bluuebunny/crossref_metadata_2025 huggingface dataset:
The pKBH+ calculation of strong bases: A revision of various methods
Authors: García Begoña , Leal José M.
Published: June 2010

The pKBH+ values have been obtained for seventeen acid-base equilibriums corresponding to thirteen aniline derivatives in dilute perchloric acid media in the pH region at 25 °C using the spectrophotometric technique. By revising the method of extrapolation to infinite dilution it was possible to introduce new methods for calculating pKBH+ values of strong bases by means of the functions logI = f(pH) and pKap = f(pH). The equation - logfBH+/fB = f(pH) - has been proved to conform to a polynomial function of the third order and is applicable to each compound.
The effect of liquid phase properties on gas holdup in bubble column reactors
Authors: Zahradník Jindřich , Peter Rudolf , Kaštánek František
Published: June 2010

The effect of liquid phase properties on gas holdup in bubble column reactors was investigated within a large set of gas-liquid systems. Air was used as a gaseous phase in all experiments, liquid phases included distilled water and aqueous solutions of alcohols and electrolytes. Gas holdup values were determined in a sieve tray bubble column 0.15 m i.d. under conditions of stable uniform gas distribution and an attempt was made to relate these data with values of bubble coalescence ratio determined for respective gas-liquid systems in a coalescence cell. Experimental results proved strong influence of solute addition on bubble coalescence reduction and on the increase of gas holdup values in aqueous solutions of both alcohols and electrolytes. An unambiguous dependence was observed between gas holdup data and values of bubble coalescence ratio in alcohols solutions, the effect of coalescence suppression on gas holdup enhancement increased markedly with increasing gas flow rates. An empirical equation was proposed for estimation of lower and upper gas holdup limits in electrolyte solutions within the coalescence suppression region, i.e. at solute concentrations above coalescence transition value.With the exception of concentrated glycerol solutions, homogeneous bubble beds were generated in all gas-liquid systems using the appropriate gas distributing plate. The positive effect of coalescence restraining on gas holdup values was even more significant in homogeneous bubble beds than under conditions of turbulent bubbling regime.
The pumping characteristics of screw rotors. III. Verification of equation for the calculation of the pumping capacity of screw rotors
Authors: Rieger František
Published: June 2010

The paper deals with the verification of certain simplifying assumptions introduced in the derivation of the equations for the pumping characteristics of screw rotors1. For this purpose data have been used, on the one hand, taken over from the literature, on the other hand, those obtained in this communication2. A method has been recommended for the calculation of the pumping characteristics of screw rotors rotating in a barrel.
Reactivity of 2-furylethylenes with nucleophilic groups and its biological significance
Authors: Rosenberg Michal , Baláž Štefan , Šturdík Ernest , Kuchár Anton
Published: June 2010

The paper describes addition-nucleophilic reactions of 1-(5-R1-2-furyl)-2-R2-R3-ethylenes with SH (thioglycolic acid), NH2 (glycine) and OH (phenol) nucleophiles, and with hydroxyl ions in aqueous media. The determined rate constants, of second order (dm3 mol-1 s-1), show that in the physiological conditions the preferential reaction will be that with thiols. The amino acid composition of proteins modified with 1-(5-nitro-2-furyl)-2-nitro-2-methoxycarbonylethylene has revealed that the only group affected was the SH group of cysteine. This finding points out the significance of addition-nucleophilic SH-interactions of 2-furylethylenes with the protein macromolecules and accounts for the high cytotoxicity of these compounds.
Substitution reactions of some (5-nitro-2-furyl)ethylene derivatives with thiols
Authors: Baláž Štefan , Végh Daniel , Šturdík Ernest , Augustín Jozef , Liptaj Tibor , Kováč Jaroslav
Published: June 2010

1-(5-Nitro-2-furyl)-2-X-ethylenes (X = Br, (+)N(CH3)3Br(-), SO2Ph) undergo substitution with 2-mercaptoacetic acid in aqueous medium to give S-(2-(5-nitro-2-furyl)ethenyl)mercaptoacetic acid which could not be identified. The rate constants of both consecutive reactions have been determined spectrophotometrically in a buffer of pH 5.0 at 25 °C.
Identification of acyl groups occurring in sesquiterpene lactones: Proton and carbon-13 NMR study
Authors: Buděšínský Miloš , Šaman David
Published: June 2010

Characteristic 1H NMR parameters of 88 acyl groups, hitherto found as ester substituents in natural sesquiterpenic lactones, were determined from the measured spectra as well as literature data. Characteristic 13C NMR chemical shifts for 45 acyl groups were obtained in the same way; for the remaining acyls with hitherto unknown 13C NMR data the values were calculated on the basis of semiempirical relationships.
Alkaloids of the two Hypecoum L. species
Authors: Táborská Eva , Mikešová Milena , Věžník František , Slavík Jiří
Published: June 2010

Alkaloids from Hypecoum procumbens L. and H. leptocarpum HOOK. F. et THOMS. were investigated. Protopine was the dominant alkaloid in both species. From H. procumbens chelerythrine and corydine were newly isolated in addition to the earlier detected alkaloids allocryptopine, sanguinarine, coptisine, and isocorydine. From H. leptocarpum allocryptopine, isocorydine and corydine were isolated for the first time, in addition to the earlier described alkaloids protopine, sanguinarine, chelerythrine and coptisine. Cryptopine was detected chromatographically. From the fraction of strongly polar alkaloids of both species magnoflorine, (-)-trans-N-methyl-stylopinium hydroxide, and in small amounts a new secoberbine alkaloid of oxohypecorinine structure, procumbine (I), and two further alkaloids of unsolved structure were isolated in the form of iodides.
A study of internal rotation in 2-furaldehyde through 13C relaxation times in the rotating frame
Authors: Mlynárik Vladimír
Published: June 2010

