J. Serb. Chem. Soc. 62(4) 295-306 (1997)
JSCS-2384
UDK 678.5/.7
Review paper
REVIEW
Materials with new properties - a challenge for polymer synthesis

BOGDAN C. SIMIONESCU, VALERIA HARABAGIU*, GETA DAVID AND MARIANA PINTEALA*

"Gh. Asachi" Technical University, Department of Macromolecules, 6600 Jassy and
*"P. Poni" Institute of Macromolecular Chemistry, 6600 Jassy, Romania

(Received 10 October 1996)
1. Introduction,
2. Free radical ring opening polymerization
3. Functional polysiloxanes and derived copolymers
3.1. Synthesis of OPSs by hydrosilation
3.2. Synthesis of OPSs by chemical transformation
3.3. Synthesis of siloxanc copolymers
4. Graft and block copolymers with poly(N-acyliminoethylene) sequences
5. Plasma-induced polymerization

Key words: free radical ring opening polymerization, functional polisiloxane, siloxane copolymers, plasma-inducal polymerization




J. Serb. Chem. Soc. 62(4) 307-317 (1997)
JSCS-2385
UDK 547.722/.728:541.251:543.424
Original scientific paper
 


Stereochemistry and 13C-NMR spectra of some phenyl selenotetrahydrofurans and selenotetrahydropyrans obtained by phenylselenoetherification

STANIMIR KONSTANTINOVIC* **, ZORICA BUGARCIC*, RASTKO VUKICEVIC*, WOLFGANG WISNIEWSKI**, ZORAN RATKOVIC*, ZORAN MARKOVIC* AND MIHAILO LJ. MIHAILOVIC***

*Department of Chemistry, Faculty of Science, University of Kragujevac, P.O.Box 60, YU-34000 Kragujevac, Yugoslavia
**Max-Plank Institut fur Kohlenforschung, P.O.Box 101353, D-45466 Mulheim - Ruhr, Germany, and
***Faculty of Chemistry, University of Belgrade, P.O.Box 158, YU-11000 Belgrade, and Institute of Chemistry Technology and Metallurgy, Belgrade, Yugoslavia

(Received 10 October 1996)
The 13C-NMR spectra of some phenyl selenotetrahydrofurans and selenotetrahydropyrans, obtained by phenylselenoetherification of the corresponding unsaturated alcohols, have been recorded and studied as a function of their stereochemistry. By using the MMX (PC MODEL) force field (extended with some new parameters), the prepared phenyl selenotetrahydropyrans have also been theoretically studied.

Key words: phenyl selenotetrahydrofurans, selenotetrahydropyrans,  stereochemistry, 13C-NMR spectra



J. Serb. Chem. Soc. 62(4) 319-325 (1997)
JSCS-2386
UDK 541.61:547.53.513.3
Original scientific paper
 


On the calculation of the algebraic structure count of polycyclic conjugated hydrocarbons by means of cell polynomial

PETER JOHN and IVAN E. GUTMAN*

Institute of Mathematics, Technical University of Ilmenau, P.O.Box 565, D-98693 Ilmenau, Germany, and
*Faculty of Science, University of Kragujevac, P.O.Box 60, YU-34000 Kragujevac, Yugoslavia

(Received 11 November 1996)
The cell polynomial (also known under the name "resonant ring polynomial" or "R-polynomial") is a proper extension of the Hosoya-Yamaguchi's sextet-polynomial-concept from benzenoid molecules to arbitrary polycyclic alternant connjugated p-electron systems. In the ease of catacondensed molecules the cell polynomial enables a straightforward evaluation of the Kekule structure count. We now show that the calculation of the algebraic structure count is a task more difficult than initially anticipated, and that it cannot be accomplished using solely the cell polynomial.

