JSCS - Vol 63, No1

J. Serb. Chem. Soc. 63(1) 1-6 (1998)
UDC 547.816:66.095.25
JSCS-2500
Original scientific paper

Condensation and ring closure reactions of 2,3-dihydro-1H-naphtho[2,1-b]pyran-4-one

M. R. SELIM

Chemistry Department, Faculty of Science, Al-Azhar University, Nasr City, Cairo, Egypt

(Received 8 June 1997)
The reaction of 2,3-dihydro-1H-naphtho[2,1-b]pyran-4-one (1) with semicarbazide or thiosemicarbazide gave the corresponding semicarbazone and thiosemicarbazone derivatives, respectively. Condensation of 1 with malononitrile or ethyl cyanoacetate produced 4-dicyanomethylene-2,3-dihydro-1H-naphtho[2,1]pyran and 4-cyanocarboethoxymethylene-2,3-dihydro- 1H-naphtho[2,1-b]pyran, respectively. Interaction of 1 with hydrazine hydrate produced the corresponding hydrazone derivative. The latter condensed with phenyl isothiocyanate to furnish the phenyl thiosemicarbazone derivative, which underwent cyclocondensation with chloroacetic acid in pyridine to produce the thiohydantoin derivative, while in ethanol and sodium acetate gave the thiazolidinone derivative. Interaction of 1 with sulfur and malononitrile gave the thienopyran derivative.

Key words: naphthopyranone derivatives, condensation reactions of, ring closure reactions.

J. Serb. Chem. Soc. 63(1) 7-11 (1998)
UDC 547.673:581.135.5
JSCS-2501
Original scientific paper

Anthraquinones from the lichen Xanthoria parietina

N. T. MANOJLOVIC, S. SOLUJIC, S. SUKDOLAK and LJ. KRSTIC*

Institute of Chemistry, Faculty of Science, P.O.Box 60, YU-34000 Kragujevac and
*Institute of Chemistry, Technology and Metallurgy, Njegoseva 12, YU-11000 Belgrade, Yugoslavia

(Received 2 July, revised 16 October 1997)
Four anthraquinones, physcion, fallacinal, fallacinol and emodin, and two polyols, mannitol and arabitol, were isolated from the lichen Xanthoria parietina. The structures of the anthraquinones were confirmed by their spectral data (NMR) and by comparison with known related compounds. The anthraquinones were tested for their antifungal activity and the minimal inhibitory concentrations were in the range 90-100 µg/ml. The inhibition effect depends on the presence of substituents (OH, OMe and OCOMe) at the C-1 and C-8 atoms of the molecule.

Key words: Xanthoria parietina, anthraquinones, antifungal activity.

J. Serb. Chem Soc. 63(1)13-19(1998)
UDC 547.416:542.93
JSCS-2502
Original scientific paper

Kinetics of the hydrolysis of N,N,N-tris(2-chloroethyl)amine

ZORAN T. LUKOVIC, BRATISLAV Z. JOVANOVIC* and NIKOLA K. BOCVAROV

Military Technical Institute, Kataniceva 15, YU-11000 Belgrade and
*Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11000 Belgrade, Yugoslavia

(Received 13 June, revised 16 October 1997)
The kinetics data for the uncatalyzed hydrolysis of N,N,N-tris(2-chloroethyl)-amine were obtained by applying a computer program for compiling and statistically processing experimental data obtained from changes in the specific conductivity of the reaction mixture with time are presented. Such a methodological approach can also be applied to following the reaction kinetics of the other reaction systems based on the changes in various physico-chemical parameters with time.

Key words: N,N,N-tris(2-chloroethyl)amine, hydrolysis of 2-haloethylamine, kinetics of hydrolysis, conductometric method, fitting of experimental data.

J. Serb. Chem. Soc. 63(1)21-24(1998)
UDC 612.621.3:612.616.3
JSCS-2503
Short communication

SHORT COMMUNICATION

Chemical behavior of 3,17b-dipropionoxy-9a-hydroxyestra-1,3,5(10)-trien-6-one

MARIJA N. SAKAC, DUSAN A. MILJKOVIC, KATARINA M. PENOV-GASI and JULIJANA A. PETROVIC

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

(Received 16 May, revised 22 September 1997)
The title compound was obtained in a yield of 45%, by the oxidation of estradiol dipropionate (1) using the chromium (VI) oxide-dimethyl pyrazole complex. The action of thionyl chloride in pyridine upon 2 afforded ,17b-dipropionoxy-6-hydroxyestra- 1,3,5(10),6,8(9)-pentaene (4) in a yield of 34.4%. Under the described dehydration reaction conditions, 3,17b-dipropionoxyestra- 1,3,5(10),9(11)-tetraen-6-one (3) and 3,17b-dipropionoxy-9x-chloroestra-1,3,5(10)-trien-6-one (5) were also formed.