Carbon-13 relaxation times in the rotating frame were used to study the exchange between unequally populated rotamers of 2-furaldehyde. Calculated free activation energy and activation enthalpy are in good agreement with the results of 1H line shape analysis. Accuracy and reliability of this method in comparison with the line shape analysis is discussed.
MO analysis of chemically interacting systems. Reaction of hydrogen abstraction by free radicals
Authors: Ponec Robert , Krupička Štěpán , Hájek Milan
Published: June 2010

The charge and spin transfer accompanying the process of the exchange of the bonds in the reaction of hydrogen abstraction by free radicals was examined in terms of intermolecular population analysis. The results obtained enable a qualitative discussion of the role of polar and steric effects in this reaction.
Adsorption of organics on thermally treated solids obtained from colloidal silica
Authors: Kopečni Miroslav M. , Milonjic Slobodan K. , Rudzinski Wladyslaw , Jagiello Jacek
Published: June 2010

Adsorption isotherms of three adsorbates on the solid beads obtained from colloidal silica were determined by means of gas chromatography at low surface coverages, when lateral interactions between the adsorbed molecules are negligible. The influence of thermal pretreatment on the adsorption properties of the solids was investigated in the temperature range from 343 to 423 K, while the solids were heated between 523 K and 1 223 K. The thermodynamic parameters of adsorption have been determined and used to discuss the adsorbate-adsorbent interactions.
Factors influencing the limiting current in pulse polarography
Authors: Bolzan Jorge A.
Published: June 2010

The variation of the limiting current as a function of h, the corrected height of the mercury column, and t, the time delay plus pulse width, are studied and compared with the similar relationships of DC polarography. Diffusion, adsorption, kinetic and catalytic processes are examined. Though pulse polarography is in almost every respect a much more powerful technique than DC polarography, it is shown that while the latter allows a distinction to be drawn between the different processes, by using the above mentioned relationships, the former is not suitable for the same purpose.
Convective diffusion to the disc electrode rotating slowly in a viscoelastic liquid
Authors: Wein Ondřej , Assaf Fawzi Hassan
Published: June 2010

Limiting diffusion currents toward the rotating disc electrodes are determined theoretically for the cases of low Reynolds numbers, Re < 10, and for viscoelastic liquids with non-zero normal stress differences, Ab > 0. The case of Newtonian fluid, Ab = 0, at low Re is considered in details and is tested by comparing the theoretical prediction with experimental data.
Diffusion effect of anemometric wire detector
Authors: Wein Ondřej , Kovalevskaya Nelia Dzuraevna
Published: June 2010

Article in Russian
Methyl 3α,6α-diacetoxy-10-oxo-(7α)-kemp-11-en-20-oate: The revised structure for the kempane derivative from the frontal gland secretion of Nasutitermes costalis soldiers
Authors: Cerrini Silvio , Lamba Doriano , Valterová Irena , Buděšínský Miloš , Vrkoč Jan , Tureček František
Published: June 2010

The structure of methyl 3α,6α-diacetoxy-10-oxo-(7α)-kemp-11-en-20-oate (II) was established by X-ray analysis for a defense compound of termites Nasutitermes costalis. The previously suggested structure I with 7β-kempane skeleton is revised.
13C and 15N NMR spectra of 3-methyl-1-phenylpyrazole-4,5-dione 4-(4'-substituted phenyl)hydrazones
Authors: Lyčka Antonín , Liptaj Tibor , Jirman Josef
Published: June 2010

13C and 15N NMR spectra have been measured of eleven 3-methyl-1-phenylpyrazole-4,5-dione 4-(4'-substituted phenyl)hydrazones (I). The 13C chemical shifts of the non-substituted compound I have been assigned with the use of the 1J(13C, 13C) coupling constants obtained from the 1D-INADEQUATE spectrum. The greatest changes in chemical shifts of the compounds I connected with the substituent at 4'-position have been observed for the nitrogen atoms Nα, Nβ, N2 and carbon C(4). These substitution chemical shifts have been correlated with the substituent constants by means of the equations SCS = ρ1σ1 + ρRσR + const., where σR means one of the values σR0, σRBA, σR-, or σR+. The best correlations have been obtained for the combinations Nα - σRBA, Nβ - σR-, N2 - σR0, and C(4) - σR0. The 15N substituent chemical shifts of the nitrogen atoms Nα and Nβ of compounds I have been compared with the analogous values of 4-substituted trans-azobenzenes.
Synthesis of 1,2, and 9-methyl derivatives of 4,9-dihydro-6-methoxy-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinoline and 4,9-dihydro-6-hydroxy-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinoline and their antiviral activity
Authors: Rádl Stanislav , Zikán Viktor
Published: June 2010

The paper describes syntheses of 4,9-dihydro-6-methoxy-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinoline (Ia), its 1-methyl derivative (Ic), 1,9-dimethyl derivative (Ie), 2-methyl derivative (IIa), and 2,9-dimethyl derivative (IIc). Demethylation of these compounds with hydrobromic acid afforded 4,9-dihydro-6-hydroxy-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinoline (Ib), its 1-methyl derivative (Id), 1,9-dimethyl derivative (If), 2-methyl derivative (IIb), and 2,9-dimethyl derivative (IId) respectively. 4,9-Dihydro-6-hydroxy-3,9-dimethyl-4-oxo-1H-pyrazolo[3,4-b]quinoline (Ig) was prepared by demethylation of Ie and/or IIc with pyridine hydrochloride. The compounds prepared were tested for antiviral activity in vivo in mice against influenza virus A2-Hongkong and encephalomyocarditis virus.
2-(tert.amino)-11-(4-methylpiperazino)dibenzo[b,f]thiepins and their 10,11-dihydro derivatives; Synthesis and neuroleptic activity
Authors: Kmoníček Vojtěch , Holubek Jiří , Svátek Emil , Metyšová Jiřina , Protiva Miroslav
Published: June 2010

