bluuebunny/crossref_metadata_2025 huggingface dataset:
Film absorption in liquids of different viscosities
Authors: Vyoral Leopold , Míka Vladimír
Published: August 2011

Experimental results on absorption of CO2 in liquid film flowing downwards the string of spheres are presented for liquids with viscosities in the range from 1 to 10.1 mPa s. The results correspond qualitatively to the Levich's analysis of mass transfer into the flowing film with wavy surface. Equation relating dimensionless numbers is proposed for calculation of the volumetric mass transfer coefficient.
The effect of solvents on the oxidation of butyraldehyde catalysed by ferrocene
Authors: Včelák Jaroslav
Published: August 2011

Oxidation of butyraldehyde to butyric acid catalysed by ferrocene in 10 solvents has been described by kinetic equations for autocatalysis. Rate constants of these equations were correlated with the properties of solvents. The oxidation rate was found to be independent of viscosity and fluidity of the reaction medium, electrophilicity expressed by ETfunction and the donor ability of solvents. Only in nonpolar solvents the oxidation rate depended on (nD)-2s. The rate of the title oxidation reaction was dependent on the polarity of reaction medium which was characterized by dipole moment and by functions of dielectric constants and increased with increasing solvent polarity. A similar dependence was also obtained with the use of solubility parameter and cohesion pressure of solvents. The rate of the oxidation increase with increasing solubility of oxygen in solvents. These dependences were used to discuss some steps of the mechanism of this oxidation.
Study of D-glyceraldehyde by circular dichroism and ultraviolet spectroscopy
Authors: Bystrický Slavomír , Sticzay Tibor , Poláková Mária , Fedoroňko Michal
Published: August 2011

The behaviour of D-glyceraldehyde in water, dimethyl sulfoxide, their mixtures and in 1,1,1,3,3,3-hexafluoro-2-propanol was studied by circular dichroism and UV spectroscopy in the 20-80°C temperature range. Fresh-prepared solutions of D-glyceraldehyde exist in a substantial measure in dimeric or oligomeric forms, which passed to a monomeric one. The different character of interaction of solvents with monomeric D-glyceraldehyde is discussed. The bisignate circular dichroic curves are associated with conformational equilibrium of rotamers. The presumption on their spatial arrangement is confronted with the quantum chemical calculation of the rotational strength.
Study of cyclization of 2-acetyl-3-methylamino-N-benzoyl-2-butenethioamide
Authors: Macháček Vladimír , El Bahaie Said , Štěrba Vojeslav
Published: August 2011

Kinetics has been studied of cyclization of 2-acetyl-3-methylamino-N-benzoyl-2-betenethioamide (Ia) and 2-acetyl-3-amino-N-benzoyl-2-butenethioamide (Ib) giving 5-acetyl-2-phenyl-1,6-dimethyl-4-(1H)pyrimidinethione (IIa) and 5-acetyl-2-phenyl-6-methyl-4-(3H)-pyrimidinethione (IIb), respectively, in aqueous buffers within pH 2 to 9. Formation of the cyclic intermediate is rate-limiting in the cyclization of Ib within the whole range. In the case of Ia the rate-limiting step consists in acid-catalyzed splitting off of water from the cyclic intermediate above pH 5 and in base-catalyzed splitting off of hydroxyl ion above pH 7.
Chemisorption of ethylene on nickel surfaces with preadsorbed oxygen
Authors: Zachař Pavel , Bastl Zdeněk , Adámek Jakub
Published: August 2011

Chemisorption of ethylene was studied on thin polycrystalline layers of nickel prepared by metal deposition in high vacuum and modified by preadsorbed oxygen. The volumetric method combined with the gas-phase analysis and the measurement of the electrical resistance changes of these layers were used. Already small amounts of preadsorbed oxygen of the order of 10-2 of the monolayer affect rather substantially the extent of ethylene chemisorption. The extent of the initial irreversible chemisorption and also the total adsorption of ethylene as a function of the amount of preadsorbed oxygen have a maximum at the surface oxygen concentration of 3 . 1013 molecule cm-2. The adsorption accompanied by the extensive dissociation of ethylene C-H bonds proceeds predominantly on nickel atoms with lower coordination (atoms on the microcrystal edges, corner atoms, etc.), where also oxygen chemisorption proceeds preferentially.
The optical and acid-base properties of chromatographically pure Chromazurol S, Eriochromazurol B and Eriochromcyanine R
Authors: Pollaková-Mouková Naděžda , Gotzmannová Dagmar , Kubáň Vlastimil , Sommer Lumír
Published: August 2011

The positons of the absorption maxima and the values of the molar absorption coefficients of all the acid-base forms and the dissociation constants of the individual acid-base transition of chromatographically pure Chromazurol S, Eriochromazurol B and Eriochromcyanine R were found by graphical and numerical interpretation of the absorbance curves measured in aqueous medium and mixed water-ethanol and water-DMF medium. These values were compared with the values given in the literature.
Initiation of oligomerisations of methyloxirane by triphenylmethyl salts containing pair anions SbCl-6 and AsF-6
Authors: Vohlídal Jiří , Pacovská Marta , Dvořák Jiří
Published: August 2011

Initiation of oligomerisations of methyloxirane (1,2-epoxypropane) by Ph3C+SbCl-6 and Ph3C+AsF-6 (Ph = C6H5) has been studied by spectral methods and by chemical analysis of the reaction mixtures and reaction products. The results obtained indicate that the triphenylmethyl salts react with methyloxirane simultaneously in two ways: a) by mechanism of the proton and electron pair transfer from methyloxirane to the Ph3C+ cation to form triphenylmethane and active centers with the end groups -CHO; b) mechanism of the direct addition of the PhC+ ion to the methyloxirane oxygen, resulting in formation of active centers with the end groups -O-CPh3. The relative importance of both mechanisms in the overall initiation process is affected by temperature and by concentration conditions in the reaction mixture.
Cyclization reactions of ketenimines with some nitrogen containing compounds
Authors: Světlík Jan , Martvoň Augustin
Published: August 2011

