bluuebunny/crossref_metadata_2025 huggingface dataset:
Purification and characterization of two forms of Cu/Zn-superoxide dismutase from bovine erythrocytes by preparative isoelectric focusing
Authors: Kovářová Hana , Šimša Jan , Křížala Josef
Published: August 2011

Two forms of Cu/Zn-superoxide dismutase with isoelectric points (pI) 6.3 and 5.2 were isolated from bovine erythrocytes by preparative isoelectric focusing. Both forms show a relative molecular weight of 32 000 daltons corresponding to the value reported for the monomer molecule. From spectral analysis the maximum in the ultraviolet region of the spectrum (276 nm) is identical for both forms of superoxide dismutase whereas the maxima in the visible region are different (for the pI 5.2 form the maximum lies at 405 nm and for the pI 6.3 form at 695 nm). The different migration of the enzymatically active zones toward the anode during electrophoresis in alkaline media corresponds to their different isoelectric points.
Ab initio calculation of the equilibrium constant of the reaction Na + H2O ⇌ NaOH + H
Authors: Kozák Ivan , Čársky Petr
Published: August 2011

Theoretical prediction of the equilibrium constant of the title reaction was obtained by a standard statistical-thermodynamic treatment for which all necessary molecular constants were generated by the ab initio SCF calculations. The experimental value at 2 030 K is quantitatively reproduced. Comparison with experiment is also made for geometry parameters and vibrational frequencies of NaOH.
The temperature and concentration dependence of viscosity and the concentration dependence of glass transition temperature for the system calcium nitrate-potassium nitrate-water
Authors: Skokánek Mojmír , Malá Jarmila , Sláma Ivo
Published: August 2011

The temperature and concentration dependence of viscosity of the system calcium nitrate-potassium nitrate-water was studied in the temperature range -20 to +75 °C for concentrations given by ionic fractions of the potassium salt of 0.1, 0.2, 0.3, 0.4, and 0.5. The mole fraction of the salts was within the range 0.047 to 0.238. The temperature and concentration dependence of viscosity has been correlated with empirical equations. An equation describing the temperature and concentration dependence of viscosity has been proposed on the basis of the variation of glass transition temperature with concentration.
Specific adsorption of tetraalkylammonium ions on bismuth from nonaqueous solvents
Authors: Palm U. , Väärtnŏu M. , Salve M.
Published: August 2011

A procedure for the calculation of the characteristics of the inner part of the electrical double layer has been elaborated on the basis of the capacity data obtained in the conditions of specific adsorption of ions, accompanied by an increase of the inner layer dimensions. The formulae derived have been verified by studying the specific adsorption of tetraalkylammonium cations from aliphatic alcohols.
Synthesis of nucleoside analogs by addition-cyclization reaction of 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate
Authors: Valentíny Marián , Martvoň Augustin , Kováč Pavol
Published: August 2011

Reactions of 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate (I) with various hydrazides gave 4-substituted 1-acylthiosemicarbazides. Their cyclization, by treatment with sodium methoxide, gave analogs of nucleosides. The reaction of (I with thioglycolic acid to give substituted 1,3-thiadiazolidine has also been studied.
Hydrolytic products of 4-aryl-2,3-dicyano-1-naphthol derivatives
Authors: Křepelka Jiří , Vančurová Iva , Holubek Jiří , Roubík Jiří
Published: August 2011

Depending on the conditions of hydrolysis, vicinal aromatic dicyano derivatives Ia-Ic gave anhydrides IIa-IIe and imides of 4-aryl-1-alkoxynaphthalene-2,3-dicarboxylic acids, IIIa,b, along with products of partial hydrolysis, decarboxylation and demethylation, IVa-IVd, IVf-IVg, and derivatives of benzo(c)fluorene, Va-Vc. The derivatives Va-Vc were also obtained by acid hydrolysis of dicyano derivatives Id-Ig. Methanolysis of the anhydride IId gave a mixture of positional isomers, IVh, which was esterified to the diester IVe. Intramolecular ring closure of the isomers IVh afforded derivatives of benzo(c)fluorene, VIa-VIb. The structures of the selected compounds were corroborated by IR and 1H NMR spectra. The compounds Va-Vc exhibited antiviral effects and interferonogenic activities in vivo.
4-(ω-(2-Amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)alkyl)benzoic acids with an antineoplastic effect
Authors: Kotva Rudolf , Křepelka Jiří , Řežábek Karel , Vachek Jaroslav
Published: August 2011

4-(ω-(2-Amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)alkyl)benzoic acids II-VI were prepared by condensation of triethyl 2-(ω-(4-carboxyphenyl)alkyl)-1,3-propanedioates VII-XI with guanidine and subsequent saponification. Compounds II-VI had an antineoplastic effect in animals with experimental transplantable tumours. The effect of compound II was comparable with that of compound I (Damvar).
Potential metabolites of the noncataleptic neuroleptics: Synthesis of 2-chloro-6-hydroxy(and methoxy)-10-[4-(2-hydroxyethyl)piperazino]-10,11-dihydrodibenzo[b,f]thiepin
Authors: Protiva Miroslav , Šedivý Zdeněk , Pomykáček Josef , Bártl Václav , Holubek Jiří , Svátek Emil
Published: August 2011

[5-Chloro-2-(2-methoxyphenylthio)phenyl]acetic acid (VI), obtained via the acetophenone derivative IV, was cyclized to 2-chloro-6-methoxydibenzo[b,f]thiepin-10(11H)-one (VIIIa). 2,10-Dichloro-6-methoxy-10,11-dihydrodibenzo[b,f]thiepin (Xa) was prepared via the alcohol IXa and its substitution reaction with 1-(2-hydroxyethyl)piperazine gave the compound III. Demethylation with boron tribromide in chlorobenzene resulted in the title compound II which is a potential metabolite of the noncataleptic neuroleptic agent docloxythepin.
Interaction of horse liver alcohol dehydrogenase with acridine orange
Authors: Kovář Jan , Dürrová Eva
Published: August 2011