Reactions of (2-iodophenyl)acetic acid with 4-(dimethylamino)thiophenol, 4-piperidinothiophenol, and 4-morpholinothiophenol in boiling aqueous potassium hydroxide solutions in the presence of copper gave the arylacetic acids IVabc which were cyclized with polyphosphoric acid at 130 °C to 8-(tert.amino)dibenzo[b,f]thiepin-10(11H)-ones Vabc. The following reactions with 1-methylpiperazine in boiling benzene in the presence of titanium tetrachloride afforded the enamines IIabc. Compounds IIa and IIc were reduced with diborane to the 10,11-dihydro compounds Ia and Ic. Compound Ia (the 8-dimethylamino derivative of perathiepin) is a typical incisive neuroleptic agent with very strong cataleptic, antiapomorphine, central depressant, and antiadrenergic activities. The morpholino derivative Ic and the enamines IIb and IIc are less active.
The correlations and quantum chemical interpretations of some molecular properties of several p-phenylenediamines and related compounds
Authors: Grampp Günter , Pluschke Peter
Published: June 2010

Quantum chemical calculations of various p-phenylenediamines and related compounds are correlated with different molecular properties, such as electrochemical E1/2-values, ionization potentials, pK-values, UV-VIS spectra, the activation energies of the homogeneous electron self-exchange rates, and the synproportionation constants. All correlations are in good agreement with the predictions of simple HMO-theory.
Thermal decomposition and chemism of hydronium jarosite
Authors: Hartman Miloslav , Veselý Václav , Jakubec Karel
Published: June 2010

A study is reported of the controlled decompositions and chemism of the technological hydronium jarosite. Chemical and spectroscopic methods were employed to determine the amounts of impurities present in jarosite. Thermogravimetric data were amassed both in the increasing and constant temperature mode. Proposed kinetic equations of Arrhenius type were tested against the results of constant temperature experiments. Differences are explored in the course of the decomposition of hydronium jarosite and that of pure ferric sulphate enneahydrate. In addition, the effects of temperature and reaction time were investigated on the amount of sulphates remaining in the calcined particles.
Conformation and electronic structure of aromatic chloroformates
Authors: Exner Otto , Fiedler Pavel
Published: June 2010

Aromatic chloroformates Ib-Ie were shown to exist in the ap conformation, in agreement with aliphatic chloroformates, i.e. the alkyl group is situated cis to the carbonyl oxygen atom as it is the case in all esters. While 4-nitrophenyl chloroformate (Ie) is in this conformation in crystal, in solution at most several tenths of percent of the sp conformation may be populated at room temperature and in nonpolar solvents only. A new analysis of dipole moments explained the previous puzzling results and demonstrated the impossibility to determine the conformation by this single method, in consequence of the strong interaction of adjoining bonds. If, however, the ap conformation is once proven, the dipole moments reveal some features of the electron distribution on the functional group, characterized by the enhanced polarity of the C-Cl bond and reduced polarity of the C=O bond. This is in agreement with the observed bond lengths and angles.
Substituent effects in aromatic photochemistry. UV irradiation of 3,4-dimethoxybenzonitrile and 3,4-dimethoxyacetophenone in the presence of inorganic anions
Authors: Kuzmič Petr , Souček Milan
Published: June 2010

Ultraviolet photolysis of 3,4-dimethoxybenzonitrile (Ia) and 3,4-dimethoxyacetophenone (IIa) in the presence of the hydroxide or cyanide anion leads to nucleophilic displacement of either the para or the meta methoxy substituent. The ratio of isomeric photoproducts is dependent upon the nature of the nucleophile. Photoreactions with the OH- anion lead exclusively to the substitution at C-3. On the other hand, both isomers are formed when acetophenone IIa is irradiated in the presence of CN-, with the C-3/C-4 substitution ratio 3:2. In the case of the photocyanation of Ia, the C-4 substituted product dominates, the C-3/C-4 ratio ranging from 1:2 to 1:6 in dependence on the nucleophile concentration. These differences between the OH- and CN- anions are related to the results of a fluorescence quenching study which has revealed that only the latter nucleophile interacts with singlet-excited substrates. A non-linear Stern-Volmer plot was observed for the quenching of the second excited state of Ia by the cyanide anion. This indicates several distinct quenching modes, in relation to the concentration dependence of regioselectivity. The activating power of –H, -CN, -COCH3, and -NO2 substituents, as measured by relative quantum yields of disappearance for 3,4-dimethoxy-R-substituted benzenes, is 1:2.5:5:580 and 1:1.5:6:1000 in their photoreactions with OH- and CN- anions, respectively.
Selectivity of nucleophilic addition to and substitution at isothiocyanatocarbonyl group. Reactions of 4-pentinoyl- and 2-(2-propinyl)-4-pentinoyl isothiocyanate with amines and methanol
Authors: Kutschy Peter , Kristian Pavol , Dzurilla Milan , Koščík Dušan , Nádaskay Róbert
Published: June 2010

4-Pentinoyl isothiocyanate reacts with primary and secondary amines by either nucleophilic addition to N=C=S group to yield the corresponding thioureas, or a nucleophilic substitution at the carbonyl group to give 4-pentinoic acid amides. The less nucleophilic diphenylamine reacts selectively to afford the product of nucleophilic addition only. 2-(2-Propinyl)-4-pentinoyl isothiocyanate, having a sterically hindered carbonyl group, furnished with primary amines a mixture of amides and thioureas, whereas the bulkier secondary amines react selectively to form thioureas only. Both isothiocyanates afford with methanol as a nucleophile exclusively the corresponding O-methyl monothiocarbamates.
Alternative syntheses of 2α,3α,17β-trihydroxy-7-oxa-B-homo-5α-androstan-6-one and some androstane brassinolide analogs
Authors: Kohout Ladislav , Černý Václav , Strnad Miroslav
Published: June 2010

The title compound XVI was synthesized from III, IV or V. Related compounds X, XIII, XVI, XVIII, XXIII, XXIV, XXVII, XXVIII, XXXV, XXXVI, XLI, and XLIII were also prepared and tested by bean second internode bioassay. They showed only low activity (by about 2-3 orders or even lower than 24-epibrassinolide).
4-Amino-1-(4-cyclopentylphenyl)butan-1-ones; Synthesis and biological screening
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: June 2010

