JSCS Vol 67, No. 5
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Impresum |
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J. Serb. Chem.
Soc. 67 (5)305-324(2002) |
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R E V I E W
The
mechanism of cathodic electrodeposition of epoxy coatings and the corrosion
behaviour of the electrodeposited coatings
VESNA B. MISKOVIC-STANKOVIC
Faculty of Technology and
Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3503, YU-11120
Belgrade, Yugoslavia
(Received
17 January 2002)
The
model of organic film growth on a cathode during electrodeposition process
proposes the current density-time and film thickness-time relationships and
enables the evaluation of the rate contants for the electrochemical reaction of
OH– ion evolution and for the chemical reaction of organic film deposition. The
dependences of film thickness and rate constants on the applied voltage, bath
temperature and resin concentration in the electrodeposition bath have also
been obtained. The deposition parameters have a great effect on the cathodic
electrodeposition process and on the protective properties of the obtained
electrodeposited coatings. From the time dependences of the pore resistance,
coating capacitance and relative permittivity, obtained from impedance
measurements, the effect of applied voltage, bath temperature and resin
concentration on the protective properties of electrodeposited coatings has
been shown. Using electrochemical impedance spectroscopy, thermogravimetric
analysis, gravimetric liquid sorption experiments, differential scanning calorimetry
and optical miscroscopy, the corrosion stability of epoxy coatings was
investigated. A mechanism for the penetration of electrolyte through an organic
coating has been suggested and the shape and dimensions of the conducting
macropores have been determined. It was shown that conduction through a coating
depends only on the conduction through the macropores, although the quantity of
electrolyte in the micropores of the polymer net is about one order of
magnitude greater than that inside the conducting macropores.
Keywords:
electrodepositon, cathodic electrodeposition, epoxy coatings, corrosion
protection, corrosion stability.
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J. Serb. Chem.
Soc. 67(5)325–329(2002) |
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An efficient synthesis of warfarin
acetals on montmorillonite clay K-10 with microwaves
LJ. KRSTIC, S. SUKDOLAK* and S. SOLUJIC*
Center of Chemistry, Institute of
Chemistry, Technology and Metallurgy, Njegoseva 12., P. O. Box 483, YU-11001
Belgrade, and
*Department of Chemistry, Faculty of Sciences, P. O. Box 60,
YU-34000 Kragujevac, Yugoslavia
(Received
24 September, revised 18 December 2001)
The
microwave promoted reaction of warfarin with methanol, or ethanol, in the
presence of montmorillonite clay K-10 as a catalyst, affords the corresponding
acetals, 2-methoxy-2-methyl-4-phenyl-3,4-dihydro-2H-pyrano[3,2-c]chromen-5-one
(2) and 2-ethoxy-2-methyl-4-phenyl-3,4-dihydro-2H-pyrano[3,2-c]chromen-5-one
(3), respectively, in good yields.
Keywords:
warfarin, cyclic acetals, montmorillonite K-10, microwaves.
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J.
Serb. Chem. Soc. 67(5)331–338(2002) |
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Investigation of asialoglycoprotein
receptor glycosylation by lectin affinity methods
IVONA BARICEVIC, LJILJANA VISOVAC, VESNA MARINOVIC and MARGITA
CUPERLOVIC
Institute for the Application of
Nuclear Energy-INEP, Banatska 31b, YU-11080 Zemun-Belgrade, Yugoslavia
(Received
24 January, revised 27 December 2001)
The
asialoglycoprotein receptor belongs to the family of calcium-dependent (C-type)
animal lectins. The purified receptor is a glycoprotein in which 10 % of the
dry weight consists of sialic acid, galactose, N-acetylglucosamine and
mannose. The carbohydrate content of the asialoglycoprotein receptor was
investigated by lectin affinity methods. The usefulness of plant lectin
affinity methods in the characterization of the saccharide content of the
asialoglycoprotein receptor, as an animal lectin, is demonstrated. RCA I, ConA,
PHA, SNA I and WGA showed greater affinity toward the asialoglycoprotein
receptor, while PSL, AAA and PNA showed negligible interactions with the
asialoglycoprotein receptor. The obtained results correlated well with the
carbohydrate content of the asialoglycoprotein receptor as determined by
chemical methods.
Keywords:
asialoglycoprotein receptor (ASGP-R), glycosylation, lectins, lectin affinity
methods
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J. Serb. Chem.
Soc. 67(5)339–346(2002) |
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Thermodynamic properties of cadmium
compounds from quantum chemical evaluations
ALEXEI N. PANKRATOV
Department of Chemistry, N. G.
