JSCS Vol 67, No. 2
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Impresum |
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J.Serb.Chem.Soc.
67(2)69–75(2002) |
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Hydride reduction of
B-norcholestane 5a,6a-epoxide
MIRA S. BJELAKOVIC*, VLADIMIR D. PAVLOVIC,*,** and LJUBINKA
B. LORENC*,**
*Center for Chemistry, ICTM, P. O.
Box 473, YU-11001 Belgrade and
**Faculty of Chemistry, University of Belgrade, Studentski trg
12–16, P. O. Box 158, YU-11001 Belgrade, Yugoslavia
(Received
4 September 2001)
B-Norcholestane
epoxide 2 is reduced with lithium aluminium hydride to give either the 3b,6a-diol 3
or the corresponding 3b,5a-diol 4, depending on the quality of the reducing reagent
employed. A plausible mechanistic explanation of the obtained results is
suggested.
Keywords:
5a,6a-epoxy-B-norcholestan-3b-yl
acetate, 5a-hydroxy-B-norcholestan-3b-yl acetate, 6a-hydroxy-B-nor-5b-cholestan-3b-yl
acetate, lithium aluminium hydride, lithium triethylborohydride.
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J.Serb.Chem.Soc.
67 (2)77–85(2002) |
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The reactivity of a,b-unsaturated
carboxylic acids.
Part
XVI. The kinetics of the reaction of cycloalkenylcarboxylic and
cycloalkenylacetic acids with diazodiphenylmethane in various alcohols
GORDANA S. USCUMLIC, JASMINA B. NIKOLIC and VERA V. KRSTIC
Department of Organic Chemistry,
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4,
YU-11001 Belgrade, Yugoslavia
(Received
15 June, revised 19 September)
The
rate constants for the reaction of diazodiphenylmethane with
1-cyclopentenecarboxylic, 1-cycloheptenecarboxylic, cyclopent-1-enylacetic and
cyclohept-1-enylacetic acids were determined in eight alcohols at 30°C using
the appropriate UV-spectroscopic method. In order to explain the kinetic
results through solvent effects, the second order rate constants of the
examined acids were correlated using a total solvatochromic equation, of the
form: log k = Ao + sp* + aa + bb, where p* is a
measure of the solvent polarity, b represents the scale of solvent
hydrogen bond acceptor basicities and a represents the scale of solvent
hydrogen bond donor acidities. The correlations of the kinetic data were
carried out by means of multiple linear regression analysis. The opposite sings
of the electrophilic and the nucleophilic parameters are in agreement with the
well-known reaction mechanism. The results presented in this paper were
compared with the kinetic data for 1-cyclohexenecarboxylic and
cyclohex-1-enylacetic acids obtained under the same experimental conditions.
Keywords:
cycloalkenecarboxylic acids, cycloalkenylacetic acids, diazodiphenyl-methane,
kinetic measurements, protic solvents.
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J.Serb.Chem.Soc.
67(2)87–97(2002) |
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Ordering of alkane isomers by means
of connectivity indices
IVAN GUTMAN, DUSICA VIDOVIC and ANKA NEDIC
Faculty of Science, University of
Kragujevac, P. O. Box 60, YU-34000 Kragujevac, Yugoslavia
(Received
3 September 2001)
The
connectivity index of an organic molecule whose molecular graph is G is
defined as C(l) = S(dudu)1, where du
is the degree of the vertex u in G, where the summation goes over all
pairs of adjacent vertices of G and where l is a pertinently chosen exponent.
The usual value of l is –1/2, in which case c = C(–1/2) is referred to as
the Randic index. The ordering of isomeric alkanes according to c follows the
extent of branching of the carbon-atom skeleton. We now study the ordering of
the constitutional isomers of alkanes with 6 through 10 carbon atoms with
respect to C( l) for various values of the parameter l. This
ordering significantly depends on l. The difference between the
orderings with respect to c and with respect to C( l) is measured by a function D and
the l-dependence
of D was
established.
Keywords:
connectivity index, Randic index, alkanes, isomer ordering.
