YU-ISSN 0352-5139
J. Serb. Chem. Soc. Vol. 67. No.5 (2002)
CONTENTS
Electrochemistry
V. B. Mi{kovi}-Stankovi}: The mechanism of cathodic electrodeposition of epoxy coatings and the corrosion behaviour of the electrodeposited coatings (Review)
305
Organic Chemistry
Lj. Krsti}, S. Sukdolak and S. Soluji}: An efficient synthesis of warfarin acetals on montmorillonite clay K-10 with microwaves
325
I. Bari~evi}, Lj. Vi}ovac, V. Marinovi} and M. ^uperlovi}: Investigations of asialoglycoprotein receptor glycosylation by lectin affinity methods
331
Physical Chemistry
A. N. Pankratov: Thermodynamic properties of cadmium compounds from quantum chemical evaluations
339
S. Markovi}, N. Raki}evi} and Dj. Mi{ljenovi}: The temperature dependence of the disproportionation reaction of iodous acid in aqueous sulfuric acid solutions
347
P. I. Premovi} and K. I. Panov: Cometary impacts into ocean: thermodynamical equilibrium calculations of high-temperature O2 generation on the early Earth
353
Inorganic Chemistry
V. M. Djinovi} and T. J. Sabo: Preparation and characterization of facial and meridional isomers of uns-cis-(ethylenediamine-N,N'-di-3-propionato)(S-arginine)cobalt(III) chloride dihydrate
367
Published by the Serbian Chemical Society, Karnegijeva 4/III,
P. O. Box 35-08, YU-11001 Belgrade, Yugoslavia
Printed by the Faculty of Technology and Metallurgy, Karnegijeva 4,
P. O. Box 35-03, YU-11001 Belgrade, Yugoslavia
J. Serb. Chem. Soc. 67 (5)305-324(2002)
UDC 621.357+620.197.5/.6
JSCS-2951
Review paper
R E V I E W
The mechanism of cathodic electrodeposition of epoxy coatings and the corrosion behaviour of the electrodeposited coatings
VESNA B. MI[KOVI]-STANKOVI]
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3503, YU-11120 Belgrade, Yugoslavia
(Received 17 January 2002)
Abstract. 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)
UDC 547.587.51+552.52:542.913+54-732
JSCS-2952
Original scientific paper
An efficient synthesis of warfarin acetals on montmorillonite clay K-10 with microwaves
LJ. KRSTI]1, S. SUKDOLAK2 and S. SOLUJI]2
1Center of Chemistry, Institute of Chemistry, Technology and Metallurgy, Njego{eva 12., P. O. Box 483, YU-11001 Belgrade, and 2Department 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)
UDC 66.095.12:547.963.1:577.112.4
JSCS-2953
Original scientific paper
Investigation of asialoglycoprotein receptor glycosylation by lectin affinity methods
IVONA BARI^EVI], LJILJANA VI]OVAC, VESNA MARINOVI] and MARGITA ^UPERLOVI]
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)
UDC 661.848:536.77:66.011
JSCS-2954
Original scientific paper
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)
UDC 542.9:546.155+535.243:536.5
JSCS-2955
Original scientific paper
The temperature dependence of the disproportionation reaction of iodous acid in aqueous sulfuric acid solutions
SMILJANA MARKOVI],1 NOVICA RAKI]EVI]2 and DJURO MI[LJENOVI]3
1Faculty of Technological Sciences, University of Pri{tina, Kneza Milo{a 7, YU-38220 Kosovska Mitrovica, 2Faculty of Natural Sciences, University of Pri{tina, P. O. Box 131, YU-37000 Kru{evac and 3Faculty 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 ºC. 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)
UDC 523.64+541.461.6:541.11.001.2:54-31:550.318.4
JSCS-2956
Original scientific paper
Cometary impacts into ocean: thermochemical equilibrium
calculations of high-temperature O2 generaton on the early Earth
PAVLE I. PREMOVI] and KATJA I. PANOV
Laboratory for Geochemistry and Cosmochemistry, Department of Chemistry, Faculty of Science, University of Ni{, P. O. Box 91, YU-18000 Ni{, 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 H2O 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)
UDC 546.733:577.112.385:547.393
JSCS-2957
Original scientific paper
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. \INOVI] and TIBOR J. SABO
Faculty of Chemistry, University of Belgrade, P. O. Box 158, YU-11001 Belgrade, Yugoslavia