bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of multiple light scattering on dynamic characteristics of light scattered from latex particles
Authors: Koňák Čestmír , Jakeš Jaromír , Petráš František , Kárská Marie , Peřina Jan
Published: February 2010

The effect of multiple light scattering on a homodyne intensity auto-correlation function and photocount distribution of scattered light has been studied. The analysis of quasielastic light scattering data has shown that even a small contribution (several percent) of multiple light scattering to the total scattered light intensity can be distinguished and identified by the Laplace transform inversion of the corresponding intensity auto-correlation function. The photocount distribution reflects the coherence time changes of the scattered light only.
Synthesis of 3-methyl-1,5-diphenyl-7-aryl-7,8-dihydro-6H-pyrazolo[4,5-b]azepines
Authors: Venkata Narsimha Reddy Chintalapani , Rajanarendar Eligeti , Krishnamurthy Ananthula
Published: February 2010

3,5-Dimethyl-4-nitro-1-phenylpyrazole (I) on treatment with chalcones II under phase transfer conditions gives the Michael adducts, 3-methyl-4-nitro-1-phenyl-5-(2-aryl-4-phenyl-4-oxo-1-butyl)pyrazoles (III). The Michale adducts on cycloreduction with stannous chloride-hydrochloric acid furnish 3-methyl-1,5-diphenyl-7-aryl-7,8-dihydro-6H-pyrazolo[4,5-b]azepines (IV). IR, 1H NMR, 13C NMR and mass spectra support the structures of III and IV.
Crystal structure of the native sesquiterpene lactone 8α-angeloyloxy-10β,11α-diacetoxyslov-3-enolide
Authors: Rychłewska Urszula , Holub Miroslav
Published: February 2010

The X-ray structural analysis of 8α-angeloyloxy-10β,11α-diacetoxyslov-3-enolide (I) confirms the structure of I deduced from spectral data and from the X-ray analysis of its derivative II. The stereostructure of I is discussed and compared with that of II and III.
Potential anticonvulsants: Some derivatives and analogues of 2-propylpentanoic acid
Authors: Valenta Vladimír , Vejdělek Zdeněk , Šindelář Karel , Protiva Miroslav
Published: February 2010

Reaction of 2-(ethoxycarbonylamino)ethanol with 2-propylpentanoyl chloride gave the ester III. N-(4-Piperidinyl)-2-propylpentanamide (V) was prepared via the 1-benzyl-4-piperidinyl derivative IV and was acylated with ethanesulfonyl chloride and 2-propylpentanoyl chloride to give the amides VI and VII. Malonic ester syntheses afforded diethyl 2-ethyl- and 2-propyl-2-(2-(methylthio)ethyl)malonate VIII and XIII which were hydrolyzed and decarboxylated to the acids X and XV which, in turn, were transformed to the amides XII and XVII. 3-Thiapentanenitrile was alkylated with propyl bromide to the nitrile XIX which was hydrolyzed to the acid XX and the amide XXI. The acids X, XV, and XX, and the amides XII, XVII, and XXI are analogues of the anticonvulsant agents valproic acid (I) and valpromide (II). Compounds XX (V⁄FB-14 721) and XXI (V⁄FB-14 722) potentiate, in doses in which they ìper seî are ineffective as anticonvulsants in mice, significantly the anticonvulsant effect of diazepam.
1H NMR studies of [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in dimethylsulfoxide by nuclear Overhauser effect (NOE) enhancement spectroscopy: cis-trans Isomerism of the His-Pro bond
Authors: Matsoukas John , Cordopatis Paul , Yamdagni Raghav , Moore Graham J.
Published: February 2010

The conformational properties of the Sarmesin analogues [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in hexadeutero-dimethysulfoxide were investigated by Nuclear Overhauser Effect (NOE) Enhancement Studies. Cis-trans isomers (ratio 1 : 6) due to restricted rotation of the His-Pro bond were observed. Interresidue interactions between the His Cα proton and the two Pro Cδ protons revealed that the major isomer was the trans.
Metastability of the system potassium chloride-potassium bromide-water
Authors: Papazova-Dencheva Karolina , Nývlt Jaroslav , Pekárek Vladimír , Šípek Milan
Published: February 2010

The metastable zone width has been determined for pure KCl-H2O and three compositions of the ternary system KCl-KBr-H2O at temperatures close to 35 and 40 °C. In agreement with literature it was confirmed that there are two different regions of solid solutions in the system KCl-KBr-H2O. The data on metastable zone width show a different crystallization behaviour of both of the solutions: the values of critical nucleation parameters calculated from the measurements exhibit a distinct asymetry which may be connected with different radii of the Cl- and Br- ions.
The crystal and molecular structure of the bis(thiocyanato)-bis(4-methylpyridine)copper(II) complex at 180 K
Authors: Kabešová Mária , Kožíšková Zlatica , Dunaj-Jurčo Michal
Published: February 2010

At 180 K, [Cu(4-Mepy)2(NCS)2] crystallizes in the monoclinic system, space group P21, Z = 6, with the elementary cell parameters a = 0.963(1), b = 2.653(2), c = 0.984(2) nm, β = 106.40(0.07)°. The central atom possesses the tetragonal bipyramidal coordination; the heterocyclic ligands are bonded in the equatorial plane of the coordination polyhedron in the trans positions, the thiocyanate ligands are bridge ones and are coordinated in both the equatorial and axial positions of the coordination polyhedron. The crystal structure involves three symmetrically independent coordination polyhedra differing in the degree of axial distortion. The thermal stability of the thiocyanate ligands in the complex is related with the steric arrangement of the thiocyanatocopper(II) chains.
(+)-3α-Hydroxylupanine, a new alkaloid from Ammopiptanthus mongolicus (MAXIM.) CHENG F.
Authors: Proksa Bohumil , Uhrín Dušan , Uhrínová Stanislava , Grossmann Eduard , Selenge Dangaa , Batsuren Dan
Published: February 2010

