Both groups of mineral adsorbents showed high AFB1 chemisorption indexes (ca). For the montmorillonite forms, ca ranged from 0.75 for the Cu-exchanged montmorillonite to 0.89 for the natural Ca-form, 0.90 for the Zn-exchanged form and 0.93 for the Co-exchanged montmorillonite. The adsorption of AFB1 on the different exchanged forms of clinoptilolite gave similar values of ca for the Cu and Ca forms (0.90) and values of 0.94 and 0.95 for the Zn- and Co-exchanged form. The impact of the mineral adsorbents on the reduction of essential nutrients present in animal feed (Cu, Zn, Mn and Co) showed that the Ca-rich montmorillonite had a higher capability for the reduction of the microelements than the Ca-rich clinoptilolite.
Keywords: clinoptilolite, montmorillonite, cation exchange, adsorption, aflatoxins.
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J.Serb.Chem.Soc. 66(8)563–569(2001)
UDC 538.556
JSCS – 2886
Original scientific paper

A study of periodic current oscillations of iron in nitric acid solutions


*Chemistry Department, Shandong University, Jinan 250100, P. R. China,
**State Key Laboratory for Corrosion and Protection, Shenyang 110015, P. R. China and
***Chemistry Department, Xuzhou Teachers’ University, Xuzhou 221009, P. R. China

(Received 4 April 2001)
The periodic current oscillations of Fe/HNO3 are presented in this paper. The effects of HNO3 concentration and imposed potential were investigated. The dropping method was used to change the local pH of the Fe/electrolyte interface, creating environments that favor the occurrence of current oscillations. Some interesting results were obtained and an explanation of the current oscillations is suggested.
Keywords: iron, nitric acid, current oscillations, electrodissolution.
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