bluuebunny/crossref_metadata_2025 huggingface dataset:
Benzyl ethers of methyl α-D-glucopyranoside
Authors: Joniak Dušan , Košíková Božena , Kosáková Ludmila
Published: January 2014

Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.
3,4-Seco-3,28-lupanedioic acids substituted in the side chain at C(5)
Authors: Valterová Irena , Klinot Jiří , Vystrčil Alois
Published: January 2014

A series of derivatives of 3,4-secolupane-3,28-dioic acid (II-XIV, XIX-XXI) containing an oxygen-containing functional group in the side chain at C(5) was prepared from nitrile I and ketone XVII. In the case of derivatives III-XIV both series of C(4)-epimers, a and b, were obtained. The configuration at C(4) was derived on the basis of the formation of an intramolecular hydrogen bond in compounds IX and XIII from the chiroptical properties of benzoates VII and it was confirmed by a stereospecific synthesis of the 4S-derivative XIIIa from 24-nor-ketone XV.
Analogues of androgens with a cyclopropane ring in 6α,7α-position
Authors: Kohout Ladislav , Fajkoš Jan
Published: January 2014

Simmons-Smith methylenation of 5α-androst-6-ene-3β,17β-diol 3-acetate 17-benzoate is described. Using the adduct as the starting material four analogues of androgens were synthetized by standard methods. The structures of products were established by spectral and chemical means.
L-Cystathionine derivatives for the synthesis of peptides
Authors: Procházka Zdenko , Jošt Karel
Published: January 2014

The preparation is described of L-cystathionine derivatives with amino protecting groups, which can readily by cleaved acidolytically and permit a selective acylation of both amino groups, and of a derivative with carboxyls protected by different groups.
New rhodomycinone from the strain Streptomyces griseoruber 4620
Authors: Přikrylová Věra , Podojil Miloslav , Sedmera Petr , Vokoun Jindřich , Vaněk Zdenko , Brazhnikova Mariya G. , Kudinova Margareta K.
Published: January 2014

New anthracyclinone, 10-deoxy-β-rhodomycinone (V), was isolated from the strain Streptomyces grisoeruber 4620 besides β-rhodomycinone (I), β-isorhodomycinone (II), α2-rhodomycinone (III), and ε-rhodomycinone (IV). The identification and the structure elucidation are based on the UV, CD, IR, 1H-NMR and mass spectra.
Isolation and structure determination of the peptides from the chymotryptic hydrolysate of the alkaline protease from Aspergillus flavus
Authors: Mikeš Otakar , Turková Jaroslava , Allen Geoffrey , Toan Nguyen bao
Published: January 2014

From the chymotryptic hydrolysate of 1.08 g of the precipitate obtained on treatment of alkaline protease from Aspergillus flavus with trichloracetic acid 134 peptides were isolated by means of ion exchange chromatography, paper electrophoresis and paper chromatography. Among these 38 peptides containing 311 amino acids were isolated in amounts exceeding 0.50μmol. The peptides were characterized by amino acid analysis, electric charge and also mostly by the terminal groups determination. In the case of peptides isolated in larger amounts the complete or at least the partial sequence of amino acids has been determined. In all peptides the total isolated amount in μmol was determined. The peptides containing basic amino acids were subfractionated with trypsin.
The effect of serum proteins on the activity of pancreatic lipase
Authors: Rokos Josef , Procházka Pavel , Nohýnek Miroslav
Published: January 2014

The whole serum, its protein fractions isolated electrophoretically, and the pure human and rabbit serum albumins inhibited hydrolysis of tributyrin by a glycerine extract of porcine pancreatic lipase or by human pancreatic juice. Out of the isolated fractions, an eluate corresponding to α-globulin had the strongest inhibitory effect. Under the given experimental conditions the inhibition by albumin depended on its concentration in the medium. Digestion of albumin by pepsin completely destroyed its inhibitory effect on the lipolytic reaction.
Perturbation theory of substituent effect. Quantum chemical study of the positive bridging effect
Authors: Ponec Robert
Published: January 2014

Mechanism of the so-called positive bridging effect was studied on the basis of an equation which can be viewed as a quantum chemical analogue of the Hammett equation. From this study it follows that the effect is presumably due to solvation effects of the reaction medium.
Evaluation of solvent effects in electronic spectra
Authors: Bekárek Vojtěch
Published: January 2014

Applicability of the Buckingham cross-term f(D,n2) = (D -1) (n2 - 1)/(2D + 1) (2n2 + 1) for evaluation of solvent shifts has been tested using 12 original and 4 published data sets concerning solvent effects in electronic spectra. The results are compared with correlation of the same data with the Bakshiev equation. Influence of the cross-term on the solvent shifts is dominant with the systems showing no direction change of the molecular dipole moment during excitation. Mutual dependence has been found between the cross-term and the Taft solvent factors π at the 90% significance level.
Stochastic model of the flow mechanically stirred solid-liquid system
Authors: Kudrna Vladimír , Machoň Václav , Hudcová Vlasta
Published: January 2014

An attempt is made to describe by use of the onedimensional stochastic model the flow system solid phase-liquid stirred by the mechanical rotary mixer. At the assumption that the solid phase is dimensionally homogenous a diffusion equation has been obtained which is solved under the boundary conditions, characterizing the method of withdrawal of the solid phase from the system. It is demonstrated that the model can express also the relations usually used for description of similar situations (ideal mixing, separation coefficients in stationary state etc.) like individual cases.
Steric effects in hydrosilylation of styrene
Authors: Kuncová Gabriela , Chvalovský Václav
Published: January 2014

