JSCS Vol 71, No. 4
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Synthesis of new trifluoromethyl-containing 1-(3,5-dialkyl-4-hydroxybenzyl)-pyrazole and -pyrazol-5-one deriatives and their corresponding aroxyls
VASILE DINOIU and JIAN-MING LÜ*
Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
*Department of Chemistry, University of Houston, Houston, TX 77 204, USA
(Received 22 February,
revised 31 August 2005)
3,5-Dialkyl-4-hydroxybenzylhydrazine 1 reacted with hexafluoroacetylacetone, and trifluoroacetylacetone yielding the pyrazoles 2 bearing trifluoromethyl and/or methyl substituents in positions 3 and 5. The sAMe hydrazine derivatives 1 afforded the pyrazol-5-ones 3 with trifluoroacetoacetic acid ethyl ester. On oxidation with lead tetraacetate in CH2Cl2, some stable aroxyls were obtained and their ESR spectra are described.
Keywords: fluorination, pyrazole, pyrazolone, trifluoromethyl-1,3-diketones.
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An efficient synthesis of novel 3’-substituted 2-aryl-5-methyl-5'thioxo-[4,4'-bi-4H-1,2,4-triazol]-3(1'H, 2H)-ones
RAVINDRA R. KAMBLE and BELGUR S. SUDHA
Department of Chemistry and Food Science, Yuvaraja’s College, University of Mysore, Mysore – 570 005, India
(Received 28 January, revised
12 September 2005)
Asimple and high yieldingmethod for the integration of two 1,2,4-triazole rings (10a–l) has been developed starting from 3-arylsydnones (1a–d). Confirmation for the structures of the newly synthesised compounds was provided by their physical, analytical and spectral data (IR, 1H NMR, 13C NMR and MS).
Keywords: 3-arylsydnones, 1,2,4-triazole, cyclocondensation, N,N-biheterocycles.
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Stabilization of a-glucosidase in organic solvents by immobilization on macroporous poly(GMA-co-EGDMA) with different surface characteristics
RADIVOJE M. PRODANOVIC*, NENAD B. MILOSAVIC*, SLOBODAN M. JOVANOVIC**, TANJA SIRKOVIC VELICKOVIC,
ZORAN M. VUJCIC and RATKO M. JANKOV
Department of Biochemistry, Faculty of Chemistry, University of Belgrade, Belgrade, Serbia and Montenegro
*Department of Chemistry, ICTM, Belgrade, Serbia and Montenegro
**Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia and Montenegro
(Received 25 April,
revised 5 July 2005)
a-Glucosidase from baker’s yeast was immobilized on macroporous copolymers of ethylene glycol dimethacrylate and glycidyl methacrylate, poly(GMA-co-EGDMA), with various surface characteristics and pore sizes ranging from 44 nmto 270 nm. Immobilization was done by glutaraldehyde on the copolymer previously modified with 1,2-diAMinoethane. The specific activity of the obtained immobilized enzyme varied from 27 to 81 U/g, depending on the employed copolymer. The half lives of the immobilized enzyme in cosolvents were influenced by the surface characteristics of the copolymer, ranging from 60 to 150 min in 35 % methanol and from 10 to 44 min in 45 % dimethyl sulphoxide (DMSO). The best stabilities were obtained when the enzyme was immobilized onto a copolymer having a pore size of 48 nm in methanol and 270 nm in DMSO.
Keywords: cosolvent, eupergit, maltase, immobilized, stability.
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UV-induced reaction kinetics in dilinoleoylphosphatidylcholine monolayers with incorporated photosensitizers
Faculty of Technology, 16000 Leskovac, Serbia and Montenegro
(Received 11 May,
revised 12 July 2005)
Mixed insoluble monolayers (Langmuir films) of 1,2-di-O-linoleoyl-3-sn-phosphatidylcholine (1,2-DLPC) and incorporated benzophenone-type photosensitizers at an air-water interface were exposed to prolonged UV-irradiation. The irradiation was initiated at a particular fixed molecular packing value. Changes of the surface pressure during the UV-induced photolysis of the sensitizers were plotted against the irradiation time and the results were interpreted in terms of themolecular lipid / sensitizer ratios inside the monolayers.
Keywords: monolayers, UV-irradiation, kinetics, lipids, photosensitizer.