From leaves of Ammopiptanthus mongolicus (MAXIM.) CHENG F. were isolated (+)-3α-hydroxylupanine (I), (1R)-3-O-methyl[1,2,4/3,5,6]-inositol (V), salicylic acid, (-)-piptanthine (III), 7-hydroxy-4'-methoxyisoflavone (VIII), 7,3'-dihydroxy-4'-methoxyisoflavone (X) and 4'-methoxyisoflavone-7-β-D-glucopyranoside (IX). All the compounds were characterized on the basis of spectral data; the first three compounds were isolated from this material for the first time.
Potential antidepressants and tranquillizers: Synthesis of some 9-(aminoalkoxy)-2,3,6,7-tetrahydro-1H,5H-benzo[ij] quinolizines and 1-(substituted amino)-3-(1-naphthoxy)-2-propanols
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: February 2010

The hydrobromide of 9-hydroxyjulolidine was reacted with hydrochloride of 2-dimethylaminoethyl chloride, 2-(1-pyrrolidinyl)ethyl chloride, 2-(1-piperidinyl)ethyl chloride, and 3-dimethylaminopropyl chloride in ethanol in the presence of sodium ethoxide to give the title bases II-V which were transformed to dihydrochlorides. Heating of 1,2-epoxy-3-(1-naphthoxy)propane with 2,3,3-trimethyl-2-butylamine, 1-methylcyclopentylamine, 1-methylcyclohexylamine, 1-methylcycloheptylamine, and 10,11-dihydroxydibenzo[a,d]cycloheptene-5-amine in ethanol afforded the second part of the title compounds (VII-XI), prepared also in the form of hydrochlorides. Only the ethers II and V showed indications of possible antidepressant activity.
Isolation of rabbit insulin
Authors: Jiráček Jiří , Barthová Jana , Barth Tomislav
Published: February 2010

Insulin extract has been prepared from rabbit disintegrated pancreas by means of acidic ethanol extraction in combination with ammonium acetate precipitation and purified by permeation chromatography. The enriched preparation of rabbit insulin has been fractionated further by affinity chromatography on AH-Sepharose 4B substituted with polylysine.
A modification of the inert gas stripping method for measuring the limiting activity coefficient
Authors: Surový Július , Ovečková Jana , Graczová Elena
Published: February 2010

A modification of the inert gas stripping method for measuring the limiting activity coefficient is proposed. Compared to the procedure used so far, the modification consists of a change in the apparatus arrangement and measurement of the decrease in solute concentration in the liquid phase only. The method has been tested by measuring the limiting activity coefficients of heptane in N-methylpyrrolidone at 25, 50 and 55 °C. The results are in good agreement with published values determined by various methods.
The application of the relaxation method to the study of Fe3+, Fe2+, H2SO4/Pt electrode system
Authors: Kisza Adolf , Każmierczak Jerzy , Miciór Elżbieta
Published: February 2010

The paper presents the application of the relaxation theory of electrode reaction in a diffusional system. The theoretical equations derived are tested by the experimental results of a simple charge transfer reaction Fe3+ + e = Fe2+ on Pt electrode in 1M H2SO4.
The effect of surfactants on the acid-base behaviour of methyl red. Part I. A spectrophotometric comparison of the effect of CPB and SDS
Authors: Jirasová Jana , Bílý Jiří , Čermáková Ludmila
Published: February 2010

The effect of a cationic (CPB) and an anionic (SDS) surfactant on the bands in the absorption spectra of methyl red was studied. The interactions of methyl red with the two surfactants were monitored on the basis of the changes in the absorption curves that were mathematically deconvoluted into Gaussian shape absorption bands. The methyl red dissociation constants were determined in the presence of the two surfactants at sub- and supercritical micelle concentrations. The methyl red conditional dissociation constants changed by ΔpKa = -1.47 for c(CPB) = 5 mmol l-1 and ΔpKa = 0.81 for c(SDS) = 4 mmol l-1. The contributions of the individual forms of methyl red to the interactions with CPB and SDS were discussed.
Complexation equilibria between gallium(III) and 4-(4'-methyl-2'-thiazolylazo)-2-methylresorcinol. Derivative spectrophotometric determination of gallium in biological samples
Authors: Jiménez Ana I. , Jiménez Francisco , Pérez Juan P. , Arias Juan J.
Published: February 2010

The reaction of Ga(III) with 4-(4'-methyl-2'-thiazolylazo)-2-methylresorcinol (H2L) at I = 0.25 mol l-1, (NaNO3) was investigated spectrophotometrically. Numerical method was used to evaluate the stability constants of the complexes formed GaH2L2 (log β122 = 37.03±0.09); GaHL (log β111 = 19.08±0.06); GaL (log β101 = 13.65±0.16). A method is developed for the determination of gallium using first and second derivative spectrophotometry and the effect of interferences has been evaluated. The method has been applied to the determination of gallium in human urine and blood serum samples.
The polarographic and voltammetric determination of 2,6-dicyano-4-nitro-2'-acetylamino-4'-diethylaminoazobenzene
Authors: Barek Jiří , Civišová Dagmar , Ghosh Ashutosh , Zima Jiří
Published: February 2010

The polarographic reduction of the title azo dye was studied and optimal conditions were found for its analytical utilization in the concentration range 1 . 10-6 - 1 . 10-7 mol l-1 using differential pulse polarography and 1 . 10-6 - 1 . 10-8 mol l-1 using fast scan differential pulse voltammetry or linear scan voltammetry at a hanging mercury drop electrode. When the latter technique is combined with adsorptive accumulation of the studied substance on the surface of the hanging mercury drop, the determination limit can be further decreased to 3 . 10-9 mol l-1.
Steric and hydrophobic effects on stereoselectivity in ternary cobalt(III) complexes of amino acid derivatives
Authors: Strašák Milan , Novomeský Pavol , Butvin Peter
Published: February 2010