3,4-Disubstituted, 3,4,5-trisubstituted 4H-1,2,4-triazoles and 2,3-disubstituted 4(3H)-quinazolinones were prepared in one step by cyclization reactions of ketenimines with formohydrazide, acetohydrazide, benzohydrazide, thiosemicarbazide or anthranilic acid in xylene or dimethylfomamide. Reaction of diphenylketene-N-phenylimine with aminoacetaldehyde dimethyl acetal gave an adduct at the C=C bond, which afforded 2-diphenylmethyl-1-phenylimidazole with dilute HCl. 13C-NMR spectra of triazoles Id, IIa and IIb are commented.
Complete monotonicity of entropy production in chemical reaction
Authors: Šolc Milan
Published: August 2011

The successive time derivatives of relative entropy and entropy production for a system with a reversible first-order reaction alternate in sign. It is proved that the relative entropy for reactions with an equilibrium constant smaller than or equal to one is completely monotonic in the whole definition interval, and for reactions with an equilibrium constant larger than one this function is completely monotonic at the beginning of the reaction and near to equilibrium.
Effect of Caro's acid in electrolytic preparation of peroxodisulphates
Authors: Balej Jan
Published: August 2011

Measurements of the current yield of oxygen and of the anode potential during electrolytic preparation of peroxodisulphates in a continually operating flow-through model electrolyser both in the stationary state and after the beginning of anolyte feeding with an increased content of Caro's acid into the anode space proved that this acid is preferentially oxidised at the anode under evolution of oxygen, whereby the current yield of peroxo compounds is lowered. Owing to this reaction taking place preferentially on the anode, the anode potential is lowered at constant current density, which is denoted as depolarization effect of Caro's acid in persulphate electrolysis.
The mode of action of the isolated form of tomato endo-D-galacturonanase
Authors: Markovič Oskar , Slezárik Alexander
Published: August 2011

The mode of action of the isolated form of tomato endo-D-galacturonanase of molecular weight close to 50 000 was investigated with oligo-D-galactosiduronic acids of polymerization degree 2-7 and their derivatives the terminal aldehyde group of which was reduced. The rate of hydrolysis, catalysed by this enzyme decreased with the shortening the chain length of oligo-D-galactosiduronates used; di(D-galactosiduronic) acid was not hydrolyzed by this enzyme at all. Tri(D-galactosiduronic) acid was cleaved into monomer and dimer, tetra(D-galactosiduronic) acid was alternatively cleaved into monomer and trimer, as well as into two dimers. The previously proposed conception that the binding site of the tomato endo-D-galacturonanase contains three subsites and that the catalytic groups are localized close to the first bond from the reducing end of the substrate segment bound in the complex were proved. The mode of hydrolysis of the reduced oligomers is in favour of the mentioned conception.
4,4-Dimethyl-A-homocholestane derivatives
Authors: Velgová Helena , Smolíková Jorga
Published: August 2011

The synthesis of epimeric bromo ketones VII, VIII, XXV and XXVI, derived from 4,4-dimethyl-A-homo-4a-cholesten-3-one (I) and 4,4-dimethyl-A-homo-5-cholesten-3-one (XIII) is described in this paper. In the case of bromo ketones VII, VIII and XXV the IR data demonstrate the presence of conformers both with a quasi-axial and a quasi-equatorial bromine atom in the equilibrium mixture, the quasi-equatorial conformer being the predominant component. On the basis of IR, CD and 1H-NMR data the conformation of the ring A in compounds VII, VIII, XXV and XXVI is discussed.
Degree of inhibition of eukaryotic DNA-dependent RNA polymerases by thuringiensin
Authors: Horská Květa , Šebesta Karel
Published: August 2011

It was shown in experiments with purified DNA-dependent RNA polymerases from calf thymus that the inhibition of these enzymes caused by thuringiensin is competitive with respect to ATP. Enzyme AI is more sensitive to the inhibitor (Ki = 0.34 μm) than enzyme B (Ki = 1.49 μm).This finding eliminates the discrepancies with respect to this subject which exist in literature.
Stereochemical course of the reaction of 2-haloethyl isothiocyanates with nucleophiles. Stereospecific route to 4,5-disubstituted Δ2-thiazolines and thiazolidine-2-thiones
Authors: Kniežo Ladislav , Kristian Pavol , Buděšínský Miloš , Havrilová Katarína
Published: August 2011

Diastereoisomeric 1-chloro-1-phenyl-2-isothiocyanatopropanes have been prepared. They reacted stereospecifically with CH3Ona, diethylamine, aniline and NaSH to give pure cis or trans-4,5-disubstituted Δ2-thiazolines and thiazolidine-2-thiones whose configuration was determined using the nuclear Overhauser effect. The preponderant conformation of diastereoisomeric 1-chloro-1-phenyl-2-isothiocyanatopropanes was estimated on the basis of coupling constants of vicinal protons.
Dipole moments of hydroxamic acids and N,O-diacylhydroxylamines
Authors: Artemenko Aleksandr I. , Tikunova Inga V. , Anufriev Evgenii K. , Jehlička Václav , Exner Otto
Published: August 2011

Dipole moments of nine aromatic hydroxamic acids Ia-Ii and of nine N,O-diacylhydroxylamines IIa-IIi were measured in dioxan solution. The results for hydroxamic acids are interpreted in terms of the Zsp conformation (A) with an intramolecular hydrogen bond contributing considerably to the total dipole moment; the conformation is similar to that of peroxy acids but the hydrogen bond is weaker. A similar interpretation is possible for N-phenylbenzhydroxamic acids using the dipole moment data from the literature. New data for N,O-diacylhydroxylamine agree with the previously established nonplanar conformation (L). If axially unsymetrical aryl groups are present, they take one of the two coplanar positions independently of the other moiety; hence the effective dipole moments do not differ too much from the assumption of a statistical population of all conformations.
MO study of molecular and electronic structure of 2H and 4H-pyrans
Authors: Kuthan Josef , Böhm Stanislav
Published: August 2011

