JSCS Vol 72, No. 7
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J. Serb.
Chem. Soc. 72 (7) 635–641 (2007)
UDC 547–304.9+547.4:615.28, JSCS–3596, doi: 10.2298/JSC0707635L; Original scientific paper
Studies on bioactive bis-1,3,5-triazinyl
dithiocarbAMates
V. D. LUNAGARIYA, R. M. DESAI and V. H.
SHAH
Department of Chemistry,
(Received 9 November 2005, revised 4 May 2007)
The compounds bis(4,6-dichloro/bis[(p-methoxyphenyl)AMino]-1,3,5--triazin-2-yl)1,2-hydrazine-1,2-dicarbodithioate/1,4-phenylenebis(carbAModithioate)/(1,1’-biphenyl)-4,4’-diylbis(carbAModithioate)/(sulphonyldi-4,1-phenylene)-bis(carbAModithioate/1,2-ethanediylbis(carbAMothioate) 4a–j were
synthesized by two different methods. In the first method (A) for
the preparation of 4a–e, 2,4,6-trichloro-1,3,5-triazine 1 was condensed with
diAMmonium 1,2-hydrazine-1,2-dicarbodithioate/1,4-phenylenebis(carbAModithioate)/(1,1’-biphenyl)-4,4’diylbis(carbamodithioate)/(sulphonyl-di-4,1-phenylene)-bis(carbAModithioate)/1,2-ethanediylbis(carbAModithioate)
3a–e to afford 4a–e which undergo reaction with p-methoxyaniline
to afford 4f–j. In the second
method (B) of preparation, 1 was condensed with p-methoxyaniline
to yield 2 followed by the action of 3a–e to yield 4a–j.
The structure of the newly synthesized compounds 4a–j was established
on the basis of elemental analyses, as well as IR and 1H-NMR spectroscopy. The
antimicrobial activities of compounds 4a–j were determined by the
cup‑plate method against grAM-positive bacteria, grAM-negative bacteria and
fungi. All the synthesized compounds showed significant antimicrobial activity.
Keywords: 1,3,5-triazine,
dicarbAModithioates, antimicrobial activity.
Full Article - PDF 183 KB
J. Serb.
Chem. Soc. 72 (7) 643–654 (2007)
UDC 547.822:544.021+66.011:615:519.876.5,
JSCS–3597 doi: 10.2298/JSC0707643D; Original scientific paper
Location of the hydrophobic pocket in the
binding site of fentanyl analogs in the m-opioid receptor
LJILJANA DOSEN–MICOVIC, MILOVAN IVANOVIC and VUK MICOVIC
Faculty of Chemistry, University of Belgrade, Studentski trg 16,
P.O.Box 158,11000 Belgrade and Center for Chemistry, ICTM, 11000
(Received 20 June 2006, revised 20 February 2007)
Fentanyl is a highly potent and clinically widely used
narcotic analgesic. The synthesis of its analogs remains a challenge in an
attempt to develop highly selective m-opioid receptor agonists with specific
pharmacological properties. In this paper, the use of flexible molecular
docking of several specific fentanyl analogs to the m-opioid receptor model, in order to
test the hypothesis that the hydrophobic pocket accommodates alkyl
groups at position 3 of the fentanyl skeleton, is described. The stereoisomers
of the following compounds were studied: cis- and trans-3-methylfentanyl,
3,3-dimethylfentanyl, cis- and trans-3-ethylfentanyl, cis-
and trans-3-propylfentanyl, cis-3-isopropylfentanyl and
cis-3-benzylfentanyl. The optimal position and orientation of these
fentanyl analogs in the binding pocket of the m-receptor, explaining their enantiospecific potency,
were determined. It was found that the 3-alkyl group of cis-3R,4S
and trans-3S,4S stereoisomers of all the active compounds occupies
the hydrophobic pocket between TM5, TM6 and TM7, made up of the AMino acids
Trp318 (TM7), Ile322 (TM7), Ile301 (TM6) and Phe237 (TM5). However, the fact
that this hydrophobic pocket can also accommodate the bulky 3-alkyl
substituents of the two inactive compounds: cis-3-isopropylfentanyl,
and cis-3-benzylfentanyl, indicates that this hydrophobic pocket in the
employed receptor model is probably too large.