The preparation, separation, and characterization of mixed ligand cobalt(III) complexes containing either the new asymmetric linear tetradentate ligand, ethylenebis-(S)-phenylalanine ((SS)-EBPhe), or known asymmetric linear tetradentate ligand, ethylenebis-(S)-valine ((SS)-EBV), and an aromatic or aliphatic diamine (dam) respectively are reported. The absolute configuration of these complexes are assigned by considering the electronic absorption, circular dichroism, infrared, 1H and 13C NMR spectra, and the known configuration of the ligands. The optically active tetradentate ligands coordinate stereospecifically because only Δ diastereoisomers are formed. The factors determining stereoselectivity in these complexes are mainly the steric and intramolecular hydrophobic ligand-ligand interactions. These intramolecular hydrophobic interactions have been confirmed by 1H NMR shift measurements in water.
Synthesis of metal free phthalocyaninetetrakis (N-cyclopropylsulfonamides)
Authors: Yahya Hazim K. , Dawood Abed A.
Published: February 2010

Metal free phthalocyaninetetrakis (N-cyclopropylsulfonamides) have been synthesized and their 1H NMR, IR and thermogravimetric studies were reported.
Sesquiterpenic lactones of Inula aschersoniana JANKA var. aschersoniana species
Authors: Błoszyk Ełżbieta , Buděšínský Miloš , Daniewski Włodzimierz M. , Pešková Eva , Drożdż Bohdan , Holub Miroslav
Published: February 2010

Aerial parts of species Inula aschersoniana JANKA var. aschersoniana have been shown to contain parthenolide (I), costunolide diepoxide (III) and the hitherto undescribed inusoniolide (IV) whose structure, including the absolute configuration, was determined using 1H NMR and CD spectroscopy.
Preparation of 3-(β-D-galactopyranosyloxy)androstane derivatives with unsaturated side chain in position 17β
Authors: Chodounská Hana , Pouzar Vladimír
Published: February 2010

Article without abstract
Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst
Authors: Stuchlý Vladimír , Klusáček Karel
Published: February 2010

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.
The effect of bubbling regime and mode of mechanical agitating on the course of hydrogenation of vegetable oil
Authors: Dědek Ivan
Published: February 2010

The effect of hydrogen distribution was studied on the rate and selectivity of hydrogenation of sunflower oil in a bubbled air-lift-type reactor and in a laboratory reactor with interchangeable agitators. It was found that the change of bubbling regime considerably influences character of the reaction. The hydrodynamic properties of agitators have even the surprising effect on the kinetics of hydrogenation. The rate and selectivity of the reaction is to be efficiently controlled by the intensity and mode of agitating in both types of reactors.
Scale-up and scale-down techniques for fermentations of polyene antibiotics
Authors: Ettler Petr
Published: February 2010

Our philosophy of successful biotechnology transfer to industrial scale covers the comparison of complex sets of microbiological, analytical and bioengineering data from cultivations in various scales and different geometries of mixing with laboratory findings. In particular, the availability of nutrients to producing microorganism should be understood, therefore for quick scaling-up procedure of polyene antibiotics produced by Streptomyces noursei we recommend to use physiological marker as total dehydrogenase activity determination. The utility of scale-down tests for identification of process fluctuation, validation of new substrate batches and simultaneous control of inoculum quality was proved.
The Na+, K+/CN-, I- binary systems
Authors: Drátovský Milan , Grüner Bohumír , Horsák Ivan , Makovička Jiří
Published: February 2010

The phase diagram of the KCN-KI binary system was measured and the published phase diagrams of the KCN-NaCN, NaI-KI and NaCN-NaI systems were verified and completed. The systems form solid solutions with minima on the liquidus and solidus curves. The solid solutions in the KCN-KI system probably have a high segregation temperature, close to the solidus curve. For the four binary systems the experimental points were fitted with liquidus and solidus curves either by applying smoothing spline functions or by using two different models. The results obtained are discussed.
Synthesis of 3'-azido-2',3'-dideoxy-6-methyluridine, 2',3'-dideoxy-6-methyluridine and 2',3'-dideoxy-2',3'-didehydro-6-methyluridine
Authors: Hřebabecký Hubert , Holý Antonín , De Clercq Eric
Published: February 2010

3'-Azido-2',3'-dideoxy-6-methyluridine (VIb) was prepared, together with its N3-isomer VIIb, by opening the 2,3'-bond in anhydronucleoside III with lithium azide in dimethylformamide and subsequent detritylation. The anhydro derivative III was synthesized from 2'-deoxy-6-methyluridine (I) by tritylation, mesylation and closure of the 2,3'-anhydro bond with 1,8-diazabicyclo[5.4.0]undec-7-ene. Dideoxy derivative XV was prepared by Barton deoxygenation of phenoxythiocarbonyl derivative IX followed by desilylation with tetrabutylammonium fluoride. Reduction of bis(phenoxythiocarbonyl) derivative XV with tributyltin hydride afforded 2',3'-dideoxy-2',3'-didehydro derivative XVI. The compound XV was obtained from arabinosyl derivative XIII which arises, along with 5,6-dihydro derivative XIV, by reaction of anhydronucleoside XII with lithium hydroxide in aqueous methanol. Desilylation of compound XVI with tetrabutylammonium fluoride resulted in quantitative removal of 6-methyluracil.
Alkaloids from Papaver albiflorum PACZ. subsp. albiflorum and P. cf. stevenianum A. D. Mikheev
Authors: Slavík Jiří , Slavíková Leonora
Published: February 2010