The inhibition of horse liver alcohol dehydrogenase by acridine orange was studied as a function of the concentration of the two coenzyme and substrate forms, the inhibitor concentration, pH, and in the presence of other inhibitors of the enzyme. The changes in optical properties, of the dye occurring during its binding to the enzyme (especially the absorption spectra and the fluorescence polarization) were also studied. The existence of an efficient resonance energy transfer from the excited NADH molecule to the acridine orange molecule in the corresponding ternary complex with the enzyme has also been demonstrated. The results obtained provide evidence showing that the binding site of alcohol dehydrogenase for acridine orange differs from the binding sites of this enzyme for both the coenzyme and the substrate. This binding site most likely is localized in a large substrate pocket of the enzyme near to the binding sites for o-phenanthroline and berberine and very close to the binding site for tricyclic psychochemicals.
Contribution to the study of the reaction between solid sodium carbonate and gaseous sulphur dioxide
Authors: Vobiš Jiří , Mocek Karel , Erdös Emerich
Published: August 2011

The heterogeneous reaction between solid sodium carbonate and gaseous sulphur dioxide of partial pressures from 1.2 to 7.5 kPa has been investigated in a fixed-bed reactor at temperatures of 54 and 81 °C in the presence of water vapour of partial pressures from 0.30 to 1.25 kPa. An independence of the reaction course of the sulphur dioxide content in the gas phase and a linear dependence of the reaction rate on the partial pressure of water vapour were found under the above conditions. The rate equation derived previously has been simplified and the set of differential equations describing the reaction in a fixed bed has been solved. The relations obtained have been applied to an evaluation of the effective rate constant. The true rate constant has been estimated to be independent of temperature.
The crystal and molecular structure of the chloro-bis(pentamethylenedithiocarbamate) iron(III)-chloroform (1 : 1) complex
Authors: Kettman Viktor , Pavelčík František , Majer Jaroslav
Published: August 2011

The crystal and molecular structure of FeCl(S2CN(CH2)5)2CHCl3 were solved by the X-ray structural analysis method and refined to R 0.073 for 1996 observed independent reflections. The compound crystallizes in a space group of symmetry P1 with the following unit cell dimensions: a = 0.6384 (5), b = 1.475 (1), c = 1.1966 (6) nm, α = 86.20 (5), β = 95.24 (6), γ = 97.45 (6)°. The experimentally measured density of the crystals of the substance is 1.60 Mgm-3 and the value calculated for Z = 2 is 1.59 Mgm-3. The basic skeleton structure is formed by the complex molecules forms closed cavities filled with chloroform molecules. The central Fe(III) ion is characterized by a quartet ground state (S = 3/2) and is pentacoordinated by a chlorine atom and 4 sulphur atoms in a tetragonal bipyramidal arrangement. The complex-chloroform interaction depends on formation of a double-branched hydrogen bond of the chloroform proton with two sulphur atoms in the coordination polyhedron.
Influence of crystallographic orientation on the kinetics of copper dissolution in sodium hydroxide
Authors: Miadoková Milica , Sušinka Peter
Published: August 2011

The kinetics and mechanism of copper dissolution in sodium hydroxide were studied on different crystal planes. Differences in the reactivity on the planes (100), (110), and (111) were observed. The differences in the kinetics and mechanism depend on the reaction regime and can be related under certain conditions to the work function.
Modelling of Fischer-Tropsch catalytic synthesis by pattern recognition method. Chemisorption of hydrogen on metals
Authors: Kuchynka Karel , Fusek Jiří , Štrouf Oldřich
Published: August 2011

Forty nine metals characterized by a set of fifteen fundamental physical variables were classified with respect to chemisorption of hydrogen. Dimensionality reduction of this physical model led to the determination of nine linearly almost independent variables. This reduced set discriminated the chemisorbing metals from the inactive ones to a satisfactory extent. The physico-chemical significance of these variables for the chemisorption of hydrogen as one of the elementary steps of Fischer-Tropsch catalytic process is discussed.
Modelling of the catalytic Fischer-Tropsch synthesis by pattern recognition. Chemisorption and dissociation of carbon monoxide on metals
Authors: Štrouf Oldřich , Kuchynka Karel , Fusek Jiří
Published: August 2011

A set of forty nine metals was classified with respect to chemisorption of carbon monoxide and a set of nineteen transition metals was similarly treated with respect to dissociation of the chemisorbed molecule. In both cases the metals were characterized by a set of fifteen variables of basic physical importance. Dimensionality reduction yielded eight linearly weakly dependent variables related to chemisorption of CO whereas the reduced set for dissociation had four parameters only. The physico-chemical significance of the characterizing linearly weakly dependent variables is discussed.
The effect of partial exchange of sulphonated macroporous styrene-divinylbenzene copolymers for different ions on their catalytic activity
Authors: Kmošták Svatomír , Setínek Karel
Published: August 2011

The catalytic activity of sulphonated macroporous styrene-divinylbenzene copolymers, the exchange capacity of which was neutralized from 30, 50 and 80% by Fe(III) ions and from 30% by Na ions and that of Wofatit Y-37 ion exchanger neutralized from 10% of its total exchange capacity by several transition metal ions and by sodium has been studied in isomerisation of cyclohexene and dehydration of 1-propanol in the gas phase at 130 °C. It was demonstrated that in both reactions transition metal ions exhibit additional effect to the expected neutralization of the polymer acid groups. In the case of cyclohexene isomerization, this effect depends on the degree of crosslinking of polymer mass of the catalyst. Such dependence has not been, however, observed in dehydration of 1-propanol. The type of transition metal ions did not exhibit any significant effect on the catalytic activity of the polymer catalysts studied.
A study of the interaction of oligoisoprenyllithium and oligostyryllithium with some electrondonors
Authors: Kmínek Ivan , Kašpar Miroslav , Trekoval Jiří
Published: August 2011