Keywords:
molecular modeling, fentanyl analogs, ligand–receptor interactions, docking
simulation
Full Article - PDF 848 KB
J. Serb.
Chem. Soc. 72 (7) 655–663 (2007)
UDC
546.36*137+582.293.378+66.061+54–145.15, JSCS–3598, doi: 10.2298/JSC0707665G;
Original scientific paper
Partitioning
of π-electrons in rings of aza-derivatives of naphthalene
IVAN GUTMAN, BORIS FURTULA and RADMILA KOVACEVIC
Faculty of Science, University of Kragujevac, P.O.Box 60, 34000
(Received 23 August 2006, revised 9 February 2007)
A recently proposed method for calculating the
π-electron contents (EC) of rings of heteroatom-containing polycyclic
conjugated molecules was applied to the aza-derivatives of naphthalene. The
main finding was that a nitrogen atom in position α (resp. β) diminishes (resp.
increases) the EC-value of the respective ring. Such a regularity in the
displacement of π-electrons can be (qualitatively) rationalized by means of
resonance-theoretical reasoning.
Keywords:
π-electron content of ring, heterocyclic conjugated molecules, quinoline,
isoquinoline, resonance theory.
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J. Serb. Chem. Soc. 72 (7) 665–671
(2007)
UDC 547.537:541.6+512.62:539.194,
JSCS–3599, doi: 10.2298/JSC0707665G; Original scientific paper
Relating
resonance energy with the Zhang–Zhang polynomial
SABINA GOJAK, IVAN GUTMAN*, SLAVKO RADENKOVIC* and ANDREJ VODOPIVEC**
Faculty of Science, University of Sarajevo, Bosnia and
Herzegovina,
*Faculty of Science, University of Kragujevac, P. O.
Box 60, 34000
**Department of Mathematics, IMFM, 1000
(Received 23 October 2006, revised 9 February 2007)
The Zhang–Zhang polynomial ζ(x) is a recently conceived tool in the mathematical
apparatus of theoretical chemistry. It combines (in a quantitative manner) the
Kekulé- and Clar-structure-based features of benzenoid molecules. It is shown
that the topological resonance energy (TRE) can be accurately
approximated as , where x ≈ 0.5, by which fact a significant
insight is gained into the structure-dependence of TRE of benzenoid
molecules.
Keywords:
benzenoid hydrocarbons, Kekulé structures, Clar structures, Zhang–Zhang
polynomial, resonance energy
Full Article - PDF 329 KB
UDC
546.36*137+582.293.378+66.061+54–145.15, JSCS–3600, doi: 10.2298/JSC0707673C;
Original scientific paper
Extraction of 137Cs from Cetraria
islandica lichen using acid solutions
ANA
CUCULOVIC, DRAGAN VESELINOVIC* and ŠĆEPAN S. MILЈANIC*
INEP-Institute for the Application of Nuclear Energy, Banatska 31b,
11080
*University of Belgrade, Faculty of Physical Chemistry,11001 Belgrade,
P.O. Box 137, Serbia
(Received 17 April 2006, revised 1 December 2006)
The extraction of 137Cs sorbed in sAMples
of C. islandica using acid solutions was investigated. An equation describing
the reduction of the 137Cs content in a dry lichen sAMple with the
number of volumes of acid solutions used for successive extractions was used.
The possibility of the existence of two different types of sorption of 137Cs
in the lichen was confirmed. Acid rains were shown to influence the extraction
of 137Cs.
Keywords: 137Cs
sorption, extraction of 137Cs from lichen, C. islandica lichen, acid
solutions.
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J. Serb.
Chem. Soc. 72 (7) 679–686 (2007)
UDC
546.831+546.226:66.095.21.097:66.022.362, JSCS–3601, doi: 10.2298/JSC0707679Z; Original scientific paper
Content of sulfates and their stability –
key factors determining the catalytic activity of sulfated zirconia catalysts
ALEKSANDRA ZARUBICA, PAULA PUTANOV* and
GORAN BOSKOVIC
Faculty of Technology, University of Novi
Sad, Cara Lazara 1, 21000
*Serbian Academy of Sciences and Arts, Knez
Mihajlova 35, 11000
(Received 27 October 2006)
Two series of sulfated zirconia catalysts were
synthesized from various precursors using mono- or multi-step sequence
preparations under laboratory conditions. Their activities/selectivities in
the isomerization reaction of n-hexane
were correlated to their textural, structural and morphological properties. The
slightly higher activity of a commercially sulfated Zr(OH)4-based
catalyst is in agreement with the differences in the content of SO42--
ions and their thermal stability, textural and structural properties, i.e., crystallite size and possible
imperfection of the incorporation of sulfate groups in the multi-step
synthesis of the catalyst having a nitrate origin. The employment of H2
as the carrier gas resulted in no catalytic activity, regardless of the
catalyst precursor, preparation method and calcination temperature. When the
isomerization reaction was performed under He, the relatively short life-times
of all catalyst sAMples were caused by fast deactivation due to coking in the
absence of H2.