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The charge percolation mechanism and simulation of Ziegler–Natta polymerizations
Part III. Oxidation states of transition metals
BRANKA PILIC, DRAGOSLAV STOILJKOVIC, IVANA BAKOCEVIC, SLOBODAN JOVANOVIC*, DAVOR PANIC** and LJILJANA KORUGIC-KARASZ***
Faculty of Technology, University of Novi Sad, Bul. Cara Lazara 1, 21000 Novi Sad, Serbia and Montenegro
*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia and Montenegro
**Technical Faculty, University of Novi Sad, Trg Dositeja Obradovi}a 3, 21000 Novi Sad, Serbia and Montenegro
***Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003, USA
(Received 21 January,
revised 12 July 2005)
The oxidation state of the transition metal (Mt) active centre is the most disputable question in the polymerization of olefins by Ziegler–Natta (ZN) and metallocene complexes. In this paper the importance and the changes of the Mt active centres are presented and discussed on the basis of a charge percolation mechanism (CPM) of olefin polymerization. Mt atoms can exist in different oxidation states and can be easily transformed from one to another state during activation. In all cases, the Mt atoms are present in several oxidation states, i.e., Mt+(n-1), Mt+(n) to Mt+(n+1), producing an irregular charge distribution over the support surface. There is a tendency to equalize the oxidation states by a charge transfer from Mt+(n–1) (donor) toMt+(n+1) (acceptor). This cannot occur since the different oxidation states are highly separated on the support. However, monomer molecules are adsorbed on the support producing clusters with stacked p-bonds, making a p-bond bridge between a donor and an acceptor. Once a bridge is formed (percolation moment), charge transfer occurs. The donor and acceptor equalize their oxidation states simultaneously with the polymerization of the monomer. The polymer chain is desorbed from the support, freeing the surface for subsequent monomer adsorption. The whole process is repeated with the oxidation-reduction of other donor-acceptor ensembles.
Keywords: Ziegler–Natta polymerization, mechanism, transition metal, oxidation state, metallocene.
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Underpotential and overpotential deposition of Al onto Cu(111) from the AlCl3–EtMeImCl room temperature molten salt
V. D. JOVIC
Center for Multidisciplinary Studies, University of Belgrade, P. O. Box 33, 11030 Belgrade, Serbia and Montenegro
(Received 20 May,
revised 22 June 2005)
The processes of underpotential (UPD) and overpotential (OPD) deposition ofAl onto Cu(111), from the room temperature molten salt AlCl3–EtMeImCl of different compositions, has been investigated by the cyclic volatmmetry (CV) and potentiostatic pulse techniques. It was shown that the CVs of the UPD are characterized by two sharp peaks, while the potentiostatic cathodic and anodic j–t-transients of this process are characterized by two waves, indicating that the UPD of Al results in the formation of two structures. The first, less dense one,most probably the (sqrt3 x sqrt3) R30 º ordered structure of Al, is formed at a more positive potential of about 200 mV vs. Al, while the second one, a complete momolayer of Al, is formed at about 20 mV vs. Al, just before the reversible potential of Al in these melts (–20mV vs. Al). The OPD of Al was detected at potentials more negative than –30 mV vs. Al, occurring through the progressive 3D nucleation and growth mechanism. Slow surface alloying of Al with Cu was found to occur at a potential close to the reversible potential of Al.
Keywords: AlCl3–EtMeImCl, room temperature molten salt, UPD and OPD, Cu(111), (sqrt3 x sqrt3) R30º, progressive 3D nucleation and growth, Al–Cu surface alloying.
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VoltAMmetric albumin quantification based on its interaction with carminic acid
WEI SUN, YUNYING HAN and KUI JIAO
College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, Shandong, P. R. China
(Received 14 January,
revised 15 August 2005)
In a weak acidic Britton–Robinson (B–R) buffer of pH 4.0, human serum albumin (HSA) can react rapidly with carminic acid (CAA) to form a suprAMolecular complex. Microelectrostatic fields in the molecular structure of HSA cause the electrostatic binding reaction of the positively charged CAA with the negatively charged HSA. CAAhas a sensitive, second order derivative linear sweep voltAMmetric reductive peak at – 0.54 V (vs. SCE) on a dropping mercury electrode (DME). After the addition of HSA to a CAAsolution, the reductive peak current of CAAdecreased without a shift of the peak potential. Based on the decrease of the peak current, a sensitive voltAMmetric method for the determination of microAMounts of the protein is proposed. The conditions for the binding reaction and the voltAMmetric detection were optimized. Under the optimal conditions, the decrease of the voltAMmetric detection were optimized. Under the optimal conditions, the decrease of the voltAMmetric peak current was in proportion to the quantity of HSA in the range of 2.0 to 70.0 mg l-1, with a linear regression equation DIp”(nA) = 11.74 C (mg l-1)–12.33 and a detection limit of 2.0 mg l-1 (3s). The method was further applied to the detection of different kinds of proteins, such as bovine serum albumin (BSA), oval albunim (OVA), lipase, etc. The established method was further applied to the determination of the albumin content in human serum sAMples and the results obtained by this method were in good agreement with the traditional Coomassie Brilliant Blue G-250 (CBB G-250) spectrophotometric method. The binding mechanism is discussed and the binding ratio was calculated from the voltAMmetric data.
Keywords: carminic acid, human serum albumin, interaction, linear sweep voltAMmetry.