Chernyshevskii Saratov State University, 83 Astrakhanskaya Street, Saratov
410026, Russia
(Received
29 August, revised 17 December 2001)
By
the PM3 method, standard entropies, heats and free energies of formation for
some cadmium compounds have been computed. Quantitative relationships Pexper vs, Ptheor, where P
is any of the mentioned properties, have been established.
Keywords:
cadmium compounds, thermodynamic properties, quantum chemical evaluation,
theory-experiment correlation.
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J. Serb. Chem.
Soc. 67(5)347–351(2002) |
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The temperature dependence of the
disproportionation reaction of iodous acid in aqueous sulfuric acid solutions
SMILJANA MARKOVIC, NOVICA RAKICEVIC* and DJURO MISLJENOVIC**
Faculty of Technological Sciences,
University of Pristina, Kneza Milosa 7, YU-38220 Kosovska Mitrovica,
*Faculty of Natural Sciences, University of Pristina, P. O. Box
131, YU-37000 Krusevac and
**Faculty of Mathematics, University of Belgrade, Studentski trg
16, P. O. Box, 550, YU-11001 Belgrade, Yugoslavia
(Received
24 June 2001, revised 6 February 2002)
The aim of this work was to examine the disproportionation reaction
of iodous acid, HOIO, in aqueous 0.18 mol/dm3 H2SO4 solution,
by spectrophotometric measurements of the absorbance. The absorbing HgI+-ion
species were generated during the observed disproportionation process. The
specific rate constants of disproportionation were calculated in the
temperature range from 12 to 30°C. The average values ranged from 1.20 to 2.94
mol-1dm3 s-1, respectively. In addition, the values of the activation energies
were determined by a graphical method. An average value of 71.20 kJ/mol was
found for the chosen temperature interval.
Keywords:
iodous acid, disproportionation reaction, iodine compounds, activation
energy, specific rate constants.
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J. Serb. Chem.
Soc. 67(5)353–365(2002) |
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Cometary impacts into ocean:
thermochemical equilibrium calculations of high-temperature O2 generaton
on the early Earth
PAVLE I. PREMOVIC and KATJA I. PANOV
Laboratory for Geochemistry and
Cosmochemistry, Department of Chemistry, Faculty of Science, University of Nis,
P. O. Box 91, YU-18000 Nis, Yugoslavia
(Received
5 November 2001)
The
early Earth’s atmosphere apparently differed from the present atmosphere mainly
in its lack of free O2, and this absence is believed to have been indispensable for the
origin of early anaerobic life forms. One of the central problems in Earth
science is to explain the apparent transition from the primitive atmosphere
(free of O2) to the present atmosphere which contains 21 % of the gas.
Theoretical models suggest that the initial form of O2 in the
Earth’s atmosphere may have been H2O, which
was converted into atmospheric O2 mainly
through photosynthesis. We have investigated an alternative (abiotic) method
for the conversion of HvO to O2: a
high-temperature shock generated during a cometary impact into an ocean (or on
land). The calculations presented here show that 1 % of the present level of O2 could have
resulted from an icy 1.3×1016 kg comet entering the early
(pre-oxygenic) Earth with a velocity of between about 11 and 30 km s-1.
Keywords:
comet, oxygen, impact, thermochemical calculation.
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J.
Serb. Chem. Soc. 67(5)367–372(2002) |
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Preparation and characterization of
facial and meridional isomers of uns-cis (ethylenediamine-N,N’-di-3-propionato)(S-arginine)cobalt(III)
chloride dihydrate
VESNA M. \INOVIC and TIBOR J. SABO
Faculty of Chemistry, University of
Belgrade, P. O. Box 158, YU-11001 Belgrade, Yugoslavia
(Received
15 October 2001, revised 30 January 2002)
Both
theoretically possible geometrical isomers, facial and meridional, of uns-cis-(ethylenediamine-N,N’-di-3-propionato)(S-arginine)cobalt(III)
chloride dihydrate were prepared by the reaction of sodium uns-cis-(ethylenediamine-N,N’-di-3-propionato)(carbonato)cobaltate(III)
with S-arginine at 75°C. The complexes were isolated chromatographically
and characterized by elemental analysis as well as electron absorption and
infrared spectroscopy.
Keywords:
cobalt(III) complexes, ethylenediamine-N,N’-di-3-propionic acid, arginine.
Copyright & copy; SHD 2002.
Last
Updated May 29, 2002.
For
more information contact: SHD@elab.tmf.bg.ac.yu