CNDO/2, STO-3G and 4-31G MO calculations have been carried for the molecules I-IV. Their molecular and electronic structure is discussed with respect to relative stabilities of the respective compounds and valence isomerism I III. Significance of application of the split-valence base in the ab initio MO calculations carried out is demonstrated.
Infrared spectra of N-acetyl-L-α-amino-acid N'-methylamides with aliphatic side chains in non-polar solvents
Authors: Smolíková Jorga , Pospíšek Jan , Bláha Karel
Published: August 2011

Infrared spectra of the L-alanine (I), L-leucine (II), L-valine (III) and L-tert-leucine (IV) N-acetyl N'-methylamides were measured. Amides I-IV are not self associated in tetrachlormethane in the concentration 2 . 10-5 mol l-1 at room temperature and in tetrachloroethylene in the concentration 1.5 . 10-4 mol l-1 at temperatures above 65° C. True conformational changes are observable only with the least flexible amide IV which exists at room temperature in a C5 conformation. This conformational type is also highly populated in the valine derivative III, but is less important in the alanine and leucine derivatives I and II in which the intramolecularly bonded C7 and the distorted hydrogen-nonbonded conformations contribute seriously.
Stimulatory effect of the 2-palmitamidoethyl ester of adenosine 5'-phosphate on the activity of rabbit skeletal muscle protein kinase
Authors: Hynie Sixtus , Smrt Jiří
Published: August 2011

2-Palmitamidoethyl ester of adenosine 5'-phosphate (PEA-AMP) stimulates the rabbit skeletal muscle protein kinase in relatively narrow range of high drug concentration. Mechanism of this effect seems to be analogous to that of cyclic AMP.
Radical products of hydroxylamines, nitrones and spin adducts in the process of gradual oxidation with coordinated peroxy-radicals
Authors: Cholvad Vlado , Staško Andrej , Tkáč Alexander , Buchanenko Anatolii L. , Malík L'ubomír
Published: August 2011

Hydroxyperoxides and cobalt-coordinated peroxy-radicals oxidize hydroxyolamines as e.g. Et2NOH, (PhCH2)2NOH, PhCH2PhNOH to the respective nitrones, and the spin adducts - nitrone and peroxy-radical - are formed. In contrast to hydroxyperoxides the coordinated peroxy radicals can oxidize the formed spin adduct, the methylene or methine groups next to nitrogen being converted into carbonyl groups. The radical intermediates corresponding to individual steps of the gradual oxidation have been identified by means of EPR spectra.
The conformation of aryl carbonates. A dipole moment study
Authors: Exner Otto , Jehlička Václav
Published: August 2011

The dipole moments of diaryl carbonates I-V in benzene solution are consistent with the Z,Z-conformation (A) in which the conformation of simple esters is repeated in the two moieties. The E,Z-form (B) was not detected; it may be either present as a quite small fraction or only with specific, overcrowded structures.
Unusual cyclization in the 11-hydroxy-1βH,5βH,6βH,7αH-guaian-6,12-olide series
Authors: Samek Zdeněk , Vaněk Tomáš , Holub Miroslav
Published: August 2011

Derivatives of the keto triester II, particularly the ether VI, were investigated by 1H-NMR and CD spectroscopy. Formation of the ether VI and comparison of its parameters with those of other described compounds prove that the originally suggested steric structure of acetylisomontanolide (VII) is correct.
Synthesis and pharmacological properties of [2-p-fluorophenylalanine]deamino-1-carba-oxytocin and its diastereoisomeric sulfoxides
Authors: Procházka Zdenko , Lebl Michal , Servítová Linda , Barth Tomislav , Jošt Karel
Published: August 2011

Systematic build-up of the peptide chain in solution led to [2-p-fluorophenylalanine]deamino-1-carba-oxytocin which after purification by countercurrent distribution was obtained in the form of diastereoisomeric sulfoxides. The sulfoxides were separated by chromatography and reduced with hydrogen bromide and acetone to the corresponding sulfide. Uterotonic and galactogogic activity of all compounds was determined; the diastereoisomeric sulfoxides differed markedly in these activities.
PCILO study of hydrogen bond and proton transfer in systems 1-methylthymine-acetamide and 1-methylthymine-acetic acid
Authors: Remko Milan
Published: August 2011

Complexes containing two hydrogen bonds of the systems 1-methylthymine-acetamide and 1-methylthymine-acetic acid have been studied by the quantum-chemical PCILO method. In accordance with experiment our PCILO calculations have shown that acetic acid forms stronger hydrogen bonds than acetamide with 1-methylthymine. Further the PCILO method has been used to study of double proton transfer in O-H...O and N-H...O bonds of the complexes 1-methylthymine-acetamide and 1-methylthymine-acetic acid. Using equilibrium O...O and N...O distances, the PCILO calculations have given one-minimum proton potential functions. The proton transfer has not been observed. At somewhat longer N...O and O...O distances (0.30 nm) the PCILO calculations indicate a second minimum as a shoulder.
A comparison of methods for determining dipole moments in solution
Authors: Exner Otto
Published: August 2011

The equation (1) - (6) serving to determine dipole moments in solution were statistically tested on selected experimental data. Two kinds of data sets were used, referring to compounds with zero and non-zero dipole moments, respectively. Essentially the same results were obtained with the methods of Guggenheim-Smith, Eq. (3), of Halverstadt-Kumler, Eq. (1), and with the complete Debye equation (2). The differences between them are less important than the error introduced by estimating the atomic polarization to 5-15% of the molecular refraction and/or by calculating the latter from increments. More sophisticated equations (4) and (5) based on the Onsager theory do not yield better results than the Debye theory, this means that the agreement with the gas phase values is not improved.
Mass spectra of 18α,19βH-ursane derivatives with a lactone arrangement of the ring E
Authors: Protiva Jiří , Klinotová Eva , Skorkovská Hana , Vystrčil Alois
Published: August 2011