The "cross" association between butyllithium (BuLi), on the one hand, and oligoisoprenyllithium or oligostyryllithium, on the other, was investigated thermometrically. Dependences of a change in the reaction enthalpy on the ratio of both components were compared with a theoretical assumption that the "mixed" associate consists of trimeric BuLi bound to the unassociated form of "living" oligomers. Thermometric titrations were used to investigate the interaction of "living" oligomers with tetrahydrofuran (THF), 1,2-dimethoxyethane, N,N,N',N'-tetramethylethylenediamine and triethyl amine. GLC analysis of the gas phase in equilibrium with solutions of electrondonors and "living" oligomers allowed the amount of free electrondonor to be determined at various ratios of the two components; the data were used in the determination of the stoichiometric coefficients of the equilibrium reactions under study. THF splits the associated forms of "living" oligomers and forms with them two types of complexes containing one or two THF molecules per one Li atom. All measurements were performed in benzene at 303 K.
The use of 2-(2-hydroxyphenylazo)-7-oxo-5,5-dimethyl-4,5,6,7-tetrahydrobenzothiazole as an extractant for Cu(II), Ni(II), Co(II), Pb(II) and Cd(II)
Authors: Vačková Margita , Kuchár Emil , Šuriková Viera
Published: August 2011

The heterocyclic azo dye, 2-(2-hydroxy-5-ethylphenylazo)-7-oxo-5,5-dimethyl-4,5,6,7-tetrahydrobenzothiazole (I), was prepared. The acid-base and optical parameters of the azo dye were found spectrophotometrically and the molar absorption coefficients and concentration dissociation constants were determined. The formation of the chelates of compound (I) with Cu(II), Ni(II), Pb(II) and Cd(II) was studied. The molar absorption coefficients and stability constants of the chelates were determined by calculations, graphical and logarithmic analysis, based on data from the A = f(pH) curves. The region of optimal extraction and the extraction constants were found for the chelates of I with Cu(II), Ni(II), Co(II) and Pb(II).
Fragmentation of isomeric dideoxy derivatives of 1,6-anhydro-β-D-hexopyranoses under electron impact
Authors: Tureček František , Trnka Tomáš , Černý Miloslav
Published: August 2011

Electron impact mass spectra of all possible dideoxy derivatives of 1,6-anhydro-β-D-hexopyranoses and their sixteen specifically deuterium-labeled derivatives are reported. The spectra of positional isomers differ considerably making possible the reliable location of the hydroxyl group by mass spectrometry. The configuration of the hydroxyl group at C(2) and C(4) has only a negligible effect on the fragmentation pattern of stereoisomers. However, mass spectra of the C(3)-configurational isomers differ sufficiently to permit a stereochemical assignment. The fragmentation paths were elucidated by means of deuterium labeling and metastable spectra.
Partial methylation of methyl 2,6-dideoxy-α-D-xylo- and α-D-lyxo-hexopyranoside
Authors: Jarý Jiří , Marek Miroslav
Published: August 2011

Rate of methylation of the hydroxyl groups in the title glycosides was investigated during their reaction with methyl iodide and sodium hydroxide in acetonitrile. Relative rate constants of the side-reactions and subsequent reactions taking place were calculated. The differences in the reaction rates of methylation of individual hydroxyl groups are discussed in connection with the possible polar and steric effects.
Cycloadditions of C-benzoyl-N-phenylnitrone with furocondensed derivatives
Authors: Fišera Lubor , Dandárová Miloslava , Kováč Jaroslav , Mesko Peter , Krutošíková Alžbeta
Published: August 2011

Single regioisomeric cycloadduct IIa was formed in a 35% yield upon cycloaddition of the title nitrone Ia with benzofuran. The 1,3-dipolar cycloaddition proceeded with derivatives of 4-R-furo[3,2-b]pyrrole V or VI to the furan ring to form only one regioisomer VIIa or VIIIa in a high yield (93-95%). Dehydrogenation of the latter with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone led to the nitrone X or XII. Also C,N-diphenylnitrone reacted with furopyrroles to afford the cycloadduct VIIIb. Exclusively endo-cycloadducts originated; their transition state was stabilized by secondary orbital interactions.
The effect of some structural modifications of the oxytocin molecule on the duration of the galactogogic response
Authors: Barth Tomislav , Slaninová Jiřina , Servítová Linda , Lebl Michal , Kotsira-Engonopoulos Christine , Tzougraki Chrysa , Photaki Iphigenia , Krojidlo Milan , Jošt Karel
Published: August 2011

The duration of the galactogogic response to analogues of oxytocin, modified mainly in the aminoterminal part of the molecule, was determined in experiments with lactating rats. The influence of the individual structural modifications was investigated by determining the dependence of both the intensity of the effect and the total effect of the compound on the log dose.
Relation of the temperature derivative of heat of vaporization to the difference of heat capacities along the saturated vapour pressure curve
Authors: Svoboda Václav , Wagner Zdeněk , Voňka Petr , Pick Jiří
Published: August 2011

A method of calculating the heat capacity difference of liquid and its vapour along saturated vapour pressure curve is discussed. The qualitative course of this difference in dependence on temperature obtained from the data on the temperature dependence of heat of vaporization of pure substances is judged.
Oxidation of benzaldehyde by dioxygen. Photoinitiated reaction
Authors: Luňák Stanislav , Lederer Pavel , Stopka Pavel , Vepřek-Šiška Josef
Published: August 2011