Key Words: Clar theory, Kekule structures, algebraic structure count, cell polynomial




J. Serb. Chem. Soc. 62(4) 327-333 (1997)
JSCS-2387
UDK 543.78/.888:541.121/.123
Original scientific paper
 


Reaction extents in systems with multiple chemical equilibria

IVAN GUTMAN, ISTVAN NAGYPAL* and ILIE FISHTIK**

Faculty of Science, University of Kragujevac, P.O.Box 60, YU-34000 Kragujevac, Yugoslavia
*Institute of Physical Chemistry, Attila Josef University, P.O.Box 105, H-6701 Szeged, Hungary and
**Institute of chemistry, Academy of Science of Moldova, 277028 Kishinev, str. Academiei 3, Republica Moldova

(Received 10 October 1996)
It is shown that in multiple-equilibrium systems the reaction extents are uniquely determined only if all the equilibria considered are stoichiometrically independent. Otherwise numerical values for reaction extents, satisfying the mass-balance conditions, can be chosen in infinitely many ways. Irrespective of this, every reaction affinity (the derivative of the Gibbs energy with respect to the reaction extent. These results corroborate the validity of the recently elaborated response-reaction-approach to chemical thermodynamics.

Key words: reaction extent, extent of chemical reaction,  multiple-equilibrium systems, chemical thermodynamics



J. Serb. Chem. Soc. 62(4) 335-341 (1997)
JSCS-2388
UDK 547.587.11:546.562:541.42849
Original scientific paper
 


Spectrophotometric study of the complex-formation equilibria between some salicylic acid derivatives and copper(II) ions

GYONGYI GY. VASTAG, TEREZIA M. SURANYI and EVGENIJA DJURENDIC

Institute of Chemistry, Faculty of Science, Novi Sad, Trg D. Obradovica 3, YU-21000 Novi Sad, Yugoslavia

(Received 7 August, revised 24 December 1996)
The equilibria occurring in solution of 1,n-di-O-salicyloyl-alkane-1,n-diols (n=2-8) and N,N-disalicyloyl-1,n-alkanediamines (n=2-4) with copper(II) ions have been studied by a spectrophotometric method. The complex-formation constants have been determined in 61.10% aqueous ethanol at 298 K and l = 0.5 mol dm-3 ((Li)Cl). As the determinations were performed in a glycinate buffer, these constants were corrected for the side reaction of copper(II) with glycine.

Key words: copper(II) complexes, salicylic acid derivatives, complex equilibria



J. Serb. Chem. Soc. 62(4) 343-348 (1997)
JSCS-2389
UDK 622.337:628.35:549.324.31
Original scientific paper

Bacterial depyritization of oil shale by thiobacillus ferrooxidans. The effect of initial pH value

VESNA DRAGUTINOVIC, MIROSLAV VRVIC*, OLGA CVETKOVIC, JOVAN VUCETIC* and DRAGOMIR VITOROVIC*

Center of Chemistry, Institute of Chemistry Technology and Metallurgy, Njegoseva 12, P.O.Box 815, YU-11001 Belgrade, and
*Faculty of Chemistry, University of Belgrade, Akademski trg, P.O.Box 158, YU-11001 Belgrade, Yugoslavia

(Received 13 December 1996)
The efficiencies of depyritization of Aleksinac (Yugoslavia) oil shale concentrates with Thiobacillus ferrooxidans (Th.f.) strain A5 were studied at initial pH values of 2.5 (favorable for Th.f. strain in a medium containing Fe(II)-ions), 2 and 1.5 (preventing the precipitation of Fe(III)-ion hydrolysis products). The investigated samples (HCl-and HCl-kerogen concentrates) were suitable as substrates for bacterial depyritization since they both originated from oil shale with less than 1 bitumen. The bioleaching efficiency was found to decrease with decreasing initial pH, which is probably due to the difference in pHs within the cell and the environment, i.e., the medium. Nevertheless, based on the ratio of the efficiency of bacterial depyritization vs. the number of microorganisms, an initial pH of 2 might be considered optimal, presumably because the precipitation of Fe(III)-ion hydrolysis products has at least been partially prevented.
Key words: oil shale, thiobacillus ferrooxidans, depyritization




J. Serb. Chem. Soc. 62(4) 349-351 (1997)
JSCS-2390
UDK 535.343.546.11:546.659'732''
Original scientific paper
 


Kinetics of hydrogen absorption in a powdered SmCo5 alloy

MILENKO SUSIC

Serbian Academy of Science and Arts, Belgrade, and Faculty of Physical Chemistry,
University of Belgrade, P.O.Box 137, YU-11001 Belgrade, Yugoslavia

(Received 15 November 1996)
It is known that the polycrystalline powdered intermetallic lanthanide SmCo5 may be brought to an active hydrogen absorber in the temperature range of 80 to 500C, with an enthalpy of 100 J/g or more. The most important kinetic and thermodynamic parameters of the process are determined, such as rate constants, enthalpies and energies of activation.