Papaver albiflorum PACZ. subsp. albiflorum (tetraploid, 2n = 28; total alkaloid content 0.001%) afforded corytuberine, protopine and allocryptopine as dominant alkaloids; in addition, small amounts of macambrine, thebaine, scoulerine, rhoeadine, papaverrubines D, C, A and E, berberine and coptisine were detected. Papaver cf. stevenianum A. D. MIKHEEV (hexaploid, 2n = 42; total alkaloid content 0.066% and 0.015%, respectively) gave berberine as the principal alkaloid (0.065% and 0.013, respectively) which was responsible for the yellow colour of latex. Corytuberine, allocryptopine, protopine and isocorydine were isolated as minor alkaloids and small amounts of corydine, mecambrine, thebaine, scoulerine, papaverrubines D, C, A and E, coptisine, cis-N-methylcanadinium hydroxide and N-methylthebainium hydroxide were detected. Alkaloid PHC 1, isolated recently as minor constituent from Papaver rhoeas var. chelidonioides O. KUNTZE, has been shown to be identical with isorhoeagenine.
Interpretation of partition between phases and chromatographic retention for a series of oxygen compounds
Authors: Miertuš Stanislav , Morávek Roman
Published: February 2010

The Gibbs free energies of solvation in water and in 1-octanol were calculated for a series of 13 oxygen compounds using the polarizable continuum approach. The values obtained were correlated with the experimental distribution constants in the water-1-octanol system and with the capacity factors related to HPLC retention. Statistically significant correlations were found between the calculated and experimental data, indicating that the model used and the methods applied describe the physical nature of the studied properties of substances in a qualitatively correct manner.
Kinetics and mechanism of the reaction of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione
Authors: Hernando José M. , Montero Olimpio , Blanco Carlos
Published: February 2010

The kinetics of the reactions of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione to form the corresponding monocomplexes have been studied spectrophotometrically in the range 5 °C to 16 °C at I 25 mol l-1 in aqueous solution. In the proposed mechanism for the two complexes, the enol form reacts with the metal ion by parallel acid-independent and inverse-acid paths. The kinetic constants for both pathways have been calculated at five temperatures. Activation parameters have also been calculated. The results are consistent with an associative activation for Fe(H2O)63+ and dissociative activation for Fe(H2O)5(OH)2+. The differences in the results for the complexes of heptanediones studied are interpreted in terms of steric factors.
Polymerization of acrylonitrile initiated by peroxomonosulphate-thiols redox systems
Authors: Manivannan Gurusamy , Maruthamuthu Pichai
Published: February 2010

Aqueous thermal polymerization of acrylonitrile (AN) initiated by peroxomonosulphate (HSO5-, PMS)-thiolactic acid (TLA) and PMS-thiomalic acid (TMA) redox systems has been carried out in the temperature range 30-50 °C. The effect of concentration of monomer, initiator, reducing agent, H+, and ionic strength on rate of polymerization, Rp, has been investigated under deaerated conditions. The Rp has been found to depend on, Rp ~ [AN]01.5 [PMS]0.5 [TLA]0.5 in PMS-TLA system and, Rp ~ [AN]02.0 [PMS]1.0 [TMA]0 in PMS-TMA system. The degree of polymerization (Xn) values and thermodynamic parameters have been evaluated. Suitable reaction scheme has been proposed and expressions for Rp and Xn have been obtained.
Isomerization of heptacyclic hydrocarbons to triamantane
Authors: Kafka Zdeněk , Vodička Luděk
Published: February 2010

Isomerization of heptacyclic hydrocarbons, heptacyclo[8,8,0,02,17,03,11,04,9,012,16,013,18]octadecane and heptacyclo[8,8,0,02,13,03,11,04,9,012,17,014,18]octadecane under various conditions in the presence of Lewis-type catalysts has been studied. The isomerization gives the heptacyclic diamantoid hydrocarbon triamantane which is the third member of the adamantanologic series.
The crystal and molecular structure of (1R*, 3S*, 4R*, 6S*)-1,4-dimethyl-3,6-diphenyl-2,5,7-trioxabicyclo[2,2,1]heptane
Authors: Novotný Jiří , Ondráček Jan , Stružka Vladimír , Kratochvíl Bohumil
Published: February 2010

The structure of 1,4-dimethyl-3,6-diphenyl-2,5,7-trioxabicyclo[2,2,1]heptane was solved by direct methods and anisotropically refined to a final R value 0.023 for 648 observed reflections (I > 3σ(I)) and 133 refined parameters. The symmetry of the structure corresponds to the P21212 space group with lattice parameters a = 16.857(2), b = 8.756(1), c = 5.245(1) Å. The unit cell contains two formula units. The molecule under study possesses twofold rotation axis, which passes through the O2 atom. The molecular structure found from X-ray data corresponds to 1H and 13C NMR spectroscopic results. Further IR spectrum and optical rotation value are included.
Preparation of (Z)-3,4-didehydronorvaline, (E)- and (Z)-3,4-didehydroornithine and (E)- and (Z)-3,4-didehydro-2,6-diaminopimelic acid
Authors: Havlíček Libor , Hanuš Jan , Sedmera Petr , Němeček Jan
Published: February 2010

(Z)-3,4-Didehydronorvaline (IIa), (E)- and (Z)-didehydroornithine (VIb and VIa, respectively) and (E)- and (Z)-3,4-didehydro-2,6-diaminopimelic acid (Xb and Xa, respectively) were prepared by addition of Grignard reagents to diethyl acetiminomalonate and subsequent reactions. The mechanism of cyclization of 2-acetamido-2-alkynylmalonate to the oxazoline derivative in a basic medium was studied by 1H NMR spectroscopy.
Oospora lactic lipase: Isolation and properties
Authors: Davranov Kakhramon , Tabak Mina J. , Diyarov Dzhamil Ch. , Sattarov Abdumurod , Gulyamova Kamola A.
Published: February 2010

Lipase (EC 3.1.1.3) of Oospora lactic UzLM-2 was purified by ammonium sulfate (0.40-0.80) fractionation, gel-filtration on Sephadex G-100, column chromatography on DEAE-Sephadex and CM-Sephadex, gel-filtration on Sephadex G-75 and was finally crystallized in concentrated aqueous solution. Crystalline preparation of the enzyme is homogeneous at disc-electrophoresis and ultracentrifugation. Sedimentation coefficient (S20w) is 3.6 S, isoelectric point (pI) at pH 4.2 and molecular mass of the enzyme is 40-43 kD. Amino acid composition analysis showed that none of sulfur-containing amino acids were detected in the crystalline enzyme, but it contains about 8% of carbohydrates and a small amount of lipids. Lipase from Oospora lactic was most active at pH 7.5 and 37 °C in olive oil, stable in the range of pH from 5.7 to 8.0 at 30-40 °C for 18 h and retained stability at 50 °C for 10 min.
Copper(II) complexes with 1-phenyl-4,6-dimethylpyrimidine-2-thione. Chemical, spectroscopic, magnetic, conductivity and polarographic studies
Authors: Battistuzzi Raffaele , Borsari Marco
Published: February 2010