Keywords: sulfated zirconia, sulfate contents, isomerization of n-hexane, activity, textural, structural
and morphological properties
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J. Serb. Chem. Soc. 72 (7) 687–698 (2007)
UDC 669.141.24+678.774:541.183:620.193, JSCS–3602, doi: 10.2298/JSC0707687C; Original scientific paper
Corrosion
inhibition of iron in hydrochloric acid by polyacrylAMide
DRAGICA CHAMOVSKA, MAJA CVETKOVSKA and TOMA GRCHEV
Faculty of Technology and Metallurgy, St. Cyril and Methodius
University, 1000 Skopje, FYRO
(Received 3 August 2006, revised 15 February
2007)
The corrosion protection and/or adsorption of
polyacrylAMide (PAA) of number average molecular weight, , between 15,000 – 1,350,000 g mol-1
on mild steel and iron (99.99 % Fe) in 3 M HCl at room
temperature was studied using spectrophotometry (the phenanthroline method),
the weight loss method and EIS (Electrochemical Impedance Spectroscopy). It was
found that the corrosion protecttion efficiency of the
PAA – adsorbed layers strongly depends on both the molar
concentration of PAA in the solution and its molecular weight, reaching
limiting values between 85 and 96 %. Simultaneously, it was also concluded
that a relatively high surface coverage could
be obtained with very low PAA concentrations (0.5 – 2 ppm),
indicating the good adsorption characteristics of PAA on mild steel and iron in
hydrochloride acid. The experimentally obtained results follow a Langmuir
adsorption isotherm. According to the best fitting parAMeters, the adsorption
coefficient B ranged between 2×107 and 4×108
mol-1 and depended strongly on the molecular weight of the PAA:
B = k (for a ≈ 0.67 and k = 2.95×104) or the size of the polymer coil. As
was found by EIS, the thickness of the adsorbed PAA layer was approx.
1.1 nm (for er = 15)
and corresponded only to the polymer segments attached to the metal surface. On
the other hand, as was found by ellipsometry, the limiting layer of the
adsorbed PAA molecules was highly voluminous and relatively thick
(100 – 200 nm), containing entangled polymer coils.
Keywords: mild steel, corrosion inhibition, polyacrylAMide, electrochemical impedance
spectroscopy, adsorption isotherm.
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J. Serb. Chem. Soc. 72 (7) 699–708 (2007)
UDC 66.094.1+546.92:544.35:66–911.48, JSCS– 3603, doi: 10.2298/JSC0707699E; Original scientific paper
Oxygen
reduction at platinum nanoparticles supported on carbon cryogel in alkaline
solution
N. R. ELEZOVIC, B. M. BABIC*, LJ. M. VRACAR** and N. V. KRSTAJIC**
Center for Multidisciplinary Studies, University of Belgrade,
*Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001
**Faculty of Technology and Metallurgy, University of Belgrade,
The oxygen reduction reaction was investigated in 0.1 M NaOH solution,
on a porous coated electrode formed of Pt particles supported on carbon
cryogel. The Pt/C catalyst was characterized by the X-ray diffraction (XRD),
transmission electron microscopy (TEM) and cyclic voltAMmetry techniques. The
results demonstrated a successful reduction of Pt to metallic form and
homogenous Pt particle size distribution with a mean particle size of about 2.7
nm. The ORR kinetics was investigated by linear sweep polarization at a
rotating disc electrode. The results showed the existence of two E – log j regions, usually referred to polycrystalline
Pt in acid and alkaline solution. At low current densities (lcd), the Tafel
slope was found to be close to –2.3RT/F, while at high current densities (hcd)
it was found to be close to –2×2.3RT/F. It is proposed that the main path in
the ORR mechanism on Pt particles was the direct four-electron process, with
the transfer of the first electron as the rate determining step. If the
activities are expressed through the specific current densities, a small
enhancement of the catalytic activity for Pt/C was observed compared to that of
polycrystalline Pt. The effect of the Pt particle size on the electrocatalysis
of oxygen reduction was ascribed to the predominant (111) facets of the
platinum crystallites.