4-Chloro-1-(4-cyclopentylphenyl)butan-1-one (IX), obtained by Friedel-Crafts reaction of cyclopentylbenzene with 4-chlorobutanoyl chloride, was subjected to substitution reactions with 4-phenylpiperidin-4-ol and a series of N-monosubstituted piperazines, and gave the title compounds I-VIII. Their salts underwent biological screening in various lines. Only compounds I, V, and VII showed clear indications of tranquillizing activity (ataxia, thiopental potentiation, hypothermic effect, inhibition of locomotor activity, antiamphetamine effect).
Enzymatically catalyzed synthesis of dipeptides containing O4-sulfotyrosine and O4-phosphotyrosine
Authors: Čeřovský Václav , Jošt Karel
Published: June 2010

Conditions for the thermolysin- or papain-catalyzed peptide bond formation between tert-butyloxycarbonyl-O4-sulfotyrosine and leucine or methionine phenylhydrazide have been found. Acylation of O4-sulfotyrosine phenylhydrazide with tert-butyloxycarbonylphenylalanine methyl ester was catalyzed by α-chymotrypsin. Tert-butyloxycarbonyl-O4-phosphotyrosyl-leucine phenylhydrazide was prepared by thermolysin-catalyzed reaction.
Overlapping equilibria: Applications to m-aminobenzoic acid
Authors: García Begoña , Domingo Pedro L. , Leal José M.
Published: June 2010

m-Aminobenzoic acid displays two protonation equilibria which overlap in the pH region, where pK2 - pK1 < 3. The results show that the equilibria occur between the pH values 6.16–1.77, with the limit of separation of the two equilibria lying between 3.60–3.44. Use has been made of several theoretical methods put forward in the bibliography for calculating pK values of overlapping equilibria and these have been corrected by including the terms of the activity coefficients, by means of the coefficients n1 and n2, which are defined and calculated by the method of separation of equilibria. The values pK1 = 3.237 ± 0.091 and pK2 = 4.767 ± 0.002 are proposed.
Interfacial interactions and the heterogeneous one-electron reduction of methyl viologen
Authors: Heyrovský Michael , Novotný Ladislav
Published: June 2010

The one-electron reversible electroreduction of methyl viologen to its radical cation in aqueous solutions on mercury electrodes proceeds, according to potential, concentration and time of electrolysis, in various ways. Methyl viologen is adsorbed in flat orientation at the electrode surface; it undergoes a surface redox process in π-interaction with the metal in a potential range positive by about 0.2 V of the beginning of the electroreduction. The actual reduction starts by electron transfer followed by adsorption of the radical cation and, at higher concentrations and in a narrow potential range, by crystallization at the electrode surface of a salt of the radical cation. In solution near the electrode the radical cation dimerizes and the dimer also adsorbs at the electrode. In the region of the standard redox potential and more negative the reduction proceeds by electron transfer from the electrode covered by a layer of the radical cation or of its dimer.
Ion chromatographic separation and determination of some sulphur anions
Authors: Vinš Ivan , Kábrt Lubomír
Published: June 2010

An ion chromatographic method was developed for the simultaneous determination of sulphate, thiosulphate, trithionate, and tetrathionate using Separon HEMA ion exchangers based on hydroxyethyl methacrylate gels. Sulphate and thiosulphate were detected by indirect photometry at 254 nm, trithionate and tetrathionate, treated separately on another chromatograph, were detected by direct photometry at 205 nm. The method was applied with success to the study of the oxidation of thiosulphate in conditions of carbonate leaching.
Hydrolysis of ternary carbides of manganese Mn3MC (M = Al, Ga, In, Sn)
Authors: Karen Pavel , Král Roman , Kubát Jaroslav , Hájek Bohumil
Published: June 2010

Perovskite type ternary carbides of manganese Mn3MC (M = Al, Ga, In, Sn) are hydrolyzable by acids, water and air moisture. Mn3AlC is hydrolyzed most readily; its linear corrosion rate with liquid water is 0.3 μm h-1 at 60 °C, whereas the value for Mn3GaC is 0.06 μm h-1. The reactivity decreases with increasing nobleness of the nontransition metal involved. The hydrolysis process gives rise to a mixture of hydrogen and methane and a low amount of higher saturated and unsaturated hydrocarbons whose fractions are consistent with the concept of the radical mechanism of the hydrolysis reaction.
Hydration of 2-methylbutenes on organic ion exchange resin catalysts
Authors: Prokop Zdeněk , Setínek Karel
Published: June 2010

The course of the hydration of a mixture of 2-methyl-1-butene and 2-methyl-2-butene in dependence on the structure of strongly acidic styrene-divinylbenzene ion exchange resin catalysts has been studied. The most efficient catalysts turned out to be macroporous ones. The reaction rate increased with increasing temperature, while the amount of the product (2-methyl-2-butanol) in the equilibrium reaction mixture decreased. Similarly, the hydration was strongly affected by the water to alkene molar ratio in the starting reaction mixture. Modification of ion exchange resin catalysts with 1-butylamine did not affect course of the hydration in the case of gel type catalysts, while with macroporous resin catalysts the addition of amine up to 0.5% of the total catalyst exchange capacity showed activating effect.
Photoaddition of alcohols to some 1,2,3,6-tetrahydropyridines
Authors: Šilhánková Alexandra , Davidová Dagmar , Šputová Michaela , Trška Petr , Vaculíková Dana , Vlková Daniela , Ferles Miloslav
Published: June 2010

Photochemical addition of methanol to 1,2,3,6-tetrahydropyridine derivatives Ia, Ib, Id-Ii and III afforded methoxypiperidines IIa-IIg and IV as Markovnikov type addition products. Reduction of 4-methyl-1-(2-propenyl)pyridinium bromide with sodium borohydride yielded 4-methyl-1-(2-propenyl)-1,2,3,6-tetrahydropyridine (Ig).
Reaction of some nucleophiles with 2,6-di-tert-butylpyrylium perchlorate
Authors: Böhm Stanislav , Prantová Renata , Šaman David , Trška Petr , Kuthan Josef
Published: June 2010

