bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics and mechanism of redox reactions of U(III) ions with monochloroacetic and dichloroacetic acids
Authors: Adamčíková Ľubica , Treindl Ľudovít
Published: October 2011

The kinetics and mechanism of the redox reactions of U3+ ions with mono- and dichloroacetic acids were studied. The influence of pH was observed mainly in the second case and led to the determination of the rate constants and activation parameters corresponding to two parallel steps, namely oxidation of U3+ with CHCl2COO- ions and oxidation of U3+ with CHCl2.COOH molecules. The influence of binary mixtures of water with methanol, ethanol, isopropanol, or tert-butenol on the reaction rate was followed. Increasing alcohol concentration influences the rate constant not only through changing dielectric constant and solvation of the reactants but also through a change of the solvent structure which plays a role in reactions with an outer sphere mechanism of the electron transfer.
7-(3-Substituted amino-2-hydroxypropyl)-8-hydroxymethyltheophyllines
Authors: Štibrányi Ladislav , Rybár Alfonz , Božeková Lýdia , Rippa Sven
Published: October 2011

N-Substituted derivatives of 7-(3-amino-2-hydroxypropyl)-8-hydroxymethyltheophylline II were prepared by addition of the respective amines to 7-epoxypropyl-8-hydroxymethyltheophylline (I) and alternatively, by alkylation of the potassium salt of 8-hydroxymethyltheophylline (IIIb) with substituted 1-amino-3-chloro-2-propanols. Compounds II were tested on peripheral vasodilating activity in vitro.
Absence of unwinding of double-helical DNA in the surface of mercury electrode charged to DNA reduction potentials at neutral pH
Authors: Paleček Emil , Kwee Sianette
Published: October 2011

The influence of adsorption of DNA on its double-stranded (ds) structure was studied with the aid of hanging mercury drop electrode (HMDE) in neutral media. Changes in DNA reducibility followed by linear sweep voltammetry served as an indication of the DNA conformational changes in the electrode surface. It has been shown that, due to contact of ds DNA with the electrode for periods many times longer than those which can be reached at the dropping mercury electrode, extensive surface denaturation of DNA can be detected only in a narrow potential range around -1.2 V. At potentials more negative than this region neither surface denaturation nor blocking of the electrode by the reduction product were observed. On the other hand, interaction of the denatured DNA with the mercury surface under the same conditions, resulted in blocking of the electrode surface by the reduction product. In agreement with the previous studies in acid media similar blocking of the surface was observed at pH 5 both with thermally denatured and ds DNAs. On the basis of the experimental data the following conclusions have been drawn: i) in neutral media the course of interfacial events of DNA is strongly dependent on DNA conformation and differs from the course suggested for acid media; ii) the deduction concerning the behavior of ds DNA on the electrode in neutral media made by other authors on the basis of their measurements in acid media is not justified.
Synthesis of 6-aminohexyl esters of uridine nucleotides
Authors: Smrt Jiří
Published: October 2011

6-Aminohexyl esters of uridine 3'-phosphate (V) and uridine 5'-phosphate (VI) were prepared by condensation of 6-trifluoroacetamidohexanol (IV) with pyridinium salts of the protected corresponding phosphates by means of N,N'-dicyclohexylcarbodiimide followed by removal of protecting groups.
The effect of acceptor modification upon the synthesis of dinucleoside phosphates catalyzed by non-specific ribonucleases of Penicillium claviforme
Authors: Gulyaeva Valentina I. , Holý Antonín
Published: October 2011

The present paper studies the effect of the modification of heterocyclic base, sugar moiety and the presence of phosphate group on the nucleoside acceptors in the synthesis of dinucleoside phosphates from adenosine 2',3'-cyclic phosphate as donor, catalyzed by nonspecific acidic extracellular and intracellular ribonucleases from Penicillium claviforme. The enzyme binds specifically the acceptor molecule, preferring cytosine nucleosides. It requires the presence of the whole sugar moiety, an exact mutual orientation of the heterocyclic base and the reaction center (5'-hydroxy group), and a suitable conformation of the acceptor molecule. The enzyme-acceptor bond is homochiral and the presence of the N3-H group in the pyrimidine ring is important. The reaction between the donor and the acceptor is bimolecular and is competitively inhibited by some purine nucleosides.
The effects controlling the oxygen basicity in alkoxysilanes (RO)nSi(CH3)4-n. The mutual polarizability effect of alkoxy groups attached to silicon
Authors: Pola Josef , Jakoubková Marie , Chvalovský Václav
Published: October 2011

