JSCS - Vol 65, No 11

JSCS Vol 65, No. 11

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J. Serb. Chem. Soc. 65(11)763–767(2000)
UDC 547.913.2/.5:547.918:547.466.1
JSCS–2801
Original scientific paper

Sesquiterpene lactones and monoterpene glucosides from plant species Picris echoides

MIRJANA MILOVANOVIC, KSENIJA PICURIC-JOVANOVIC, MIODRAG DJERMANOVIC*, VERICA DJERMANOVIC** and MILUTIN STEFANOVIC*

Faculty of Agriculture, Department of Food Technology, Nemanjina 6, P. O. Box 127, YU-11081 Zemun,
*Faculty of Chemistry, Studentski trg 16, P. O. Box 158, YU-11001 Belgrade and
**Institute of Chemistry, Technology and Metallurgy, Center for Chemistry, Njegoseva 12, YU-11000, Belgrade, Yugoslavia

(Received 20 June 2000)
Investigation of the constituents of the aerial parts of domestic plant species Picris echoides afforded the sesquiterpene lactones, i.e., guaianolides jacquilenin (1), 11-epi-jacquilenin (2), achillin (3) and eudesmanolide telekin (4). The chemical indentification of the two monoterpene glucosides (–)-cis-chrysanthenol-b-D-glucopyranoside (5) and its 6’-acetate 6 is also repoted. The guaianolide achillin (3) and the two monoterpene glucosides 5 and 6 were isolated for the first time from this plant species. Isolation was achieved by column chromatography and the structures were established mainly by the interpretation of their physical and spectral data, which were in agreement with those in the literature.
Keywords: Picris echoides, Lactuceae, sesquiterpene lactones, monoterpene glucosides.

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J. Serb. Chem. Soc. 65(11)769–772(2000)
UDC 547.923/.924:66.094.3
JSCS–2802
Original scientific paper

Peracids oxidation of cholesta-5,8-dien-3b-yl acetate

MILAN M. DABOVIC, IVANKA J. PETROVIC, NATALIJA M. KRSTIC and LJUBINKA B. LORENC

Center for Chemistry, Institute of Chemistry, Technology and Metalurgy, P. O. Box 815, YU-11001 Belgrade and Faculty of Chemistry, University of Belgrade, Studentski trg 16, P. O. Box 158, YU-11001 Belgrade, Yugoslavia

(Received 17 July 2000)
Expoxidation of cholesta-5,8-dien-3b-yl acetate (1) with peracids takes place preferentially at the more highly substituted D⁸-olefinic double bond to give: (a) with monoperphthalic acid, 8a,9a-epoxycholest-5-en-3b-yl acetate (2) (in 39 % yield) and 9a-hydroxy-5a,6a-epoxycholest-8(14)-en-3b-yl acetate (3) (in 30 % yield); and (b) with m-chloroperbenzoic acid, the 8a,9a-epoxide 2 (64 %) and 5a,6a-epoxy derivative 3 (20 %). Some chemical transformations of the obtained epoxides are described.
Keywords: cholesta-5,8-dien-3b-yl acetate, peracid oxidations, steroidal epoxides, reactivity of.

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J. Serb. Chem. Soc. 65(11)773–780(2000)
UDC 547.556.13:678.675:542.9
JSCS–2803
Original scientific paper

Synthesis of monoazo disperse dyes based on 2-aminoheterocycles and their dyeing performance on nylon fabrics

HARI RAGHAV MARADIYA and VITHAL SOMA PATEL*

V.P. and R.P.T.P. Science College, Vallabh Vidyanagar 388 120, Gujarat State, India and
*Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar 388 120, Gujarat State, India

(Received 16 May 2000)
Novel monoazo disperse dyes based on various 2-aminoheterocycles were prepared using N-methyl-N-(2-hydroxyethyl)aniline as the coupling component. All the dyes were applied as disperse dyes on nylon fabric. These dyes have been found to give a wide range of colour shades with very good depth, brightness and levelness on nylon fabric. The visible absorption spectra, elemental analysis and R_f values were investigated. The percentage dye bath exhaustion on fabric was found to be very good. The dyed fabric showed very good to excellent fastness to light, washing, rubbing and perspiration. The sublimation fastness was found to be excellent.
Keywords: nylon fabric, disperse dyes, exhaustion, fastness, 2-aminoheterocycles, N-methyl-N-(2-hydroxyethyl)aniline.

