bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorinated analogues of the tricyclic neuroleptics; 7-Fluoro and 7-trifluoromethyl derivative of 10-(4-methylpiperazino)-10,11-dihydrodibenzo[b,f]thiepin
Authors: Šindelář Karel , Svátek Emil , Holubek Jiří , Ryska Miroslav , Metyšová Jiřina , Šedivý Zdeněk , Protiva Miroslav
Published: January 2014

Reaction of 3-fluorothiophenol with (2-iodophenyl)acetic acid gave the acid VIII which was cyclized with polyphosphoric acid to the ketone XII. The first title compound VI was prepared via the intermediates XV and XVIII. Treatment of the ketone XII with 1-methylpiperazine in the presence of titanium tetrachloride resulted in the enamine XXIII. The similarly prepared acid IX was cyclized to the ketone XIII. By-products were the di-acid X and the enol-lactone XXIV, affording by alkaline hydrolysis the keto acid XXV. The synthesis of the second title compound VII was carried out from the ketone XIII via the intermediates XVI and XIX. 10,11-Dihydrodibenzo[b,f]thiepin-3,11-diol (XVII) gave by treatment with methanesulfonyl chloride and by the following reaction with 1-methylpiperazine the salt of 1-methylpiperazine with dibenzo[b,f]thiepin-3-ol (XXII) and 1-methyl-4-(methylsulfonyl)piperazine (XXVI)). Whereas the compound VI has low central depressant and cataleptic activity, the corresponding enamine XXIII is very potent in both lines. The trifluoromethyl derivative VII has the character of a neuroleptic but its depressant and cataleptic activity are ten times lower than those of the 8-trifluoromethyl isomer.
Synthesis and chiroptical properties of heterodetic cyclic hexapeptides related to oxytocin ring moiety
Authors: Frič Ivo , Leonteva Lyudmila I. , Maloň Petr , Jošt Karel , Bláha Karel
Published: January 2014

Cyclic disulfides of cysteinyl-tetraglycyl-cysteine (Ia), cysteinyl-tyrosyl-triglycyl-cysteine (Ib) and cysteinyl-tyrosyl-isoleucyl-diglycyl-cysteine (Ic) were synthesized by classical methods of peptide synthesis. The actions of solvent and of side chains in the positions 2 and 3 on the conformational arrangement of the peptide backbone and the disulfide group were investigated by means of CD spectroscopy. Some mechanisms which co-operate in stabilizing the oxytocin conformation were identified. Hence, it may be deduced, that the amino acid sequence in the positions 1-3 determines the spatial arrangement characteristic for oxytocin, at least in a protonating medium.
Activation of adenylate cyclase from rat renal medulla by some oxytocin analogs
Authors: Klenerová Věra , Munclinger Miroslav , Hynie Sixtus , Barth Tomislav , Jošt Karel
Published: January 2014

The ability of carba-analogs of oxytocin to activate adenylate cyclase was followed on the crude enzyme preparation from rat renal medulla. Their stimulating effects on adenylate cyclase activity were in a correlation with their antidiuretic potency. There is discussed the dependence of the affinity of carba-analogs of oxytocin to stimulate adenylate cyclase and their antidiuretic potency on the character of changes in the primary structure of these drugs.
Covalent attachment of proteins to Spheron by means of benzoquinone
Authors: Stambolieva Nicolina , Turková Jaroslava
Published: January 2014

The dependence of the amount and the activity of coupled chymotrypsin and trypsin on the activation time and pH, coupling time and pH, enzyme concentration in the reaction mixture and the molar ratio CaCl2/trypsin concentration were investigated for case where enzymes are covalentlybound to the hydroxyalkyl methacrylate gel (Spheron) by means of benzoquinone.
New semi-empirical rules for estimating cross second virial coefficients
Authors: Malijevský Anatol , Novák Josef P.
Published: January 2014

By using the statistical-thermodynamic interpretation of the theorem of corresponding states, new rules have been derived for estimating cross second viral coefficients.
Influence of oxygen on Belousov-Zhabotinskii reaction
Authors: Treindl Ľudovít , Fabian Peter
Published: January 2014

This work deals with the effect of oxygen on basic parameters of the Belousov-Zhabotinskii reaction in the presence of Ce4+/Ce3+ redox catalyst and malonic acid, citric acid, or 2,4-pentanedione as substrates. Oxygen lowers the duration of the induction period and the first oscillation period as well as the corresponding activation parameters. Oxygen lowers also rate constants and activation parameters for oxidation of malonic and citric acids with Ce4+ ions. It is concluded that the effect of oxygen on the Belousov-Zhabotinskii reaction consists mainly in its catalytic influence on the oxidation of the substrate with Ce4+ ions.
Extraction of some metals into solutions of 1-phenyl-3-methyl-4-benzoylpyrazolone-5 in freon 113
Authors: Navrátil Oldřich , Linhart Pavel
Published: January 2014

The partition of 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HA) between aqueous solutions of HClO4 and NaClO4, ionic strength 0.1, and Freon 113 or its 2 : 1 mixture with benzene was studied. The logarithms of the HA distribution constants are 2.84 ± 0.10 and 3.39 ± 0.15 for the two organic phases, respectively. The extraction curves of cerium(III) and europium(III) revealed that in dependence on the pH of the aqueous phase, the metals are transferred into the organic phase in the form of the MA3 complexes (M = Ce, Eu). The stability constants of the complexes MAn in the aqueous phase were determined along with their distribution and extraction constants. For cobalt, zinc, and hafnium, a part of the extraction curves could only be studied, only the extraction constants were therefore determined. The sparing solubility of HA in Freon 113 can be circumvented by using a Freon-benzene mixture 2 : 1, which is still practically incombustible.
Spectrophotometric study of reaction of sodium 6-hydroxy-5-dibenzo(a,j)phenoxazone-11,13-disulfonate with aluminium ions in the presence of cationoid tensides
Authors: Son Nguyen Truong , Lasovský Jan , Ružička Eduard
Published: January 2014

