JSCS Vol 68, No. 2
Adobe Acrobat version
|
These articles were
created using Adobe Acrobat and some were compressed using WinZip |
To download the latest |
|
|
To download the text of the whole issue
click here |
|
Impresum |
|
J.Serb.Chem.Soc.
68(2)67–76(2003) |
To download this article click here 110 KB |
Effect of substituents on the
13C-NMR chemical shifts of 3-methylene-4-substituted-1,4-pentadienes. Part I.
NATASA V. VALENTIC ZELJKO VITNIK*, SERGEI I. KOZHUSHKOV**, ARMIN
DE MEIJERE**, GORDANA S. USCUMLIC and IVAN O. JURANIC*
Faculty of Technology and
Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3503, YU-11120
Belgrade, Yugoslavia,
E-mail: naca@elab.tmf.bg.ac.yu,
*Faculty of Chemistry, University of Belgrade, Studentski trg
12-16, P. O. Box 158, YU-11001 Belgrade, Yugoslavia,
E-mail: zvitnik@helix.chem.bg.ac.yu or
ijuranic@helix.chem.bg.ac.yu, and
**Institut für Organische Chemie der Georg-August-Universität
Göttingen, Tammannstrasse 2, D-37077 Göttingen, Germany,
Fax: ++49 551 399475; E-mail: skozhus@gwdg.de or
Armin.deMeijere@chemie.uni-goettingen.de
(Received
17 September 2002)
The
principles of linear free energy relationships were applied to the 13C
substituent chemical shifts (SCS) of the carbon atoms in the unsaturated chain
of 3-methylene-4-substituted-1,4-pentadienes. Correlations of the SCS with the
substituent parameters of Swain and Lupton provide a mutually consistent
picture of the electronic effects in these compounds. The pattern of the
electronic effects can be fully rationalized by a model based on the direct
transmission of substituent effects through-space (direct through-space field
effects), and via conjugative interactions (resonance effects), or by
substituent-induced polarization of the p-system in the unsaturated chain (p-polarization
effect). Semi-empirical MNDO-PM3 calculations suggest the s-cis
conformation of 3-methylene-4-substituted-1,4- -pentadienes as the one with
minimal heat of formation.
Keywords:
[3]dendralenes, unsaturated chain carbon 13C SCS,
substituent effects, reverse 13C SCS effect, MNDO-PM3 calculations.
|
J.Serb.Chem.Soc.
68(2)77–84(2003) |
To download this article click here 93 KB |
Isomerization of an enzyme-coenzyme
complex in yeast alcohol dehydrogenase-catalyzed reactions
VLADIMIR LESKOVAC, SVETLANA TRIVIC* and DRAGINJA PERICIN
Faculty of Technology Novi Sad and
+Faculty
of Science Novi Sad, Yugoslavia
(Received
5 August, revised 8 November 2002)
In
this work, all the rate constants in the kinetic mechanism of the yeast alcohol
dehydrogenase-catalyzed oxidation of ethanol by NAD+, at pH
7.0, 25°C, have been estimated. The determination of the individual rate
constants was achieved by fitting the reaction progress curves to the
experimental data, using the procedures of the FITSIM and KINSIM software
package of Carl Frieden. This work is the first report in the literature
showing the internal equilibrium constants for the isomerization of the
enzyme-NAD+ complex in yeast alcohol dehydrogenase-catalyzed reactions.
Keywords:
yeast alcohol dehydrogenase, kinetic mechanism of action.
|
J.Serb.Chem.Soc.