Keywords: oxygen reduction reaction, Pt nanoparticles, carbon support, alkaline
solutions
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J. Serb. Chem. Soc. 72 (7) 709–712 (2007)
UDC 547.261+66.094.3+544.032.4:541.124, JSCS– 3604, doi: 10.2298/JSC0707709L; Extended abstract
EXTENDED ABSTRACT
The
kinetics and mechanism of methanol oxidation on Pt and PtRu catalysts in
alkaline and acid media
JELENA LOVIĆ
ICTM–Department of Electrochemistry, Njegoseva 12, 11001
(Received 29 January 2007)
The kinetic of methanol electrochemical oxidation for a series of
platinum and platinum–ruthenium catalysts was investigated. A correlation
between the beginning of OHad adsorption and methanol oxidation was
demonstarated on Pt single crystals and Pt nanocatalyst. The activity of the
nano-structured Pt catalyst was compared with single crystal platinum
electrodes assuming the Kinoshita model of nanoparticles. The ruthenium-containing
catalysts shifted the onset of methanol oxidation to more negative potentials.
The effect was more pronounced in acid than in alkaline media. Based on the
established diagnostic criteria, the reaction between COad and OHad
species according to the Langmuir–Hinshelwood mechanism was proposed as the
rate determining step in alkaline and acid media on Pt and PtRu catalysts.
Keywords: methanol oxidation, role of anions, temperature effect, reaction
mechanism.
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J. Serb. Chem. Soc. 72 (7) 713–722 (2007)
UDC 666.266+678.686:66–977:53.083.98, JSCS–3605, doi: 10.2298/JSC0707713P; Original scientific paper
The influence of high and low temperatures
on the impact properties of glass–epoxy composites
SLAVISA PUTIC, MARINA STAMENOVIC, BRANISLAV BAJCETA, PREDRAG STAJCIC and
SRDJAN BOSNJAK*
Faculty of Technology and Metallurgy, Belgrade, Republic of Serbia
*Faculty of Mechanical Engineering, Belgrade,
(Received 5 December 2005, revised 29 November 2006)
The aim of this paper is to present the influence of high and low
temperatures on the impact properties glass–epoxy composites. The impact strength
an is presented for four different glass–epoxy composite structures at three
different temperatures, i.e., at room
temperature t = 20 °C, at an elevated temperature t = +50 °C and at a low
temperature t = –50 °C. Standard mechanical testing was carried out on the
composite materials with specific masses of reinforcement of 210 g m-2
and 550 g m-2 and orientations 0°/90° and ±45°. Micromechanical
analysis of the failure was performed in order to determine real models and
mechanisms of crack and temperature influence on the impact properties.
Keywords: glass woven–epoxy composite material, impact test, high and low
temperature impact tests, micromechanical analysis
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UDC 66.094.3+678.664+621.78.063+544.478, JSCS–3606, doi: 10.2298/JSC0706723C; Original scientific paper
Thermo-oxidative stability of waterborne
polyurethanes with catalysts of different selectivity evaluated by
non-isothermal thermogravimetry
SUZANA M. CAKIC, GORAN S. NIKOLIC and JAKOV V. STAMENKOVIC
Faculty of Technology, Bulevar oslobodjenja 124, 16000
(Received 11 January 2006, revised 12 March 2007)
Abstract: Thermogravimetry was used for the evaluation of the
thermo-oxidative stability of waterborne polyurethanes (wbPUR) containing
catalysts of different selectivity. From Arrhenius plots, activation energies
of between 50 and 120 kJ mol-1 for wbPUR were determined, depending
on the temperature interval, selectivity of the catalyst and degree of
degradation. Waterborne polyurethanes without catalyst showed lower thermal
stability than waterborne polyurethanes with catalysts of different
selectivity. Non-isothermal thermogravimetry indicated the presence of
different degradation processes and enabled the kinetics parAMeters at higher
degrees of degradation to be evaluated.
Keywords: waterborne polyurethanes, thermo-oxidation, thermogravimetry,
thermal stability, activation energy.
Full Article -
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Copyright
&AMp; copy; SHD 2007.
July 08, 2007.
For more information contact: JSCS@tmf.bg.ac.yu