Key words: estradiol derivatives, oxidation of estradiol dipropionate.

J. Serb. Chem. Soc. 63(1) 25-30 (1998)
UDC 539.144.3/.184
JSCS-2504
Original scientific paper

On the pairing of molecular orbital energy levels of heteroconjugated molecules

IVAN GUTMAN, SWARNA M. PATRA* and RAMA K. MISHRA*

Faculty of Science, University of Kragujevac, P.O. Box 60, YU-34000 Kragujevac, Yugoslavia and
*Chemical Physics Group, Department of Chemistry, Sambalpur University, Jyoti Vihar 768019, India

(Received 11 July 1997)
The pairing theorem (discovered by Coulson and Rushbrooke in 1940) predicts pairing of the molecular orbital energy levels of alternant hydrocarbons, as calculated within the Huckel molecular orbital (HMO) model. In the general case, the pairing theorem does not apply to nonalternant hydrocarbons or alternant conjugated systems containing heteroatoms. It was recently observed that, in certain heteroconjugated molecules (both alternant and nonalternant), some HMO energy levels remain paired irrespective of the nature of the heteroatoms, i.e., irrespective of the values of the HMO parameters h and k. We now provide an explanation of this regularity.

Key words: Pairing theorem, heteroconjugated molecules, H?ckel molecular orbital theory, chemical graph theory.

J. Serb. Chem. Soc. 63(1) 31-40 (1998)
UDC 547.62:547.672
JSCS-2505
Original scientific paper

Wiener indices of benzenoid hydrocarbons containing two linear polyacene fragments

IVAN GUTMAN and VLADIMIR JOVASEVIC

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

(Received 4 September 1997)
Using a recenetly developed method for calculating the Wiener index (W), a general expression is deduced for W of a benzenoid hydrocarbon B (a,b), containing two linear polyacene side chains, with a and b hexagons, respectively, attached to a benzenoid system B = B (0,0), a + b = h = const. It is shown that W {B(a,b)} is a quadratic function of a and/or b. This function usually attains its minimum at a = b or a = b + 1, but for pertinently chosen benzenoid systems B, the minimum can be at any value of a, 1 < a < h.

Key words: Wiener index, benzenoid molecules, elementary edge-cuts.

J. Serb. Chem. Soc. 63(1) 41-51 (1998)
UDC 668.819.45:541.138.2/.3
JSCS-2506
Original scientific paper

Electrochemical study of metal-tetrasulfonated phthalocyanines adsorbed on gold, platinum and iron electrodes and their role in electrochemical oxygen reduction

TANJA R. VIDAKOVIC, MILKA L. AVRAMOV-IVIC*, VERA Z. IVANOVIC, S. K. ZECEVIC and B. Z. NIKOLIC

Faculty of Technology and Metallurgy, Karnegijeva 4, University of Belgrade, P.O.Box 494, YU-11001 Belgrade and
*ICTM-Centre for Electrochemistry, University of Belgrade, Njegoseva 12, Belgrade, Yugoslavia

(Received 13 August, revised 14 October 1997)
Cyclic voltammetric studies of iron- and cobalt-tetrasulfonated phthalocyanine (FeTSPc, CoTSPc, or MeTSPc) adsorbed on Au, Pt, (polycrystalline and low index plane single-crystals) and Fe, as well as of oxygen reduction have been performed. Redox processes which are seen in the case of MeTSPc adsorption on carbon surfaces, are not observed here. The effect of MeTSPc adsorbed on Au and Pt on oxygen reduction in alkaline medium is rather inhibitive, on Au/MeTSPc in acidic solution is negligible, while catalysis was observed on Fe/MeTSPc surface in alkaline medium. The catalytic effect of the Fe/MeTSPc surface can be connected with a change in the oxide film properties.

Key words: cyclic voltammetry, phthalocyanine, macrocyclic, adsorption, oxygen reduction, catalysis, oxide film.

J. Serb. Chem. Soc. 63(1) 53-62 (1998)
UDC 691.71:620.193:678.674-002.4
JSCS-2507
Original scientific paper

The acid resistance and corrosion stability of polyester coatings on phosphatized steel

VESNA MISKOVIC-STANKOVIC and NATASA DJORDJEVIC*

Faculty of Technology and Metallurgy, University of Belgrade, P.O.Box 494, YU-11000 Belgrade and
*Institute for Technology of Nuclear and Other Mineral Raw Materials, Franse d'Eperea 86, YU-11000 Belgrade, Yugoslavia