New copper(II) complexes of general composition: CuLX2.nH2O (X = Cl-, n = 0.25; X = NO3-, n = 0.5), Cu2L3Cl4.2H2O, CuL2X2.H2O (X = ClO4-, BF4- and NO3-) and Cu2L7X4 (X = ClO4-, BF4- and NO3-), where L = 1-phenyl-4,6-dimethylpyrimidine-2-thione, have been isolated. Chemical and thermal analyses, conductivity, magnetic susceptibility, infrared and ligand field spectroscopic data and, for the perchlorate complexes also polarographic studies, are reported. Diagnostic IR bands frequencies of counter-ions, χ(Cu-X) modes and ligand field spectra for the mono-and bis-ligand compounds, having an equatorial [CuNSCl2], [CuNSO2] and [CuN2S2] microsymmetry, indicate a coordinating character of some anions, suggesting an elongated octahedral geometry for these complexes. For the [Cu2L7]X4 (X = ClO4-, BF4- and NO3-) complexes, which exhibit at room temperature subnormal magnetic moments, a polynuclear structure with the copper(II) in a roughly square-pyramidal environment, is proposed. Polarographic data for the perchlorate complexes and for the Cu(ClO4)2-L system at various ligand concentrations, have shown that in DMF solution the prevailing species are [CuL2]2+, [CuL3]2+ and [Cu2L7]4+ confirming the oxidation state II for the copper ions in the [Cu2L7]X4 complexes.
Molecular structure of sym-fac-[(1,5,9-triazanonane)-(R,S)-aspartato]cobalt(III) perchlorate monohydrate and its relationship to the optically active [Co(dtp)(S)-Asp]+ isomers
Authors: Ondráček Jan , Soldánová Jitka , Jursík František
Published: February 2010

The crystal and molecular structure of the title compound was determined by X-ray diffraction. The structure was solved by the heavy-atom method and refined to an R value of 0.118 for 997 observed reflections. The unit cell is monoclinic with a = 11.980(1), b = 12.130(1), c = 12.641(1) Å, β = 108.18(1)°, Z = 4. The space group is P21/c. The crystals are composed of sym-fac-[Co(dtp)(R,S)-Asp]+, ClO4-, and H2O held together probably in a network of hydrogen bonds. The structural data obtained allow an explanation for the sym-fac-[Co(dtp)(S)-Asp]+ isomer optical activity contributions which can arise from the distorted chair conformation of one of the two dpt fused chelate rings, the donor atom distortions from the defined plane, and the (S)-aspartic acid vicinal chirality.
IR-spectroscopic study of the condensation products of heat-degradation of polyethylene and polypropylene in inert atmosphere
Authors: Svoboda Miroslav , Štokr Jan , Schneider Bohdan
Published: February 2010

Infrared spectra of condensates generated by heating of polyethylene and polypropylene in inert atmosphere for various times at 300, 400, 500 and 600 °C were measured. The condensed products were characterized by means of infrared spectra. It was found that IR-spectra are suitable for determining the thermal history of polyethylene and polypropylene degradation.
Stereoselective synthesis of (6Z,9Z)-6,9-nonadecadiene and (6Z,9Z)-6,9-heneicosadiene, sex pheromones of Bupalus piniarius and Utethesia ornatrix
Authors: Vig Om P. , Kad Goverdhan L. , Sharma Madan L. , Dogra Vijay , Sharma Sanjiv , Huq Mohammad A. , Sabharwal Arun
Published: February 2010

Stereoselective syntheses of (6Z,9Z)-6,9-nonadecadiene (II), sex attractants of female moths Bupalus piniarius and Utethesia ornatrix, have been reported.
3,7-Dialkyl-8-alkyl- or -aryl-3,7-dihydropurine-2,6-diones
Authors: Rybár Alfonz , Hesek Dušan , Szemes Fridrich , Alföldi Juraj , Tegza Marian
Published: February 2010

3,7-Dialkyl-8-alkyl- or -aryl-3,7-dihydropurine-2,6-diones XII-XIV were synthesized from 5-alkylamino-6-amino-1-alkyl-2,4(1H,3H)-pyrimidinediones VII-IX by three methods: the first is based upon an acid catalyzed cyclization of the starting derivatives VII-IX with orthoesters of carboxylic acids in dimethylformamide. In the second and third methods the 5-((N-acyl)(N-alkyl)amino) derivatives X, XI, obtained by acylation of VII-IX were cyclized either in aqueous solution of alkali metal hydroxides, or in dimethylformamide in the presence of alkali metal hydroxides, or in dimethylformamide in the presence of alkali metal carbonates. Intermediates VII-IX were prepared from 6-amino-1-alkyl-2,4(1H,3H)-pyrimidinediones I-III via the corresponding 5-bromo derivatives IV-VI and by their aminolysis with the appropriate alkylamines.
Peptide synthesis under high pressure by aminolysis of methyl and phenyl esters
Authors: Gut Vladimír , Makarova Zinaida G. , Molokoedov Alexander S. , Zhulin Victor M.
Published: February 2010

High pressure may, depending on solvent, enhance the reactivity of methyl and phenyl ester of the N-protected dipeptide Ala-Ala with the amino component, valine tert-butyl ester, yielding the protected tripeptide. Results of this reaction in several solvents are discussed.
Synthetic experiments aiming at 1,2,4,5-tetrahydro-3-benzothiepin derivatives
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: February 2010