The title compound IV reacted with sodium borohydride to give the 4H-pyran VIIa and the dienone VIIIa whereas its reaction with sodium cyanide afforded exclusively the dienone VIIIb. Reaction of the salt IV with tert-butylmagnesium chloride or bromide gave a mixture of the 4H-pyran VIIa and the corresponding 4-tert-butyl derivative V. Upon treatment with hydrogen sulfide and hydrogen chloride, this mixture afforded 2,4,6-tri-tert-butyl-4H-thiopyran XI whereas aromatization with chloranil and subsequent reaction with ammonium acetate resulted in 2,4,6-tri-tert-butylpyridine (X). Analogously, the perchlorate IV reacted with ammonium acetate to give 2,6-di-tert-butylpyridine (VI). Addition of triphenylphosphine and potassium phthalimide to IV afforded exclusively the 4H-pyran derivatives XII and XIII. A similar reaction of nitromethyl anion led to the 4,4'-bis(4H-pyran) derivative XIV. Mechanism of the studied reactions and the reasons for the low reactivity of the sterically hindered pyridine derivative VI with electrophilic reagents are discussed.
Solvolysis of some 1-(8α-ergolinyl)-3,3-diethylureas and their salts
Authors: Černý Antonín , Beneš Jan , Vachek Jaroslav , Pešák Milan , Stuchlík Josef , Stuchlík Milan , Sedmera Petr , Flieger Miroslav , Vokoun Jindřich
Published: June 2010

Nine salts of 1-(8α-ergolinyl)-3,3-diethylurea (II) were prepared and their solubility in water and the stability of the aqueous solutions at 60 and 100 °C were studied. The main product of hydrolysis is 6-methyl-8α-aminoergoline IV. The urethan VII is formed in the ethanolic solution. Both decomposition products are also formed under long-term storage at +5 °C. The course of hydrolysis of N-propyl homologue III is similar. The decomposition of 9,10-didehydro derivative I is much slower under the conditions used.
Human serum albumin. A study of the nature of its hydrophobic binding sites
Authors: Štrop Petr , Mikeš František , Havranová Marie , Žižkovský Václav
Published: June 2010

Spectroscopic labels and hydrophobic chromatography on two different supports were used to compare the size and accessibility of the hydrophobic binding sites of human serum albumin with the accessibility of non-polar residues on the surface of other globular proteins. The binding of the labels 1-alkyl-4-(3-ethoxy-4-hydroxystyryl)pyridinium bromides (HPB) with alkyl chains of different length was investigated in the ultracentrifuge and by spectrophotometry. n-Butyl (C4-HPB) and decyl (C10-HPB) labels bind to albumin with association constants of 8 . 103 and 4 . 104, respectively, at pH 5·50, and with constant of 2·6 . 105 for the C10-HPB label at pH 9·2. Whereas C4-HPB interacts with the site of local polarity of albumin not different from the bulk solution, both the C10-HPB and C16-HPB on the other hand bind to hydrophobic sites, where the solvation of the chromophore is largely reduced as evidenced by the 46 nm shift to higher wavelengths in its spectrum. For other proteins the shift was less then 5 nm. Ten molecules of C10-HPB and four molecules of C16-HPB can be attached to one molecule of albumin. The changes in the spectrum of the bound label induced by palmitate reveal that these binding sites are essentially the same as those for fatty acids. From chromatographic experiments with labeled albumin at different pH carried out on Octyl-Sepharose and Spheron the conclusion was made that the latter support interacts preferentially with the non-polar side chains on the surface of proteins. The retention and the recovery of albumin and defatted albumin was investigated as a function of salt and alcohol concentration and compared with the same parameters of other proteins. In agreement with the proposed structure of the domains of albumin evidence was obtained that the outer surface of the albumin molecule is at neutral pH predominantly hydrophilic, and that the exceptionally large hydrophobic areas are localized solely in crevices.
Description of the flow of mechanically agitated liquid in a system with cylindrical draft-tube and radial baffles
Authors: Fořt Ivan , Hošťálek Miloslav , Laufhütte Hans Dietrich , Mersmann Alfons Bertram
Published: June 2010

A model is described of two-dimensional vortex turbulent flow of homogeneous liquid in a cylindrical tank with flat bottom and radial baffles at its walls agitated with an inclined plane blade impeller rotating in a cylindrical draft-tube. The obtained field of the mean Stokes stream function expresses the streamline distribution in the system. As the boundary conditions of the used solution of stream equation serve partly the values of the mean Stokes stream function on the system boundaries (bottom, liquid level, walls of tank and draft-tube, tank axis), partly the radial profiles of axial and radial components of mean velocity on the level of draft-tube lower base obtained by the laser-doppler anemometry. It follows from the comparison with results of previously published studies that in systems with cylindrical draft-tube and axial high-speed impeller, the convective flow intensity of agitated liquid is higher and the streamline distribution in system is more uniform providing that the conical bottom with 120° vertex angle is used instead of the flat bottom.
The preparation of the salts of heteropolyacids by tempering a mixture of the solid components
Authors: Drátovský Milan , Mosinger Jiří
Published: June 2010

The method of prolonged tempering of a mixture of the solid components Na4As2O7 + ZO3 + Na2ZO4 (Z = Mo, W) was successfully used to prepare new compounds in the pure state and thermoanalytical analysis yielded the empirical formula, Na24As2Z22O83. The two compounds melt congruently and have a melting point of 597 °C (Z = Mo) and 691 °C (Z = W). To make the determination of the empirical formula more objective, a computation method was developed for treatment of the thermoanalytical data and two computer programs were written.
Organotin derivatives of alkanedisulfonic acids
Authors: Kizlink Juraj , Rattay Vladimír
Published: June 2010