Hydrosilylation of styrene, 2-phenyl-1-propene, trans-1-phenyl-1-propene by (CH3)R2SiH (R = C2H5, i-C3H7, i-C4H9) and R'3SiH (R' = i-C3H7, t-C4H9) in the presence of [RhCl.{P(C6H5)3}3] (I), [{RhCl(C2H4)2}2] (II) and H2PtCl6 as catalysts has been studied. The reaction of styrene with (CH3)R2SiH catalysed by complex I in benzene leads to α- and β-adduct as well as to a substitution product. Analogous addition of (i-C3H7)3SiH catalysed by complexes I and II produces selectively trans-1-triisopropylsilyl-2-phenylethylene. Reaction of 2-phenyl-1-propene with CH3(C2H5)2SiH gives 1-diethylmethylsilyl-2-phenylpropane, 1-diethylmethylsilyl-2-phenyl-2-propene and 1-diethylmethylsilyl-2-phenyl-1-propene. Hydrosilylation of trans-1-phenyl-1-propene by diethylmethylsilane catalysed by complex I gave 1-diethylmethylsilyl-2-phenylpropane and 3-diethylmethylsilyl-1-phenylpropane. Conversion of 2-phenyl-1-propene and trans-1-phenyl-1-propene in their reaction with diethylmethylsilane catalysed by complex I was found to be much lower compared to the reaction with styrene and attained maximum at 60°C. The selectivity and rates of above reactions can be influenced by the presence of air oxygen.
Catalytic activity of rhodium(I) complexes containing poly(siloxy)alkyldiphenylphosphines
Authors: Kavan Vladimír , Čapka Martin
Published: January 2014

Kinetics of homogenous hydrogenation of 1-heptene catalysed by rhodium(I) complexes prepared in situ from di-μ.μ'-chloro-bis(dicyclooctenerhodium) and phosphine L (L = 2-(diethoxymethylsilyl)ethyldiphenylphosphine, 3-(diethoxymethylsilyl)propyldiphenylphosphine and their copolymers with diethoxydimethylsilane) have been studied at 64°C under normal hydrogen pressure. The dependence of the catalyst activity on the type of L( monomeric, polymeric, supported on silica) has been examined. The effects of Rh : P molar ratio, the concentration of phosphine groups in siloxane copolymers and of the method of catalyst fixation to support on catalyst performance are discussed.
Substituent effects in hydrolysis of 3-carbamoyl-1,3-diphenyltriazenes
Authors: Pytela Oldřich , Večeřa Miroslav , Vetešník Pavel
Published: January 2014

Fifteen substituted derivatives of 3-(N-methylcarbamoyl)-1,3-diphenyltriazene and nine substituted derivatives of 3-(N-phenylcarbamoyl)-1,3-diphenyltriazene have been synthesized. With 22 derivatives kinetic measurements have been carried out in acid, neutral and alkaline regions, and the respective catalytic constants have been determined. From the kinetic results the Hammett reaction constants have been calculated and used for discussion of the reaction mechanism suggested earlier.
Synthesis and properties of 1,3-bis(4-nitrophenyl)-1-butene
Authors: Čík Gabriel , Blažej Anton , Antoš Kamil , Hrušovský Igor
Published: January 2014

1,3-Bis(4-nitrophenyl)-1-butene was prepared by nitration of 1,3-diphenyl-1-butene (I) with fuming nitric acid in acetic acid. The double bond in I was protected by addition of bromine which was eliminated after the nitration. The UV, IR and 1H- spectra of the synthesized compounds are interpreted.
New derivatives of 1-benzylidenisoindolin-3-one from narceine imide
Authors: Proksa Bohumil , Votický Zdeno
Published: January 2014

Isolation and identification of the (E)-isomer of narceine imide and the synthesis of new derivatives of 1-benzylidenisoindolin-3-one from (Z) and (E) isomers of the minor opium alkaloid narceine imide are described.
Bimolecular kinetic scheme with a stable and an unstable limiting cycle of two oscillating components
Authors: Tockstein Antonín , Komers Karel
Published: January 2014

A simple reaction kinetic scheme of two oscillating components was found, whose analog solution shows a stable limit cycle separated from a stable focus by an unstable limit cycle. The scheme leads to trajectories which alternate between the types of limit cycles and stable spirals on changing the rate constants. Modifications of the basic scheme, which consists of five consecutive reactions with two accelerating parallel steps, were studied and its chemical realization was proposed.
Preparation of Fe3+HNaY zeolites followed by ESR spectra of the Fe3+ ion
Authors: Wichterlová Blanka , Kubelková Ludmila , Jírů Pavel , Kolihová Dana
Published: January 2014

Preparation of Fe3+ zeolites by ion exchange was followed by ESR spectra of the Fe3+ ion which make it possible to distinguish between the position of Fe3+ in cationic sites of the zeolite structure, in the Si-Al-O skeleton proper and in nondefinied Fe3+-O type clusters. In particular, attention has been paid to the pH of aqueous FeCl3 solutions, where the ion exchange took place. Conditions were determined for the preparation of Fe3+HNaY and Fe3+NaY zeolites with isolated Fe3+ ions in cationic sites of the zeolite structure.
The crystal structure of nickel(II) dimethyldithiocarbamate
Authors: Lokaj Jan , Garaj Ján , Kettmann Viktor , Vrábel Viktor
Published: January 2014

Crystal and molecular structure of nickel(II) dimethyldithiocarbamate, Ni[S2CN(CH3)2]2 was solved by X-ray structural analysis and refined by the least squares method to R = 0.06 for 1065 reflections. The compound crystallizes in a space group P I and the triclinic unit cell has the dimensions: a = 6.521 (7), b = 6.798 (9), c = 7.633 (4), α = 67.21 (8)°, β = 67.34 (6)° γ =85.59 (9)°. The experimentally observed density is 1.75 g cm-3 and the calculated value for Z = 1 is 1.73 g cm-3. In the structure , the Ni atom occupies a special position in the centre of symmetry and is coordinated by four sulphur atoms in a plane: Ni-S 0.2218 (4) and 0.2198 nm S1-Ni-S2 angle 79.62 (8)°. The ligand S2CNC2 is nearly planar.
A method of mass transfer calculation in a back-flow model
Authors: Vrba Josef
Published: January 2014