Article without abstract
Optimum criterion of extractor design and operation
Authors: Procházka Jaroslav , Sovová Helena , Bízek Vladislav , Heyberger Aleš
Published: February 2010

For optimizing a production plant an objective function, "optimum criterion", was formulated and an optimum criterion of a part of the plant, an apparatus, consistent with that of the plant was proposed. This was specified for a counter-current extraction column with mechanical agitation and various sets of constraints were discussed. An optimization algorithm of complex system based on alternating minimization of individual parts and of the whole system was suggested.
The solubility of cupric selenate and the bonding conditions in the compound Cu(HSeO3)2
Authors: Mička Zdeněk , Čermák Miroslav , Nižňanský Daniel
Published: February 2010

The solubility diagram for CuSeO3-SeO2-H2O at 298 K was studied for the first time, and was employed to define the conditions for the formation of Cu(HSeO3)2. The bonding conditions including the behaviour of protons in the hydrogen bonds were described for this compound.
Reactions of isomeric oxo-2(3)-oxahomodiamantanes. Dehydration of tetracyclic diols with concentrated phosphoric acid
Authors: Janků Josef , Isaev Sergei D. , Cybulskii Leonid V. , Vodička Luděk , Yurchenko Alexander G.
Published: February 2010

Reduction of 11-oxo-10-oxapentacyclo[7.4.1.14,13.02,7.06,12]pentadecane (lactone I) and 10-oxo-11-oxapentacyclo[7.4.1.14,13.02,7.06,12]pentadecane (lactone II) with lithium aluminium hydride afforded 4-hydroxymethyl-12-hydroxytetracyclo[7.3.1.02,7.06,11]tridecane (diol III) and 4-hydroxy-12-hydroxymethyltetracyclo[7.3.1.02,7.06,11]tridecane (diol IV). Diol III reacted with concentrated phosphoric acid to give 3-methyltetracyclo[6.4.1.02,6.05,10]tridecanone-9 (V) as practically the sole product. Diol IV afforded a complex mixture of products in which were identified 2-methyl-3-oxadiadamantane (VI; 57%), 10-oxa-2(3)-homodiadamantane (VII; 20%), 3-hydroxydiadamantane (VIII; 3%), diadamantane (X; 7%) and diadamantanone (IX; 2%).
Amino terminal sequence of type 3 streptococcal M protein extraction products
Authors: Kluh Ivan , Kühnemund Otto , Pavlík Manfred , Morávek Ladislav , Havlíček Jiří
Published: February 2010

The amino terminal hypervariable part of the M protein molecule was chosen as a basis for the preparation of a synthetic peptide vaccine against group A streptococci. As part of the mapping of various serological types the main products of extraction of type M Streptococcus pyogeneswith limited pepsin (Pep) hydrolysis at pH 5.5 and with phage-associated lysin (PAL) were sequenced. Two entirely different sequences were obtained. The sequence of PAL M3 shows the absence of the α-helical potential in the shorter N-terminal region as is characteristic of the N-terminus of the M protein molecule. The main product of limited hydrolysis Pep M3 (pH 5.5), which shows the presence of the α-helical potential from the very amino terminal residue of its chain, does not involve most likely the proper N-terminus of the M protein. Extraction with pepsin under conditions of very limited proteolysis (pH 5.8) yielded a fragment with N-terminal sequence identical with that of PAL M3 (extracted nonproteolytically).
Preparation of enzyme electrode for D-glucose determination by immobilization of glucose oxidase on collagen membrane
Authors: Vrbová Eva , Marek Miroslav
Published: February 2010

An enzyme electrode for the determination of D-glucose was prepared by immobilization of glucose oxidase (EC 1.1.3.4.) on an activated collagen membrane using glutaraldehyde and the Ugi reaction resp. and by subsequent fixation of the membrane to an oxygen sensor of the Clark type. Two different procedures for the modification of the support, the composition of the reaction mixture and the immobilization time were examined. The electrode prepared was tested as regards the effect of pH and temperature on the magnitude of the response. The range of the linear dependence of the sensor response on substrate concentration (1.7 . 10-5 - 2.0 . 10-3), the apparent Michaelis constant of the immobilized enzyme (KM(app.) = 4.16 . 10-3 mol dm-3) and the stability of the biosensor as function of storage mode and number of assays performed with one electrode were determined. In view of the high stability and linear range of the concentration dependence the enzyme electrode is suitable for the determination of D-glucose in samples analyzed in agricultural and food laboratories.
Stability of NH4+ and [Zn(NH3)4]2+ in nitrobenzene saturated with water
Authors: Makrlík Emanuel
Published: February 2010

General relations among thermodynamic parameters characterizing complex-formation equilibria in both phases of a two-phase extraction system and ion transfers across the interface of this system have been derived. Using the mentioned relations and known parameters stability constant of [Zn(NH3)4]2+ and protonization constant of NH3 in nitrobenzene saturated with water have been calculated for a temperature of 25 °C.
The evidence and applications of equilibria between hydroxide and alkoxide ions in aqueous-alcoholic systems
Authors: Mollin Jiří , Staňková Pavlína , Staňková Oldřiška
Published: February 2010

The composition of solvolysis products of butyl bromide, acetanhydride, and benzoyl chloride has been followed aqueous alcohol in alkaline and (except for butyl bromide) also in neutral regions. The results have been used as a piece of evidence of the existence of equilibrium between hydroxide and alkoxide ions and for evaluation of the possibility of calculation of the concentration ratio of hydroxide and alkoxide ions from the concentration ratios of the products as well as for evaluation of selectivities of the solvolytic reactions for mechanistic purposes.
How to achieve a high information gain of results of quantitative analyses
Authors: Eckschlager Karel
Published: February 2010

The effect of procedure optimization, good laboratory practice and quality data control on the information gain of quantitative analyses and on its time stability is discussed.
Interpretation of chromatographic characteristics of mobile phase in liquid chromatography by means of solvent parameters
Authors: Pytela Oldřich , Hálová Jaroslava , Ludwig Miroslav
Published: February 2010