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Physical modelling of representative particles of electrodeposited copper powders
KONSTANTIN I. POPOV, NEBOJSA D. NIKOLIC*, SNEZANA B. KRSTIC and MIOMIR G. PAVLOVIC*
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia and Montenegro
*ICTM – Institute of Electrochemistry, University of Belgrade, Njegoseva 12, 11000 Belgrade, Serbia and Montenegro
(Received 27 January,
revised 29 July 2005)
A method for the estimation of the size of the representative particle of a copper powder is given. Cross sections of representative particles of flowing and non-flowing powders estimated by this procedure are also presented.
Keywords: copper powder particles, copper powder flowability.
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Prediction of the particle circulation rate in a draft tube spouted bed suspension dryer
ZORANA LJ. ARSENIJEVIC, ZELJKO B. GRBAVCIC* and RADMILA V. GARIC-GRULOVIC
Institute for Chemistry, Technology and Metallurgy, Njegoseva 12, 11000 Belgrade, Serbia and Montenegro
*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia and Montenegro
(Received 10 May,
revised 27 June 2005)
A model for predicting the particle circulation rate in a draft tube spouted bed dryer with inert particles is proposed and verified. The calculation algorithm requires three input values: the gas velocity in the draft tube, one data point for the static pressure in the draft tube, and the pressure gradient in the annulus. The particle circulation rate can be estimated by solving the continuity andmomentum equations for turbulent accelerating two-phase flow. The numerical solution is based on an iterative procedure until the assumed value of the particle circulation rate produces the prescribed value of the fluid static pressure at a certain axial position. Experiments were performed in a cylindrical column of 215 mm diAMeter with a draft tube of 70 mm diAMeter and length of 900 mm. Polyetylene pellets were used as the inert particles with a diAMeter of 3.3 mm, a density of 921 kg/m3 and a sphericity of 0.873. The model predictions of the particle circulation rate are in good agreement with the experimental data.
Keywords: spouted bed, draft tube, dryer, circulation rate.
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Magnetic properties of nanostructured SiO2 : Eu3+ powders
VOJISLAV SPASOJEVIC, MIROSLAV DRAMICANIN, VUKOMAN JOKANOVIC*, ZELJKA ANDRIC, JOVAN BLANUSA,
VLADAN KUSIGERSKI, MIODRAG MITRIC, MARIN TADIC and ANA KAPICIC
Vinca Institute of Nuclear Sciences, P. O. Box 522, 11001 Belgrade , Serbia and Montenegro
*Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade, Serbia and Montenegro
(Received 9 May, revised
2 June 2005)
Eu-doped silica nanoparticles with different concentrations of europium (3 %, 6%and 15 at. %) were prepared by a hydrothermal procedure. Light scattering measurements of the silica colloids as well as TEM microscopy, revealed a narrow size distribution of the particles, ranging from 5 to 10 nm. X-Ray diffraction showed that all the powders were AMorphous. Magnetic susceptibility vs. temperature measurements showed a behaviour typical for Eu3+ ions, with a plateau below 60 K, and an increase of the mass susceptibility with Eu concentration. The splitting of zero-field cooled (ZFC) and field-coled (FC) susceptibility branches increased with the europium concentration, indicating the presence of interparticle interactions. At temperatures below 40 K, a contribution of parAMagnetic impurities obeying the Curie law was observed. Heat treatment of the powders at 823 K and 1073 K increased the magnetic susceptibility. The appearance of a small peak at 70 K indicated the presence of small quantities of ferromagnetic EuO in the powders after heating.
Keywords: magnetic properties, nanoparticles, rare earth, silica, light scattering.
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The effect of edge interlAMinar stresses on the strength of carbon/epoxy lAMinates of different stacking geometry
MOMCILO STEVANOVIC, MILAN GORDIC, DANIELA SEKULIC and ISIDOR DJORDJEVIC
Vinca Institute of Nuclear Sciences, P. O. Box 522, 11000 Belgrade, Serbia and Montenegro
(Received 22 February,
revised 22 July 2005)
The effect of edge interlAMinar stresses on strength of carbon/epoxy lAMinates of different stacking geometry: cross-ply, quasi-isotropic and angle-ply lAMinates with additional 0º and 90º ply was studied. Coupons with two widths of lAMinates with an inverse stacking sequence were tested in static tensile tests. The effect of edge interlAMinar stresses on strength was studied, by comparing the values of the tensile strength of lAMinate coupons of the sAMe width with an inverse stacking sequence, as well as, by comparing the values of the tensile strength of the sAMe lay-up lAMinate coupons but of different widths. The edge effects were analysed by observing failure, identifying the interlayer where axial cracks at the free edge were initiated or inhibited and by computing interlAMinar stresses and strains in the interlayer near the free edge of the coupon. The established edge effect was first correlated to the sign of the normal edge interlAMinar stress. The extent of the edge effect was then successfully correlated to the edge interlAMinar normal stress normalized to the size of the edge boundary region in which the stress appeared.
Keywords: fibre polymer composites, strength, edge interlAMinar stresses, complementary energy.
J.Serb. Chem. Soc 71(3) 433(2006)
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Copyright &AMp; copy; SHD 2006.
June 20, 2006.
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