68(2)85–95(2003) |
To download this article click here 124 KB |
Synthesis, structural study and
electrochemical properties of copper(II) complexes derived from benzene- and p-toluenesulphonylhydrazones
L. LARABI, Y. HAREK, A. REGUIG and M. M. MOSTAFA*
Chemistry Department, Faculty of
Science, Tlemcen University, Tlemcen, Algeria and
*Chemistry
Department, Faculty of Science, Mansoura University, Mansoura, Egypt
(Received
12 February, revised 9 September 2002)
The
synthesis and characterization of benzene- and p-toluenesulphonylhydrazones
derived from salicylaldehyde and 2-hydroxy-1-naphthaldehyde and their Cu(II)
complexes are reported. The compounds were characterized on the basis of
elemental analyses, electronic and IR spectra, magnetic moments, and conductance
measurements. The electrochemical behavior of the Cu(II) complexes was
investigated in DMSO by cyclic voltammetry (CV), rotating disc electrode (RDE)
and coulometry. The oxidative polymerization of the copper complexes on a
glassy carbon electrode was carried out in DMSO.
Keywords:
sulphonylhydrazone-Cu(II) complex, cyclic voltammetry.
|
J.Serb.Chem.Soc.
68(2)97–107(2003) |
To download this article click here 137 KB |
Thermochemical equilibrium
calculations of high-temperature O2 generation
on the early Earth: Giant asteroid impacts on land
PAVLE I. PREMOVIC
Laboratory for Geochemistry, Cosmochemistry
and Astrochemistry, University of Ni{, P. O. Box 91, YU-18000 Ni{, Serbia,
Yugoslavia
(Received
29 October, revised 17 November 2002)
Earth’s
atmosphere is composed primarily of N2 and O2. The origin of free O2 in the
early Earth’s atmosphere is still subject of considerable debate.1 Theoretical
models suggest that the initial form of free O2 in the
atmosphere has been oceanic H2O. Recent
computation modelling has suggested that a superheated (ca. 2000 K) H2O vapor
atmosphere of 1.4x1021 kg (the present mass of the oceans) lasting for about 3000 y
could probably have been formed on Earth by an enormous (ca. 1028 J)
asteroid impact. In this report, the occurrence of the thermochemical dissociation
of the vapor, creating a primitive oxygenic (ca. 0.1 of the present level (PAL)
of free O2) atmosphere.
Keywords:
oxygen, atmosphere, thermochemistry, photochemistry, Earth, asteroid,
impact.
|
J.Serb.Chem.Soc.
68(2)109–118(2003) |
To download this article click here 101 KB |
Excitation and analytical
characteristics of an ethanol loaded U-shaped arc
MARIJA RASKOVIC, IVANKA HOLCLAJTNER-ANTUNOVIC, MIRJANA TRIPKOVIC*
and DRAGAN MARKOVIC*
Faculty of Physical Chemistry,
University of Belgrade, P. O. Box 137, YU-11001 Belgrade and
*Institute of Physics, P. O. Box 57, 11001 Belgrade, Yugoslavia
(Received
26 June 2002)
The
effect of the ethanol load on the discharge and analytical parameters of an
argon stabilised U-shaped DC arc has been recorded. Measurements of the radial
distribution of the apparent temperatures and the electron number density of
the DC plasma showed that ethanol addition causes a decrease in both plasma
parameters. The changes in the plasma characteristics, as well as in transport
and atomisation processes of the analyte cause a general change in the spectral
line intensities, which depends on the physical characteristics of the analyte
and the quantity of ethanol loaded into the plasma. Improved detection limits
were obtained for V and Mn when a 10 % (v/v) water–ethanol solution was
nebulized into the plasma.
Keywords:
U-shaped DC arc, emission spectroscopy, ethanol addition, radial temperature
distribution, electron number density distribution, equilibrium plasma
composition, detection limits.
|
J.Serb.Chem.Soc.