Instead of solving a set of N nonlinear equations (as has been proposed by the author and his coworker), the problem may be solved iteratively as a linear one. The proposed method converges rapidly and the number of iterations is practically constant regardless of the number of stages in countercurrent cascade N and the degree of nonlinearity of equilibrium formula. The method proved to be suitable for computation on desk-top calculator.
Quantum-chemical calculation as an aid in synthesis of prostaglandins, attempt of prediction of relative stability of four stereoisomeric methyl 7-hydroxy-2-oxa-3-oxobicyclo[3.3.0]octane-6-carboxylates
Authors: Kuthan Josef , Böhm Stanislav , Mostecký Jiří
Published: January 2014

Partial optimization of conformation structure of quantum-chemical models of the stereoisomeric lactones I to IV has been carried out by the CNDO/2 method. The calculated energy characteristic and electron distributions have been used for discussion of some factors affecting retention of 5,6-trans-configuration in the key intermediate of prostaglandin syntheses (formulaI) with regard to conditions of the preparative experiments.
EHT study of system 1-methyl-1,4-dihydronicotinamide-acetaldehyde
Authors: Krechl Jiří , Kuthan Josef
Published: January 2014

With the use of the method of local energy minima it has been postulated that energetically preferred tight configurations of the supermolecule 1-methyl-1,4-dihydronicotinamide-acetaldehyde (I) can be formulated as the mutual orientations of the both partners Ia,b. Possible biochemical aspects of these arrangements are discussed.
On applicability of CNDO/S-ci method to calculation of electronic spectra. 1-Methyl-3-carbamoylpyridinium cation and 1,4-dihydronicotinamide
Authors: Krechl Jiří , Kuthan Josef
Published: January 2014

Further arguments have been gathered to support the applicability (as a variable) of the parameter χ fixed by del Bene and Jaffe in the CNDO/S method. For the heteroaromatic ion I the value 0.585 suggested by these authors is suitable, but for the 1,4-dihydropyridine derivative II agreement between experimental a calculated spectrum can be obtained with χ 0.4. Furthermore, effects of the optimum molecular geometry and width of the configuration interaction on the results of the theoretical treatment are discussed.
Quantum-chemical study of dissociation of meta and para substituted benzoic acids at all-valence-electrons level
Authors: Danihel Ivan , Kuthan Josef
Published: January 2014

Relative differences of electronic energies of meta and para substituted benzoate anions II and the parent acids I have been correlated with the substituent empirical parameters type σ and with pKX values of ionization of the acids I. The energies obtained by the EHT method only give linear correlation in the para substituted series of the studied compounds, whereas the analogous CNDO/2 energies lead to homogenous correlation for both meta and para substituents X. Effects of π and σ electrons are discussed as well as effects of electronic repulsion and attraction on the resulting microscopic substitution effect.
Hydrogenolysis of nitrogen-containing compounds on cobalt-molybdenum catalysts
Authors: Černý Mirko
Published: January 2014

Hydrogenolysis of N-(1-hexyl)piperidine, N-(1-pentyl)piperidine and 1-pentyl-1-hexylamine on sulphidized CoO-MoO3 catalysts has been investigated. The primary reaction in the hydrogenolysis is the cleavage of the bond between the nitrogen atom and the methylene group of the alkyl substituent or of the methylene ring. Alkylation and transalkylation reactions on the nitrogen play also a role.
Catalytic activity of rhodium(I) complexes containing (ω-trimethylsilylalkyl)diphenylphosphines
Authors: Jakoubková Marie , Čapka Martin
Published: January 2014

Kinetics of homogenous hydrogenation of 1-heptene catalysed by rhodium(I) complexes prepared in situ from μ,μ'-dichloro-bis(cyclooctenerhodium) and phosphines of the type RP(C6H5)2 (R = -CH3, -(CH2)nSi(CH3)3; n = 1-4) have been studied. The substitution of the ligands by the trimethylsilyl group was found to increase significantly the catalytic activity of the complexes. The results are discussed in relation to the electron density on the phosphorus atom determined by 31P NMR spectroscopy and to its proton acceptor ability determined by IR spectroscopy.
Kinetics of hydrosilylation of tert-butylphenylketone by diphenylsilane catalysed by [Rh(1,5-COD)(-)-DIOP]+ClO-4
Authors: Kolb Ivan , Hetflejš Jiří
Published: January 2014

Kinetic analysis of the title reaction has been made by the method of initial reaction rates. On the basis of the rate data, kinetic isotope effect and spectroscopic study of the reaction of the organosilicon hydride with the catalyst, the reaction model was proposed involving the following steps: the displacement of the diene by reaction with the silicon hydride from a rhodium-arene complex in an induction period of the hydrosilylation, the oxidative addition of the organosilicon hydride to the rhodium-arene complex, followed by the interaction of the ketone with the silylhydridorhodium (III) species in the rate determining step. The process is characterized by the following activation parameters: ΔU = 54.5 ± 8.5 kJ mol-1 and ΔS = -88± 25 J mol-1.K-1. The significant role of the entropic factor was supported by the analysis of the temperature dependence of the asymmetric efficiency of the catalyst.
The effect of solvents on hydrosilylation of phenylalkenes catalysed by [RhCl{P(C6H5)3}3]
Authors: Kuncová Gabriela , Chvalovský Václav
Published: January 2014