Relative basicity of the oxygen in alkoxysilanes (RO)nSi(CH3)3-n having n = 1-4 and various electrondonating and electronwithdrawing groups R measured as Δν(OH) of phenol due to its interaction with these compounds in CCl4 is shown to be chiefly controlled by the electronic effect of substituents R. Linear regression analysis of the Δν(OH) vs n relatioship for individual series (RO)nSi(CH3)4-n suggests the operation of the polarizability effect of RO groups becoming more important with increasing electronwithdrawing nature of R.
Hydrosilylation of allylamine catalysed by platinum complexes
Authors: Vybíral Vlastimil , Svoboda Petr , Hetflejš Jiří
Published: October 2011

Chloroplatinic acid modified with triphenylphosphine, -arsine and -stibine, some platinum-alkene and platinum-phosphine complexes were found to be efficient catalysts for the addition of triethoxysilane to allylamine yielding γ- and β-aminopropyltriethoxysilane. All the catalysts exhibited higher activity and some also higher selectivity compared to chloroplatinic acid. The effect of reaction conditions and the catalyst upon the proportion of both isomeric adducts is reported.
Effect of lanthanide shift reagents on 1H NMR spectra of aminopyridines
Authors: Lyčka Antonín , Šnobl Dobroslav
Published: October 2011

The effect of Eu(dpm)3 and Pr(dpm)3 on the proton spectra of 2-amino-, 3-amino- and 4-aminopyridines has been studied by the 1H NMR spectroscopy in tetrachlomethane and deuteriochloroform at 25 °C. Relative changes of the induced chemical shifts of pyridine carrying electron-donor substituents (amino group) are the same as the values given in literature for pyridine ring with electron-acceptor substituents.
Differential heats of dissolution in the potassium bichromate-water system at 25 °C
Authors: Rychlý Rudolf , Vacek Václav , Skřivánek Jaroslav , Pekárek Vladimír
Published: October 2011

Differential heats of dissolution in the potassium bichromate-water system were measured in the range of molal concentrations 0.065-0.491 m at 25 °C. The dependence of the heat of dissolution on the concentration was expressed as L (kJ/mol) = 76.9368-43.5608 ##j m + 27.6798m. The measured values were compared with published data and their consistency with measured integral values was discussed.
Effect of ionizing radiation on the kinetics of reduction of NiO-MgO mixed oxids with hydrogen
Authors: Pospíšil Milan , Tvrzník Miroslav
Published: October 2011

The low-temperature reduction of the mixed system nickel oxide-magnesium oxide with hydrogen was studied thermogravimetrically in the region 260-470 °C. The two oxides form in the whole composition region solid solutions, some physicochemical parameters of which vary nonmonotonically with the sample composition. The kinetics and degree of reduction of nickel oxide are appreciably affected by the presence of the unreduced magnesium oxide, in higher concentrations lowering the reaction rate. The kinetics of the reduction can be quantitatively described by the equation 1-(1-α)1/3 = kt, valid in dependence on the composition in differently wide ranges of the degree of reduction α. The reaction rate can be varied, particularly for samples with low contents of magnesium oxide, by heat treatment in inert atmosphere at 700 °C, and for all samples by irradiation by gamma rays or fast neutrons. The reduction rate grows with the increasing content of magnesium oxide up to a constant value. The positive effect increases with the increasing gamma dose and, according to the kind of radiation, in the order γ, n. The variation of the reactivity of irradiated or thermally treated mixed oxides is due predominantly to the shift of the equilibrium of the lattice defects, formation and stabilization of new centres, which affect the rate of nucleation of the forming metal phase.
Behaviour of iodide, iodate and periodate in TLC with alcohol-aqueous ammonia eluent
Authors: Beneš Jaroslav
Published: October 2011

The behaviour of I-, IO3- and IO4- in silica gel thin layer chromatography and their separation with ammonia-alcohol eluents (saturated open-chain C1 to C5 alcohols being used) have been studied with the help of radioisotopes. Changes in RF values of the studied anions caused by changes of the alcohol, ratio of the organic to aqueous phase in the mixture, and overall analytical concentration of ammonium ions have been determined. Influence of alcohol on kinetics of development of the chromatograms with the alcohol-water mixtures has been determined, too.
Oxidation of acetylferrocene and 1,1'-diacetylferrocene with cerium(IV) sulphate in sulphuric acid medium
Authors: Holeček Jaroslav , Handlíř Karel , Klikorka Jiří
Published: October 2011

Oxidation of acetylferrocene and 1,1'-diacetylferrocene with cerium(IV) sulphate has been studied in aqueous sulphuric acid solutions having the overall acidity H0 = +1 to -2. The first step in oxidation of the both ferrocene derivatives consists in a fast one-electron oxidation giving the corresponding unstable ferricenium cations. Their disappearance from the solution is connected with destruction of the sandwich molecule and further redox reactions. Complete destruction of acetylferrocene necessitates two equivalents of the oxidizing agent, the same reaction of 1,1'-diacetylferrocene proceeds by action of three equivalents of the oxidizing agent. On the basis of detailed kinetic measurements mechanism of the oxidation and destruction of the both derivatives has been suggested, and rate constants of decomposition of the sandwich molecules have been determined.
Heat of dilution in potassium bichromate-water system at 25 °C
Authors: Vacek Václav , Pekárek Vladimír , Rychlý Rudolf , Skřivánek Jaroslav
Published: October 2011