The preparation of dibutyltin and tributyltin alkanedisulfonates from alkyltin oxides and the corresponding alkanedisulfonic acids has been studied. The products, obtained in 56 – 74% yield, were tested as biocides against bacteria, yeasts, and moulds as well as fungicides against wood rot and their activity was compared with that of bis(tributyltin) oxide.
Polarographic reduction of p–substituted 1-phenyl-3-aminocarbonylpyridinium salts
Authors: Krechl Jiří , Mižaninová Daniela , Volke Jiří , Kuthan Josef
Published: June 2010

The substitution effect of different groups (H, NO2, COOH, Br, Cl, NHCOCH3, CH3, OCH3, OH, and N(C2H5)2) on the polarographic behaviour of p–substituted 1-phenyl-3-aminocarbonylpyridinium cations has been investigated, in particular on their half-wave potentials in aqueous phosphate buffers pH 6·65 (10% DMF) and in anhydrous solutions of dimethylformamide with 0·05 mol l-1 (n-C4H9)4N+BF4- as supporting electrolyte. The half-wave potentials of the reduction wave which corresponds to the uptake of a single electron (wave B) and to the formation of the primary radical, obey a Hammett correlation in a similar way as it is in the case of 1-benzyl-3-aminocarbonylpyridinium cations. The slope ρπ,R in the Hammett plot equals 0·093 V for 10% DMF and 0·179 V for anhydrous DMF and compares thus with this slope obtained with the 1-benzyl derivatives where 0·095 V was found for water and 0·127 V for anhydrous acetonitrile. The transfer of the substitution effect from the substituent in the para position on the benzene nucleus to the heterocyclic ring in thus equally active in both substances and depends more strongly on the solvent than on the structure of cations of both types. The low sensitivity in both series towards a change in the substituent is explained by the fact that during the uptake of the electron the benzene and the pyridine nucleus are not even approximately coplanar. This is why the π-overlap between the two nuclei is considerably restricted. The analysis of sampled dc-polarographic waves has confirmed that the one-electron uptake is followed by a chemical reaction, most probably a dimer formation or a reaction of the primary product with the starting substance.
Synthesis of 3-(6,11-dihydrodibenzo[b,e]thiepin-11-ylidene)propanoic acid and related compounds
Authors: Polívka Zdeněk , Lichá Irena , Taufmann Petr , Svátek Emil , Holubek Jiří , Protiva Miroslav
Published: June 2010

The alcohol XIa, obtained by reaction of dibenzo[b,e]thiepin-11(6H)-one with vinylmagnesium bromide, was transformed by treatment with hydrogen bromide in acetic acid to the bromo compound XIIa which was converted via the nitrile XIIIa to the title acid VIIIa. The pure (E)-isomer was prepared and correlated via the dimethylamide XVIIIa with (E)-prothiadene (Ia). Similar procedures in the 2-methyl-6,11-dihydrodibenzo[b,e]thiepin and 10,11-dihydrodibenzo[a,d]cycloheptene series afforded the acids VIIIb and IV. The acids VIIIab were oxidized with hydrogen peroxide to the sulfoxides IXab and to the sulfones Xab. The acid IV is the suggested metabolite of the antidepressant amitriptyline (II) and the acids VIIIab-Xab are potential metabolites of the antidepressant prothiadene (Ia) and the antihistamine agent methiadene (Ib). The amides VII and XVIab were prepared from the acids via the acid chlorides. The (Z)-isomer of prothiadene (XXII) was prepared from dibenzo[b,e]thiepin-11(6H)-one by the Wittig reaction. The acids IV, VIIIab and IXab showed some antiinflammatory activity.
Ag(I) complexes of F2α prostaglandins
Authors: Veselý Ivan , Šaman David , Stibor Ivan
Published: June 2010

PGF2α I and its synthetic analogs Cloprostenol II and Fluprostenol III form crystalline complexes with AgNO3. Application of these compounds to the production of pure prostaglandins is described. 1H and 13C NMR spectra are also discussed.
Formation of CT complexes and electron transfer from excited molecules of anthracene derivatives to methylviologen in aqueous and micellar media
Authors: Řehák Viktor , Boledovičová Jana
Published: June 2010

Disodium 1,5- and 1,8-anthracenedisulphonate (ADS) and 9-acetylanthracene form coloured CT complexes with methylviologen (MV2+) in aqueous and micellar media. The complex formation constants and molar absorptivities were determined by the Benesi-Hildebrandt method. In the fluorescence quenching, its static component plays the major role. The dynamic quenching component is determined by the rate constant of electron transfer from the S1 state of ADS to MV2+.
A lattice model of electrolytes for the whole concentration range
Authors: Horsák Ivan , Sláma Ivo
Published: June 2010

Based on the quasi-lattice concept, a simple model is proposed for calculating the quantities of mixing of strong electrolyte solutions over the whole concentration range from pure solvent to pure salt. This model is analogous to the regular solution model for non-electrolyte systems. Relationships for the activity coefficients of the solvent and salt have been derived, and the behaviour of the model in the limit of infinite dilution is discussed by comparison with the Debye-Huckel theory. The adequacy of equations derived from the proposed model has been tested by fitting published experimental data for the activities of water in the systems (Li, K)NO3-H2O and (Ag, Tl)NO3-H2O, which have been measured over the whole concentration range.
Transformation of methanol to hydrocarbons over Y zeolites with varying Si/Al ratio
Authors: Křivánek Miloslav , Dung Nguyen Thiet , Jírů Pavel
Published: June 2010

The catalytic activity of Na, H-Y zeolite samples with a varying Si/Al ratio (2·5 to 20) in the transformation of methanol was determined. The amounts of formed individual aliphatic hydrocarbons as function of reaction time were correlated with the amount of Bronsted and Lewis centres on the catalysts. The effect of coke formation on the over-all course of the reaction has been demonstrated.
An experimental dynamic method of investigation of counter-current absorption of oxygen in water in a packed bed column
Authors: Moravec Pavel , Staněk Vladimír
Published: June 2010