Hydrosilylation of styrene, 2-phenyl-1-propene and trans-1-phenyl-1-propene by trialkylsilicon hydrides of the type CH3R2SiH (R = C2H5, i-C3H7, i-C4H9) catalysed by [RhCl{P(C6H5)3}3] in the presence of benzene, 1,3,5-triethylbenzene, 1,2,3,4-tetraethylbenzene, pentaethylbenzene, hexaethylbenzene, 1,2,3,4-tetrahydronaphthalene, cyclohexane, tetrahydrofurane (THF), tributylphosphate (TBP), dimethylacetamide (DMA), trimethylphosphate (TMP), tributylphosphate (TBP) and hexamethylphosphorictriamide (HMPA) has been studied both in anaerobic conditions and in the presence of air oxygen. Aromatic solvents were found to affect the composition of reaction products similarly as benzene. The use of THF, TBP, TMP, DMA and HMPA as solvents for hydrosilylation of styrene by the above silanes suppresses formation of the α-adduct when the reaction is carried out under anaerobic conditions. The yields of hydrosilylation of 2-phenyl-1-propene and trans-1-phenyl-1-propene by CH3(C2H5)2SiH are decreased by the addition of THF, TBP, TMP and DMA while they are increased by using HMPA as the solvent.
Syntheses, spectral properties and pesticide activity of O-ethyl-S-propyl-O-(1-alkyl, phenyl-5-chloro, alkoxy-6-oxo-1H-pyridazine-4-yl)esters of dithiophosphoric acid
Authors: Konečný Václav , Varkonda Štefan , Kubala Vojtech
Published: January 2014

Syntheses of O-ethyl-S-propyl-O-(1-alkyl, phenyl-5-chloro, alkoxy-6-oxo-1H-pyridazine-4-yl) esters of dithiophosphoric acid are described. The compounds were investigated for their IR and UV spectra and for their contact and system activities as insecticides, acaricides, ovicides, fungicides and herbicides. Some of the compounds proved efficient acaricides; compound VIII also had an insecticide activity.
Reactions of benzoyl isothiocyanates with azomethines
Authors: Uher Michal , Kováč Štefan , Iliaš Peter , Floch Ľubomír , Martvoň Augustin
Published: January 2014

Preapartion of substituted 1,3,5-oxadiazine-4-thiones and s-triazines by reacting benzoyl isothiocyanates with azomethines and hydrolysis of the obtained oxadiazinethiones is described. The observed, IR, Raman, UV and 1H-NMR spectral characteristics of the prepared substances are discussed.
Evaluation of aeration capacity of fermentors by adaptive identification method
Authors: Sobotka Miroslav , Votruba Jaroslav
Published: January 2014

A new method of evaluation of the aeration capacity, kLa from data measured with the use of an oxygen electrode was proposed, based on the algorithm of adaptive identification. In this way, even the time dependence of kLa in the course of a dynamic experiment can be obtained. The results from mechanically stirred fermentors and apparatuses of the bubbled column type show that the commonly used assumption about the time independence of kLa does not hold for intensively aerated apparatuses.
Effect of various cations on the initial rate of formation of peroxodisulphates
Authors: Balej Jan , Kadeřávek Martin
Published: January 2014

Preparation of peroxodisulphates by electrolysis of mixed solutions of sulphuric acid and various sulphates was studied at low degree of conversion; the partial polarization curves of peroxodisulphate formation and of oxygen evolution obtained from the overall anodic polarization curves and current yields of the principal anodic processes were examined. The mechanism of the effect of various cations on the rate of anodic formation of peroxodisulfates is discussed.
Formation of hydrogen phosphites of alkaline earth metals
Authors: Lukeš Ivan , Ebert Miroslav
Published: January 2014

In this paper a study of heterogeneous systems MHPO3 -H3PO3 -H2O (M = Mg, Ca, Sr) at a temperature of 25°C using the Filippov's eutonic method has been described. Values of change in standard Gibbs energy for reactions of the studied systems have been found. Effect of the cation on hydrogen bond between the H2PO2-3 groups is discussed.
The effect of dehydroxylation of HNaY zeolites on the interaction with ethylene and propylene
Authors: Kubelková Ludmila , Nováková Jana , Wichterlová Blanka , Jírů Pavel
Published: January 2014

The extent of dehydroxylation of HNaY zeolites of various degree of decationization was varied by the termal treatment in vacuo over the temperature range 620-890 K. The solid phase was investigated by means of infrared spectroscopy, the gaseous phase by means of mass spectrometry. Lewis acid-base pair centres were formed by the dehydroxylation and these initiated at 310 K the oligomerization of ethylene in zeolite cavities. The reaction occurred via the cationic mechanism. A certain ratio of Lewis centers to OH groups was necessary in order to achieve the maximum oligomerization rate on given type of zeolite. It was showed up in a shift of the maximum to higher activation temperatures with less decationized zeolites, more stable with respect to the dehydroxylation. The zeolite activity increased with increasing decationization. The same trend was found also for the oligomerization related to one Lewis center. The presence of Lewis centers affected the oligomerization rate of propylene, too, though Broensted centers played the dominant role in this case. After the thermal decomposition of the oligomers aliphatic and cyclic hydrocarbons, mostly saturated compounds, were found in the gaseous phase. The isotopic exchange of propylene-d6 at 570K occurred via a multiple mechanism, the value of its rate being of the same order of magnitude as with the hydroxylated forms. In view of the varying amount of slowly exchanging SiOH groups in various decationized zeolites, the dependence of the exchange rate of structural zeolites on the decationization could not be established.The isotopic exchange of ethylene-d4 occurred via a single mechanism with a slightly increased rate in comparison with the hydroxylated forms.
Thermal effects of dissolution of aluminium halogenides in acetonitrile and tetrahydrofuran
Authors: Gálová Miriam , Kladeková Daniela
Published: January 2014