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J.Serb.Chem.Soc.
67 (2)99–102(2002) |
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Two theorems on connectivity
indices
IVAN GUTMAN
Faculty of Science, University of
Kragujevac, P. O. Box 60, YU-34000 Kragujevac, Yugoslavia
(Received
3 September 2001)
Two
general cases are pointed out for which the ordering of molecules according to
the connectivity index C(l) is the same for all values of the exponent l.
Keywords:
connectivity index, isomer ordering.
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J.Seb.Chem.Soc.
67 (2)103–109(2002) |
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A kinetic model for the consumption
of stabilizer in single base gun propellants
LJILJANA JELISAVAC and MILOS FILIPOVIC
Military Technical Institute,
Kataniceva 15, YU-11000 Belgrade, Yugoslavia
(Received
14 May, revised 16 October 2001)
A
suitable kinetic model for the consumption of stabilizer (diphenylamine) in
single base gun propellants was investigated and successfully verified. The
model assumes that a reaction of shifting order can be applied for the
consumption of diphenylamine in single base gun propellants. It was found that
the experimental data were well evaluated by a first-order reaction at high
concentrations of diphenylamine in the propellant, but by a zero-order reaction
at low concentrations during the final phase of the propellant life time. The
mechanism of diphenylamine depletion was discussed with relation to the model and
the ageing behavior of the propellants. The kinetic parameters of this model,
which permit the calculation of the time up to complete consumption of the
diphenylamine, were determined. The results were compared with the kinetic data
obtained by a widely accepted model, which combines formally reactions of first
and zero order, designated as an “exponential and linear” model. All
comparisons gave satisfactory agreement.
Keywords:
single base gun propellants, stabilizer (diphenylamine) consumption, chemical
stability, kinetic model.
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J.Serb.Chem.Soc.
67(2)111–113(2002) |
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N O T E
Protonation
site for anilines in aqueous media
ALEXEI N. PANKRATOV and INNA M. UCHAEVA
Department of Chemistry, N. G.
Chernyshevskii Saratov State University, 83 Astrakhanskaya Street, Saratov
410026, Russia
(Received
29 August 2001)
By
means of the PM3 method it has been shown that the protonation of 2-, 3-,
4-methoxyanilines, 4-methylthioaniline, 2-, 3-, 4-aminobenzoic acids, 2-, 3-,
4-nitroanilines in the gaseous phase proceeds via the amine nitrogen atom. The
same result, attributed to the aqueous medium, was obtained for
4-methoxyaniline, 4-aminobenzoic acid and 4-nitroaniline.
Keywords:
anilines, protonation, quantum chemical computation.
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J.Serb.Shem.Soc.
67(2)115–122(2002) |
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The synthesis and characterization
of nickel(II) and copper(II) complexes with the polydentate dialkyl
dithiocarbamic acid ligand 3-dithiocarboxy-3-aza-5-aminopentanoate
SRECKO R. TRIFUNOVIC , ZORICA MARKOVIC*, DUSAN SLADIC**, KATARINA
ANDJELKOVIC**, TIBOR SABO** and DRAGICA MINIC***
Department of Chemistry, Faculty of
Science, University of Kragujevac, P. O. Box 60, R. Domanovica 12, YU-34000
Kragujevac,
*Faculty of Metallurgy and Technology, YU-81000 Podgorica,
**Faculty of Chemistry, University of Belgrade, P. O. Box. 158,
Studentski trg 16, YU-11000 Belgrade and
***Faculty of Physical Chemistry, University of Belgrade, P. O.
Box 173, YU-11001 Belgrade, Yugoslavia
(Received
26 April, revised 3 October 2001)
Square
planar complexes of Ni(II) and Cu(II) with potassium
3-dithiocarboxy-3-aza-5-aminopentanoate have been prepared by direct synthesis.
The obtained neutral complexes were characterized by elemental analysis,
magnetic susceptibility measurements, infrared and electronic spectra. The
thermal behaviour of both the Ni(II) and Cu(II) complexes, and the ligand
itself was investigated by DSC and TG.
