JSCS Vol 65, No. 1
Adobe Acrobat version
|
These articles were created using Adobe
Acrobat and were compressed using WinZip |
To
download the latest
|
|
|
To download the text of the whole issue
click here |
To
download the latest
|
|
Impresum 
(39 KB - pdf file); Content of Vol 65, No. 1 (89 KB - WinZip file); Instruction for authors (37 KB - pdf file)
J.
Serb. chem. Soc. 65(1)1-13(2000)
UDC 547.593.22/.23:541.572:518.5
JSCS-2720
Original scientific paper
Use of semiempirical quantum
chemical approaches in computation of molecular dipole moments of tropones and
tropolones
ALEXEI N. PANKRATOV
Department of Chemistry, N. G.
Chernyshevskii Saratov State University, 83 Astrakhanskaya Street, Saratov
410026, Russia
(Received 14 April,
revised 26 July 1999)
Using the MNDO, AM1 and PM3 methods, the dipole
moments (µ) of 28 tropones and 34 tropolones molecules have been computed. The
potentials of the above approaches for the evaluation of m have been revealed.
The correlations µexper = bµtheor have been established.
Keywords: semiempirical quantum chemical
method, dipole moment, theory - experimental correlation, tropones, tropolones.
To download this
article click here (670 KB WinZip file)
J.
Serb. Chem. Soc. 65(1)15-25(2000)
UDC
549.5(546.42):66.094.3:546.35(54-44)
JSCS-2721
Original scientific paper
Characterization and carbon monoxide
oxidation activity of La1-ySryCr1-xRuxO3
perovskites
A. TERLECKI-BARICEVIC, S. PETROVIC, D. JOVANOVIC, LJ. KARANOVIC*
and C. MARINOVA**
ICTM-Department of Catalysis and
Chemcial Engineering, Njego{eva 12, YU-11000 Belgrade,
*Laboratory of Crystallography, Faculty of Mining and Geology,
University of Belgrade, Djusina 7, YU-11000 Belgrade, Yugoslavia and
**Institute of General and Inorganic Chemistry, BAN, 1113 Sofia,
Bulgaria
(Received 6 July 1999)
The oxidation of CO over La1-ySryCr1-xRuxO3 perovskite type oxides with y=0.3 and 0 Ł x Ł
0.100 have been studied. X-ray fluorescence analysis confirmed that content of
elements in the bulk corresponds to the established nominal perovskite
stoichiometry, indicating that no significant oxidation of ruthenium into
volatile polyvalent oxides with their consequented escape from the sample
occurred in air up to the temperature of 1000°C. According to X-ray diffraction
analysis, all sampls achieved the perovskite hexagonal with the presence of
some SrCrO4. X-ray photoelectron spectroscopy analysis of
ruthenium samples shows higher Ru and Sr surface concentraitions than in the
bulk. The binding energy for Ru3p is virtually the same
in all samples and consistent with that of Ru4+ (463.6-464.3eV). Kinetic studies were performed in a differential
recycle reactor with a recycling ratio 80. The results show that substitution
of Ru4+ for Cr3+ in La1-ySryCrO3 leads to a significant
increase in both the activity and the activation energy. The global CO
oxidation rate, referred on the BET surface area, correlates with the surface
Ru4+ atomic concentraiton. Hence, the activity
reflect the surface enrichment in ruthenium. Moreover, an identical apparent
activation energy E = 93 kJ/mol and the same specific rate per ruthenium
surface ion were obtained for samples with a Ru content x ł 0.05 suggest that
exposed Ru4+ ions mainly participate in the reaction.
Keywords: perovskite, ruthenium, CO
oxidation.
To download this article click here (586 KB WinZip file)
J.
Serb. Chem. Soc. 65(1)27-35(2000)
UDC 546.65:547.581.2:541.428.49
JSCS-2722
Original scientific paper
Complexes of light lanthanides with
2,4-dimethoxybenzoic acid
WIESLAWA FERENC and AGNIESZKA WALKOW-DZIEWULSKA
Department of Inorganic and General
Chemistry, Faculty of Chemistry, Maria Curie-Sklodowska University, Pl 20-031
Lublin, Poland
(Received 19 July,
revised 21 October 1999)
The complexes of light lanthanides with
2,4-dimethoxybenzoic acid of the formula: Ln(C9H9O4)3·nH2O where Ln = La(III), Ce(III), Pr(III), Nd(III),
Sm(III), Eu(III), Gd(IIII), and n = 3 for La(III), Gd(III), n = 2
for Sm(III), Eu(III), and n = 0 for Ce(III), Pr(III), Nd(III) have been
synthesized and characterized by elemental analysis, IR spectroscopy,
thermogravimetric studies and X-ray diffraction measurements. The complexes
have colours typical for Ln3+ ions (La, Ce, Eu, Gd-white, Sm-cream, Pr-green,
Nd-violet). The carboxylate group in these complexes is a symmetrical,
bidentate, chelating ligand. They are crystalline compounds characterized by
various symmetry. On heating in air to 1273 K the 2,4-dimethoxybenzoates of the
light lanthanides decompose in various ways. The hydrated complexes decompose
in two or three steps while those of anhydrous ones only in one or two. The
trihydrate of lanthanum 2,4-dimethoxybenzoate first dehydrates to form the
anhydrous salt, which then decomposes to La2O3via the intermediate
formation of La2O2CO3. The hydrates of Sm(III), Eu(III), Gd(III) decompose in two
stages. First, they dehydrate forming the anhydrous salts, which then decompose
directly to the oxides of the respective metals. The anhydrous complexes of
Ce(III), Pr(III) decompose in one step, while that of Nd(III) in two. The
solubilities of the 2,4-dimethoxybenzoates of the light lanthanides in water
and ethanol at 293 K are in the order of: 10-3 mol dm-3 and 10-4-10-3 mol dm-3, respectively.