The character of the mass spectra of a series of 25 18α,19βH-ursane derivatives with a six-membered or five-membered lactone bridge in the ring E does not depend, surprisingly, on the substitution in the ring E. In all instances of 3β-acetoxy- and 3β-hydroxy derivatives the dominant ions of the spectrum are formed by the loss of the methyl radical and the ethylene molecule, while the lactone ring and further oxygen-containing functions in the ring E are not fragmented.
Isolation of plasma membranes from chick embryo chorioallantoic membranes and identification of main nucleolytic activities
Authors: Pristašová Svetlana
Published: August 2011

The method of isolating plasma membranes from chick embryo chorioallantoic membranes is described along with some morphological and chemical properties of these membrane preparations. Besides 5'-nucleotidase, alkaline phosphodiesterase, alkaline phosphatase, ribonucleaseendonuclease and 2',3'-cyclic nucleotide 3'-phosphohydrolase activities, the plasma membranes possesses a high activity of 2',3'-cyclic nucleotide 2'-phosphohydrolase. They exert negligible activities for glucose 6-phosphatase and succinate dehydrogenase.
Substitution at hydrazo group and stability of some hydrazo compounds
Authors: Madajová Vlasta , Zelenský Imrich
Published: August 2011

The effects of pH and of substitution at the hydrazo group on the rate of disproportionation were studied for some hydrazo compounds. Spectrophotometric investigation of the acid-base equilibria, polarographic measurements, and preparative electroreduction evidenced that the disproportionation is always acid catalyzed. The nonmonotonic dependence of the disproportionation rate on the pH of the solution is due to a change in the electron donor or electron acceptor effect of the substituent resulting from a shift in the acid-base equilibrium between the various forms of the hydrazo compound in question.
Synthesis and reactions of cis-3-(2-furyl)propenoyl isocyanate
Authors: Kutschy Peter , Kristian Pavol , Dandárová Miloslava , Kováč Jaroslav
Published: August 2011

cis-3-(2-furyl)propenoyl isothiocyanate has been synthesized and its properties have been compared with those of the trans-isomer. Treatment of the foregoing isothiocyanates with benzylamine, piperidine or diazomethane yielded the corresponding thiourea and thiadiazole derivatives having unchanged configuration. Oxidation of the thiourea derivatives with bromine, or reaction of the isomeric isothiocyanates with NaSH and diphenylamine is independent of the configuration of the starting substances: the same thiazoline or perhydro and dihydrothiazine derivatives are formed. It has been concluded, based on 1H and 13C-NMR data that, relative to the C=C bond, the furan ring in cis- and trans-3-(2-furyl)propenoyl derivative exists in s-cis and s-trans conformation, respectively.
Synthesis of arylthioacetamidoximes as potential antidepressants
Authors: Červená Irena , Hrubantová Marta , Bartošová Marie , Protiva Miroslav
Published: August 2011

Reactions of thiophenol and 16 of its derivatives with chloroacetonitrile afforded arylthioacetonitriles IVb-XXb which were treated with hydroxylamine and gave arylthioacetamidoximes IVa-XXa. Compounds VIIa-IXa, XIIa, XVIa and XVIIIa exhibited antireserpine activity in the test of ptosis in mice and compounds IXa and XVIIa in the test of reserpine hypothermia in mice.
Complexes of divalent platinum with diphenylphosphineacetic acid
Authors: Pangrác Jiří , Podlahová Jana
Published: August 2011

Diphenylphosphineacetic acid (HA) acts as a monodentate P-donor towards divalent platinum; the anion acts as a bidentate P,O-donor. Three types of complexes have been prepared, PtX2(HA)2, PtXA(HA) and PtA2 (X = Cl, Br, I, SCN), whose formation is determined primarily by the type of X, the acidity of the medium and the polarity of the solvent. It follows from electronic, infrared and 31P-NMR spectra that all the prepared complexes are cis-square planar in structure.
Polymer oxidation catalyst containing acidic functional groups
Authors: Prokop Zdeněk , Setínek Karel
Published: August 2011

The catalyst containing redox sites in addition to acid functional groups was prepared by sulphonation of a macroporous chloromethylated styrene-divinylbenzene copolymer with concentrated sulphuric acid at elevated temperatures. Its activity was tested for the oxidation of 2-propanol by molecular oxygen at 120 °C and was found to be comparable to that of the iridium on carbon catalyst.Neutralisation of acid functional groups by alkali metal led to proportional decrease in the oxidation activity. The results of EPR spectroscopic study of these catalysts show that the redox properties of the polymer are caused by carbon clusters which are capable of electron exchange.
Vibrational spectra of solid bis(acetonitrile-d3) platinum(II) dichloride
Authors: Řeřicha Roman , Ripková-Vlčková Blanka
Published: August 2011

The IR absorption (4 000-200 cm-1) and Raman spectra (800-100 cm-1, He-Ne laser) of solid [(MeCN)2PtCl2]-d0 and -d6 complexes, prepared under the same conditions, were measured. With d6-species, a single IR band at 2 331 cm-1 for the fundamental CN stretching frequency was found instead of a multiplet typical for d0-species. Such multiplet has been usually taken as an indirect evidence of a cis-configuration of the ligands around the Pt atom. The vibrational spectra of the d6-species do not corroborate proposals of either cis- or trans-configuration.
Carbonyl fluoride formation by cw-CO2 laser-induced and sulfur hexafluoride-sensitized decomposition of hexafluoroacetone
Authors: Pola Josef , Engst Pavel , Horák Milan
Published: August 2011