The paper applies the methods of correlation analysis and analysis of latant variables (PCA, PLS, canonical correlation) to study the interrelations of general chromatographic characteristics in the adsorption and partition chromatography (ε0, P', χe, χd, χn, Iap) and interpretation posibilities of these characteristics by means of general solvent parameters. The analyzed set of chromatographical parameters has been found to be relatively heterogeneous, its dominant properties being expressible by two principal components including 75.6% of source variability. The chemometrical solvent scale with three parameters PAC, PBC, PPC proved suitable for interpretation of the chromatographic parameters. This scale in the PLS method with two necessary latent variables explains 64.9% of the variability of matrix of chromatographic characteristic and enables their description. An elution solvent series has been constructed on the basis of this chemometrical solvent scale by the method of multicriterial decision ELECTRA III.
Reactivity of proton and general acid with 1,3-bis-(4-methylphenyl)triazene in aqueous methanol
Authors: Pytela Oldřich , Nevěčná Taťjana , Kaválek Jaromír
Published: February 2010

The effect of concentration of benzoic acid and composition of the binary solvent water-methanol on the rate of decomposition of 1,3-bis(4-methylphenyl)triazene has been studied. It has been found that both general acid catalysis by undissociated benzoic acid and catalysis by the proton are significant. The rate constant kHA of general acid catalysis decreases monotonously with decreasing amount of water in the mixture due to preferred solvation of the activated complex as compared with the educts. The rate constant kH of the catalysis by proton in its dependence on methanol concentration exhibits a minimum for 80% (by wt.) of methanol in the mixture. This phenomenon is caused by formation of the conjugated acid from more basic methanol and proton with simultaneous solvation by water and methanol; the particle thus formed is a weaker acid as compared with the complexes existing in water or in methanol. The kH value is higher in methanol than in water due to preferred solvation of the educts as compared with that of the transition state.
Studies in Vilsmeier-Haack reaction. Application to quinoxalinones
Authors: Awad Ibrahim M. A. , Hassan Khairy M.
Published: February 2010

The 3-methyl group in quinoxalinones I and II has been found to undergo diformylation by Vilsmeier reagent to give the corresponding aminoacrolein derivatives (III, IV). Condensation and/or interaction of III or IV with some secondary heterocyclic amines and/or with hydrazine, phenylhydrazine and hydroxylamine affords the related 3-methyl-N-(1H)-2-quinoxalinone and 1,3-dimethyl-2-quinoxalinone derivatives (VII-XVIII), some with pronounced fluorescence activities. All synthesized compounds have been screened in vitro for their antimicrobial activities against Gram-positive and Gram-negative bacteria. The structures of these compounds were confirmed by elemental analysis, IR and 1H NMR spectroscopy.
MNDO CI study of the photoisomerization of pentadieniminium
Authors: Ertl Peter
Published: February 2010

Photoisomerization mechanism in model retinal-like protonated Schiff base pentadieniminium was investigated by using MNDO method with configuration interaction. Isomerizations around various double bonds were studied and twisted biradical geometries in S0 and S1 states were optimized. Photoisomerization proceeds exclusively around the central double bond where the twisted S1 state is strongly stabilized and the S0-S1 gap is minimal.
Electrostatic effects in ionization equilibria: An MNDO study of proton and hydrogen transfer reactions of 4-fluorobutanol
Authors: Friedl Zdeněk , Böhm Stanislav
Published: February 2010

MNDO molecular orbital calculations have been carried out for sp and ap conformers of 4-fluorobutanol and some 4-X-bicyclo[2.2.2]octanols (X = F, Cl). The results are analyzed in terms of substituent effects on proton transfer enthalpies δ ΔH0 and homolytic bond dissociation energies δDH0 (A-H) and compared with the previously reported data for 5-fluoropentanoic acid and 4-fluorobutylamine. The results are further compared with the prediction of the electrostatic theory. It is shown that the substituent polar effect FD on the acidities of halogenoalcohols is largely due to substituent interaction in the anions and only to a smaller extent to interactions in the neutral alcohol. A small contribution (about one-tenth for the ap conformer) is probably also made by the substituent effects on homolytic bond dissociation energies DH0 (A-H).
The light-scattering Mueller matrices for Rayleigh and Rayleigh-Gans-Debye approximation
Authors: Holoubek Jaroslav
Published: February 2010

Recent theoretical work has shown that the complete set of polarized elastic light-scattering studies should yield information about scatterer structure that has so far hardly been utilized. We present here calculations of angular dependences of light-scattering matrix elements for spheres near the Rayleigh and Rayleigh-Gans-Debye limits. The significance of single matrix elements is documented on examples that show how different matrix elements respond to changes in particle parameters. It appears that in the small-particle limit (Rg/λ < 0.1) we do not loose much information by ignoring "large particle" observables.
Kinetics of guyard's reaction with regard to permanganate chemical oscillators
Authors: Mrákavová Marta , Treindl Łudovít
Published: February 2010

Phosphoric acid is a necessary component of permanganate chemical oscillators. When Mn(II) ions are present in a stoichiometric excess, the reaction is of first order with respect to the concentration of MnO4- ions and of fractional order with respect to the concentration of Mn(II). When MnO4- ions are in a stoichiometric excess, the reaction is autocatalytic in nature and the inflexion time increases linearly with the concentration of H3PO4; analysis of the sigmoidal curve gave the rate constant of the non-catalytic step, k1, and that of the catalytic step, k2, which is indirectly proportional to the concentration of H3PO4. The probable mechanism of the Guyard reaction involves a reversible equilibrium between Mn(IV) and colloidal MnO2 and subsequent coagulation to form a MnO2 suspension. Similarly to permanganate chemical oscillators, phosphoric acid or its ions play the key role, since they stabilize the colloidal MnO2 which serves as a reservoir of Mn(IV) ions.
The polarographic and voltammetric determination of the 3'-halogen derivatives of N,N-dimethyl-4-aminoazobenzene
Authors: Barek Jiří , Kubíčková Jana , Mejstřík Viktor , Petira Oldřich , Zima Jiří
Published: February 2010