(Received 8 October 1997)
Protective polyester coatings on phosphatized steel were obtained with different combinations of diols (2-butyl-2-ethyl-1,3-propanediol or 2,2-dimethyl-1,3-pro-pa-ne-diol), organic acids (1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydrophthalic acid anhydride or adipic acid) and hexamethoxymethylme-lamine as a crosslinking agent. The acid resistance and corrosion stability of these coatings were investigated during exposure to different corrosive agents (30% H₂SO₄, 3% NaCl) using the acid resistance test, electrochemical impedance spectroscopy (EIS) and measurement of the film thickness, gloss and hardness. It was shown that coatings based on polyesters with more branched structures of the diol (2-butyl-2-ethyl-1,3-propanediol) and of the organic acid (hexahydrophthalic acid anhydride), which enable better crosslinking, exhibit better acid resistance and corrosion stability. Coatings with the optimal polyester/melamine ratio, which is close to the theoretical ratio for complete crosslinking, also show better protective properties.

Key words: polyester coatings, corrosion, electrochemical impedance spectroscopy.

J. Serb. Chem. Soc. 63(1) 63-73 (1998)
UDC 691.6:66.065
JSCS-2508
Original scientific paper

Nucleation and crystallization of cordierite glass

MIHAJLO B. TOSIC, NIKOLA S. BLAGOJEVIC,* LJUBICA M. PAVLOVIC and MIRJANA A. DJURICIC

Institute of the Technology of Nuclear and Other Mineral Raw Materials, Franse d'Epere 86, YU-11000 Belgrade and
*Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11000 Belgrade, Yugoslavia

(Received 5 February, revised 29 August 1997)
This paper presents the experimental results of a DTA investigation of the nucleation and crystallization in cordierite glass containing 7.9 mol% TiO₂. The temperature of the maximum nucleation rate of m-cordierite was determined to be T_n = 730 + 5 °C. The temperature T_n is lower than the transformation temperature T_g which indicates that homogeneous nucleation of µ-cordierite does not occur in this glass. The methods of DTA and optical microscopy agree in terms of determining T_n. The curve of the nucleation rate determined by DTA does not correspond to the curve determined by optical microscopy. The energy of activation for the crystallization of µ-cordierite was determined to be Ea = 497 + 50 kJ/mol. The nucleation of a-cordierite in this glass could not be investigated by DTA. In all the performed experiments, the glass crystallised into m-cordierite which was then structurally transformed at higher temperatures to the phases: a-cordierite and rutile.

Key words: glass, cordierite, crystallization, nucleation.

J. Serb. Chem. Soc. 63(1) 75-84 (1998)
UDC 632.594:543.5/.54
JSCS-2509
Original scientific paper

Adsorptive stripping voltammetric determination of the herbicides atrazine and ametryne

LJUBISA M. IGNJATOVIC, DRAGAN S. VESELINOVIC, DRAGAN A. MARKOVIC and NIKOLA S. VUKELIC

Faculty of Physical Chemistry, University of Belgrade, P.O.Box 137, Belgrade, YU-11001, Yugoslavia

(Received 20 May 1997)
The optimum conditions were established for the determination of the herbicides atrazine and ametryne by differential-pulse voltammetry at a hanging mercury drop electrode in the concentration range from 1×10^-5 to 1×10^-7 mol dm^-3 using a supporting electrolyte at pH 3.0. The sensitivity of the determination can be improved through adsorptive accumulation of the investigated substances on the surface of the hanging mercury drop electrode: differential-pulse adsoprtive stripping voltammetry enables the determination of atrazine (at pH 3.0) and ametryne (at pH 3.0 and 5.0) in the concentration range from 1×10^-7 to 1×10^-9 mol dm^-3. The method described is selective: the herbicides under study can be determined in their mixture according to the dependence of the peak current on pH. The procedure was applied to the selective determination of atrazine and ametryne in various standard solutions, with results of satisfactory accuracy and precision. Recoveries were 97.5-105%.

Key words: atrazine, ametryne, adsorptive stripping voltammetry.

J. Serb. Chem. Soc. 63(1) 85-92 (1998)
UDC 533.15/.16/.17:533.6.013.12
JSCS-2510
Original scientific paper

Pressure drop in a gas-flowing solids-fixed bed contactor

ZLATICA J. PREDOJEVIC, DRAGAN Lj. PETROVIC, VLADIMIR MARTINENKO and ALEKSANDAR DUDUKOVIC*

Faculty of Technology, Bul. Cara Lazara 1, YU-21000 Novi Sad and
*Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11000 Belgrade, Yugoslavia

(Received 27 January 1997)
The influence of the velocity of the gas and solid and of the voids in the packing on the pressure drop in a gas-flowing solids-fixed bed contactor were investigated. Correlations for the pressure drop without flowing solids, in the preloading and loading regimes and the loading point are proposed.

Key words: gas-flowing solids-fixed bed contactor, pressure drop, correlations.

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