68(2)119–130(2003) |
To download this article click here 128 KB |
Temperature effect on graphite KS44
lithiation in ethylene carbonate + propylene carbonate solution: galvanostatic
and impedance study
B. BLIZANAC, S. MENTUS, N. CVIJETICANIN and N. PAVLOVI*
Faculty for Physical Chemistry, Studentski
trg 12–16, Belgrade and
*The Military Technical Institute of the Yugoslav Army, Katani}eva
15, Belgrade, Yugoslavia
(Received
18 August, revised 23 October 2002)
Graphite
Lonza KS44 in a solution 1 M LiClO4 in a
propoylene carbonate + ethylene carbonate (1 M:1 M) mixture was lithiated and
delithiated galvanostatically at room temperature and at the elevated
temperature of 55°C. Voltage–time profiles and complex impedance diagrams were
recorded and are discussed for this particular system. It was confirmed that
this type of graphite shows a relatively small current loss consumed by
exfoliation, if lithiated at room temperature. However, the voltage–time curve
of the first charging at 55°C shows a long voltage plateau at 0.7 V vs. Li/Li+, which corresponds
to 540 mAh g-1 of irreversible capacity attributed to exfoliation. The solid
electrolyte layer formed at elevated temperature, although less protecting in
the sense of electrolyte reduction, shows a remarkably higher electrical
resistance than that formed at room temperature. A comparison of the impedance
diagrams of lithiated and delithiated samples allows the conclusion that mass
transfer through the graphite, not that through the solid electrolyte layer,
plays a dominant role in the mass transfer limitations.
Keywords:
graphite, lithiation, reversible capacity, galvanostatic charging, solid
electrolyte layer.
|
J.Serb.Chem.Soc.
68(2)131–135(2003) |
To download this article click here 78 KB |
Kinetic determination of ultramicro
amounts of As(III) in solution
ALEKSANDAR R. IGOV, RANKO M. SIMONOVIC* and RANGEL P. IGOV**
“Nitex” Nis, Yugoslavia,
*Faculty of Science, University of Pristina, Yugoslavia and
**Faculty of Science, University of Nis, Yugoslavia
(Received
26 August, revised 23 October 2002)
A
new catalytic reaction is proposed and a kinetic method developed for the
determination of ultramicro amounts of As(III) on the basis of its catalytic
activity in the oxidation of ethylenediamine-N,N’-diacetic-N,N’
dipropionic acid (EAP) by KMnO4 in the
presence of hydrochloric acid. Under optimal conditions, the sensivity of the
method is 20 ng/cm3. The probable relative error is 7.6 – 14.5 % for the
concentration range 50 – 200 ng/cm3 As(III).
The effect of certain foreign ions upon the reaction rate were determined for
the assessment of the selectivity of the method. The method has relatively good
selectivity. Kinetic equations were proposed for the investigated process.
Keywords:
kinetic method, As(III) determination,
ethylenediamine-N,N’-diacetic-N,N’-dipropionic acid.
|
J.Serb.Chem.Soc.
68(2)137–145(2003) |
To download this article click here 130 KB |
Sulfur retention by ash during coal
combustion. Part I. A model of char particle combustion
MLADEN ILIC, BORISLAV GRUBOR, and VASILIJE MANOVI*
Institute for Nuclear Sciences
“Vinca”, P. O. Box 522, YU-11001 Belgrade and
*Faculty of Mining and Geology University of Belgrade, Djusina 7,
YU-11000 Belgrade, Yugoslavia
(Received
18 July, revised 18 October 2002)
A
model for the combustion of porous char particles as a basis for modeling the
process of sulfur retention by ash during coal combustion is developed in this
paper. The model belongs to the microscopic intrinsic models and describes the
dynamic behavior of a porous char particle during comustion, taking into
account temporal and spatial changes of all important physical properties of
the char particle and various combustion parameters. The parametric analysis of
the enhanced model shows that the model represents a good basis for the
development of a model for the process of sulfur retention by ash during coal
combustion. The model enables the prediction of the values of all parameters
necessary for the introduction of reactions between sulfur compounds and
mineral components in ash, primarily calcium oxide.
Keywords:
dynamic model, char combustion, sulfur retention by ash.
Copyright & copy; SHD 2002.
February
26, 2003.
For
more information contact: SHD@tmf.bg.ac.yu