Molar enthalpies of dissolution of aluminium chlorides, bromides, and iodides in acetonitrile and tetrahydrofuran at 295 K have been determined experimentally. results of the measurements carried out in presence of air humidity point to the fact that both solvents preferential solvation of the solute by water molecules takes place. In an inert atmosphere, all the values obtained are negative. molar heat of dissolution has for AlCl3 the lowest negative value: -181 kJ mol-1 in acetonitrile and -107.8 kJ mol-1 in tetrahydrofuran. For AlBr3 and AlI3 exothermicity of dissolution is considerably higher: -817 and -887 kJ mol-1 for acetonitrile, and -489 and -713 kJ mol-1 for tetrahydrofuran. The transfer from water into both organic solvents has an endothermic character for AlCl3 only; for AlBr3 and AlI3, the character of transfer is unambiguously exothermic. The obtained results are interpreted as effects of interaction between the solute and the solvent.
Application of solvaton model to quantum-chemical study of influence of solvation on the chemical process NH3 + HF → NH+4 + F-
Authors: Miertuš Stanislav , Bartoš Josef
Published: January 2014

Influence of solvent (H2O) on the system NH3 + HF NH+4 + F- has been studied with the use of the solvaton model at the level of the semiempirical CNDO/2 method. The solvent has been found to cause changes in equilibrium geometries and charge distributions particularly in the polar components of the system. Hydration stabilizes much more the charged components, hence the reaction equilibrium should be shifted to the right in aqueous medium. Hydration also facilitates the proton-transfer from HF to NH3, and the ion pair H3NH+...F- should be the most stable intermediate in aqueous medium according to the calculations.
Contribution to the determination of relative increment of internal energy at low deformation of cross-linked rubber
Authors: Pollák Vladimír , Romanov Andrej
Published: January 2014

The relative charge of the internal energy, fU/f, during deformation of cross-linked elastomers, poly(ethylene-co-propylene) and poly(ethylene-co-vinyl acetate), was determined at various temperatures. Anomalies in the dependence of fU/f on relative dilatation in the region of small deformations ( 35%) are to a large extent besides other factors due to the sensibility of the formula used to calculate fU/f to temperature changes.
Modification of polypropylene with 2,3[epoxypropyl]methacrylate
Authors: Citovický Pavol , Chrástová Viera , Mejzlík Jiří , Majer Josef , Benč Gabriel
Published: January 2014

2,3[Epoxypropyl] methacrylate is in water emulsion bound on a low-oxidized isotactic polypropylene powder. Polymerization is carried out at low temperature in the presence of an activator of the initiator - chelate of Fe2+ -dinatrium salt of ethylenediaminetetraacetic acid; under these conditions epoxy group is preserved. The homopolymer formation is decreased with the increasing chelate concentration. From these results and those obtained when styrene was used follows, that the monomer type is one of the factors which can principally influence the formation of certain polymer type in this polymerization system.
Reactions of pyridyl isothiocyanates with diazoalkanes and azoimide
Authors: Marchalín Miroslav , Martvoň Augustin
Published: January 2014

Reaction of 2-, 3- and 4-pyridyl isothiocyanates with diazomethane or diazoethane afforded the corresponding 5-(pyridyl substituted)amino-1,2,3-thiadiazoles or 5-(pyridyl substituted)-amino-4-methyl-1,2,3-thiadiazoles; reaction with azoimide gave 5-(pyridyl substituted)amino-1,2,3,4-thiatriazoles and 5-(2-pyridylamino)tetrazole, which underwent a thermal rearrangement to yield 1-(2-pyridyl)-5-aminotetrazole. The synthesized derivatives are characterized by IR, UV, mass and 1H-NMR spectra.
Synthesis, spectral properties and pesticide effect of pyridazinyl-4-oxy-1,3,2-dioxaphospholane-2-thione and 1,3,2-dioxaphosphorinane-2-thiones
Authors: Konečný Václav , Varkonda Štefan
Published: January 2014

The synthesis of new 2-(1-alkyl, phenyl-5-alkoxy, alkylthio, chloro-6-oxo-1H-pyridazinyl-4-oxy)-1,3,2-dioxaphospholane-2-thiones and 1,3,2-dioxaphosphorinane-2-thiones is described. The synthesized products were characterized by IR and UV spectral data and their contact and systemic insecticide, acaricide, ovicide and fungicide activities were measured, the highest being found the ovicide effect.
The reaction of 2-cyano-3-(5-phenylsulphonyl-2-thienyl) acronitrile with nucleophiles
Authors: Kada Rudolf , Knoppová Viera , Kováč Jaroslav , Balag Miroslav
Published: January 2014

5-Phenylsulphonyl- and 5-phenylthio-2-thiophenaldehydes react with malononitrile and methyl cyanoacetate under the conditions of Knoevenagel reaction to give the corresponding condensation products. It has been found that when 2-cyano-3-(5-phenylsulphonyl-2-thienyl)-acrylonitrile is treated with nucleophiles the phenylsulphonyl group is substituted.
Preparation, spectral properties and biological activities of 5-bromo-6-methyl-2'-deoxyuridine and 5-iodo-6-methyl-2'-deoxyuridine
Authors: Holý Antonín , De Clercq Erik
Published: January 2014

Reaction of 3',5'-di-O-benzoyl-6-methyl-2'-deoxyuridine (IIa) with elementary bromine or iodine afforded 5-halogeno derivatives IIc and IId which on methanolysis gave 5-bromo-6-methyl-2'-deoxyurine (Ic) and 5-iodo-6-methyl-2'-deoxyurine (Id), respectively. The CD spectra of Ic, Id and 6-methyl-2'-deoxyuridine (Ia) are compared and discussed with regard to determination of the nucleoside conformation. Unlike 5-bromo- and 5-iodo-2'-deoxyuridine, the 6-methyl derivatives Ic and Id exhibit neither antibacterial nor antiviral activity. Nor do they exert any antimetabolic effect on the de novo DNA synthesis in primary rabbit kidney cells.
The second virial coefficient of a non-associating gas with anisotropic interactions
Authors: Ševčík Miloš , Boublík Tomáš
Published: January 2014