In weakly acidic medium, pH 3.5-6.5, the title dye forms with aluminium ions a complex with the Al : L ratio 1 : 1. In the presence of cetylpyridinium or carbethoxypentadecyltrimethylammonium, ternary complexes AlL3Sr (r = 6 or 9, respectively) are formed. The equilibrium constants of the complexing equilibria in the binary and ternary systems concerned were calculated, and a method of photometric determination of aluminium has been suggested.
A refined empirical model of the sigma-inductive effect
Authors: Exner Otto , Fiedler Pavel
Published: January 2014

The classic theory of the sigma-inductive effect fails in the case of more complex polycyclic molecules since it is not possible to define unambiguously the "number of paths" to be introduced into Eq. (2a). Therefore, three more sophisticated procedures were suggested and tested: 1) a model based on the charge distribution according to Smith-Eyring, or, 2) according to Del Re, and 3) a simple generalization of the classic description - Eq. (7). All the models meet some basic requirements, viz. they are compatible with the Taft equation and predict transmission of the inductive effect in either direction with the same intensity. If tested on experimental dissociation constants of carboxylic acids in mixed aqueous solvents, the third model appears to be the most satisfactory. The fit is actually better than expected for a purely topological approach, nevertheless it is impaired by solvent effects, in particular when polycyclic and open-chain acids are compared. In addition, the precision would be ultimately restricted if topologically equivalent but sterically different molecules were confronted. It follows that previous reasoning in favour of the through-space transmission of substituent effects is invalidated by our improved model. On the other hand, our results do not allow to claim the through-bonds transmission as the only process operating.
Reactions of substituted 1,3-diphenyltriazenes with phenyl isocyanates. Catalysis and substituent effects
Authors: Plandorová Blanka , Pytela Oldřich , Večeřa Miroslav , Vetešník Pavel
Published: January 2014

Reactions of phenyl isocyanate with 12 monosubstituted and 15 symmetrical disubstituted 1,3-diphenyltriazanes have been studied in tetrahydrofurane at 25°C. The found rate constants correlate with the Hammett substituent constants, the slopes being - 1.206 and - 1.682 in case of the monosubstituted and the disubstituted compounds, respectively. Under conditions of pseudomonomolecular reaction catalysis by the products and that by the catalysts used in reactions of isocyanates with amines or hydroxy compounds have not been observed. Rates of reactions of 6 substituted phenyl isocyanates with the parent 1,3-diphenyltriazane have also been measured. In this case the found rate constants correlate with the Hammett substituent constants, the slope being +1.038. The results indicate that the reaction involves rate limiting formation of a six-membered cyclic complex which successively undergoes only a rapid reorganization of electrons.
2-Benzylidene[3]ferrocenophane-1,3-diones and their spectral properties
Authors: Sališová Marta , Toma Štefan , Solčániová Eva
Published: January 2014

2-Benzylidene[3]ferrocenophane-1,3-diones were synthesized by condensation of substituted benzaldehydes and [3]ferrocenophane-1,3-dione with triethylamine as catalyst. Benzaldehydes bearing electron-accepting substituents gave bicyclic compounds as by-products; these were formed by extension of the three-membered bridged system to a seven-membered one. A correlation between ν(C=O) vibrations and σ+ constants of substituents was found. The UV and 1H-NMR spectra of the prepared compounds are commented.
Preparation of 2- and 2,5-disubstituted 1,3,4-oxadiazoles from tetrazoles and carboxylic acids
Authors: Považanec František , Kováč Jaroslav , Svoboda Jozef
Published: January 2014

The intermediate N-acylated tetrazoles, prepared from 5-substituted tetrazoles, N,N'-dicyclohexylcarbodiimide and carboxylic acids, undergo decomposition to form 2-, or 2,5-disubstituted 1,3,4-oxadiazoles in high yield.
Alkaloids from Bocconia frutescens L.
Authors: Táborská Eva , Věžník František , Slavík Jiří
Published: January 2014

Allocryptopine and protopine were isolated from the roots, stalks and leaves of Bocconia frutescens L. as the main alkaloids and chelerythrine, sanguinarine, chelirubine (not present in leaves), berberine and coptisine as the minor ones. In addition to this (-)-isocorypalmine and (-)-scoulerine were isolated from leaves and traces of rhoeadine were found in the leaves and stalks. From the quaternary fraction of all three parts of the plant columbamine and (-)-α-canadine methohydroxide were also isolated in the form of iodides.
On the qualitative theory of Shockley surface states of the (111) face of NbC and the nature of bonding in this compound
Authors: Tomášek Mojmír , Pick Štěpán , Schwarz Karlheinz
Published: January 2014

Qualitative theory of Shockley surface states is applied to the analysis of the (111) surface of the niobium carbide crystal. The existence of Shockley states is predicted in two hybridizational gaps. One of (p, t2g) character lies just below the Fermi energy and the other of (eg, t2g) character is at higher energies. The relation between Shockey states and bonding is discussed. A strong (p, t2g) covalent component of the metal-nonmetal bond is found.
Reactions of chloroplatinum(IV) complex with thiourea and its alkyl derivatives
Authors: Kováčová Jolana , Gažo Ján
Published: January 2014

Reaction of the PtCl2-6 ions with thiourea, N-methyl-, N,N'-dimethyl-, and N,N,N'-trimethylthiourea, respectively, led to complexes analogous to those formed on the reaction of the PtCl2-4 ion with these ligands. Formamidine disulfide or its alkyl derivatives were identified as the oxidation products. N,N,N',N'-Tetramethylthiourea and N,N'-ethylenethiourea afforded in the same conditions the Pt(IV) complexes; reduction of Pt(IV) to Pt(II) was not observed.
Structure of dimeric monoisopropoxydicaprolactamoalane and diisopropoxymonocaprolactamoalane
Authors: Kříž Otomar , Čásenský Bohuslav , Macháček Jiří
Published: January 2014