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J. Serb. Chem. Soc. 65(11)781–788(2000)
UDC 547.588.14:54.022:542.9
JSCS–2804
Original scientific paper

Determination and structural correlation of the pK_a values of p-substituted trans-2,3-epoxy-4-oxo-4-phenylbutanoic acids

L. PFENDT, G. POPOVIC*, M. KOSTIC, LJ. STEVOVIC**, B. DRAKULIC**, and I. JURANIC

Faculty of Chemistry, University of Belgrade, P. O. Box 158, YU-11001 Belgrade,
*Faculty of Pharmacy, Univeristy of Belgrade, P. O. Box 146, YU-11001 Belgrade and
**Institute of Chemistry Technology and Metallurgy, Center for Chemistry, Belgrade, Njegoseva 12, YU-11000 Belgrade, Yugoslavia

(Received 27 February, revised 28 June 2000)
The pK_a values for a series of eight p-substituted trans-2,3-epoxy-4-phenyl butanoic acids (p-substituted trans-b-aroylepoxyacrylic acids) have been determined potentiometrically in aqueous media at 25°C at an ionic strength of 0.1 mol/dm3 (NaCl). The transmission of polar effects from the substituents on the phenyl nucleus to the carboxylic group through the side chain involving a carbonyl group and an epoxide ring was investigated. The pK_a values were correlated with structure using the Hammett, Taft and Yukawa-Tsuno approaches. The Hammett r constant (0.34) was compared with analogue values for structurally similar acids.
Keywords: a,b-epoxy acids, pK_a-values, LFER, transmission coefficients, synthesis of trans-b-aroylepoxyacrylic acids.

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J. Serb. Chem. Soc. 65(11)789–798(2000)
UDC 661.8-78:543.51/.52:536.4:546.65
JSCS–2805
Original scientific paper

Spectrochemical and thermal behaviours of the 2,4- and 3,4-dimethoxybenzoates of rare earth elements

WIESLAWA FERENC and AGNIESZKA WALKÓW-DZIEWULSKA

Department of Inorganic and General Chemistry, Maria Curie-Sklodowska University, PL 20-031 Lublin, Poland

(Received 3 April, revised 17 July 2000)
The physicochemical properties and thermal stability in air of the 2,4- and 3,4-dimethoxybenzoates of rare earth elements were compared in order to observe the influence of the position of the –OCH₃ substituent on their thermal stability. The complexes of these two series are crystalline, hydrated or anhydrous salts with colours typical of trivalent rare earth ions. The carboxylate group is a bidentate, chelating ligand. The thermal stability of the 2,4- and 3,4-dimethoxybenzoates of the lanthanide elements was studied in the temperature range 273–1173 K. The positions of methoxy- groups in the benzene ring influence the number of crystallization water molecules in the complexes and their thermal stability, which is connected with the varying influence of inductive and mesomeric effects of the –OCH₃ substituent on the electron density in the benzene ring.
Keywords: 2,4- and 3,4-dimethoxybenzoates of rare earth elements, thermal stability of complexes, influence of methoxy- groups on the properties of dimethoxybenzoates, influence of substituents.

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J. Serb. Chem. Soc. 65(11)799–801(2000)
UDC 519.1/.4:339.124/.126.34/.184
JSCS–2806
Original scientific paper

No Hückel graph is hyperenergetic

I. GUTMAN, Y. HOU**, H. B. WALIKAR**, H. S. RAMANE*** and P. R. HAMPIHOLI***

Faculty of Science, University of Kragujevac, P. O. Box 60, YU-34000, Kragujevac, Yugoslavia,
*Department of Mathematics, University of Science and Technology of China, Hefei, Anhui 230026, China,
**Department of Mathematics, Karnatak University Campus, Post Bag 3, Belgaum - 509 001 India, and
***Gogte Institute of Technology, Udyambag, Belgaum - 590 008, India

(Received 10 July 2000)
If G is a molecular graph with n vertices and if l₁, l₂, ..., l_n are its eigenvalues, then the energy of G is equal to E(G) = |l₁| + |l₂|+ ... + |l_n|. If E(G) > 2n – 2, then G is said to be hyperenergetic. We show that no Hückel graph (= the graph representation of a conjugated hydrocarbon within the Hückel molecular orbital model) is hyperenergetic.
Keywords: total p-electron energy, energy of graph, hyperenergetic graphs.