The cw-CO2 laser-induced gas phase decomposition of hexafluoroacetone sensitized with sulfur hexafluoride (both 0.7-5.2 kPa) affords, besides perfluorinated hydrocarbons and minor amounts of trifluoroacetyl fluoride, carbonyl fluoride the formation of that obeys first-order kinetics and is favored with higher SF6 content.
Catalytic hydrogenation of dehydrolinalool and dehydrolinalyl acetate
Authors: Červený Libor , Kuncová Marcela , Růžička Vlastimil
Published: August 2011

Catalytic hydrogenation of dehydrolinalool and of dehydrolinalyl acetate has been studied in the liquid phase under atmospheric pressure at 20 °C with the aim to obtain selectively linalool and linalyl acetate. High selectivities have been obtained with the palladium on CaCO3 catalyst which was partially poisoned by lead.
Reaction of chlorodifluoropropenoates with potassium fluoride
Authors: Svoboda Jiří , Paleta Oldřich , Dědek Václav
Published: August 2011

Reaction of methyl 3-chlorodifluoropropenoate (I) with potassium fluoride afforded methyl trifluoropropenoate (II) which was dimerized to dimethyl perfluro-4-methyl-2-pentenedioate (III). The reaction rate of I was not affected by the presence of the monomer II. Methyl 2-chlorodifluoropropenoate (VII) on treatment with potassium fluoride underwent dimerization and the unstable dimer X was transformed at -20 °C into methyl 2-chloro-3,5,5-trifluoro-4-methoxycarbonyl-2,4-pentadienoate (XIII) and dimethyl 2-chloro-3-fluoro-4-trifluoromethyl-2-pentenedioate (XIV). These reactions involve a transfer of chlorine atom from the dimer X to the primarily formed 1-chloro-3,3,3-trifluoro-1-methoxycarbonylethanide (VIIa) which is transformed by this carbanion interconversion into methyl 2,2-dichlorotrifluoropropanoate (XI). The propenoate VII adds methanol in the presence of potassium fluoride whereas the propenoate I does not react under these conditions.
Projected surface energy bands, Shockley surface states and stability of ordered substitutional alloys with CsCl structure: The example of β'-CuZn
Authors: Tomášek Mojmír , Pick Štěpán
Published: August 2011

Qualitative theory of Shockley surface states is applied to β'-CuZn with the aim to analyse the character and location of its hybridizational gaps and to draw general conclusions on other ordered substitutional alloys with CsCl structure as well. The results are used to propose the role which hybridizational gaps and chemical bonding can play in order-disorder phenomena of such alloys. Some special questions of relevance to these phenomena are also qualitatively discussed.
Correlation energy in triplet electronic states. Application of the many-body Rayleigh-Schrödinger perturbation theory in the restricted Roothaan-Hartree-Fock formalism
Authors: Čársky Petr , Hubač Ivan
Published: August 2011

Explicit formulas over orbitals are given for the correlation energy in triplet electronic states of atoms and molecules. The formulas were obtained by means of the diagrammatic many-body Rayleigh-Schrodinger perturbation theory through third order assuming a single determinant restricted Roothaan-Hartree-Fock wave function. A numerical example is presented for the NH molecule.
Study on the precision of the activated charcoal solvent desorption procedure - Correlation of desorption efficiencies
Authors: Koval Martin
Published: August 2011

The described method uses activated charcoal sampling tubes for air sampling. Adsorbed compounds are eluted by the static desorption procedure with 1 ml of carbon disulphide, 0.5 ml of the supernatant is filtered off and, after internal standard addition, analysed on a gas chromatograph. Using synthetic calibration mixtures of model organic compounds with air, cumulative sampling and desorption efficiencies for 24 substances were determined for concentration ranges and sample volumes according to current Czechoslovak hygienic standards. Experimental results were treated with the single factor analysis of variance and the precision of the described procedure was estimated for the studied model compounds on the basis of residual sums of squares. Calculated values of cumulative sampling and desorption efficiencies and their precisions were compared with available published data and an acceptable agreement was found. In addition to that, cumulative sampling and desorption efficiencies were also found to be significantly correlated to molar volumes and other related molecular properties for some types of compounds.
Hydrogenolytic cleavage of pyridine on different cobalt-molybdenum and nickel-tungsten catalysts
Authors: Černý Mirko , Kraus Miloš
Published: August 2011

Composition of the reaction products formed by hydrogenation of pyridine at 300 °C and 15 MPa in the presence of 15 sulphided and unsulphided molybdenum and tungsten catalysts promoted by cobalt and by nickel, respectively, using alumina as the support in most cases, has been examined. It has been proved that the catalyst composition affects both its hydrogenation activity and the ratio of transalkylation to cracking (or hydrocracking) reactions. Relations between the catalyst composition and its activity and selectivity found for the reaction of pyridine differ from those reported for hydrogenolytic cleavage of thiophene, hydrogenation and isomerization of cyclohexene.
Perturbation theory of non-polar convex molecule fluids
Authors: Boublík Tomáš
Published: August 2011

The second-order perturbation expansion is proposed for describing the equilibrium behaviour of non-polar fluids whose intermolecular interactions are expressed by the Kihara non-central pair potential. The definition of the predominant action range of the attractive and repulsive forces as well as the expression for the first-order perturbation term correspond to the WCA formulation for particles with central interactions; to determine the second-order perturbation term the extended macroscopic compressibility approximation is used. The system of soft convex bodies parallel to molecule cores is taken as the reference system; its equilibrium behaviour is described by thermodynamic functions of representative hard convex bodies with temperature and density dependent thickness. For calculating these functions, a very accurate equation of state was used; the average correlation function was approximated on the basis of the correlation function of corresponding hard spheres. The perturbation method was used for determining thermodynamic functions of nitrogen and for studying its phase behaviour; the calculated coexistence curve is compared with experiment.
Synthesis of bridgehead bicyclo[2.2.2]octanols
Authors: Kopecký Jan , Šmejkal Jaroslav , Hanuš Vladimír
Published: August 2011