An experimental method and technique are described in the paper of simultaneous detection of the transfer functions outlet-gas-stream-to-inlet-gas-stream and outlet-liquid-stream-to-inlet-gas-stream for the absorption of oxygen into water in a counter-current packed bed column. Both transfer functions were simultaneously monitored by means of three oxygen electrodes operating on the polarographic principle. The signals of these electrodes were processed in three steps to yield parameters of the model of physical absorption of gas. The first step was on-line evaluation of the Fourier coefficients of the principal harmonic component in all three monitored streams. The second step was the calculation of the frequency characteristics of both transfer functions while the third step yielded parameters of the model by optimization in the frequency domain. The method permits simultaneous evaluation of the parameters of the flow of both phases in the column and the interfacial transfer of oxygen.
The determination of crystal structure of chromium(II) phosphite dihydrate, CrHPO3 2 H2O
Authors: Brynda Jiří , Kratochvíl Bohumil , Císařová Ivana
Published: June 2010

The crystal structure of CrHPO3.2 H2O has been solved by the heavy atom method. The compound crystallizes in the orthorhombic space group P212121 with the unit cell parameters a = 679·25(8), b = 915·61(8), c = 752·2(1) pm, Z = 4. The structure was refined to the final reliability factor R = 0·043 for 1 040 observed reflexions (I > 1·96σ(I)). The structure consists of chains formed by CrO6 octahedra connected each other in vertices. The chains are interconnected by phosphite tetrahedra HPO3. Hydrogen bridges of water-phosphite tetrahedron and water-water types form space cross-linking of the whole structure. Bond distances Cr-O in the tetragonally distorted octahedron range from 201·2 to 304·9 pm. The interatomic distances P-O in phosphite tetrahedron are between 152·1 and 152·7 pm. The degree of the distorsion DISQ of HPO3 tetrahedron and CrO6 octahedron is discussed on the basis of known structures of phosphites and chromium(II) compounds.
Bimetallic sulphide catalysts Ni-M-Sx/SiO2 prepared by unconventional method involving thiourea complexes
Authors: Hillerová Eva , Sedláček Jiří , Zdražil Miroslav
Published: June 2010

An unconventional method of preparation of hydrodesulphurization catalysts was tested. A series of M-Sx/SiO2 and Ni-M-Sx/SiO2 catalysts was prepared, where M was V, Cr, Mn, Mo, W or Nb, respectively. A mixture of a salt of the metal M, thiourea, glycerol, sulphur, isopropanol, and silica gel was thermally decomposed to obtain the M-Sx/SiO2 catalysts. Nickel was deposited from solution of nickel acetate in methanol. Activity of catalysts was tested in benzothiophene hydrodesulphurization and their surface composition was characterized by XPS. The activity of samples containing Ni-Mo and Ni-W was in the rank of classical Co-Mo/Al2O3 catalysts but other samples exhibited only low activity and no synergism. The increase in binding energy of Ni after mixing with second metal M was observed not only for Mo and W but also for V, Cr, and Mn. It is concluded that this shift is probably not the main cause of synergism as suggested in the literature.
The kinetic study of the addition of tetrachloromethane to styrene in the presence of copper complexes
Authors: Hun Li Gwang , Nondek Lubomír
Published: June 2010

Kinetics of the addition of tetrachloromethane to styrene catalyzed by copper-amine complexes was studied. The pseudo-first order kinetics in respect to styrene and the catalyst was observed at an excess of tetrachloromethane. The reaction mechanism involving a catalytic cycle compatible with the kinetic observations is proposed. The experimental activation energy, being about 104 kJ mol-1, indicates a catalytic mechanism.
Preparation and photochemistry of 3-cyanosubstituted condensed isoxazolines containing an oxygen atom
Authors: Oremus Vladimír , Fišera Lubor , Štibrányi Ladislav
Published: June 2010

The 1,3-dipolar cycloaddition of cyanonitrile oxide to 2,3- and 2,5-dihydrofurane, 7-oxabicyclo[2,2,1]-2-heptene and derivatives of 1,3-dioxep-5-ene is described. The condensed isoxazolines Ia, IIIa, Va, Vc, Vd thus prepared are rearranged on irradiation into cyanosubstituted heterocyclic enaminoaldehydes IIa, IVa, VIa, VIc. The quantum yields of the photorearrangement of cyanoderivatives are higher than those of the phenyl derivatives, being within the limits from 0·068 to 0·19. The reaction of II with hydrazine gives the derivative IX of oxazino[4,5-d]pyridazine.
Synthesis of C-extended analogs of serum thymic factor
Authors: Černý Martin , Kasafírek Evžen , Rovenský Jozef , Pekárek Jan
Published: June 2010

New analogs of the serum thymic factor, (Phe-NH210)-FTS, (Gln1, Phe-NH210)-FTS, and (des Glp1, Phe-NH210)-FTS were synthesized. Their biological activities were evaluated in the recovery assay of T lymphocytes. The activity of (Phe-NH210)-FTS is comparable to the activity of FTS. Nonapeptide (des Glp1, Phe-NH210)-FTS shows the highest activity so far observed. Analog (Gln1, Phe-NH210)-FTS is an inhibitor.
Kinetics of alkaline hydrolysis of mono- and dimethyl esters of 2,3- and 3,4-thiophenedicarboxylic acids, cyanothiophenecarboxylic acids and their dihydroanalogues
Authors: Struhárik Milan , Hrnčiar Pavel , Loos Dušan
Published: June 2010

Kinetics of alkaline hydrolysis of mono- and dimethyl esters of 2,3- and 3,4-thiophenedicarboxylic acids and their dihydroanalogues have been studied in 70% dioxane. The rate measurements have been carried out by the titrimetric method and the k1, k2 rate constants evaluated by the Frost-Schwemer method. The activation parameters of these reactions have been calculated. The results are compared with kinetic parameters of alkaline hydrolysis of methyl and dimethyl phthalates. The hydrolysis rate is significantly affected by the cyclic system to which the methoxycarbonyl groups are bound, the reactivity order being: Dihydrothiophene > thiophene > benzene. Also measured were the kinetics of alkaline hydrolyses of methyl 4-cyano-3-thiophenecarboxylate and 3-cyano-2-thiophenecarboxylate and of their dihydroanalogues. No meaningful preference of the hydrolysis of the group at the position 2 has been observed in case of 2,3-isomers. However, it has been confirmed that the hyper- and hypo-ortho transfer of electronic effects operates in the thiophene nucleus.
Hydroboration of N,N-dimethyl(2-vinylbenzyl)amine
Authors: Kafka Stanislav , Trška Petr , Kytner Jan , Taufmann Petr , Ferles Miloslav
Published: June 2010