Key words: hydrogen absorption, kinetics of, SmCo5, intermetallic lanthanide




J. Serb. Chem. Soc. 62(4) 353-359 (1997)
JSCS-2391
UDK 547.262:541.18.045.5:549.67
Original scientific paper
 


Laboratory process for ethanol drying in a fixed bed of the zeolite 3A

SVETOMIR MIJOVIC, MILAN MITROVIC and DUSAN VUCELIC*

Institute of General and Physical Chemistry, Studentski trg 12-16, P.O.Box 551, YU-11000 Belgrade and
*Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, P.O.Box 137, YU-11001 Belgrade, Yugoslavia

(Received 7 June 1996, revised 17 Januaty 1997)
The conditions for the process of a liquid phase dehydration of ethanol were investigated. The dehydration was performed in a fixed bed adsorption column of granular molecular sieve 3A, which was confirmed, as it is already known, to be the most efficient desiccant for organic solvents. The dynamic capacity of the adsorbent, as well as the cross-over ratio between the mass transfer zone (MTZ) and the heat wave developed during the adsorption step, were determined. The results of the experiments form the basis for the design of an industrial process to produce absolute ethanol, using a temperature swing adsorption (TSA) cycle.

Key words: adsorption drying, ethanol drying, zeolite 3A, cross-over ratio




J. Serb. Chem. Soc. 62(4) 361-365 (1997)
JSCS-2392
UDK 666.94.053:622.785:666.942.3
Original scientific paper
 


Sintering of mechanically activated raw material mixtures used for obtaining portland-cement clinker

ZIVKO SEKULIC, SINISA MILOSEVIC, DEANA ZIVANOVIC, ALEKSANDRA ROSIC* and MIODRAG STEFANOVIC**

Institute for Technology of Nuclear and Other Mineral Raw materials, Franse d`Eperea86, YU-11000 Belgrade,
*Faculty of Mining and Geology, Laboratory for Crystallography, Djusina 7, YU-11000 Belgrade, and
** Cement Factory "Novi Popovac", Popovac, Yugoslavia

(Received 21 November 1996)
In this study the sintering of unactivated and mechanically activated raw material mixtures used for obtaining portland cement clinker was investigated. The optimal times for mechanical activation of the individual components and raw material mixtures were previously determined. The mechanical activation experiments were performed in a vibro mill with rings. It was found that mechanical activation of the raw material mixture caused not only an increase of the specific surface energy, but also structural changes in certain mineral components of the starting mixture, causing an increase of their reactivity, followed by intensified mass transfer during sintering. In this way, the sintering process was made more efficient, and the degree of the reactions occurring in the solid phase during the formation of the clinker mineral was higher. The effects of the mechanical activation method were also evident in the results of diffractometric analyses of the main clinker minerals. An increase of the tricalciumsilicate content from 51%, in the clinker produced from the inactivated raw material mixtures, to 62%, in the clinker produced from the activated mixture, at the sintering temperature of 1350C, (about 100C lower than the temperature which is standard for cement clinker production), was registered.

Key words: mechanical activation, vibro mill, portland cement clinker, sintering




J. Serb. Chem. Soc. 62(4) 367-369 (1997)
JSCS-2393
UDK 546.15:543.242:546.215
Note
 


NOTE
Simulation of iodine oxidation by hydrogen peroxide in acid media, on the basis of the model of Bray-Liebhafsky reaction

MIRJANA RADENKOVIC, GUY SCHMIT* and LJILJANA KOLAR-ANIC**

Vinca Institute of Nuclear Science, P.O.Box 522, YU-11001, Belgrade,
*Faculty of Applied sciences, U. L. B. CP-165, B-1050 Bruxelles, Belgium and
**Faculty of Science, University of Belgrade, P.O.Box 137, YU-11001 Belgrade, Yugoslavia