The paper describes syntheses of bicyclo[2.2.2]octan-1-ol, its 4-methyl and 4-phenyl derivatives, and bicyclo[2.2.2]octane-1,4-diol.
Reaction of 1,3-diphenyltriazene with phenyl isocyanate. Solvent effect, activation parameters and kinetic isotopic effect
Authors: Lejdar Erhard , Pytela Oldřich , Večeřa Miroslav , Vetešník Pavel
Published: August 2011

Effect of 14 solvents has been studied on the reaction of phenyl isocyanate with 1,3-diphenyltriazene. For ten of these solvents temperature dependence of the reaction velocity has been determined and the respective activation parameters calculated. Hydrogen atom of the triazene imino group has been replaced by deuterium, and the deuterium kinetic isotopic effect has been studied in seven solvents. The results confirm the mechanism suggested in a previous communication.
Some 2-substituted derivatives of 5-(2-amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)pentanoic acid
Authors: Kotva Rudolf , Křepelka Jiří , Černý Antonín , Pujman Vojtěch , Semonský Miroslav
Published: August 2011

On condensation of 6-substituted trialkyl esters of 2-carboxy-1,7-heptanedioic acids XIII-XXIII with guanidineand subsequent saponification 2-substituted 5-(2-amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)pentanoic acids II-XII were prepared. From the pharmacological point of view some of the substances prepared had a potentiating effect on the antileukemia effect of 5-fluorouracil in mice and the antineoplastic effect manifested by a diminution of the tumours in animals with experimental tumours.
Preparation of tantalum phosphate, its structure and some properties
Authors: Hölgye Zoltán
Published: August 2011

The composition and some properties were studied for tantalum phosphate precipitate forming on heating a solution containing tantalum in the fluoro complex, hydrofluoric acid, sodium phosphate, and nitric or hydrochloric acid. Annealing of the precipitate leads to the defined compound TaOPO4. The tantalum-to-phosphate group ratio is 1 : 1 also in the precipitate freely dried at room temperature; in this form, tantalum undergoes hydrolysis in alkaline or weakly acidic solutions, whereas in strongly acidic solutions the hydrolysis is substantially suppressed. Annealed precipitate is stable in usual conditions. The dried precipitate exhibits sorption properties, whereas the annealed precipitate does not.
Covalent attachment of chymotrypsin to poly[N-(2-hydroxypropyl)methacrylamide]
Authors: Lääne Ants , Chytrý Vladimír , Haga Mati , Sikk Peeter , Aaviksaar Aavo , Kopeček Jindřich
Published: August 2011

Chymotrypsin has been covalently bound on a water-soluble biocompatible carrier poly[N-(2-hydroxypropyl)methacrylamide] by three different methods. The catalytic activity of the polymer bound enzyme in the reaction with low-molecular substrates coincided with the activity of native chymotrypsin. The protective effect of the carrier polymer in chymotrypsin thermoinactivation at pH 8.0 was larger than at pH 6.1, particularly at higher concentrations of the enzyme (at 10-5M), which indicates that the polymer protects chymotrypsin not only against irreversible thermoinactivation but also against autolysis. Significant protective effect of the carrier polymer in the interaction of the polymer bound enzyme with high-molecular soybean trypsin inhibitor has been found.
Reactions of benzoyl isothiocyanates with 5-substituted tetrazoles
Authors: Uher Michal , Foltín Jozef , Považanec František , Kováč Jaroslav
Published: August 2011

A method of preparing 2,5-disubstituted 1,3,4-oxadiazoles from benzoyl isothiocyanates and 5-substituted tetrazoles is described. The transformation of the tetrazole into a 1,3,4-oxadiazole ring takes place readily under neutral conditions giving high yields of the desired products.
Derivatives of 2,3-difluoro-2-butenedioic acid and their isomerization reactions
Authors: Svoboda Jiří , Paleta Oldřich , Dědek Václav
Published: August 2011

The vinylic nucleophilic substitution of methyl trifluoropropenoate (I) with potassium cyanide affords methyl 2,3-difluoro-3-cyanopropenoate (II) in the form of a mixture of cis- and trans-isomers in 95 : 5 ratio. Simultaneously the dimerization of propenoate I to dimethyl perfluoro-4-methyl-2-pentenedioate (III) also takes place to a lesser extent. On acid catalysed methanolysis of compound II dimethyl 2,3-difluoro-2-butenedioate (VI) is formed with the same content of configurational isomers. Diester VI with a relative cis : trans ratio of 35 : 65 was obtained on dehalogenation of dimethyl 2,3-dichloro-2,3-difluorobutanedioate (V), which was prepared by addition of chlorine to the cyano derivative II and subsequent acid catalyzed methanolysis. When reacting them with potassium fluoride in dimethyl sulfoxide compounds II and VIunderwent anionic cis-trans isomerization reaction. In the 0-80 °C interval the cis isomers prevail in the equilibrium mixture, and the conversion cis → trans is endothermic: in the 40-80 °C interval for IIa → IIb ΔH = 12.8 kJ mol-1, for VIa → VIb ΔH = 38.6 kJ mol-1. The influence of the cis-effect of the fluorine atoms on the thermodynamic stability of the configurational isomers of compounds II and VI is discussed.
Some derivatives of 4-aryl-2,3-dicyano-1-naphthol
Authors: Křepelka Jiří , Vančurová Iva , Holubek Jiří
Published: August 2011