Keywords: 2,4-dimethoxybenzoates of the light
lanthanides, thermal stability of the complexes, spectrochemical investigations,
solubility of the complexes.
To download this
article click here (454 KB WinZip file)
J.
Serb. Chem. Soc. 65(1)37-45(2000)
UDC 547.781/.785:543.42:539.125.42
JSCS-2723
Original scientific paper
A spectrophotometric study of the
protonation processes of some N-[1-(benzimidazol)-1-yl]methylbenzamide
derivatives
NADA U. PERISIC-JANJIC, JEVREM D. JANJIC* and MARIJA LAZAREVIC**
Institute of Chemistry, Faculty of
Sciences, Trg Dositeja Obradovica 3, YU-21000 Novi Sad, Yugoslavia,
*Institute of Physics, Faculty of Sciences, Trg Dositeja
Obradovica 4, YU-21000 Novi Sad, Yugoslavia, and
**Faculty of Technology and Metallurgy, St. Cyril and Metodius
University, R. Boskovic 16, 91000 Skopje, Macedonia
(Received 20 July,
revised 12 September 1999)
The protonation of N-[1-(benzimidazol)-1-yl]methylbenzamide
derivatives in aqueous acids (H2SO4) media was investigated, using a spectrophotometric method. The
investigated compounds have two protonation processes. The first protonation
process occurs in weakly acidic aqueous solutions (pH range) and refers to the
protonation of the benzimidazole part of the molecule. The second protonation
process occurs in concentrated sulfuric acid solutions and refers to
protonation of the amide group. The protonation constants of the second process
were calculated by the Hammett and Cox-Yates method. The effect of chemical
structure on the ionisation constants is discussed. A correlation between the
protonation constants and antimicrobial activity was established.
Keywords: spectrophotometry,
N-[1-(benzimidazol)1-yl]methylbenzamide derivatives, protonation constants,
antimicrobial activity.
To download this
article click here (549 KB WinZip file)
J.
Serb. Chem. Soc. 65(1)47-53(2000)
UDC 615.779:541.138.3:541.135.52
JSCS-2724
Original scientific paper
Electroreduction of cefetamet on
mercury platinum and gold electrodes
M. AVRAMOV-IVIC, V. KAPETANOVIC*, M. ALEKSIC* and P.
ZUMAN**
ICTM, Department of
Electrochemistry, Njegoseva 12, YU-11000 Belgrade, Yugoslavia,
*Faculty of Pharmacy, Department of Physical and Analytical
Chemistry, Vojvode Stepe 450, YU-11000 Belgrade, Yugoslavia and
**Department of Chemistry, Clarkson University, Potsdam New York,
USA
(Received 19 May,
revised 12 October 1999)
The electroreduction of cefetamet (CEF) using
gold and platinum electrodes has been investigated in slightly alkaline medium
(pH 8.40) where adsorption, previously observed at mercury electrode, was
pronounced. This investigation was performed in order to determine whether the
adsorption interfers with the reduction process even at solid electrodes and to
compare with a mercury electrode.
Keywords: cefetamet electroreduction,
platinum, gold and mercury electrode.
To download this article click here (306 KB WinZip file)
J. Serb. Chem. Soc. 65(1)55-63(2000)
UDC 543.251:546.76
JSCS-2725
Original scientific
paper
The properties of chromium
electrodeposited with programmed currents.
Part
I. Direct current
BISENIJA M. PETROVIC and TANJA M. KOSTIC*
Military Technical Institute YA,
Kataniceva 15, YU-11000 Belgrade and
*Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11000
Belgrade, Yugoslavia
(Received 4 July,
revised 27 October 1999)
The electrodeposition of chromium in programmed
direct current (DC) was investigated in the regime of high current density (77
A dm-2). Chromium was deposited in a system of
plane-parallel electrodes in chromic-sulphuric acid solution, on specimens of
steell, during one hour. The basic properties of deposits, the appearance,
thickness, morphology, microhardness and brightness were investigated.
Thicknesses of the coatings (between 28 and 82 µm) were measured at 36 points
on the surface of the specimens by the non-destructive ferromagnetic method.