The photoinitiated oxidation of benzaldehyde is catalyzed by traces of transition metal ions. The photocatalytic effects of transition metals are explained in terms of the formation of their unstable oxidation states which act as catalysts of the thermal oxidation. The reaction catalyzed by Fe(II) and Fe(III) ions is discussed in detail.
Electronic structure and 11B-NMR spectra of nine-vertex heteroboranes: 4-CB8H14, 4-NB8H13, 4-SB8H12 and 4,6-C2B7H13
Authors: Dolanský Jiří , Heřmánek Stanislav , Zahradník Rudolf
Published: August 2011

11B-NMR Spectra of 4-CB8H14, 4-NB8H13, 4-SB8H12 and 4,6-C2B7H13 are presented, together with a detailed assignment of individual signals. Correlations of 11B NMR chemical shifts with some STO-3G and CNDO/2 density matrix properties are evaluated. Similarities in the electronic structure and the nature of heteroatom bonding are discussed.
Properties of electrochemically generated primary anion radicals of 2,5-dimethyl-1-nitrophenylpyrroles
Authors: Kubáček Pavel
Published: August 2011

The first step of electrochemical reduction of 2,5-dimethyl-1-nitrophenylpyrroles on a platinum electrode in anhydrous acetonitrile consists in an one-electron process producing relatively stable anion radicals. The prediction based on HMO calculations concerning an almost complete localization of the LFMO in the nitrophenyl part of the studied molecules is fully confirmed by means of EPR spectroscopy. Magnitude of the found proton splitting constants is very close to the values found for anion radical of nitrobenzene. The splitting by nucleus of nitrogen atom of pyrrole cycle can be explained exclusively by the mechanism of π-σ spin polarization of σ C-N bond and by the spin population at the carbon atom. The EPR method has also been used for following the kinetics of decomposition of anion radicals of the molecules studied.
Oxidation of glycolaldehyde by manganese(III) sulphate
Authors: Barek Jiří , Berka Antonín , Pokorná-Hladíková Alena
Published: August 2011

Glycolaldehyde was found to be oxidized by manganese(III) sulphate with exchange of two electrons to give formaldehyde and formic acid. The kinetics of the reaction was studied and the reaction mechanism deduced. A convenient procedure is suggested for an indirect determination of glycolaldehyde based on its oxidation with excess manganese(III) sulphate and subsequent retitration of the unreacted reagent with ferrous sulphate.
1-(3-Chloro-2-butenyl)-3-methylpyrazole and 1-(3-chloro-2-butenyl)-5-methylpyrazole from oxidation products of hydrazo-3-chloro-2-butene
Authors: Hrabák František , Webr Jiří , Doskočilová Danica
Published: August 2011

By oxidation of hydrazo-3-chloro-2-butene, (I), 1-(3-chloro-2-butenyl)-3-methylpyrazole (VII) and 1-(3-chloro-2-butenyl)-5-methylpyrazole (IV) are formed; the structures of these compounds have been proved by 1H NMR, UV, IR and mass spectrometry.
PMO-treatment of the structure-reactivity relationships in free radical addition reactions of cycloalkenes
Authors: Ponec Robert , Hájek Milan , Málek Jaroslav
Published: August 2011

The effect of ring strain in molecules of C5-C8 cycloalkenes and that of electronegativity of the attacking radicals upon reactivity of cycloalkenes in 1,2 addition reactions was studied by using a simple perturbation approach. The trends of the experimentally determined reactivities of cycloalkenes towards CH3, CCl3, CF2CF2CF3, CH3CO, NCCHCO2H5, C2H5, C2H5S and Br radicals were found to be in an acceptable agreement with the trends of the calculated Fukui's delocalisabilities Dr. The reactivity of cycloalkenes appears to be influenced by I-strain in the cycloalkene molecules as well as by electronegativity of the attacking radicals.
Synthesis and acetylation of metallocene analogues of chalcones. The double bond acetylation of α,β-unsaturated ketones
Authors: Toma Štefan , Federič Jozef , Solčániová Eva
Published: August 2011

Metallocene analogues of chalcones with a metallocene (ferrocene, ruthenocene, cymantrene) bound to the β-carbon atom of the multiple bond, or to the carbonyl group were prepared. The double bond of ferrocene and ruthenocene analogues of chalcones was acetylated when the metallocene was bound to the β-carbon atom of the double bond. No similar double bond acetylation was observed with cymantrene or N-methylpyrrole analogues of chalcones.
Synthesis of pyrido[1,2-a]-1,3,5-triazines. Reactions of 2-pyridyl isothiocyanate with compounds containing a C=N bond
Authors: Marchalín Miroslav , Světlík Jan , Martvoň Augustin
Published: August 2011

New pyrido[1,2-a]-1,3,5-triazine derivatives were prepared by the [4+2]cycloaddition reaction of 2-pyridyl isothiocyanates with isocyanate, aldimines, and N,N'-diphenylcarbodiimide. On the other hand, reaction of 2-pyridyl isothiocyanate with aliphatic carbodiimides afforded [2+2]cycloaddition products, 1,3-thiazetidines.
Ab initio calculations of the ground state potential function of the hydroxyl anion by means of the many-body Rayleigh-Schrödinger perturbation theory
Authors: Kozák Ivan , Špirko Vladimír , Čársky Petr
Published: August 2011

Many-body Rayleigh-Schrödinger perturbation theory (MB-RSPT) up to third order applied to OH- in the range of interatomic distances from 0.0815 to 0.1175 nm. The energy data obtained are combined with the experimental RKR (ground state) potential of HF, and, a ground state potential of OH- is constructed (over a wide range of internuclear distances) within the framework of the reduced potential curve method. With the use of this potential the corresponding rotation-vibration Schrödinger equation is solved for 16OH-. The computed spectroscopic constants are compared with best reported calculations and available experimental evidence. The comparison indicates that MB-RSPT may be used as an adequate (and convenient) tool for the study of negative ions.
Vibration spectra of sulphur tetranitride
Authors: Toužín Jiří
Published: August 2011