Reactions of vicinal aromatic dibromo derivatives Ia-d with the system copper(I) cyanide-tetramethylurea gave the vicinal dicyano derivatives IIa-d; products of partial substitution, Va-d, demethylation and deacetylation, IIIa-c, were also formed. The compounds IIIa-c were also prepared by direct demethylation of compounds IIa-c with the system anhydrous aluminium chloride-dichloroethane. The structures of selected compounds were determined by spectral methods. Compounds IIa-d have proved to have a moderate antineoplastic effect in animals with some transplantable experimental tumours.
Esters of 1-[4,4-bis(4-fluorophenyl)butyl]-4-(4-chloro-3-trifluoromethylphenyl)-4-piperidinol
Authors: Rajšner Miroslav , Dlabač Antonín , Protiva Miroslav
Published: August 2011

1-[4,4-Bis(4-fluorophenyl)butyl]-4-(4-chloro-3-trifluoromethylphenyl)-4-piperidinol (I) was transformed by reactions with acetyl chloride, decanoyl chloride and 3,4,5-trimethoxybenzoyl chloride to the esters II-IV. The acetate II, administered orally, was compared with the amino alcohol I in the tests of antiapomorphine actions in rats and dogs and was found inactive. The decanoate III, which was administered intramuscularly to dogs, proved properties of an ultra-long-acting depot neuroleptic.
Comparison of different methods for estimating activity coefficients in binary mixtures of hydrocarbons
Authors: Dohnal Vladimír
Published: August 2011

The accuracy and reliability of a number of different methods for predicting activity coefficients in binary solutions of hydrocarbons was tested. Various modifications of the regular solution model and of the one-parameter Wilson equation and various group-contribution methods were applied to a set of 53 binary mixtures of hydrocarbons of different types. The agreement of the calculated and experimental dependence of activity coefficients on composition was considered. On using the best methods requiring the knowledge of pure component properties only, it is necessary to expect on the average an error of 7% in the value of activity coefficient. When using the group-contribution methods, which employ condensed information on related systems for the prediction, the mean error in the activity coefficient estimation lies about 4%.
Effect of medium on 1H-NMR spectra
Authors: Bekárek Vojtěch , Šimánek Vilém
Published: August 2011

1H NMR spectra of benzene, salicylaldehyde, 2-nitroaniline, 4-nitroaniline and 4-aminotoluene have been measured in 13 solvents. The solvent-induced changes in chemical shifts of the proton signals of these compounds have been correlated with refractive index and relative permittivity (D) by the Rummens equation extended by the term f(D) = ((D - 1)/(2D + 1))2.
Influence of solvent on kinetics of reactions of Cr(II) ions
Authors: Ševčík Peter , Tkáč Ján
Published: August 2011

This paper deals with the study of redox reactions of Cr(II) ions with hydroxylamine, hydrazoic acid, maleic acid, di- and trichloroacetic acids in so-called typically aqueous mixtures of water with methyl alcohol, isopropyl alcohol, or tert-butyl alcohol. The kinetics of the redox reaction with dichloroacetic acid was studied also in the medium of aqueous acetone and in a typically nonaqueous medium water-acetonitrile. The dependences of activation Gibbs energies on the mole fraction of the nonaqueous component have no minima and maxima characteristic for the thermodynamic behaviour of the mentioned binary systems. However, the change of the activation Gibbs energy with the mole fraction of tert-butyl alcohol is not monotonous with all the studied reactions of Cr(II) ions. At a constant mole fraction of the nonaqueous component, the usual trend of the influence on the rate constants decreases in the sequence tert-butyl alcohol > isopropyl alcohol > methyl alcohol. Tert-butyl alcohol hinders most strongly the redox reaction with trichloroacetic acid, whereas it accelerates the reaction of Cr(II) ions with maleic acid and hydroxylamine.
Polymer structure and catalytic activity of ion exchangers
Authors: Jeřábek Karel
Published: August 2011

Catalytic activity of ion exchangers prepared by partial sulphonation of styrene-divinylbenzene copolymers in reesterifications of ethyl acetate by methanol and propanol, hydrolysis of ethyl acetate and in synthesis of bisphenol A has been compared with data on polymer structure of these catalysts and with distribution of the crosslinking agent, divinylbenzene, calculated from literature data on kinetics of copolymerisation of styrene with divinylbenzene. It was found that the polymer structure of ion exchangers influences catalytic activity predominantly by changing the local concentration of acid active sites. The results obtained indicated that the effect of transport phenomena on the rate of catalytic reactions does not depend on the degree of swelling of the ion exchangers in reaction medium but it is mainly dependent on the relative affinity of reaction components to the acid groups or to the polymer skeleton.
Effect of impregnation of activated carbon with chloroplatinic acid solution in acetone and subsequent heat treatment on the carbon pore structure
Authors: Machek Vladimír , Růžička Vlastimil , Janáček Leoš
Published: August 2011

The effect of saturation of support with acetone and of subsequent heat treatment on the pore structure was studied for two types of activated carbon and platinum hydrogenation catalysts prepared from them. The observed distribution of the pore volumes with respect to the pore radii was compared with the initial pore structure of the untreated carbon. Changes in the pore distribution were found even in mild preparation conditions (calcination and reduction at 100 to 300 °C). These changes are particularly pronounced in the region of bulkier macropores and depend on the carrier nature. Coating of support with platinum does not affect the support pore structure in the preparation conditions applied.
Neuroleptic agents derived from perathiepin: 6,7-Dichloro derivative of 10-(4-methylpiperazino)-10,11-dihydrodibenzo[b,f]thiepin and related compounds
Authors: Jílek Jiří , Pomykáček Josef , Metyšová Jiřina , Protiva Miroslav
Published: August 2011