Hydroboration of N,N-dimethyl(2-vinylbenzyl)amine followed by oxidation afforded a mixture of primary and secondary alcohol, i.e. 2-(2-dimethylaminomethylphenyl)ethanol and 1-(2-dimethylaminomethylphenyl)ethanol, together with the reduction product – 2-ethyl(N,N-dimethylbenzylamine).
Procedure for large-scale preparations of oligoethylene glycol toluenesulphonates
Authors: Stibor Ivan , Kocián Oldřich , Holý Petr , Závada Jiří
Published: June 2010

Phase transfer catalysis allows a synthesis of oligoethylene glycol di-p-toluenesulphonates IVa-e and V from the corresponding diols Ia-e and II, respectively, in yields ##a 95%. A preferential tosylation of primary hydroxyl groups in the diols IIIa and IIIbcan be also accomplished almost quantitatively under the phase-transfer conditions.
Hydrophilic 1-(carboxymethyl)-5-fluorouracil amides: Preparation and cytostatic activity
Authors: Pischel Helmut , Holý Antonín , Veselý Jiří , Wagner Günther , Cech Dieter
Published: June 2010

The following N-substituted amides IV were prepared by reaction of 1-(carboxymethyl)-5-fluorouracil p-nitrophenyl ester (II) with primary or secondary hydroxyalkylamines III: 2-hydroxypropyl (IVa), 3-hydroxypropyl (IVb), 2,3-dihydroxypropyl (IVc), 3-hydroxy-2-methyl-2-propyl (IVd), 1,3-dihydroxy-2-propyl (IVe), 1-deoxyglucitol-1-yl (IVg), 2-deoxyglucitol-2-yl (IVh), methyl-2,3-dihydroxypropyl (IVi), methyl-1-deoxyglucitol-1-yl (IVk), and n-butyl-2,3-dihydroxypropyl (IVl). None of these compounds had any cytostatic activity towards murine leukemia L-1210 cell growth in a tissue culture at 10-5 mol l-1.
Stereochemistry and degradation of thionuphlutine S-methiodide
Authors: Cybulski Jacek , Scholl-Aleksandrowicz Anna , Wojtasiewicz Krystyna , Wróbel Jerzy T.
Published: June 2010

The structure of thionuphlutine S-methiodide is presented, based on the 13C NMR spectra analysis. The S-methiodide was degraded under the conditions of Hofmann degradation.
A study of structure of meta and para substituted phenyl and benzoyl isothiocyanates by the MNDO method
Authors: Danihel Ivan , Kristian Pavol , Böhm Stanislav , Kuthan Josef
Published: June 2010

On the basis of the optimized MNDO calculations of a selected series of meta and para substituted phenyl and benzoyl isothiocyanates it has been found that the –NCS group is non-linear in both the cases (the deviation from linearity is about 9°). For the phenyl isothiocyanates the values of CNC angles are in the region of 146.1° - 149.0°, and for the benzoyl isothiocyanates the respective regions for the CNC and OCN angles are 146.4° - 152.1° and 117.1° - 118.5°. In the meta substituted benzoyl isothiocyanates the –CONCS group is perpendicular to the phenyl residue. The results are discussed from the point of view of the electron distribution and dipole moments of the compounds studied.
Kinetics of component reactions of the Belousov-Zhabotinskii type oscillation system with oxalic acid and hypophosphite ions
Authors: Ševčík Peter , Adamčíková Ľubica
Published: June 2010

The authors studied the kinetics of oxidation of oxalic acid and hypophosphite ions with bromate ions, aqueous solution of bromine, and Mn(III) ions in the medium of aqueous sulphuric and perchloric acids. The kinetics of these two-component reactions of the Belousov-Zhabotinskii type oscillation system was considerably influenced by the addition of a third component.
Electrochemical reduction of maleic and fumaric acids and their dimethyl esters in methanol at a mercury electrode
Authors: Sazou Dimitra , Karabinas Pantelis
Published: June 2010

The electrochemical reduction of maleic and fumaric acids and their dimethyl esters have been investigated by cyclic voltammetry on HMDE in pure methanol. The cyclic voltammograms of the free acids show two successive reduction waves due to the influence of the different strength of the carboxylic groups on the double bond reduction. The reduction mechanism is verified by examining the effect of different supporting electrolytes, proton donors, and strong bases on the reduction waves. The double bond reduction of the corresponding dimethyl esters takes place in one step.
Determination of the activity coefficients in the aliphatic alcohol-non-polar solvent systems
Authors: Hejda Jaromír , Jedináková Věra
Published: June 2010

A method is proposed for the determination of the activity coefficients in aliphatic alcohols-non-polar solvent systems that are the main component of the organic phase in the boric acid extraction from aqueous solutions.
Experimentelle untersuchungen der hydrodynamik ausgewählter kolonnenfüllungen
Authors: Jiřičný Vladimír , Staněk Vladimír , Grabbert Gert , Strassberger Lothar , Winkler Kurt
Published: June 2010

Im vorliegenden Artikel werden die Ergebnisse hydrodynamischer Untersuchungen (des Hold-up und des Druckverlustes) an ungeordneten Kolonnenfüllungen aus keramischen Pallringen und einem neuen, in der DDR entwickelten keramischen Füllkörpertyp vorgestellt. Die Messungen wurden in Kolonnen mit Innendurchmessern von 190 mm und 123 mm durchgeführt. Die Ergebnisse stimmen mit den Korrelationen des Hold-up überein, die unter Annahme eines Automodellverhaltens von Füllkörperkolonnen gewonnen wurden.