Molecular weight and 1H-NMR and IR spectral measurements evidence that in dimeric aluminium isopropoxide in which one or two isopropoxyls have been replaced by caprolactam ligand, only the oxygen atoms of the isopropoxyl take part in the bridge formation between the two aluminium atoms.
The liquid side mass transfer coefficient in a film of liquid trickling down an expanded metal sheet packing
Authors: Lacina Jan , Kolář Václav
Published: January 2014

The paper presents experimentally obtained values of the liquid side mass transfer coefficient in a liquid film trickling down an expanded metal sheet packing and their analysis based on the model of unsteady absorption.
Electrostatic effects on conformational equilibria. Solvent dependence
Authors: Friedl Zdeněk , Fiedler Pavel , Exner Otto
Published: January 2014

The conformational equilibrium E ⇄ Z of methyl 2-fluorobenzoate was determined from the intensity of the carbonyl bands in 17 aprotic solvents of different polarity. The estimated values ΔG0 depend linearly on the reciprocal permittivity of the solvent as expected according to the electrostatic theory in combination with common cavity models. If a small correction is admitted for the unequal absorption coefficients of the two rotamers and/or for the steric effect of fluorine, the results agree very well with electrostatic calculations; the values extrapolated to vacuum agree also resonably with CNDO/2, INDO and PCILO, but not with STO-3G calculations. On the whole, the electrostatic theory seems to work better with conformational equilibria than with proton transfer reactions. This conclusion does not depend on the solvent used or on any particular cavity model.
Electrochemical oxidation of 2-furylacetic acid derivatives
Authors: Janda Miroslav , Šrogl Jan , Körblová Eva , Stibor Ivan
Published: January 2014

Depanding on reaction conditions, the electrochemical methoxylation of 2-furylacetonitrile (I) afforded either (2,5-dimethoxy-2,5-dihydro-2-furyl)acetonitrile (V) or (5-methoxy-2,5-dihydro-2-furfurylidene)acetonitrile (VIII). Analogous reaction of methyl 2-furylacetate (II) gave either methyl (2,5-dimethoxy-2,5-dihydro-2-furyl)acetate (VI) or methyl (5-methoxy-2,5-dihydro-2-furfurylidene)acetate (IX). The electrochemical ethoxylation of ethyl 2-furylacetate afforded- among other products - also γ-lactone of ethyl 3-hydroxy-2,4-hexadienedioate (X).
Synthesis of some 2-aryl-6-amino-2,3-dihydro-1,2,4-benzotriazin-3-ones
Authors: Slouka Jan , Bekárek Vojtěch
Published: January 2014

Acylation of 2,4-diaminobenzene and its derivatives Ia-Ih with ethyl chloroformate gives high yields of the corresponding 2,4-bis(ethoxycarbonylamino)azobenzenes IIa-IIh which, on boiling in acid medium, are cyclized with simultaneous splitting off of the second ethoxycarbonyl group to give the mesomeric 6-amino-2-aryl-3-oxo-2,3-dihydro-1,2,4-benzotriazinium cations IIIa-IIIh; the latter have been transformed into the free bases IVa-IVh or their tautomers Va-Vh. Constitution of the prepared compounds has been studied by IR spectroscopy. Influence of medium on valence vibrations of the carbamate NH groups in the compounds II has also been studied.
(E-Z)-isomerisation of chloroolefins
Authors: Procházka Miloš , Adamcová Jindřiška , Paleček Miloš
Published: January 2014

Equilibrium constants for the (E-Z) isomerisation of the compounds R-CH=CH-Cl were determined and the experimental values compared with energy differences, calculated by the CNDO/2 method.
Synthesis of arylacetic acids and their effect on activation of fibrinolysis. Quantitative relations between structure and biological activity
Authors: Kuchař Miroslav , Brunová Bohumila , Roubal Zdeněk , Schlanger Jiří , Němeček Oldřich
Published: January 2014

A series of arylacetic acids, III, has been prepared and evaluated for activation of fibrinolysis and inhibition of heat-denaturation of serum albumin. regression analysis revealed that either activity was influenced mainly by lipophilicity of the aromatic substituents. The graph showing activation of fibrinolysis by acids III takes a linear course up to a maximum, followed by a step decrease. Also included in the series are p-benzyloxy derivatives of the arylacetic acids. Their lipophilicity has been evaluated by thin-layer chromatography, the method of reversed phase being employed. However, the lipophilicity parameters thus obtained fail to describe the hydrophobic bonding of these derivatives to the active site; tabulated values of the parameter π were better in this respect.
Amides of 4,4-bis(4-ethylphenyl)-2,3-dibromo-cis-2-butenoic acid
Authors: Hartl Jiří , Chocholoušová Jaroslava , Semonský Miroslav
Published: January 2014

Amides of 4,4-bis(4-ethylphenyl)-2,3-dibromo-cis-2-butenoic acid (III-LI) have been synthetized and administered to animals with experimental tumours. Their antineoplastic effects did not exceed that of the acid I. However, some of the compounds exhibited a more or less selective effect in animals with certain transplantable tumours.
Alkaloids from Strempeliopsis strempelioides K. SCHUM.
Authors: Laguna Abilio , Dolejš Ladislav , Novotný Ladislav
Published: January 2014

From the leaves of Strempeliopsis strempelioides K. SCHUM. (Apocynaceae), an indigenous species from Cuba, the following alkaloids were isolated: (+)-Demethylaspidospermine, (-)-aspidosine, (+)-tubotaiwine, (-)-vallesine, (+)-condylocarpine and (+)-eburnanomine. From stem bark of the plant the following alkaloids were isolated: (-)-Aspidospermine, (+)-deacetylaspidospermine, (+)-vincadifformine, (_)-apparicine, (+)-tubotaiwine, (+)-condylocarpine and (+)-demethylaspidospermine. All the structures were proposed on the basis of spectral evidence and chemical reactions.
Synthesis of peptides, glyco derivatives and glycopeptides from bacterial cell walls
Authors: Zaoral Milan , Ježek Jan , Krchňák Viktor , Straka Radovan
Published: January 2014