The second virial coefficient in systems with permanent and induced multipole interactions was studied by using a statistical-thermodynamics correlation based on the perturbation theory of fluids. Several pair potential combinations of the Lennard-Jones function with different, subsequently more complex anisotropic contributions, were considered; the improvement in the description of intermolecular interactions due to these non-central contributions brought about an improvement in the interpretation of experimental data. The characteristic dependence of the parameters ε/k on σ at different temperatures was obtained for all of the three systems studied (Ar, CH4 and CH3F). It was found that if experimental values of the second virial coefficient of methyl fluoride are correlated by a relation derived from the Stockmayer potential, two sets of the ε/k and σ can be employed.
Extraction of iron with dibenzyl sulfoxide solution sorbed on silica gel
Authors: Vláčil František , Khanh Huynh Dang
Published: January 2014

The amount of dibenzyl sulfoxide (DBSO) sorbed on silica gel from toluene solutions was measured for different silica gel hydrophobization procedures and in dependence on the initial DBSO concentration in the solution. From silica gel impregnated with DBSO solution, the sulfoxide is washed out by hydrochloric acid even if the acid has been saturated by shaking with 0.05M solution of DBSO in toluene. The effect of HCl and DBSO concentrations on the recovery of iron was investigated both for liquid-liquid extraction and for extraction with the extractant solution sorbed on silica gel. The recoveries for the two cases are equal, which implies that the ratios of the activity coefficients of the reagent and of the extracted complex for the liquid-liquid extraction and for the extraction with the extractant sorbed on hydrophobized silica gel are the same.
Dipole moments induced in larger molecules. 1- And 4-substituted diamantanes
Authors: Exner Otto , Jehlička Václav , Vodička Luděk , Jakoubek Pavel
Published: January 2014

Dipole moments of fourteen monofunctional diamantane derivatives were measured in benzene solution. The values found are almost equal for 1-substituted (IIa-IIg) and 4-subtituted (IIIa to IIIg) isomers but both are distinctly higher than those of the corresponding adamantane derivatives (I). This trend is not accounted for in terms of the classic Smith-Eyring theory of induced moments which works reasonable well for smaller molecules. Probably some basic assumptions of the theory of dielectrics (a spherical molecular cavity with a dipole in its centre) are no more fulfilled for diamantane derivatives.
Pyrazolidine derivatives from the condensation reaction of hydrazobenzene with aliphatic aldehydes
Authors: Hanuš Vladimír , Hrazdira Milan , Exner Otto
Published: January 2014

The condensation reaction of hydrazobenzene with ethanal yields products of the pyrazolidine structure, III or V, according to whether it is carried out in the absence or presence of alcohols, respectively. Propanal reacts similarly to VIII while no reaction could be achieved with butanal. The structural evidence is based mainly on the mass and 1H NMR spectra which disprove the structures IV and VI, originally suggested by Rassow. The reaction is analogous to the condensation of aliphatic aldehydes with N-phenylhydroxylamine yielding 1,2-oxazolidine derivatives VII.
EHT study of reactivity of methylene group in 1-methyl-1,4-dihydronicotinamide
Authors: Krechl Jiří , Kuthan Josef
Published: January 2014

It has been demonstrated that the EHT method predicts an almost plane form of the heterocyclic ring in 1-methyl-1,4-dihydronicotinamide I (R = CH3) and also reflects satisfactorily character of the covalent bonds in the 4-methylene group. An attempt has been made of calculation of the reaction profile of elimination of the centre 4', and electronic mechanism of its splitting off is discussed.
The stereospecific loss of water from B-homocholestanols under electron impact
Authors: Tureček František , Kohout Ladislav
Published: January 2014

The mass spectra of six isomeric B-homocholestanols are reported. The spectra differ in relative intensities of ions originating by losses of water, acetic acid and ethylene. The differences are rationalized with the help of labelled compounds and metastable spectra.
Absolute configuration at C(20) of the derivatives of 21-nor-5α-cholane-20,24-diol
Authors: Pouzar Vladimír , Havel Miroslav
Published: January 2014

Derivatives of 21-nor-5α-cholane-20,24-diol XI and XIX were prepared by stepwise construction of the side-chain in the position 17β. Their absolute configuration at C(20) was determined on the basis of chemical correlation with the derivatives of 21-nor-5α-cholan-20-ol, XVI and XXIV. The absolute configuration of alcohols XVI and XXIV was determined from the ratio of the yields in which they are formed during the reduction of ketone X and using the benzoate rule. To compounds XI-XVIII the configuration 20R and to compounds XIX-XXVI the configuration 20S has been assigned.
Topological analysis of energy hypersurface
Authors: Pancíř Jiří
Published: January 2014

Topological approximations discussed in the preceeding paper are used for construction of topological energy hypersurfaces of chemical reactions on two levels of a sophistication. A method of a linear change of off diagonal matrix elements reproduces adequately Woodward-Hoffmann rules but it provides only qualitative information about energetical relations. A physically more rigorous hypothesis where the reaction driving force is a function of hybridization changes at reaction sites provides energy hypersurfaces which are correct from a quantitative viewpoint. The method suggested treats the total energy as a function of abstract reaction angles which reflect topological changes accompanying the reaction course. A reaction mechanisms analysis leads then to the analysis of topological energy hypersurfaces which can be treated similarly to that of conventional geometrical hypersurfaces. Formulas for atomic integrals necessary in the construction of Hartree-Fock and CI matrices are derived in the basis of reaction angles mentioned and approximations leading to the semiempirical type of a calculation are discussed.
Theoretical study of acetylene in the external electrical field
Authors: Pancíř Jiří , Haslingerová Ivana
Published: January 2014