Keywords:
nickel(II), copper(II), dithiocarbamate, synthesis, complexes, thermal
analyses.
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J.Serb.Chem.Soc.
67(2)123–126(2002) |
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N O T E
Synthesis
and characterization of tris[butyl-(1-methyl-3-phenyl-propyl)-dithiocarbamato]-cobalt(III)
seskvitoluene
GORAN N. KALUDJEROVIC, VESNA M. DJINOVIC, SRECKO R. TRIFUNOVIC*,
ISMET M. HODZIC and TIBOR J. SABO
Faculty of Chemistry, University of
Belgrade, P. O. Box 158, Studentski trg 16, YU-11001 Belgrade and
*Department of Chemistry, Faculty of Science, University of
Kragujevac, P. O. Box 60, YU-34000 Kragujevac, Yugoslavia
(Received
24 May, revised 6 September 2001)
A
new bidentate ligand butyl-(1-methyl-3-phenyl-propyl)-dithiocarbamate (bmFpdtc) was
prepared, as the sodium salt. In the reaction of hexaaminecobalt(III) chloride
with NabmFpdtc, the
corresponding tris[butyl-(1-methyl-3-phenyl-propyl)-dithiocarbamato]cobalt(III),
[Co(bmFpdtc)3] complex
was prepared. The complex was characterized by elemental analysis, infrared,
electronic absorption, 1H and 13C-NMR
spectroscopy.
Keywords:
cobal(III) complex, dithiocarbamate, bidentate ligand.
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J.Serb.Chem.Soc.
67(2)127–134(2002) |
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Glass-ceramic enamels derived from
the Li2O-Na2O-Al2O3-TiO2-SiO2 system
DRAGICA S. GAVRILOVSKI, NIKOLA S. BLAGOJEVIC*, MILORAD P.
GAVRILOVSKI and SNEZANA R. GRUJIC*
SARTID – Institute for Metallurgy,
Goranska 12, YU–11300 Smederevo and
*Faculty of Technology and Metallurgy, University of Belgrade,
Karnegijeva 4, YU–11001 Belgrade, Yugoslavia
(Received
24 May, revised 18 October 2001)
The
results of research on the conditions for obtaining model glass-ceramic
enamels, derived from the basic Li2O-Na2O-Al2O3-TiO2-SiO2 system, by
varying the initial composition and thermal treatment conditions, are presented
in this paper. Segregation of the crystal phases in the glassy-matrix was
carried out during subsequent thermal treatment. The formation of different
crystal phases was evidenced through the results of differential-thermal
analysis and X-ray powder diffraction analysis.
Keywords:
glass-ceramic enamels, thermal treatment, silicate coatings,
crystallization.
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J.Serb.Chem.Soc.
67(2)135–142(2002) |
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Modelling glass-ceramic enamel
properties
DRAGICA S. GAVRILOVSKI, NIKOLA S. BLAGOJEVIC* and MILORAD P.
GAVRILOVSKI
SARTID – Institute for Metallurgy,
Goranska 12, YU–11300 Smederevo and
*Faculty of Technology and Metallurgy, University of Belgrade,
Karnegijeva 4, YU–11001 Belgrade, Yugoslavia
(Received
14 June, revised 19 September 2001)
The
results of an investigation of the chemical and thermal characteristics of
glass-ceramic enamels, derived from the Li2O-Na2O-Al2O3-TiO2-SiO2 system,
obtained by employing the methods of mathematical experiment planning, are
presented in this paper. Adequate mathematical models, showing the dependence
of the chemical and thermal stability on the chemical composition of enamel
systems, after different thermal treatment procedures, were obtained. Based on
the testing carried out, it was concluded that in the obtained glass-ceramic
enamels the chemical resistance is decreased, but at the same time, the thermal
stability is increased, relative to reference coatings.
Keywords:
glass-ceramic enamels, mathematical planning, chemical stability, thermal
stability.
Copyright & copy; SHD 2002.
Last
Updated March 12, 2002.
For
more information contact: SHD@elab.tmf.bg.ac.yu