Syntheisi in solution and in solid phase was used to prepare alanyl-D-isoglutamine (VI), alanyl-D-isoglutaminyl-Nε-p-toluenesulfonyl-lysyl-D-alanine ester (XIII), alanyl-D-isoglutaminyl-Nε-acetyl-lysyl-D-alanine methyl ester (XIV), alanyl-D-isoglutaminyl-Nε-acetyl-lysyl-D-alanyl-pentaglycine methyl ester and amide (XXXI, XXXII), alanyl-D-isoglutaminyl-Nε-acetyl-lysyl-D-alanyl-pentaglycyl------------- alanyl-D-isoglutaminyl-lysyl-D-alanine methl ester (XXXV), alanyl-D-isoglutaminyl-Nε-acetyl-lysyl-D-alanyl-pentaalanyl-----------------alanyl-D-isoglutaminyl-lysyl-D-alanine methyl ester (XXXVII), N-acetylmuramyl-alanyl-D-isoglutaminyl-Nε-acetyl-lysyl-D-alanyl-pentaglycine amide (XXXIX), N-acetylmuramyl-alanyl-E-isoglutaminyl-Nε-acetyl-lysyl-D-alanyl-pentaglycyl------------------------ alanyl-D-isoglutaminyl-lysyl-D-alanine methyl ester (XLI), and N-acetylmuramyl-alanyl-D-isoglutaminyl-Nε-acetyl-lysyl-pentaalanyl-----------------------------N-acetylmuramyl-alanyl-D-isoglutaminyl-lysyl-D-alanine methyl ester (XLIII). The tetrapeptides, nanopeptides, and tridecapeptides show a pronounced pyrogenic effect. Immunoadjuvant activity was observed not only with the glycopeptides but also with nonapeptide XXXI.
Solution of Laplace's equation in interelectrode space for shaped electrodes
Authors: Novák Petr , Kimla Arnošt , Roušar Ivo , Cezner Václav , Mejta Vladimír
Published: January 2014

The Laplace equation was solved in the interelectrode space for shaped electrodes (two-dimensional case) by the method of finite differences (FDM), Galerkin's method (GM), and collocation method (CM). A comparison shows that for electrode shapes with a continuously changing surface (continuous first and second derivatives), the solutions by all three methods are equivalent, giving identical distribution of local current densities on the electrode surface. The use of GM and CM is, however, not practical because of high requirements on the computer time and memory as compared with FDM. Moreover, the GM and CM fail in the case of discontinuities in the electrode shape.
Interaction of Ir(CO)Cl(PPh3)2 with metal ions
Authors: Večerník Josef , Mašek Jiří , Vlček Antonín A.
Published: January 2014

The interaction between Ir(CO)Cl(PPh3)2 ( further abreviated as Irk) and Hg(ClO4)2 or Hg(DMSO)6(ClO4)2 leads to a consecutive formation of complexes of the type [(Irk)nHg](ClO4)2 (n = 1, 2, 3) and [(Irk)3Hg(ClO4)x](ClO4)2-x depending on the Irk : Hg2+ ratio. In presence of metalic mercury a further complex with the stoichiometry [(Irk)4Hg](ClO4)2 was identified. The Vasca complex Ir(CO)Cl(PPh3)2 acts as a ligand also towards further metal ions, such as Cu2+ and Fe3+, forming complexes with the stoichiometry (Irk)CuCl2 and (Irk)2FeCl3, respectively. Spectroscopic and polarographic characterization of these complexes is given.
Nickel(II) complexes of phosphinetriacetic acid
Authors: Podlahová Jana
Published: January 2014

The interaction of phosphinetriacetic acid (H3X) with nickel(II) was examined under various conditions using potentiometric study of solution equilibria, preparation of solid complexes, spectra (electronic and IR) and other methods. In aqueous solutions, the ligand acts as tridentate through the phosphorus atom and two carboxylic groups to form hexacoordinate complexes, NiX-, NiHX and NiX4-2. At 0.8 X/Ni 1.7 and pH 6-8, these complexes are slowly transformed to Ni3X2, an insoluble polymeric compound. In non-aqueous solvents, trans-square planar complexes Ni(hal)2(H3X2) (hal = Cl, Br, I) are formed, which contain the ligand coordinated through the phosphorus atom alone. While the solid iodocomplex is also planar, the solid chlorocomplex is hexacoordinated with carbonyl oxygens in axial sites. Both isomeric forms of the bromocomplex were isolated in the solid state.
Medium effect on alkaline hydrolysis of diphenic acid monomethyl ester
Authors: Benko Ján , Holba Vladislav
Published: January 2014

The alkaline hydrolysis of diphenic acid monomethyl ester was studied in mixtures of water with methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, tert-butyl alcohol, and acetone. The dependences of the rate constant on the concentration of the nonaqueous component at different temperatures were obtained and the activation parameters at an isodielectric composition of the reaction medium were determined. The influence of the ionic strength on the reaction rate in the mentioned media was studied and conclusions were drawn as to the role of specific interactions between the reacting ions in the kinetics and mechanism of the studied reaction.
Relation between the infrared spectra of metal dithiocarbamates and their crystal structure and electronic effects of substituents
Authors: Oktavec Drahomír , Beinrohr Ernest , Síleš Bohumil , Štefanec Jozef , Garaj Ján
Published: January 2014

The IR spectra of dithiocarbamic acids alkali salts and Ni(II), Cu(II), and Zn(II) chelates are studied in the region of 3 800-200 cm-1. The results are correlated with X-ray diffraction data. The position of the absorption bands of the dithiocarbamates is affected mainly by the nature of the central atom and the character of the group bonded to the nitrogen atom, influencing the charge density distribution at the C-N and M-S bonds. The structure of the coordination sphere affects the M-S and C_N bonds, which, however, manifests itself only in the IR band shape, the ν(C-N), ν(C-S), and ν(M-S) band position remaining unaltered.
Complex equilibria and spectrophotometric determination of copper with 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol
Authors: Hrdlička Aleš , Langová Marie
Published: January 2014