Available data on infrared and Raman spectra of S4N4 in solid state and solutions have been verified and completed. On the basis of normal coordinate analysis an attempt has been made to define with more precision the interpretation of vibration spectra of this compound given in earlier reports.
Vibration spectra of imidodiselenate and imidodisulphate anions
Authors: Toužín Jiří , Růžička Antonín
Published: August 2011

Infrared and Raman spectra of potassium salts of N(SeO3)23-, N(SO3)23-, and HN(SO3)22- anions have been measured. Normal coordinate analysis has been used for their interpretation and characterization of bonding relations in the anions studied.
Pseudo-ternary sections in K2H2P2O7-K3HP2O7-K3H2P3O10-K4HP3O10-H2O system
Authors: Ebert Miroslav , Eysseltová Jitka , Lukeš Ivan , Nassler Jindřich
Published: August 2011

The solubility was studied in K2H2P2O7-K3HP2O7-H2O, K3H2P3O10-K4HP3O10-H2O, K2H2P2O7-K3H2P3O10-H2O, K3HP2O7-K4HP3O10-H2O, and K4HP3O10-K2H2P2O7-H2O systems in the temperature region of +10 to -25 °C. The results obtained are discussed with regard to the possible application of the systems as components in multicomponent PK type liquid fertilizers.
Analysis of the system precipitation reactor-separation unit. Porosity of the filtration cake as a function of properties of the solid phase
Authors: Söhnel Otakar
Published: August 2011

Porosity of the filtration cake, formed at filtration of model suspensions of CaCO3, BaCrO4 and ZnO is not a function of suspension concentration as long as the solid phase forming the suspension is of the same granulometric composition. The calculated surface area of the solid phase, effective as concerns filtration at ΔP = 30 kPa, is smaller than the actual surface area determined by absorption of nitrogen. Porosity of the filtration cake formed at filtration of suspensions of Mg(OH)2, CaCO3, SrCO3 and BaCO3 prepared by precipitation is a linear function of the initial concentration of precipitated solutions since it is affected by the size and polydispersity of originating particles in dependence on concentration of precipitated solutions. The cakes formed at filtration of precipitated suspensions of CaCO3, SrCO3 and BaCO3 aged for up to 2 hours from the instant of their preparation have a constant porosity which is independent of the time of suspension aging.
Styrene-divinylbenzene polymer oxidation catalyst
Authors: Prokop Zdeněk , Setínek Karel
Published: August 2011

Some additional data about properties and applicability of a styrene-divinylbenzene polymer catalyst containing acidic and redox functional groups are reported. It is shown that the catalysts of this type can be prepared reproducibly and exhibit catalytic properties comparable to the properties of noble metal catalysts.
Effect of solvent on catalytic hydrogenation of 1-octine
Authors: Červený Libor , Vostrý Boris , Růžička Vlastimil
Published: August 2011

The effect of solvent on the course of the consecutive reactions in liquid phase was studied for hydrogenation of 1-octine on a platinum catalyst at 25 °C using a series of 32 solvents. The reaction orders with respect to 1-octine, 1-octene, and hydrogen were determined by measuring the dependence of the initial reaction rates on the initial solute concentrations and on the partial pressure of hydrogen. The rate constants obtained for the hydrogenation stages were successfully correlated with the semiempirical parameters of the solvents.
2-Phenyl- and 2-benzamido-benzimidazoles
Authors: Sluka Jaroslav , Daněk Jaroslav , Bedrník Petr , Buděšínský Zdeněk
Published: August 2011

2-Phenylbenzimidazoles I-VI with chlorine atom or methoxy group on the benzene ring were prepared by a modified method. Acylation of 2-aminobenzimidazole with substituted benzoyl chlorides afforded the 2-benzamidobenzimidazoles VII-XXXVI. All these compounds were tested for anthelmintic and coccidiostatic activity.
The synthesis of cyclopentane derivatives with a relation to prostanoic acid
Authors: Doležal Stanislav , Jarý Jiří
Published: August 2011

A synthesis of 2-(ω-acetoxyalkyl)-2-cyclopenten-1-ones II was worked out. By radical addition of alkanoic acids to cyclopentenones II and to esters of ω-(2-oxo-5-cyclopentenyl)alkanoic acids III 2-[3-oxo-2-(ω-acetoxyalkyl)cyclopentyl]alkanoic acids V and/or esters of ω-[5-(1-carboxyalkyl)-2-oxocyclopentyl]alkanoic acids IV were prepared. The homologues and norderivatives of prostanoic acid prepared were isolated by preparative chromatography on silica gel and their 1H NMR and IR spectra measured.
Synthesis and properties of 5-styryl-2-furancarboxylic acids
Authors: Knoppová Viera , Beňo Anton , Kováč Jaroslav
Published: August 2011

5-(4-X-Styryl)-2-furancarboxylic acids (X = H, Br, NO2, COOCH3, (CH3)2N) were prepared by oxidation of the appropriate 5-(4-X-styryl)-2-furaldehydes, or alternatively by alkaline hydrolysis of the corresponding methyl esters. The latter were obtained by reacting the 4-substituted benzaldehydes with 5-methoxycarbonylfuryltriphenylphosphonium chloride. The UV and IR spectra of products are commented. The apparent pK values of the synthesized acids were employed for calculation of the transmission coefficient π' through the benzene-furan system bridged by a -CH=CH- group.
1-(3-Dimethylamino-1-phenylpropyl)piperazines and related compounds: Synthesis and pharmacological screening
Authors: Jílek Jiří , Pomykáček Josef , Němec Jiří , Protiva Miroslav
Published: August 2011