(Received 15 November 1996)
The kinetics of iodine oxidation by hydrogen peroxide in acid media has been investigated. The Bray-Liebhafsky oscillatory reaction takes place in the same reaction system and the process of iodine oxidation by hydrogen peroxide presents an important part of its mechanism. The dependence of the rate of iodine oxidation by hydrogen peroxide presents an important part of its mechanism. the dependence of the rate of iodine oxidation on the initial value of the hydrogen peroxide concentration, [H2O2]0, and the existence of an unusual phenomenon, the maximum value of the experimentally found reaction rate constant, in respect to [H2O2]0 have been successfully simulated on the basis of a kinetic model of the Bray-Liebhafsky reaction.

Key words: Bray-Liebhafsky reaction, iodine oxidation, kinetic models




J. Serb. Chem. Soc. 62(4) 371-374 (1997)
JSCS-2394
UDK 546.623:541.5:541.127.1
Original scientific paper
 


Kinetic determination of Al(III) in solution

RANGEL P. IGOV, VIOLETA D. MITIC and TODOR G. PECEV

Department of Chemistry, Faculty of Philosophy, University of Nis, Cirila i Metodija 2, YU-18000 Nis, Yugoslavia

(Received 9 July, revised 6 December 1996)
A new kinetic method is elaborated for the determination of Al(III) traces in solution, on the basis of their inhibiting effect on purpurin oxidation by H2O2 in boric buffer catalyzed by Co(II) ions. Using a spectrophotometric technique, a sensitivity of 6.010-8 to 1010-8 g cm-3 Al(III) was achived. The relative error was 1.8 % to 5.7% for Al(III) in the concentration intervals of  5.010-8 to 1010-8 g cm-3. The kinetic equations for this process are given. The method has relatively good selectivity.

Key words: aluminum, kinetic determination, purpurin




J. Serb. Chem. Soc. 62(4) 375-380 (1997)
JSCS-2395
UDK 546.492:543.06:541.127.1
Original scientific paper

A new kinetic method for the determination of Hg(II)

R. P. IGOV, G. MITIC, S. MILETIC and S. MITIC

Department of Chemistry, Faculty of Philosophy, University of Nis, Cirila i Metodija 2, YU-18000 Nis, Yugoslavia

(Received 20 September 1996, revised 6 January 1997)
A kinetic method is described for the determination of Hg(II) based on its inhibiting effect on the oxidation of sodium 2-thiosemicarbazone-1,2-naphthoquinone-4-sulphonate by hydrogen peroxide. The sensitivity of the method is 0.1 g cm-3. The relative error ranges between 2.4 and 13.5% for the concentration interval 1.0 to 0.2 g cm-3. The effect of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. Kinetic equations were proposed for the investigated process.

Key words: kinetic method, mercury determination, sodium 2-thio-semicarbazone-1,2-naphthoquinone-4-sulphonate




J. Serb. Chem. Soc. 62(4) 381-386 (1997)
JSCS-2396
UDK 546.26:541.18.08:543.545
Original scientific paper
 


Separation of C60 and its radical adducts by high performance liquid chromatography (HPLC)

ZORAN SAPONJIC and NADA DIMITRIJEVIC

Laboratory for Radiation Chemistry and Physics, Vinca Institute of Nuclear Science, P.O.Box 522, YU-11001, Belgrade, Yugoslavia

(Received 20 September, revised 19 November 1996)
The possibility of separating a mixture of radical adducts of fullerene was investigated using non-aqueous reversed-phase HPLC on C18 silica. Mobile phases of different compositions, all containing benzene as a main solvent, were used. Results have shown that the separation factors increase with increased concentration of polar solvent in the mobile phase. Also, a better separation was obtained with polar solvents of higher dielectric constants, the order of separation was as follows: acetonitrile > methanol > propanol-2 > i-butanol.

Key words: fullerene, HPLC, radical adducts


J. Serb. Chem. Soc. 62(4) 387 (1997)

Errata



 


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