J. Serb. Chem. Soc. 62(10) 915-943 (1997)
Electrically and optically active polymers - perspective materials for electronics
Institute of Macromolecular Chemistry, Academy of Science of the
16206 Prague, Chech Republic
11 October 1996)
2. Electroactive polymers
4. From silicon to molecular chips
Key words: polymers, electrical conductivity, optical activity, electronic materials
Electrical conductivity of poly(acrylic acid) gels
J. V. STAMENKOVIC, P. I. PREMOVIC* and S. V. MENTUS**
Faculty of Technology, Leskovac,
*Faculty of Philosophy, Nis and
**Faculty of Physical Chemistry, YU-11000 Belgrade, Yugoslavia
6 February, revised 3 May 1997)
Complete solution transformation into ionically conducting hydrophilic rubber like gels occurs on g-ray polymerization of 1.5 - 10 M aqueous solutions of acrylic acid. Both the hydrophilicity and conductivity of this material are due to the volume distributed carboxylic groups. The conductivity of the gels was improved by addition of strong electrolytes, either sulphuric acid or sodium hydroxide, to the initial monomer solution. With the addition of sulphuric acid conductivities exceeding 10-1 S cm-1 were achieved.
Key words: poly(acrylic acid), electrical conductivity, gels
Structure-activity relations. Part 16. Biologically active 2,4-diphenylphthalazin-1(2H)-ones and 2,6-diphenylpyridazin-3(2H)-ones
KEITH BOWDEN, ANDREW BROWNHILL and FAISAL MALIK
Department of Biological and Chemical Sciences - Central Campus,
University of Essex,
Wivenhoe Park, Colchester, Essex, UK, CO4 3SQ
25 May 1997)
Molecular graphic studies of a series of "bleaching" herbicides, which are inhibitors of desaturation of phytoene, have led to the design, synthesis and study of substituted 2,4-diphenylphthalazin-1(2H)-ones and 2,6-diphenylpyridazin-3(2H)-ones. The former have been shown to be potent inhibitors of the desaturation of phytoene and "bleaching" herbicides.
Key words: "bleaching" herbicides, molecular modeling, structure-activity relations, desaturation of phytoene
Synthesis of 2-aryl-substituted thiazolidine-4-carboxylic acids by intramolecular cycloaddition of in situ formed azomethine derivatives of L-cysteine
RADE MARKOVIC and BILJANA RAJKOVIC
Faculty of Chemistry, University of Belgrade, P.O.Box 158, YU-11001 Belgrade, Yugoslavia
21 January 1997)
The azomethines 6, prepared from aromatic aldehydes and aniline, react with L-cysteine, affording a mixture of epimeric 2-aryl-substituted thiazolidine-4-carboxylic acids 5, which are precursors of biologically and medicinally important compounds. The key step is the formation of the arylidene Schiff base of L-cysteine 7, formed in situ by the transimination of the original Schiff base 6 with L-cysteine in the presence of a catalytic amount of mineral acid. The former as common synthetic intermediate 7, is transformed, via intramolecular cyclization, into 5 in good yields (57-71.5%).
Key words: Schiff base, L-cysteine, transimination, cycloaddition, azomethines, intramolecular cyclization
Structure-reactivity relationship in the Pd(II)-catalyzed carbonylation of cyclic and acyclic unconjugated dienes
RADE MARKOVIC and CURTIS B. ANDERSON*
Faculty of Chemistry, University of Belgrade, P.O.Box 158,
YU-11001 Belgrade, Yugoslavia
*Department of Chemistry, University of California, Santa Barbara, CA 93106, USA
16 January, revised 29 May 1997)
The oxidative catalytic carbonylation under mild experimental conditions of a series of four dienes with isolated double bonds, i.e., 1,5-cyclooctadiene, norbonadiene, dicyclopentadiene and 1,5-hexadiene, has been studied. It was shown that the structural characteristics of the starting cyclic or acyclic diene affect markedly the stereochemical outcome and reaction pathways in terms on the type and the ratio of carbonylated versus noncarbonylated products. The conversion of the stoichiometric carbonylation reaction of the s-Pd(II)-1,5-cyclooctadiene complex and the Pd(II)-p-complexes of norbornadiene and dicyclopentadiene in the catalytic process has been investigated from a preparative purposes, as well as a mechanistic point of view.
Key words: unconjugated dienes, carbonylation, catalysis, palladium
Quinolones substituted by different moieties. Part 2. Reactions of 1,2-dihydro-4-hydroxy-1-methyl-2-oxoquinoline-3-carbaldehyde with acyclic active methylene compounds
MOSTAFA M. ISMAIL, ALIM ABDEL-HALIM and MOHAMED ABASS
Chemistry Department - Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt
14 March 1997)
Some interesting heterocycles were synthsized either as substituents or fused to quinolone moiety, by condensationof 1,2-dihydro-4-hydroxy-1-methyl-2-oxoquinoline-3-carbaldehyde with some acyclic active methylene compounds, viz., malonic ester, acetoacetic ester, malononitrile, cyanocetamide, cyanomethylbenxothiazole and N-acyl (or benzoyl) glycines. Most of the newly synthesized products were identified chemically using more than one route for their preparation in order to elucidate their structures or improve their yield. Most of the obtained compounds have promising biological activity.