Substitution reactions of N,N-dimethyl-3-chloro-3-phenylpropylamine with 1-methylpiperazine and a series of analogues afforded 1-(3-dimethylamino-1-phenylpropyl)piperazines I-V. A similar substitution with piperidine resulted in the diamine VIII. Hydrolysis of the carbamate V gave the secondary amine VI which was transformed by alkylation with cyclopropylmethyl bromide to compound VII. 3-Dimethylamino-3-phenylpropanol was treated with thionyl chloride to give N,N-dimethyl-3-chloro-3-phenylpropylamine (IX) which reacted with 1-methylpiperazine and afforded the triamine X. The maleates of the amines prepared exhibited hypotensive effects of short duration (III, IV, VI, VII, X) and moderate antiarrhythmic effects (V-VIII). The phenylpiperazine derivative III showed a significant antiarrhythmic action and a high local anaesthetic activity.
Synthesis of some 19-hydroxylated androgen analogues with the cyclopropane ring in 4,5-position
Authors: Joska Jiří , Fajkoš Jan
Published: August 2011

Synthesis of 19-hydroxylated analogues of 17α-methyltestosterone and 17α-methylandrostanediols with the cyclopropane ring in position 4β,5β is described.
Synthesis and absolute configuration at C(20) of 21,26,27-trinor-5α-cholestan-25→20-olide derivatives
Authors: Pouzar Vladimír , Havel Miroslav
Published: August 2011

Reaction of the aldehyde I with 4-(methoxymethoxy)butylmagnesium chloride yielded compounds II and VII which were converted into diols III and VIII, respectively. By oxidation of the diols III and VIII were obtained saturated lactones XVI and XX, respectively, which were converted into unsaturated lactones XIX and XXIII, respectively. On the basis of chemical correlation with methyl ethers XIV and XV of a known configuration at C(20), the compounds II-VI, XII, XVI-XIX were assigned the 20R-configuration whereas 20S configuration was established for the compounds VII-XI, XIII and XX-XXIII.
Properties and characteristics of partly purified glutamate dehydrogenase from sheep rumen mucosa
Authors: Holovská Katarína , Lenártová Viera , Havassy Ivan
Published: August 2011

The purification of glutamate dehydrogenase from sheep rumen mucosa on DEAE-cellulose afforded two enzyme fractions with glutamate dehydrogenase activity. The enzyme fraction II (tissue glutamate dehydrogenase) was freed of contaminating proteins in the subsequent purification step on Sephadex G-200. The approximate relative molecular weight (260 000) of tissue glutamate dehydrogenase (fraction II) was determined by gel filtration on Sephadex G-200 and the approximate relative molecular weight of its polypeptide chain (48 000) was established by polyacrylamide gel electrophoresis in SDS. The pH-optimum of fraction II was 7.9. The effect of substrate concentration on the rate of the enzymatic reaction was examined and the following apparent Michaelis' constants were found for the individual substrates: NADH 6.25 . 10-5 mol/l, 2-oxoglutarate 4.5 . 10-3 mol/l, and NH4+ 77 . 10-3 mol/l.
Criterion equation for calculation of the current limiting electrochemical machining by formation of sparks
Authors: Novák Petr , Roušar Ivo , Cezner Václav , Mejta Vladimír
Published: August 2011

The current density used in electrochemical machining can be increased only up to a certain value, above which the formation of electric sparks on the cathode (tool) is observed, whereby the latter and its insulation are damaged. The present work is devoted to the measurement of this critical current density for the case of electrochemical drilling of small holes by means of metal capillaries provided with an external insulation. The results are correlated by a criterion equation which gives the values of the limiting currents for sparking, IS , with an average error of ±9%.
The effect of halides, pseudohalides, and some organic substances on the initial rate of peroxodisulphate formation
Authors: Balej Jan , Kadeřávek Martin
Published: August 2011

The effects of various additions of halides, pseudohalides and selected organic substances on the overall anodic polarization curves and the polarization curves of oxygen evolution and peroxodisulphate formation were examined under conditions of low degree of sulphate-to-peroxodisulphate conversion. Of the tested substances, SCN- and CN- ions, thiourea, urea and acetonitrile have proved to cause the greatest increase in the current yields of peroxodisulphate. However, the current yield varies as a function of the concentration of additive and the total current density, and goes through a maximum in both cases. The observed phenomena are discussed in terms of potential-dependent adsorption of additives or their oxidation products or intermediates on the oxidized surface of platinum anode.
Effect of nitrate and chromate on the localized corrosion of iron and nickel
Authors: Toušek Jaromír
Published: August 2011

The combined effect of some inorganic inhibitors - chromate and nitrate - on the rate of localized corrosion of iron and nickel was investigated. The efficiency of these inhibitors and the mechanism of their effect were found to depend on the potential. If the breakdown potential is lower than the second passivation potential, the corrosion rate decreases owing to the competitive adsorption of inhibitor and of aggresive ions and owing to a change in the activation energy of the metal dissolution. Substances that are strongly adsorbed on the electrode act in this region as strong inhibitors. In the range of the second passivation potential there operates another mechanism consisting in a favourable effect of the water molecules in the inhibitor hydration sphere on the rate of the passivation reaction. In this range, even such substances that are only weakly adsorbed on the electrode can act as strong inhibitors.
CW-CO2 laser-induced and SF6-sensitized decomposition of trifluoroacetic acid
Authors: Pola Josef
Published: August 2011

CW-CO2 laser-induced and SF6-sensitized decomposition of trifluoroacetic acid affords reaction products different from those yielded by a conventional heating and offers a new way for decomposition of this compound. The kinetics of the laser-induced reaction is also different, being of a second order and of a first order in SF6. The reaction scheme proposed for the laser-induced process shows .CF2CO2. biradical to be mainly decomposed to carbon monoxide and carbonyl fluoride and implies that the fate of this species during conventional thermal decomposition is controlled by heterogeneous surface reaction.
Application of a voltammetric flow-through cell to flow-injection-analysis (FIA)
Authors: Ivaska Ari , Ryan Tom H.
Published: August 2011