The complex equilibria of copper with 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol were studied spectrophotometrically using graphical analysis and numerical treatment of the absorbance data by the PRCEK or SPEKTFOT program on a Tesla 200 computer. Of the two reagents, 4-(2-pyridylazo)resorcinol forms more complexes including the 1 : 2 complexes, with a greater bathochromic shift of λmax with respect to the reagent. Especially the CuL2-2 complex of 4-(2-pyridylazo)resorcinol with ε = 7.9 . 104 at 500 nm permits sensitive spectrophotometric determination of copper. Procedures for the spectrophotometric determination of copper in weakly alkaline media were evaluated.
The reaction of UO22+ with chromazurol S and the spectrophotometric determination of uranium in the presence of Septonex
Authors: Kanický Viktor , Havel Josef , Sommer Lumír
Published: January 2014

This work is concerned with a detailed study of the reaction of UO2+2 with chromazurol S in the presence of cationic tenside Septonex, which was found to be very promising of the group of cationic tensides. From the study were drawn a number of conclusions regarding the effect of the cationic tenside on the reaction of triphenylmethane dyes with salicylic acid groups with metal cations. Optimum conditions for the spectrophotometric determination of uranium with chromazurol S in the presence of Septonex were found.
Study of structure and activity of cobalt bromide complexes in the oxidation of alkylaromatic hydrocarbons
Authors: Hronec Milan
Published: January 2014

Catalytic activity of tetrabromocobalt(II) complexes and halo complexes of the type CoX2L2 respectively with ligands involving as donor atom, nitrogen, sulphur, phosphorus, arsenic, or antimony was studied in oxidation of alkylaromatic hydrocarbons. The preparation of the nitrogen compounds in the complex formation and in the elementary reaction stages was investigated. Highly catalytically active tetrahedral complexes of the types CoBr2-4 and (CoBr3OAc)2-. Triethanolamine-coordinated cobalt bromide and chloride complexes react in acetic acid or its anhydride with oxygen, the triethanolamine ligand being oxidized as well. In addition to their participation in the cobalt complex formation, nitrogen compounds influence the recovery of the active forms of the catalyst; they do not, however, affect the rate of dehalogenation of organic bromides.
The ortho effect in ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides: A 1H-NMR study
Authors: Krasnec Ľudovít , Solčániová Eva , Hrnčiar Pavol
Published: January 2014

The 1H-NMR spectra of ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)-phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides have been studied. The chemical shifts observed for the methine proton were correlated with various constants of the substituents. In addition to simple correlations, two- and three-parameter correlations were also made. Statistically most important one-parameter correlations were observed for σp-constants. Apart from the common electronic effects, in the transfer of effects of the substituents from the ortho-position upon the chemical shift of the methine proton the field effect plays also an important role. The deviations observed in the case of substances substituted in both ortho-positions confirm the assumed considerable distortion of the coplanarity of the studied systems.
Iodoacetate inactivation of rape alcohol dehydrogenase
Authors: Stiborová Marie , Leblová Sylva
Published: January 2014

Iodoacetate inactivates rape alcohol dehydrogenase (ADH, EC 1.1.1.1). The inactivation rate follows the kinetics of the first order, is pH-dependent, and decreases below pH 7.5. Besides irreversible alkylation of the sulfhydryl groups of the enzyme iodoacetate also forms a reversible complex with rape ADH. The coenzyme (NAD) and its analogs (ATP, ADP, AMP) competitively protect the enzyme against alkylation; o-phenanthroline also protects the enzyme against alkylation yet noncompetitively with respect to iodoacetate. Imidazole and o-phenanthroline compete with one another for binding to the protein molecule of rape ADH. Whereas o-phenanthroline decreases the inactivation rate imidazole increases the rate of iodoacetate inactivation.
Isolation of plant lactate dehydrogenase by affinity chromatography and role of histidine in the molecule of the enzyme
Authors: Barthová Jana , Plachá Pavla , Leblová Sylva
Published: January 2014

Lactate dehydrogenase (EC 1.1.1.27) was isolated from soybean seedlings (Glycine max. L.) by affinity chromatography on an AMP-Sepharose 4B column. The enzyme obtained was inactivated by treatment with diethyl pyrocarbonate; the inactivation rate was proportional to the molar ratio of the enzyme to the reagent. The plot of the inactivation rate versus pH shows that of all the functional groups of the protein the imidazole groups of histidine only were modified by diethyl pyrocarbonate. By this procedure 20 histidine residues were ethoxyformylated in the molecule of soybean lactate dehydrogenase yet 8 only, i.e. two in every subunit were essential for thae activity of the enzyme. A comparison of the effect of diethyl pyrocarbonate on the lactate dehydrogenase apoenzyme with its effect on the binary complexes of the enzyme with coenzymes or on ternary complexes with its both substrates permits the conclusion that histidine is involved not only in the proton transfer during the redox reaction but also in the coenzyme-binding site.
Heat transfer between two fluid phases
Authors: Vodák František
Published: January 2014

The interface (or the surface phase) in an n-component fluid is studied on a model of the discontinuity surface in continuum. Balance equations, equations for entropy production, phenomenological equations and heat transfer equations are derived, which comprise bulk phase temperatures, the temperature of the interface (or the temperature of the surface phase), the surface heat conductivity coefficient and heat transfer coefficients as explicit quantities.
Catalyst based on nickel and molybdenum of a high specific surface
Authors: Taras Petr , Pospíšil Milan
Published: January 2014

Reduction of mixed oxides NiO-MoO3 of varying composition by hydrogen in the temperature range 653-773 K was studied as well as several physico-chemical parameters of the reduction products - methanation catalysts.Initial oxides contain - depending on their composition - a varying concentration of nickel molybdate as a free phase. The reduction of molybdenum oxide is catalytically influenced by nickel reduced and takes place, depending on its actual concentration, to the lower oxidation degrees eventually to the metallic molybdenum. On the other hand, the molybdenum present stabilizes nickel microcrystallites during the reduction by hydrogen. Resulting active catalytic systems exhibit a high specific surface. The rate, degree, and apparent activation energy of the reduction are markedly dependent on the initial sample composition. The reduction kinetics can be qualitatively described by an equation of the zone model of solid phase decomposition.
Perturbation theory of substituent effect. Quantum chemical estimation of the Hammet ρ constants
Authors: Ponec Robert
Published: January 2014