The polarographic reduction of the 3'-halogen derivatives of N,N-dimethyl-4-aminoazobenzene was studied in mixed water-methanol medium and optimum conditions were found for the determination of these genotoxic substances by tast polarography in the concentration range 1 . 10-4 to 2 . 10-6 mol l-1, differential pulse polarography at a dropping mercury electrode in the range 1 . 10-4 to 2 . 10-7 mol l-1 and fast scan differential pulse voltammetry at a hanging mercury drop electrode in the range 1 . 10-6 to 2 . 10-8 mol l-1. The increase in the sensitivity resulting from adsorptive accumulation of the studied substances on the surface of a hanging mercury drop can be utilized in the determination using the latter method in the concentration range 1 . 10-8 to 2 . 10-9 mol l-1.
Stationary states of chemical reactor connected to a separation unit
Authors: Horák Josef , Rosol Petr , Piálek Lubomír
Published: February 2010

Stationary states are analyzed of an isothermal chemical reactor connected by direct recycle with a separation unit from which a part of mixture enriched by the initial substances is returned into the reactor. It was found out that recycling can be the cause of the existence of multiple stationary states of system. The effect is discussed of kinetic law of chemical reaction and separation function of separation unit on the number of stationary states and their stability. The method based on the determination of trajectories of pseudostationary states of the initial substance concentrations in phase plane was used for analysis.
Kinetic investigation of the oxidation of bromide ions by cobalt(III). Reaction in the presence of p-toluic acid
Authors: Schlosserová Júlia , Hronec Milan , Veselý Václav
Published: February 2010

The rate of Co(III) reduction under inert atmosphere in the presence of p-toluic acid (PTA) and hydrobromide obeys the rate law d[Co(III)]/dt = k[Co(III)]2 [Co(II)]-1 [PTA] [HBr]. The proposed reaction mechanism involves the reduction of Co(III) by Br- ions and formation of a cation-radical from p-toluic acid. p-Xylene is attacked by bromine species and not directly by Co(III). The rate constants of Co(III) and Br- consumption as well as apparent activation energies were estimated.
Formation of acetals and cleavage of the five-membered ring in the bromination of isatin in alcohols
Authors: Gasparič Jiří , Vontor Tomáš , Lyčka Antonín , Šnobl Dobroslav
Published: February 2010

Bromination of isatin (I) in alcohols affords in good yield 5,7-dibromo-3,3-dialkoxy-2-indolinones (IIIa and IIIb) which arise by reaction catalysed with hydrogen bromide liberated in the bromination. The reaction affords also minor amounts of 2,4,6-tribromoaniline (IV) formed by splitting off of two carbon atoms from the isatin five-membered ring.
Synthesis of isomeric 1,1'-phenylene-bis(6-azauracil-5-carbonitriles)
Authors: Slouka Jan
Published: February 2010

The described synthesis of all three isomeric 1,1'-phenylene-bis(6-azauracil-5-carbonitriles) IVa-IVc starts from the respective 1-nitrophenyl-6-azauracil-5-carbonitriles Ia-Ic which were reduced to the corresponding amino derivatives IIa-IIc, diazotized, and coupled with ethyl cyanoacetylcarbamate to give the isomeric hydrazones IIIa-IIIc which were finally cyclized to the title compounds containing two 6-azauracil rings. A general formula is presented for calculation of mutual distance of arbitrary atoms in any planar molecules.
Synthesis of new polyfunctionally substituted pyridazines, phthalazines, cinnolines and thieno[3,4-c]pyridazines
Authors: El-Kousy Salah , El-Sakka Ibraheim , El-Torgoman Abdel Monem , Roshdy Hesham , Elnagdi Mohamed Hilmy
Published: February 2010

The reaction of ethyl 2-arylhydrazono-3-oxobutyrates (Ia, Ib) with active methylene ketones afforded pyridazin-5-carbonitrile derivatives. The methyl function in the ethyl pyridazin-3-carboxylate derivatives IIa, IIb reacted with arylidenemalononitrile to yield the phthalazine derivatives Va-Vf and with elemental sulfur to yield the thienopyridazines XIXa, XIXb. The cinnolines are producted from reaction of IIa, IIb with diethyl acetonedicarboxylate.
Purine nucleoside phosphorylase: Isolation and characterization
Authors: Šedivá Katarina , Votruba Ivan , Holý Antonín , Rosenberg Ivan
Published: February 2010

Purine nucleoside phosphorylase (PNP) from mouse leukemia cells L1210 was purified to homogeneity by a combination of ion exchange and affinity chromatography using AE-Sepharose 4B and 9-(p-succinylaminobenzyl)hypoxanthine as the matrix and the ligand, respectively. The native enzyme has a molecular weight of 104 000 and consists of three subunits of equal molecular weight of 34 000. The results of isoelectric focusing showed that the enzyme is considerably microheterogeneous over the pI-range 4.0-5.8 and most likely consists of eight isozymes. The temperature and pH-optimum of phosphorolysis, purine nucleoside synthesis and also of transribosylation is identical, namely 55 °C and pH 7.4. The transribosylation reaction proceeds in the presence of phosphate only. The following Km-values (μmol l-1) were determined for phosphorolysis: inosine 40, 2'-deoxyinosine 47, guanosine 27, 2'-deoxyguanosine 32. The Km-values (μmol l-1) of purine riboside and deoxyriboside synthesis are lower than the values for phosphorolysis (hypoxanthine 18 and 34, resp., guanine 8 and 11, resp.). An affinity lower by one order shows PNP for (-D-ribose-1-phosphate, (-D-2-deoxyribose-1-phosphate (Km = 200 μmol l-1 in both cases) and phosphate (Km = 805 μmol l-1). The substrate specificity of the enzyme was also studied: positions N(1), C(2) and C(8) are decisive for the binding of the substrate (purine nucleoside).