A new voltammetric flow-through cell has been designed to be used as an electrochemical detector in HPLC (high performance liquid chromatography) and may also be used as a voltammetric detector of FIA (flow-injection-analysis). The cell is of wall jet type and has a volume of approximately 1μl. Performance of the cell was tested and the flow-characteristic determined by analysing paracetamol which is oxidized at a glassy carbon electrode and is frequently used as a pain-killing drug. Application of d.c. (direct current) and n.p. (normal pulse) voltammetric working modes in FIA were studied. D.c. was found to be more sensitive and should be used when low sample concentrations are determined. N.p. was, however, found to give more reproducible results at high concentrations. A known tablet formulation containing paracetamol was analyzed by the proposed method and a good agreement was found between the result obtained and the manufacturer's certificate.
Neighboring group participation and rearrangement in hypobromous acid addition to 10β-vinyl cholestane derivatives
Authors: Kočovský Pavel , Tureček František
Published: August 2011

Hypobromous acid addition to the diene VII yields two epimeric dibromo 6β,19a-epoxides, XVI (main product) and XVII, via the intermediary bromohydrin XIII. Products due to C-C bond formation were not observed. This fact is attributed to the mutual perpendicular arrangement of π-orbitals of the two double bonds in the diene VII. Hypobromous acid action upon the 5α,6β-diol IX and the dimethoxy derivative X afforded analogous products of 6(O)n participation by the 6β-substituent, i.e. the cyclic ethers XXII, XXIII and XXIV, XXV. Under the same conditions the 6β-acetoxy derivative XI gave a mixture of the cyclic ethers XXII and XXIII as products of 6(O)n participation, and the rearranged ketone XXVI. Mechanism of this rearrangement is discussed.
17β-[4-(1,3-Thiazolyl)]-androst-5-ene derivatives
Authors: Drašar Pavel , Tureček František , Havel Miroslav
Published: August 2011

17β-[4-(1,3-Thiazolyl)]-androst-5-ene with a formamide and ethoxycarbonyl group in position 2' of the 1,3-thiazole ring were synthesized and their structures studied by means of hydrogenolytic degradation and spectroscopic methods.
Mixed aromatic-aliphatic acetals; Their preparation, 1H and 13C-NMR spectra and hydrogenolysis by ethereal solution of chloroalane
Authors: Dušek Jiří , Sklenář Vladimír , Jonas Jaroslav
Published: August 2011

The corresponding p-X-phenylisobutyl acetals to acetaldehyde (I), 2-(p-X-phenoxy)tetrahydropyrans (II), 2-(p-X-phenoxy)tetrahydrofurans (III), and cyclohexyl(p-X-phenyl)acetals of acetaldehyde (IV) were prepared by addition of p-X-substituted phenols to isobutyl vinyl ether, 2,3-dihydro-4H-pyran, 2,3-dihydrofuran, and cyclohexyl vinyl ether, respectively. The structures of acetals I-IV were confirmed by their 1H and 13C NMR spectra. Diastereotopic protons of the methylene and geminal methyl groups are anisochronous in the 1H NMR spectra of acetals I. 13C NMR spectra of acetals IV demonstrate anisochronous behaviour of cyclohexane ring diastereotopic carbon atoms. The constants σp+ for several groups calculated using 13C NMR spectra are: 1-isobutoxy-1-ethoxy- (-0.56), 2-tetrahydropyranyloxy- (-0.58), 2-tetrahydrofuryloxy- (-0.59), and 1-cyclohexyloxy-(1-ethoxy) (-0.57). Experimental relative rate constants of hydrogenolysis of acetals I and II by ethereal solution of chloroalane yield best correlations with σp+ constants of the substituent X, providing the values ρ = 2.61 and ρ = -1.09 for compounds of the series I and II, respectively. The importance of these results for finding the rate determining step of the studied reaction is discussed.
Synthetic utilization of α-amino-γ-bromobutyric acid in the preparation of non-coded amino acids; IR study of homoserine
Authors: Procházka Zdenko , Smolíková Jorga , Maloň Petr , Jošt Karel
Published: August 2011

α-Amino-γ-bromobutyric acid and its derivatives were utilized in the preparation of some non-coded (non-proteinogenic) amino acids and their derivatives. The bromine atom was replaced by hydrogen, hydroxyl, iodine and nitro, amino, and thiocyanato groups. Homolanthionine was prepared by two methods. Homoserine has been shown to exist in three crystalline modifications whose differences in the IR spectra indicate conformational changes.
Natural convective diffusion to a sphere
Authors: Kimla Arnošt , Míčka Jiří
Published: August 2011

The problem of natural convective diffusion to a sphere was solved both analytically for the asymptotic case Gr.Sc → ##h and numerically for values of the product Gr.Sc from about 1 000 to 20 000. Evaluation of numerical results gave basic characteristics of the velocity profile and the form of the diffusion layers. A formula for the total diffusion current to a sphere in the mentioned range of the product Gr.Sc was obtained by combining the analytical solution with the numerical results.
Effect of the course of the second derivative of Gibbs' energy in binary mixtures on the liquid-liquid equilibrium in ternary system
Authors: Novák Josef P. , Matouš Jaroslav , Šobr Josef , Pick Jiří
Published: August 2011

The effect of the course of G11(x1) in binary systems is studied on the binodal curve shape, the extent of heterogeneous region and the inclination of tie-lines in the ternary system. The effect of individual quantities is shown both on model calculations and on the systems acetonitrile-benzene-n-heptane, water-benzene-ethanol and water-benzene-2-propanol. The UNIQUAC and the modified Wilson equations were employed for calculating.
A simple and exact method for calculating diffusion coefficients from the data of polarization interferometer. Extension to the case of polymers with narrow distribution of molecular weight
Authors: Porsch Bedřich , Sundelöf Lars-Olof
Published: August 2011