Key words: substituted quinolones, synthesis, structure elucidation of
Thermooxidative stability of some polyimides
KATARINA POPOV-PERGAL, MIROSLAV PERGAL, DRAGAN BABIC* and MILENA MARINOVIC*
Institute of Chemistry, Faculty of Science, University of Novi Sad, Trg Dositeja Obradovica 3, YU 21 000 Novi Sad and *The Vinca Institute of Nuclear Science, P.O.Box 522, YU-11001 Belgrade, Yugoslavia
5June 1996, revised 25 February 1997)
Different polyimide resin types were synthesized using N,N'-4,4'-bis-maleimidodiphenylmethane and five structurally different diamines. The molecular structure characteristic so used compounds were obtained by computer analysis. In addition to the previous paper, in which the thermal stability was studied in nitrogen atmosphere, the thermogravimetric characterization was performed in oxygen in order to define the thermooxidative stability of synthesized resins. The results have shown somewhat different order of thermooxidative stability compared to the findings in nitrogen atmosphere. The difference was attributed to the different structural characteristics of the studied samples.
Key words: polyimides, thermooxidative stability
hermal and structural changes during the synthesis of metaphosphate glass
SLAVICA BOGDANOV, VERICA MLADENOVIC, KATARINA KILIBARDA* and SVETLANA MITROVSKI**
Military Technical Institute, Kataniceva 15, YU-11000 Belgrade
*Serbian Glass Factory, Technical and Optical Glass, YU-35230 Paracin and
**ICTM - Center for Catalysis and Chemical Engineering, Njegoseva 12,
YU-11000 Belgrade, Yugoslavia
11 October 1996)
Methaphosphate glass was synthesized by melting a mixture of analytical grade Na-hexametaphosphate, Al-metaphosphate and silver as silver as silver nitrate. The thermal and structural changes in the courses of synthesis were investigated by DTA and IR structural analysis. The characteristic temperatures of glass transformation and softening were found to be 477°C and 522°C, respectively. The glass was characterized by measuring its thermal expansion coefficient, index of refraction and optical density. The glass was characterized by measuring its thermal expansion coefficient, index of refraction and optical density. the glass was found to be transparent in the VIS spectral region. The structure of the synthesized glass corresponded to a mixture of linear polyphosphates and cyclic metaphosphates.
Key words: metalphosphate glass, dosimeter glass, synthesis
Influence of fly ash with low content of 3CaO Al2O3 on the sulfate resistance of portland cement
MIRJANA CURIC, JONJAUA RANOGAJEC, RADOVAN OMORJAN and SASA MILETIC*
Faculty of Technology, University of Novi Sad, Bulevar Cara
YU-21000 Novi Sad and *Institute for Material Science, YU-11000 Belgrade, Yugoslavia
20 September 1996, revised 8 May 1997)
This paper presents an investigation of the resistance to the influence of sulfate solution conducted on three kinds of Portland cement with rather high content of 3CaO-Al2O3 (5.45-11.84 wt %). Also, the paper considers the resistance of all cements blended with 30 wt. % of fly ash whose 3CaO-Al2O3 content was almost negligible so as to lower the 3CaO-Al2O3 content of the mixtures to 3.82-8.29 wt %. Experiments were conducted on a 3x2 series of test samples prepared in accordance with Kind's method (GOST 4798-69). Then, they were exposed to the influence of aggressive solutions with 1 and 2 kg m-3 of SO42- ions as well as 0.320 kg m-3 of NH4+ ions. Also, pure water was used as a neutral fluid. The experiments lasted six months, while flexural strengths were measured after 1, 2, 4 and 6 months. By dividing the flexural strength of corroded samples with the strength of a referent ones a kind of corrosion resistance factor was obtained as a numerical quantifier of a sample's quality. The results were analyzed separately, no-ash samples and ash samples were considered to be two different systems. The behavior of each (under the influence the influence of both ions from the solutions in two concentrations) was considered. The samples with fly ash proved generally more resistant for all concentrations and duration of the degradation.
Key words: cement, fly ash containing cement, sulfate corrosion of cement
Catalytic determination of micro amounts of As(III) using its catalytic effect on the oxidation of sodium pyrogallol-5-sulphonate by dichromate
S. S. MITIC, V. V. ZIVANOVIC and M. V. OBRADOVIC
Department of Chemistry, Faculty of Philosophy, University of Nis, YU-18000 Nis, Yugoslavia
27 November 1996, revised 29 May 1997)
A kinetic method is described for the determination of As(III) based on its catalytic effect on the oxidation of sodium pyrogallol-5-sulphonate by Cr2O72-. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance of the colored product at 436.8 nm. Micro amounts of As(III) (0.375-3.75 µg cm-3) can be determined with good accuracy and reproducibility. The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. The kinetic parameters of both of the catalyzed and uncatalyzed reactions are reported.
Key words: As(III) determination, kinetic method, sodium pyrogallol-5-sulphonate oxidation
Comparison of two sample introduction techniques for the determination of arsenic and selenium by direct current are plasma atomic emission spectrometry DCP-AES
MILOVAN STOILJKOVIC and NEBOJSA PAVLOVIC
The Vinca Institute of Nuclear Science, Department of Physical Chemistry, P.O.Box 522, YU-11001 Belgrade, Yugoslavia
3 March 1997)
Nebulization of solution (NS) and batch mode hydride generation (HG) techniques, followed by direct current arc plasma atomic emission spectrometry (DCP-AES) were compared for trace arsenic and selenium determination. Calibration graphs and detection limits (established for standard solutions) were determined at non-standard wavelengths. About 85 and 65 times lower detection limits for As and Se, respectively, were achieved with HG than with NS. A hydride generation techniques was then used for the trace determination of arsenic in white wheat flour and selenium in commercially available Ferksevit capsules, used as a diet supplement.
Key words: arsenic, selenium, trace determination, hydride generation technique