In this paper the stable configuration of an acetylene molecule exposed to the external homogeneous electrical field F = (0-10) . 1010 Vm-1 was searched. With all starting configurations considered the only minimum which was found on the energy hypersurface corresponds to the stable orientation of the D ##h h symmetry. Calculated eigenvalues of the Hessian matrix showed that this orientation is stable either rotationally or vibrationally. Calculations were performed on the semiempirical level using the ZDO approximation.
Changes in ribosomes from ischemic spinal cord
Authors: Burda Jozef , Chavko Mikuláš , Maršala Jozef
Published: January 2014

The paper deals with changes in polyribosomal profiles and with incorporation of amino acids into spinal cord ribosomes of dogs after ligature of their lumbar aortas. The polyribosomal profile was unchanged after 80 minutes' ischemia, but ischemia for two 40 min periods with 40 min recirculation in between resulted in disintegration of polysomes into their ribosomal subunits. Recirculation for 48 h was sufficient for return to control values. The incorporation activity of ribosomes in vitro was unchanged, but cell saps isolated from ischemic cells reduced incorporation of amino acids into ribosomes. The results are discussed in terms of concentration changes of adenine nucleotides under the given experimental conditions.
Study of hemoglobin stabilization during lyophilization with saccharides
Authors: Přistoupil Tomáš I. , Ulrych Stanislav , Kramlová Marie
Published: January 2014

Isotonic solutions of 6% hemoglobin were lyophilized with 2-10% glucose, sucrose and dextran and were stored at different conditions for periods up to one year. The lyophilizates dissolved in water were analyzed for their content of methemoglobin and of precipitate, as for the absorption spectra and oxyhemoglobin dissociation curves. Sucrose was found to have a significantly higher effect than glucose in stabilizing the original properties of the hemoglobin samples especially during long time storage. The effect of dextran was negligible.
A quantum chemical study of butene reactions on molybdate catalysts
Authors: Beran Stanislav , Jírů Pavel , Wichterlová Blanka
Published: January 2014

Both the EHT and IEHT methods were used in the study of interaction of various butene forms with models of catalytic active centers (Mo-O-metal), in which the Mo atom is in its +4 or +6 oxidation state and is tetrahedrally or octahedrally coordinated. The influence of an additional metal atom incorporated in the molybdate lattice was also studied. The results suggest that the interaction of all butene forms with the studied models of catalytic surface centers leads to the formation of stable adsorption complexes and that the butene molecule thus chemisorbed can undergo a direct cis-trans or a double-bond isomerization. It is shown that the probability of occurrence of both these reactions depends strongly on the symmetry of the surface center of the catalyst, on the valence of the Mo atom, and increases with the electron acceptor capability of the additional metal.
Interpretation of the 9,10-antraquinone chromophore by configuration analysis
Authors: Fabian Jürgen , Nepraš Miloš
Published: January 2014

In order to disclose the validity of former phenomenological interpretations and rules concerning the spectral absorption feature of antraquinone dyes, electronic wave functions of 9,10-antraquinone and some derivatives have been subjected to the configuration analysis (CA). The calculations demonstrate the possibilities and limitations of the different approaches. The results enable us to make the consistent interpretation in terms of molecular fragments.
Association of some benzyldialkylamines and their salts in benzene solutions
Authors: Jedináková Věra , Dvořák Zdeněk
Published: January 2014

The degrees of association of benzyldibutylamine, benzyldihexylamine, and benzyldibutylamine nitrate in benzene were calculated from their cryoscopic and osmometric data by using the computer program MOP. The amines examined are present as monomers in the solution, benzyldibutylamine nitrate forms tetramers at the temperatures applied (5.5, 25 and 37 °C).
Evaluation of the diffusion coefficient from experimental data on dynamic sorption in a continuous stirred tank reactor
Authors: Brunovská Alena , Ilavský Ján , Buriánek Juraj
Published: January 2014

A method for the estimation of the diffusion coefficient from the sorption measurements in an isothermal continuous stirred tank reactors has been described. Experimental results have been presented and the diffusion coefficient has been evaluated.
The reactions of oligoalcohols with arsenic, arsenous, boric and germanic acids
Authors: Mikan Antonín , Bartušek Miloš
Published: January 2014

The reactions of sorbitol, mannitol, adonitol, dulcitol, glucose and glycerol with H3AsO4, H3AsO3, H3BO3 and GeO2 acids in dilute aqueous solutions were studied by potentiometric neutralization titrations. The formation of the following chelates was demonstrated: As(V)L3-, As(III)L(OH)2-, HAs(III)L(OH)2, BL2-, GeL2(OH)- and GeL32- and the equilibrium constants for their formation were found. Conditions for formation of these chelates of organic oligohydroxy compounds are discussed.
Synthesis, separation, and identification of 4-bromoadamantan-2-one stereoisomers
Authors: Vodička Luděk , Tříska Jan , Hájek Milan
Published: January 2014

A one-step synthesis of mixture of stereoisomers of 4-bromoadamantan-2-one based on the reaction of adamantan-2-one with hydroxylamine hydrochloride in hydrobromic acid is described. The pure stereoisomers were isolated by elution chromatography on silica gel, and their NMR spectra with the Eu(FOD)3 shift reagent, mass spectra, IR spectra, and dipole moments were measured.
Synthesis and properties of 7,7-diaminoquinone methides
Authors: Pavlíčková Libuše , Vašíčková Soňa , Souček Milan
Published: January 2014