The simple equation derived previously for calculating the diffusion coefficient and the zero-time correction from the data of the polarization interferometer is shown to be valid not only in the case of binary systems but also for the diffusion of polymer solutes with moderately broad molecular weight distribution and results in a diffusion coefficient, which is an average value of a well-defined type. In addition, it is shown experimentally that the equation is applicable with sufficient accuracy also to the evaluation of diffusion coefficients of polymers having a polydispersity index as high as Mw/Mn = 2.
Pulse polarography of heavy metal ions in polyelectrolyte solutions: Behavior of Pb2+ and Cd2+ in PMA solutions
Authors: Van Leeuwen Herman P. , Threels Wim F. , Cleven Rob F. M. J.
Published: August 2011

An orientational study is presented of the pulse polarographic features of Pb2+ and Cd2+ in aqueous solutions of polymethacrylic acid, partially esterified. Normal pulse polarography with varying pulse duration was applied, and the resulting Cottrell plots were used to check the diffusion-controlled character of the currents. Values for binding constants under various conditions are presented. It could be established that the binding of Pb2+ increases with decreasing Pb2+/PMA ratio, which is a typical polyelectrolytic effect. It is in accordance with indications from Henderson-Hasselbalch analysis of the NPP current data. Variation of the pH, corresponding with variation of the overall charge on the polymer, confirms the polyelectrolytic character of the binding. The latter finding is also supported by indications from experiments at different electrolyte concentrations. At rather negative initial potentials and sufficiently low Cd2+/PMA ratio the polarograms for Cd2+ show the maxima which are typical for induced reactant adsorption.
Laser Raman polarization spectra of natural zeolite-natrolite
Authors: Pechar František , Gregora Ivan , Rykl Drahoš
Published: August 2011

Raman polarization spectra of single crystal of natrolite Na2Al2Si3O10.2 H2O have been measured in the region 4 000 to 50 cm-1 at room temperature. The spectra have been measured in the conventional rectangular geometry. The found maxima of the polarization spectra of single crystal of the mineral investigated can be divided into four groups according to pertinence to individual vibrations: (i) translation and rotation vibrations of water molecules in interaction with the crystal lattice, (ii) internal vibrations of the bonds Al-O, Si-O inside the tetrahedrons, (iii) internal vibrations of bonds of the water molecules, (iv) external vibrations between the (Al,Si)O4 tetrahedrons.
Oxidation of ferrous sulphate in neutral and weakly alkaline solutions
Authors: Šolcová Alexandra , Šubrt Jan , Vinš Jaroslav , Hanousek František , Zapletal Vladimír , Tláskal Jaroslav
Published: August 2011

Oxidation of FeSO4 by air oxygen has been studied in aqueous solutions of constant acidity. The effect of various reaction conditions (of acidity, temperature, concentration of FeSO4, and of the air flow through the suspension) on the yield of various modifications of ferric oxide-hydroxides in the product mixture is described and the mechanism of the process is discussed. Reaction products prepared in the neutral and weakly alkaline solutions contain predominantly lepidocrocite (γ-FeOOH), amorphous Fe2O3.n H2O (ferrihydrite), at higher pH values also goethite (α-FeOOH) is formed. Their mutual ratios depend strongly on the solution acidity.
Examination of the potential of copper during its dissolution in sodium hydroxide
Authors: Sušinka Petr , Miadoková Milica
Published: August 2011

Parallel to kinetic measurements, the potential of copper was monitored on the (100), (110), and (111) crystallographic planes during its spontaneous reaction in sodium hydroxide in oxygen atmosphere. A quantitative relation was obtained for the potential in dependence on the experimental conditions, indicating that unless a passivating layer of copper(II) oxide is formed on the surface, the metal does not act as an oxygen electrode. The potential change in the given medium was found to depend only on the amount of copper(I) oxide formed, obeying the relation E = (RT/nF) ln (mCu2O) + K; use was made of this relation for a quantitative determination of the growth of the copper(I) oxide layer.
Conditions for the existence of potassium antimonates with a M(I): Sb ratio greater than one
Authors: Drátovský Milan , Karlíček Jiří
Published: August 2011

During a solubility study on the ternary system KOH-KSbO3-H2O, a method was found for the preparation of the crystalline (X-ray active) compound KSbO3.2.3 H2O and a new compound, K4Sb2O7.(5.6-5.8) H2O, was discovered. Both of these substances and an anhydrous substance with composition K4Sb2O7 crystallize in the tetrahedral system. Their constitution was characterized on the basis of their IR spectra.
A comparative study of the SF6-sensitized interaction of a cw-CO2 laser radiation with methyltrichloro derivatives of carbon, silicon and germanium
Authors: Pola Josef , Bellama John M. , Chvalovský Václav
Published: August 2011

A comparative study of the gas-phase interaction of methyltrichloro derivatives of carbon, silicon and germanium (CH3MCl3 where M = C, Si and Ge) with sulfur hexafluoride either excited by a cw-CO2 laser radiation or under conventional static pyrolytic conditions is reported. 1,1,1-Trichloroethane and methyltrichlorogermane do not react with SF6 under laser irradiation and undergo their decomposition leading to the same products as afforded by heating: CH3CCl3 yields Cl2C=CH2 and HCl, and CH3GeCl3 gives HGeCl3 along with CH4 and C2H2. Mixtures of methyltrichlorosilane and SF6 afford under the both conditions products of the CH3SiCl3 decomposition -CH4, C2H2, HCl and SiCl4 and products of the CH3SiCl3-SF6 reaction -SiF4, SCF2 and CS2. Possible reasons for the different reactivity of CH3MCl3 compounds toward SF6 are briefly discussed. The decompositions of CH3GeCl3 to HGeCl3 offers new way for the preparation of the latter compound.