The reaction of 2,3-dichlorothiophenol with 2-iodobenzoic acid gave 2-(2,3-dichlorophenylthio)benzoic acid (V) which was transformed in four steps to the homological acid IX. Cyclization resulted in 6,7-dichlorodibenzo[b,f]thiepin-10(11H)-one (X) which was converted via the alcohol XI to the trichloro compound XII. Substitution reactions of XII with 1-methylpiperazine and 1-(2-hydroxyethyl)piperazine afforded the title compound I and its hydroxyethyl analogue II. Reaction of the ketone X with 1-methylpiperazine and titanium tetrachloride gave the enamine III. Compounds I-III exhibit mild central depressant and relatively strong cataleptic activity.
Structure and molecular spectra of ethyl benzoate and diethyl terephthalate
Authors: Štokr Jan , Sedláček Pavel , Doskočilová Danica , Schneider Bohdan , Lövy Jan
Published: August 2011

Infrared and Raman spectra of ethyl benzoate and diethyl terephthalate were measured in their crystalline forms, in the glassy state and in the melt. With liquid samples, the NMR coupling constants 3JCH of the group -CO.O.CH2- were also measured. By analysis of these measurements it was found that in the liquid state of ethyl benzoate the following conformers are present: forms with a fully planar structure; forms with the methyl group twisted out of the aromatic and ester group plane by rotation about the O-C2H5 bond; and forms with non-planar mutual orientation of the ester group and the aromatic ring, formed by rotation about the Car-CO or CO-O bonds. The first two forms are also present in the crystalline modifications of ethyl benzoate. Diethyl terephthalate in the liquid state is present in forms analogous to those of ethyl benzoate; in addition, it contains isomers differing by the mutual orientation of the two ester groups on the aromatic ring.
Small angle X-ray scattering study of porosity variation in a styrene-divinylbenzene copolymer
Authors: Baldrian Josef , Kolarz Božena N. , Galina Henrik
Published: August 2011

Porosity variations induced by swelling agent exchange were studied in a styrene-divinylbenzene copolymer. Standard methods were used in the characterization of copolymer porosity in the dry state and the results were compared with related structural parameters derived from small angle X-ray scattering (SAXS) measurements as developed for the characterization of two-phase systems. The SAXS method was also used for porosity determination in swollen samples. The differences in the porosity of dry samples were found to be an effect of the drying process, while in the swollen state the sample swells and deswells isotropically.
The effect of magnesium ions on the uterotonic activity of carba analogues of oxytocin modified in position 4
Authors: Slaninová Jiřina , Lebl Michal , Barth Tomislav , Jošt Karel
Published: August 2011

Five analogues of deamino-1-carba-oxytocin, in which the γ-carboxyl group of glutamine in position 4 had been modified (free acid, monomethylamide, dimethylamide, hydrazide, p-tolylamide), were investigated regarding their uterotonic activity in vitro. The slope of the dose-response curve and the magnitude of the maximum response were compared with those of oxytocin in magnesium-free and 0.5 mM Mg-containing media. In the case of [4-glutamic acid] deamino-1-carba-oxytocin, the RMg2+ value equalled 22. The other compounds had RMg2+ values of 2-3. All the analogues evoked the same maximum response as oxytocin in both the media tested.
Adsorption on heterogeneous surfaces: Numerical analysis of models for the Dubinin-Radushkevich equation
Authors: Smutek Miloš , Zukal Arnošt
Published: August 2011

A numerical method, based on the integral equation of the adsorption on energy heterogeneous surfaces, is suggested for the evaluation of overall isotherm. It is shown that for the distribution of adsorption energies given by Eq. (1.11) and different models of the adsorption behaviour, the overall isotherms obey approximately the Dubinin-Radushkevich equation. The strong energy heterogeneity smears effectively the differences between the localized and mobile adsorption and leads to the same character of the overall isotherm with only a slightly changed heterogeneity parameter.
Fluorinated tricyclic neuroleptics with prolonged action: 3-Fluoro-8-halogeno derivatives of 10-piperazino-10,11-dihydrodibenzo[b,f]thiepins
Authors: Protiva Miroslav , Šindelář Karel , Metyšová Jiřina , Holubek Jiří , Ryska Miroslav , Svátek Emil , Šedivý Zdeněk , Pomykáček Josef
Published: August 2011

Reactions of (4-fluoro-2-iodophenyl)acetic acid with 4-fluoro and 4-bromothiophenol gave the acids IIIa and IIIc which were cyclized to 3-fluoro-8-halogenodibenzo[b,f]thiepin-10(11H)-ones IVa and IVc. The title compounds Ia and IIc were obtained via the intermediates VIac and VIIac. Reactions of (4-fluoro-2-mercaptophenyl)acetic acid or 6-fluorobenzo[b]thiophen-2(3H)-one with 4-chloronitrobenzene afforded the nitro acid IIIe which was reduced to the amino acid IIIf. Cyclization gave the amino ketone IVf which was transformed to the iodo ketone IVd. Proceeding via the intermediates VId and VIId led to the final product IId. Compounds Ia and IIcd have strong central depressant and cataleptic activity; prolongation of the effect is connected merely with the central depressant component of the action.
Application of a self-cleaning rotating electrode (S.R.E.) for polarographic analysis of industrial slags
Authors: Noninski Christo I. , Tzvetkov Tzveti B. , Noninski Vesselin C.
Published: August 2011

Preliminary results obtained for MnO2 determination point to good perspectives in practical analysis.
Extraction of hafnium by means of some substituted 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-ones
Authors: Navrátil Oldřich , Smola Jiří
Published: August 2011

Distribution between aqueous phase and benzene or chloroform was studied for 1-phenyl-3-methyl-4-benzoylpyrazol-5-ones with 2-chloro, 4-methoxy, 3-nitro, and 4-nitro substitution in the benzoyl group (ionic strength of the aqueous phase 0.1) and for hafnium in their presence (ionic strength 2.0). The distribution and dissociation constants of the reagents and the extraction constants of their hafnium complexes were determined. Hafnium was found to be extracted as the HfA4 species. The extraction parameters of the derivatives in question do not differ substantially from those of the parent substance.