Diaminoquinone methides Xa-Xe were prepared by aminolysis of the dicyanoquinone methide IX. From the isolated intermediates XI and XIII a four-step mechanism was deduced, involving addition and elimination steps in the order Ad-E-Ad-E. Condensation of N,N,N',N'-tetramethylchloroformamidinium chloride with 2,6-ditert-butylphenol afforded bis(dimethylamino)-quinone methide Xc which on transamination was converted to the diaminoquinone methides Xa and Xb. Analysis of physico-chemical data of diaminoquinone methides leads to the conclusion that their structure can be represented by the zwitterionic formula XVII rather than the quinonoid formula X.
Fluorinated analogues of tricyclic neuroleptics: 6,9-difluoro derivative of 10-(4-methylpiperazino)-10,11-dihydrodibenzo[b,f]thiepin
Authors: Červená Irena , Hrubantová Marta , Svátek Emil , Holubek Jiří , Ryska Miroslav , Metyšová Jiřina , Protiva Miroslav
Published: January 2014

The acid VI, obtained from 2,5-difluorothiophenol (IV) and (2-iodophenyl)acetic acid, afforded by cyclization with polyphosphoric acid 6,9-difluorodibenzo[b,f]thiepin-10(11H)-one (VII) in a satisfactory yield. Two further steps led to the chloro derivative X giving by a substitution reaction with 1-methylpiperazine the title compound III. This substance exhibits some 10% incoordinating activity of the unsubstituted compound I and an indication of cataleptic activity, in contrast to the inactive analogous dichloro compound II. The bulky atom of chlorine in the vicinity of the methylpiperazine residue interferes evidently with the CNS activity; the influence of the atom of fluorine is much less pronounced in this line.
Derivatives of 4-aryl-2,3-dihalogeno-1-naphthol
Authors: Křepelka Jiří , Zikán Viktor , Holubek Jiří , Semonský Miroslav
Published: January 2014

Using intramolecular cyclization of the in situ prepared chlorides of acids XVI-XX, catalysed with zinc chloride, corresponding 4-aryl-2,3-dihalogeno-1-naphthols III-VII were prepared. Methylation or acetylation of compounds I, IV-VI gave O-methyl-derivatives VIII-XI or O-acetyl derivatives IXII-XV, respectively. Compounds III-XV displayed a weak antineoplastic effect in animals with some transplantable tumours.
Occurence of morphine as a minor alkaloid in papaver decaisnei hochst.
Authors: Slavík Jiří
Published: January 2014

From the mature capsules of the species Papaver decaisnei HOCHST. papaverine was isolated as the main alkaloid and morphine, rhoeadine and coptisine as the minor components. The presence of a small amount of narcotine, thebaine, codeine, protopine, corytuberine and traces of papaverrubines A, C, D and E and thebaine methohydroxide was also proved.
Triterpenes and steroids from ganoderma applanatum
Authors: Protiva Jiří , Skorkovská Hana , Urban Jiří , Vystrčil Alois
Published: January 2014

Five already described triterpenes and steroids were isolated from the fungus Ganoderma applanatum. Its main components are friedelin, ergosta-7,22-dien-3-one and ergosta-7,22-dien-3β-ol, which are accompanied by small amounts of friedoolean-5-en-3-one and ergosterol. Palmitic acid is a further component.
Analogues of deamino-1-carba-oxytocin with an aliphatic amino acid in position 4: chemical synthesis and biological activities
Authors: Lebl Michal , Machová Alena , Hrbas Pavel , Barth Tomislav , Jošt Karel
Published: January 2014

Linear octapeptides were prepared by stepwise synthesis in solution. Cyclization by the method of active esters yielded analogues of deamino-1-carba-oxytocin with valine, leucine or isoleucine in position 4 instead of the glutamine residue. The basic pharmacological activities of the analogues were determined; their natriuretic action was lower than that of oxytocin.
Evaluation of pseudopotential integrals over gaussian lobe basis functions
Authors: Biskupič Stanislav , Pelikán Peter
Published: January 2014

A mathematical analysis of molecular integrals of pseudopotential interactions in molecules is presented. The integrals are expressed over Gaussian lobe functions in the form suitable for computer programming.
Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenolysis of thiophene
Authors: Fott Pavel , Schneider Petr
Published: January 2014

Kinetics have been studied of the reaction system taking place during the reaction of thiophene on the cobalt-molybdenum catalyst in a gradientless circulation flow reactor at 360 °C and atmospheric pressure. Butane has been found present in a small amount in the reaction products even at very low conversion. In view of this, consecutive and parallel-consecutive (triangular) reaction schemes have been proposed. In the former scheme the appearance of butane is accounted for by rate of desorption of butene being comparable with the rate of its hydrogenation. According to the latter scheme part of the butane originates from thiophene via a different route than through hydrogenation of butene. Analysis of the kinetic data has revealed that the reaction of thiophene should be considered to take place on other active sites than that of butene. Kinetic equations derived on this assumption for the consecutive and the triangular reaction schemes correlate experimental data with acceptable accuracy.
Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenation of ethylene and butene
Authors: Fott Pavel , Schneider Petr
Published: January 2014

Hydrogenation has been studied of ethylene and butene in a circulation flow reactor on a cobalt-molybdenum catalyst at 360 °C and atmospheric pressure. The effect has been investigated of simultaneous hydrodesulphurization of thiophene on the hydrogenation. The results have confirmed that different active sites for hydrogenation and hydrodesulphurization must be considered in the kinetic description of simultaneous hydrogenation of ethylene and hydrodesulphurization of thiophene. For isolated hydrogenation of ethylene and butene the absence of hydrogen sulphide in the reaction mixture considerably enhances the hydrogenation activity of the catalyst due to the change of its state.
Some organic lithium compounds as initiators of the anionic polymerization of methyl methacrylate
Authors: Lochmann Lubomír , De Rajib L. , Janča Josef , Trekoval Jiří
Published: January 2014

The presence of α-lithio ketone in the initiation mixture formed by a reaction between butyllithium and methyl pivalate was demonstrated. In the initiation of the polymerization of methyl methacrylate α-lithio ketones exhibit high efficiency, which can be enhanced by the effect of lithium alkoxides, in particular of lithium tert-butoxide.