Based upon a simple model describing the substituent effect only by a change in the Coulombic integral Δαμ, a relation is derived which can be viewed as a quantum chemical analogue of the Hammet equation. This relation and knowledge of the reaction constant ρ for a reaction on a skeleton chosen as a standard make it possible to predict theoretically the magnitude of the ρ constant for this reaction on an arbitrary conjugated skeleton provided that for the latter the Hammet equation holds.
Perturbation theory of substituent effect. Importance of the field effect in transmission of the substituent effect
Authors: Ponec Robert
Published: January 2014

Various quantum chemical approaches to the problem of transmission of the substituent effect were compared. It was shown that inclusion of the electronic repulsion (field effect) was necessary to give a true picture of differences in ρ constants for reactions of the cis and trans isomers of substituted unsaturated carboxylic acids; the same holds for an adequate description of transmission of the substituent effect from the meta position on a given skeleton.
Properties of electrochemically generated primary cationradicals of phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles
Authors: Kubáček Pavel
Published: January 2014

The first step of electrochemical oxidation of 2-phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles in anhydrous acetonitrile produces relatively stable cationradicals which have been studied by means of EPR spectroscopy using the method of internal electrochemical generation of radicals under reduced temperature. The same electrochemical behaviour of the both studied derivatives and identical EPR spectra of their cationradicals can be explained within the Huckel MO method. The largest contribution to the magnitude of splitting constant of nitrogen nucleus is due to π-σ-spin polarization of C-N bonds caused by high spin abundance of pz-AO of carbon atoms. Half-life of decomposition of the studied cationradicals is 4 min at -30°C.
Selective determination of aromatic nitroso compounds
Authors: Ružička Eduard , Palešková Marija , Jílek Jaromír Antonín
Published: January 2014

A method is suggested for selective determination of aromatic nitroso compounds based on titration with tin dichloride solution in glycerol, the substance to be determined being dissolved in absolute ethanol saturated with dry hydrogen chloride. The titration end point was determined potentiometrically, amperometrically, or visually using phenoxazine type redox indicators.
Internal diffusion effect and hydrogenation selectivity of 1,5-cyclooctadiene
Authors: Hanika Jiří , Chlumská Jitka , Růžička Vlastimil
Published: January 2014

A relatively selective hydrogenation of 1,5-cyclooctadiene to cyclooctene has been achieved in cyclooctane solution at atmospheric pressure using a powder catalyst with 0.6% (by wt.) palladium on γ-alumina. The cyclooctene yields are temperature independent within 30 to 50°C, they are, however, markedly decreased with the use of the tablet catalyst.
Reactions of α,β-unsaturated acyl isothiocyanates with phenylhydrazine
Authors: Kutschy Peter , Kristian Pavol , Dzurilla Milan , Kováč Jaroslav
Published: January 2014

3-(2-Furyl)propenoyl isothiocyanate or 3-phenylpropenoyl isothiocyanate react with phenylhydrazine to give an isomeric mixture of 1,4- and 2,4-disubstituted thiosemicarbazides which cyclize under alkaline conditions to the corresponding 1,3-disubstituted Δ3-1,2,4-triazoline-5-thiones and 1,5-disubstituted 3-mercapto-1,2,4-triazoles, respectively. The structure of the prepared substances was confirmed by independent syntheses. Methylation of isomeric triazoles as well as methylation followed by cyclization of the corresponding thiosemicarbazides afforded, respectively, 1,5-disubstituted 3-methylthio-1,2,4-triazoles and 1,3-disubstituted 5-methylthio-1,2,4-triazoles. The structure of the synthesized products is discussed on the basis of their IR, 1H-NMR and mass spectra.
Cyclopropanes of 5-nitrofurane series. Reactions of diazomethane with 1-(5-nitro-2-furyl)-1-trichloromethylsulphonyl-2-R-ethylenes
Authors: Prousek Josef , Jurášek Adolf , Kováč Jaroslav
Published: January 2014

Diazomethane reacts with trisubstituted ethylenes of 5-nitrofurane series within the temperature range -60°C to +20°C with direct formation of cyclopropane derivatives IV without pyrazoline intermediates. This reaction does not proceed as a 1,3-dipolar cycloaddition but goes via nonfinished stepwise mechanism discussed in the present paper. The cyclopropane derivative IVa has been prepared as a model substance via the new reaction from 5-nitrofurfuryltrichloromethyl sulphone (I) and paraformaldehyde. The synthesized derivatives were identified by IR, UV, 1H-NMR and mass spectra.
5-Nitrophenyl-2-furfuryl-N-onium bromides
Authors: Krutošíková Alžbeta , Kováč Jaroslav
Published: January 2014

The title compounds were prepared by reaction of 5-nitrophenyl-2-furfuryl bromides with tertiary amines as pyridine, α,β-picolines, trimethylamine, triethylamine and tripropylamine. Their IR, UV and 1H-NMR spectra are interpreted.
Cyclic analogues of insect juvenile hormone
Authors: Hejno Karel , Šorm František
Published: January 2014

The preparation and the juvenilization effect of some derivatives of 3,7-dimethyl-9-(5-methyl-2-oxolanyl)-2,6-nonadenoic, 3,7-dimethyl-9-(5-methyl-2-oxolanyl)-2-nonenoic (methyl, ethyl and isopropyl ester, monomethyl and dimethylamide) and 3,7-dimethyl-9-(-methyl-2-oxolanyl)-2,4-nonadenoic acid (methyl, ethyl and isopropyl ester) have been described.
Crystal and molecular structure of the tetradecahydrate of cobalt(II) (R,S)-ethylenediamine-N,N'-disuccinato-cobaltate(III)
Authors: Pavelčík František , Soldánová Jiřina , Majer Jaroslav
Published: January 2014