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J. Serb. Chem. Soc. 65(11)803–810(2000)
UDC 662.3/.311.1/.312
JSCS–2807
Original scientific paper

Calculation of complex chemical equilibrium compositions of composite rocket propellants combustion products

MILOS FILIPOVIC and NIKOLA KILIBARDA

Military Technical Institute, Kataniceva 15, YU-11000 Belgrade, Yugoslavia

(Received 12 May, revised 3 July 2000)
An adequate method for calculating chemical equilibrium in a predominantly gaseous, multi-component reactive mixture was investigated and successfully applied. This method involves the stated equilibrium reaction scheme, including, first, the formation of chemical species, of which concentrations prevail in the mixture, then the formation of gaseous atomic species by dissociation of previous ones, and, finally, the formation of complex chemical species from the atomic species. A computer program, which permits calculations of equilibrium compositions by the iteration procedure, has been developed. The results of calculations have been compared with data obtained by the programs OPHELIE, MICROPEP, and the program SPP, as documented in the NASA-Lewis Code, which is presently the world-wide standard. All comparisons gave satisfactory agreement.
Keywords: composite propellants, combustion, combustion products, chemical equilibrium.

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J. Serb. Chem. Soc.65(11)811–818(2000)
UDC 543.544.2:661.183.7
JSCS–2808
Original scientific paper

Correlation between retention and C-18 silica gel surface coverage in reversed-phase liquid chromatography

MARIJANA M. ACANSKI, SLOBODAN M. PETROVIC, VJERA M. PEJANOVIC* and JULIJANA A. PETROVIC*

Department of Applied Chemistry, Faculty of Technology, University of Novi Sad, Bulevar cara Lazara 1, P. O. Box 340, YU-21000 Novi Sad and
*Institute of Chemistry, Faculty of Science, University of Novi Sad, Trg D. Obradovica 3, YU-21000 Novi Sad, Yugoslavia

(Received 21 October 1999)
The effect of C-18 silica gel surface coverage on the retention behaviour of some estrone derivatives in reversed phase high performance liquid chromatography has been studied. Two commercial columns with different C-18 coverage, Spherisorb ODS-1 (8 % carbon content) and Li Chrosorb RP-18 (22 % carbon content), using methanol-water as the eluent, were used.
Keywords: HPLC, reversed phase, estrone derivatives.

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J. Serb. Chem. Soc. 65(11)819–827(2000)
UDC 669.586:620.18
JSCS–2809
Original scientific paper

The structure of bright zinc coatings

NEBOJSA D. NIKOLIC, KONSTANTIN I. POPOV*, ZLATKO RAKOCEVIC**, DEJAN R. \UROVIC**, MIOMIR G. PAVLOVIC and MIODRAG STOJANOVIC***

ICTM-Institute of Electrochemistry, Njegoseva 12, Belgrade,
*Faculty of Technology and Metallurgy, Karnegijeva 4, Belgrade,
**Vinca Institute of Nuclear Sciences, Belgrade and
***Military Technical Institute YA, Kataniceva 15, Belgrade, Yugoslavia

(Received 26 June 2000)
The structures of bright zinc coatings obtained from acid sulfate solutions in the presence of dextrin/salicyl aldehyde mixture were examined. It was shown by the STM technique that the surfaces of bright zinc coatings are covered by hexagonal zinc crystals, the tops of planes of which are flat and mutually parallel and which exhibit smoothness on the atomic level. X-Ray diffraction (XRD) analysis of the bright zinc coatings showed that the zinc crystallites are oriented in the (110) plane only.
Keywords: bright zinc coating, STM technique, X-ray diffraction analysis.

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J. Serb. Chem. Soc. 65(11)829–837(2000)
UDC 541.182.43-002.2:678.742
JSCS–2810
Original scientific paper

Characterization of water-in-oil emulsions produced with microporous hollow polypropylene fibers

GORAN T. VLADISAVLJEVIC, SABINE BRÖSEL* and HELMAR SCHUBERT*

Institute of Food Technology and Biochemistry, Faculty of Agriculture, University of Belgrade, P. O. Box 127, YU-11081 Belgrade-Zemun, Yugoslavia, and
*Institute of Food Process Engineering, Faculty of Chemical Engineering, Universiti of Karlsruhe (TH), Kaiserstrasse 12, D-76128 Karlsruhe, Germany

(Received 20 December 1999)
The preparation of fine and monodispersed water-in-oil (W/O) emulsions by utilizing hydrophobic hollow polypropylene fibers with 0.4 mm pores was investigated in this work. The experiments were carried out using demineralized water as the disperse phase, mineral oil Velocite No. 3 as the continuous phase, and polyglycerol polyricinoleate (PGPR 90) in the concentration range of 2.5 – 10 wt % as the oil-soluble emulsifier. The size of the water droplets in the prepared emulsions and the droplet size distribution strongly depend on the content of the disperse phase, the transmembrane pressure difference, and the emulsifier concentration. Stable emulsions with a very narrow droplet size distribution and a mean droplet diameter lower than 0.27 µm were produced using 10 wt % PGPR 90 at a pressure difference below 30 kPa.
Keywords: emulsification, membrane emulsification, water-in-oil emulsions, hollow fiber, polypropylene hollow fibers.

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