Based on these results, graphic models of the surface distribution of the
deposits were made. Three ranges of thickness could be seen on the model (range
1 - average thickness 29.87 µm, range 2 - average thickness 42.0 µm and range 3
- thickness 67.87 µm). For the whole speciments, the average thickness was 50.8
µm with a coefficient of variation of 0.3281. The basic properties of the
coating, morphology and brightness changed depending on the deposit thickness
being very different at different points of one and the same specimen. For this
reason these chromium deposits should not be considered reliable protection
against aggressive gases at high pressures and temperature of systems from
corrosion, wear and erosion.
Keywords: electrodeposition of chromium,
programmed direct current, properties of the deposits, thickness, morphology,
microhardness, brightness, distribution of the deposits on the surface,
modelling.
To download this
article click here (468 KB WinZip file)
J. Serb. Chem. Soc. 65(1)65-72(2000)
UDC 543.251:546.76:62.001.57
JSCS-2726
Original scientific paper
The properties of chromium
electrodeposited with programmed currents.
Part
II. Reversing current
BISENIJA M. PETROVIC and TANJA M. KOSTIC*
Military Technical Institute YA,
Kataniceva 15, YU-11000 Belgrade and
*Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11000
Belgrade, Yugoslavia
(Received 4 July,
revised 27 October 1999)
The electrodeposition of chromium in programmed
reversing current (RC), was investigated in the regime of high cathodic current
density (77 A dm-2) and anodic current density (55 A dm-2). The ratio of the cathodic and anodic time (60 : 1) was used.
Chromium was deposed on a steel substrate from a chromic-sulphuric acid
solution, during one hour. Anode and cathode were suited in a system of
parallel plates. Basic properties of deposits, like thickness, morphology,
microhardness, brightness were examined. Surface distribution of the deposits
was obtained from the measurements of the thicknesses of the deposits (between
32 and 67 µm). A ferromagnetic non-destructive method was used in the
measurements. Based on the results, graphic models of deposit surface
distribution were made. Two ranges of the thickness could be seen on the model
(range 1 - average thickness 35.1 µm and range 2 - average thickness 57.81 µm).
These results were statisticaly analysed by colums, rows and by the whole
surface. For the whole specimens, the average thickness was 45.39 µm with a
coefficient of variation of 0.2582. The basic properties of the deposits did
not change with a variation of the thickness. Because of this, the coatings
deposited with the reversing current could be much more considered reliable in
wear and corrosion protection systems than ones deposited by direct current.
Keywords: electrodeposition of chromium,
programmed reversing current, properties of deposits, thickness, morphology,
microhardness, brightness, distribution of deposits, modelling.
To download this
article click here (472 KB WinZip file)
J.
Serb. Chem. Soc. 65(1)73-81(2000)
UDC 669.017.1:546.42' 47'' 621''' 681'''' 811''''': 620.193
JSCS-2727
Original scientific
paper
Corrosion behaviour of an
AlZnSnSrGa alloy in aqueous solutions of NaCl and Na2SO4
P. ZIVKOVIC, J. PJESCIC and S. MENTUS*
Faculty of Metallurgy and
Technology, Podgorica University and
*Faculty of Physical Chemistry, University of Belgrade, Studentski
trg 12, YU-11000 Belgrade, Yugoslavia
(Received 26 February,
revised 20 Septembar 1999)
The alloy composed of Al(95.53%), Zn(2.85%),
Sn(0.515%), Ga(0.1%) and Sr(0.009%), with the weight percents in the
parentheses, was prepared by melting, using Al(99.84%), a product of the
Aluminium Plant-Podgorica, as the base material. The corrosion behaviour of
this alloy was tested in relation to the behaviour of the base metals, by both
open curcuit potential and polarization resistance methods, in aqueous
solutions of both NaCl and Na2SO4, the concentration of which varied within the range 0.00051- 0.51
mol dm-3. Over the whole salt concentration ranges, the corrosion parameters
indicate that the corrosion rate of the alloy is significantly higher than the
rate of the base material. For instance, for the concentration range 0.00051-
0.51 mol dm-3, the stationary open circuit potentials,
related to SCE, in NaCl solutions were -1.200 to -1.460 V for the alloy and -
0.693 to - 0.920 V for Al, while in Na2SO4 solutions, the stationary open circuit potentials were - 1.190 to
- 1.465 V for the alloy and - 0.780 to - 0.860 V for Al. At the same time, the corrosion
current density in NaCl solutions varied within 11- 89 mA cm-2 for the alloy and 0.35- 0.80 for Al, while in Na2SO4 solutions it amounted to 5.7-52 mA cm-2 for the alloy and 0.28 - 0.88 mA cm-2 for Al.
Keywords: corrosion, Al, Al alloys, neutral
solutions.
To download this
article click here (510 KB WinZip file)
Copyright & copy; SHD 2000.
Last
Updated January 28, 2000.
For
more information contact: SHD@elab.tmf.bg.ac.yu