Crystals of Co3((R,S)-EDDS)2 . 14 H2O are monoclinic with lattice parameters a = 1.1393, b = 1.1856, c = 1.5267 nm, β = 114.6°. The space group is P21/c, Z = 2. The structure was solved by the heavy atom method and refined by the least squares method to R = 0.082. The crystals are composed of binuclear [CO2((R,S-EDDS)2]2- anions, [CO(OH2)6]2+ cations and crystal water molecules. The cobalt atom in [Co2((R,S)-EDDS)2]2- is coordinated octahedrally by two nitrogen atoms and three oxygen atoms from different carboxyl groups in a single [(R,S)-EDDS]4- molecule and one oxygen atom from a neighbouring [(R,S)-EDDS]4- molecule. The [Co(OH2)6]2+ cation is coordinated octahedrally.
Synthesis and properties of some icosahedral carborane B,B'-dithiols
Authors: Plešek Jaromír , Janoušek Zbyněk , Heřmánek Stanislav
Published: January 2014

Reaction of icosahedral carboranes with excess sulfur over AlCl3 converts in high yields o-carborane to 9,12-, and m-carborane to 9,10- and 5(4),9-dithiols which were transformed by CH2Br2 to the appropriate cyclic thioformal derivatives. Reaction of 9,12(HS)2-1,2-C2B10H10 with acetone and AlCl3 afforded a cyclic thioketal, the structure of which was confirmed by X-ray structure analysis. All structures were proposed on the ground of 1H-, 11B-NMR and mass spectra.
O-O bond activation with cobalt(II)-ethylenediamine complexes in ion-exchange resins
Authors: Andreev Atanas , Prahov Lachezar , Shopov Dimitar
Published: January 2014

The formation of Oxygen paramagnetic adducts of Co(II) containing ion-exchange resins in the presence of adsorbed ethylenediamine has been found. The EPR parameters of a complex of the type Co(III) (en)2O-2 and of O-2 species formed in the presence of Co(en)2+3 have been described. The catalytic properties of Co-ethylenediamine surface complexes with respect to the hydrogen peroxide decomposition reaction have been investigated and a probable mechanism has been suggested.
NMR study of ligand exchange in some metal dithiocarbamates
Authors: Beinrohr Ernest , Garaj Ján
Published: January 2014

The 1H-NMR spectroscopy was employed to study solutions of the dithiocarbamates of Cr(III), Fe(III), Co(III), Ni(II), Cu(II) and Zn(II) in carbon disulphide. It was confirmed that, in spite of the marked thermal stability of these complexes, ligand exchange occurs in solution, where the rate of exchange decreases in the order: Zn(II) Ni(II), Fe(III) Cu(II) Co(III), Cr(iii). The exchange practically does not occur in Co(III) and Cr(III) complexes.
Preparation of cycloheptanols symmetrically labelled with deuterium
Authors: Tureček František
Published: January 2014

Cycloheptanols labelled symmetrically with deuterium in inaccessible positions were prepared by multistep syntheses. The key intermediates of the syntheses were the corresponding labelled octanedioic acids. The method of two-phase oxidation of olefins to carboxylic acids was modified so that it would be utilizable for the preparation of dicarboxylic acids.
Synthesis of acyl 1-acetoxy-2-phenoxyethanes and the corresponding hydroxy derivatives
Authors: Lukáč Ivan , Zvara Ivan , Kulíčková Magdaléna , Hrdlovič Pavol
Published: January 2014

Acyl 1-acetoxy-2-phenoxyethanes Ia-Id were prepared by aluminium chloride or polyphosphoric acid-catalyzed Friedel-Crafts acylation. Subsequent hydrolysis gave the corresponding alcohols IIa-IId. The formation of ortho-isomers during acylation was not observed.
Preparation of 2-amino-1,6-anhydro-2-deoxy-β-D-mannopyranose by intramolecular substitution of the tosyloxy group in sterically hindered position of 1,6-anhydro-2-O-p-tolylsulfonyl-β-D-glucopyranose
Authors: Černý Miloslav , Večerková Hana , Černý Ivan , Pacák Josef
Published: January 2014

1,6 : 3,4-Dianhydro-2-O-p-tolylsulfonyl-β-D-galactopyranose (I) was converted to 1,6-anhydro-4-O-benzyl-2-O-p-tolylsulfonyl-β-D-glucopyranose (II) and then reacted with benzylisocyanate to give 3-O-(N-benzylcarbamoyl) derivative III. The cyclization of this substance under the effect of potassium tert-butoxide in tert-butanol gave 3-benzyl-(1,6-anhydro-4-O-benzyl-2,3-dideoxy-β-D-mannopyrano) [2,3-d]oxazolidin-2-one (IV) which was hydrolysed to 1,6-anhydro-4-O-benzyl-2-benzylamino-2-deoxy-β-D-mannopyranose (VIII). Catalytic debenzylation of VIII on palladium on charcoal in the presence of hydrochloric acid gave the hydrochloride of 2-amino-1,6-anhydro-2-deoxy-β-D-mannopyranose (IX), which was acetylated to triacetate XI. Depending on the conditions during catalytic debenzylation of the oxazolidine derivative IV either O-debenzylated derivative VI alone was obtained, or the completely debenzylated oxazolidine derivative VII.
Synthesis of 11-hydroxylated androstane derivatives
Authors: Fajkoš Jan , Joska Jiří
Published: January 2014

Reaction conditions for selective reduction of 3- and 17-oxo groups are described and applied to syntheses of 11-hydroxylated derivatives.
The reaction of 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane with cytosine arabinoside and 1-(6-deoxy-α-L-talofuranosyl)uracil
Authors: Markiewicz Wojciech T. , Padyukova Nelly Sh. , Samek Zdeněk , Smrt Jiří
Published: January 2014

1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (I) reacts with cytosine arabinoside (II) in pyridine under the formation of 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)cytosine arabinoside (IIIa) and with 1-(6'-deoxy-α-L-talofuranosyl)uracil (V) under the formation of 2',3'-O-(tetraisopropyldisiloxane-1,3-diyl) 1-(6-deoxy-α-L-talofuranosyl)uracil (VIa).
Mathematical simulation of electrochemical machining taking into account the influence of electrode polarization, electrolyte temperature and bubble formation on the form of the workpiece
Authors: Novák Petr , Roušar Ivo , Kimla Arnošt , Cezner Václav , Mejta Vladimír
Published: January 2014

To study the influence of polarization on the form of the workpiece, a method of transformation of the interelectrode space to a rectangle (for a two-dimensional system) was proposed. The potentials in this region were calculated by the superrelaxation method. The results of the calculation show a pronounced effect of polarization on the final form of the workpiece in comparison with an analogous calculation involving no electrode polarization. The Joule heat evolved in the streaming electrolyte and gas bubbles formed during electrolysis have also a pronounced influence on the course of the machining process.
Calculation of solvent effect on conformation stability and anomeric effect in dimethoxymethane
Authors: Tvaroška Igor , Bleha Tomáš
Published: January 2014

Solvent effect has been investigated on relative stability of the dimethoxymethane (DMM) conformers formed by rotation about the central C-O bonds. Potential energy of the isolated molecule in the whole conformation space determined by torsion angles (φ1, φ2) has been calculated by the PCILO semiempirical quantum-chemical method. For determination of potential energy of DMM in solvent environment the procedure by Sinanoglu has been used in which the solvation energy is divided into electrostatic, dispersion and cavity terms. The calculation predicts that DMM in CCl4 solution as well as in vapour phase exists almost exclusively in its most stable(sc, sc) conformation with slight population of the (ap, sc) conformations. On the contrary, in aqueous solution an almost exclusive occurrence of the (ap, ap) conformation can be expected. The predicted abundances of the DMM conformers agree well with the available experimental data for DMM and similar molecules. Also the role of environmental factors on the anomeric (gauche) effect has been analyzed which makes itself in preference for sc to ap conformations in a number of polar molecules. It has been shown that the original intramolecular preference for the sc conformation can be compensated by intermolecular solute-solvent interactions, and the anomeric effect can disappear with increasing solvent polarity. The calculated solvation energies have been used for estimation of dilution enthalpies of DMM, too.
Synthesis and characterization of cobalt(III) mixed complexes of diamines and monohydroxamic acids
Authors: Hájek Bohumil , Benda František
Published: January 2014

Mixed complexes of the type [Co(en)2RCONHO]2+, [Co(phen)2RCONHO]2+, [Coen(RCON.HO)2]+, [Co(NH3)4RCONHO]2+, and [Co(NH3)2(RCONHO)2]+ were prepared by substitutions of hydroxamates RCOHNO- (R = C6H5, C2H5, CH3) with [Co(en)2CO3]+, [CoH2O(en)2OH]2+, cis-[CoCl2(en)2]+ in the form of a paste, [Co(NH3)6]3+ in the presence of active charcoal, and by oxidation of a solution of Co(II) and the corresponding ligands.
CO2 laser-induced decomposition of methyl iodide sensitized by sulfur hexafluoride
Authors: Dathe Klaus , Engst Pavel , Pola Josef , Horák Milan
Published: January 2014

Gaseous mixtures of methyl iodide and sulfur hexafluoride yield upon irradiation by a continuous-wave CO2 laser iodine, methane, ethane, ethylene and acetylene - the products of methyl iodide decomposition. The decomposition rate and the mutual ratio of the products is dependent on the delivered irradiation energy, the methyl iodide/sulfur hexafluoride ratio and the energy of the exciting photon. Methyl iodide-d3 in the mixture with SF6 behaves similarly as methyl iodide yielding perdeuterated methane, ethane, ethylene, acetylene and iodine.
The Ritter reaction of the acrylonitrile oligomer
Authors: Janout Václav , Čefelín Pavel
Published: January 2014

The Ritter reaction of oligomeric models of poly(acrylonitrile) with tert-butyl alcohol in tetramethylene sulphone leads to the respective N-tert-butylamides and proceeds via the second-order kinetics. The rate constants increase only little on passing from the monomeric to the trimeric model. The decrease in the activation enthalpy ΔH is almost compensated for by the decrease in the activation entropy parameter. No effect of the neighbouring functional group on the reaction kinetics could be observed. A new conformational equilibrium is established during the reaction.
Reactivity of cycloalkenes in the radical addition reaction with ethyl cyanoacetate
Authors: Hájek Milan , Málek Jaroslav
Published: January 2014

The effect of ring size on the reactivity of C5 to C12 cycloalkenes in the copper(II) oxide catalysed and dibenzoyl peroxide initiated addition reaction with ethyl cyanoacetate was determined at 90°C using the method of competition reactions. cis-Cyclooctene exhibited the highest and cyclohexene as well as cis-cyclodecene the lowest reactivity. Relative reactivities of C5, C6 cis-C7 and cis-C8 cycloalkenes could be correlated with the Allinger's strain energies. In the copper(II) oxide catalysed reaction, the relative reactivities of cycloalkenes were surprisingly higher than in the dibenzoyl peroxide initiated reaction; this result is indicative of certain differences in the mechanism of the initiation and propagation steps in both systems. The radical addition of ethyl cyanoacetate to cycloalkenes represent a novel and convenient route to alkyl α-cyanocycloalkaneacetates.
Electron spectra of 1-tetralone, homophthalide, 3,4-dihydroisoquinoline, and 3,4-dihydroisoquinolinium compounds
Authors: Šantavý František , Válka Ivo
Published: January 2014

The electron spectra of 1-indanone (I), 1-tetralone (II), phthalide (III), homophthalide (IV), 3,4-dihydroisoquinoline (VII), and 3,4-dihydroisoquinolinium (VIII) compounds, substituted by electron donating groups (hydroxy, methoxy or methylenedioxy groups) on the aromatic nucleus, resemble when the electron donors are at the same distance from the electron accepting substituent. In the compounds VII and VIII, the electron spectra were measured in ethanol at acidic and alkaline pH, and the change in the spectra of the compounds VIII in alkaline medium was clarified.