The values of the heat of dilution in the potassium bichromate-water system at 25 °C, derived from the empirical concentration dependence of the integral and differential heats of dissolution, are compared with the Debye-Huckel limiting relation. Some features of these dependences are discussed.
The effect of parent substance genesis on the reactivity of active sodium carbonate towards sulphur dioxide
Authors: Mocek Karel , Lippert Erich , Husek Dušan , Erdös Emerich
Published: October 2011

The reactivity of sodium carbonate towards sulphur dioxide was studied in dependence on the effect of genesis of sodium hydrocarbonate as the parent substance of the reacting solid. The reactivity expressed by means of the effective rate constant differed approximately one half of order of magnitude among five various samples. A qualitative correlation has been found between the bulk density of the parent substance and the reactivity of active sodium carbonate prepared thereof. Experimental evidence is given that the effect of genesis of the parent substance is not decisive for the reactivity of the active sodium carbonate towards sulphur dioxide. Henceforth, as the decisive factor for the reactivity of the sodium carbonate the way of its preparation from the parent substance must be considered.
Convective diffusion toward the sphere in laminar flow around the sphere
Authors: Kimla Arnošt , Míčka Jiří
Published: October 2011

The problem of convective diffusion toward the sphere in laminar flow around the sphere is solved by combination of the analytical and net methods for the region of Peclet number λ ≥ 1. The problem was also studied for very small values λ. Stability of the solution has been proved in relation to changes of the velocity profile.
Polarographic reduction of α-(4-ethylbenzoyl)-α,β-dibromopropionic acid on mercury dropping electrode
Authors: Počtová Miloslava
Published: October 2011

A mechanism of the electrochemical reduction of β-(4-ethylbenzoyl)-α,β-dibromopropionic acid is suggested based on the results of classical polarography and polarography with Kalousek's switch and on the identification of the polarographically active intermediate products. The substance converts to β-4-ethylbenzoylacrylic acid on the electrochemical elimination of the bromine atoms, and the latter acid is reduced further to β-4-ethylbenzoylpropionic acid. The most negative polarographic wave corresponds to the reduction of the carbonyl group in the benzoyl part of the last acid.
Interfacial mass transfer in turbulent flow accompanied by irreversible first order chemical reaction
Authors: Kolář Václav , Brož Zdeněk
Published: October 2011

Relations describing the mass transfer accompanied by an irreversible first order chemical reaction are derived, based on the formerly published general theoretical concepts of interfacial mass transfer. These relations are compared with experimental results taken from literature.
Electronic structure and properties of alkoxymethylenemalonic acid derivatives
Authors: Ilavský Dušan , Krechl Jiří , Trška Petr , Kuthan Josef
Published: October 2011

Six compounds RO(H)C=C(X)CN with R = CH3 or C2H5 and X = CO2CH3, CO2C2H5 or CN are characterized by some spectral data (IR, UV, 1H NMR - solvent effect). The PMR spectra did not confirm the presence of two geometrical isomers. Employing the quantum chemical calculations of the substance with R = CH3 and X = CO2CH3 based on EHT, PPP, HMO and CNDO/2, the geometrical isomerism is discussed in relation to the experimental dipole moments. The HMO indices of chemical reactivity agree with our present synthetic insight into nucleophilic substitution of the derivatives under study.
1-Pivaloylacetanilide derivatives
Authors: Kořínek Josef , Poskočil Jaroslav , Arient Josef
Published: October 2011

A series couplers have been prepared on the basis of 4,4-dimethyl-3-oxo-N-phenylpentaneamide. Some of them have been converted into the respective azomethine dyestuffs the absorption maxima of which have been compared with those of the corresponding couplers based on 3-oxo-3,N-diphenylpropaneamide.
Synthetic use of the ribosyl derivatives of 2,4- and 2,5-thiazolidinediones
Authors: Hřebabecký Hubert , Točík Zdeněk , Beránek Jiří
Published: October 2011

On ribosidation of 2,4-thiazolidinedione (2,5-thiazolidinedione, respectively), the 3-β-D-ribofuranosyl derivative is formed in high yield, either the benzoyl derivative Ia (IIa) or the acetyl derivative Ib (IIb). The unsubstituted ribosyl derivative Ic is formed from the acetyl derivative Ib by methanolic hydrogen chloride. The benzoylated ribosyl-2,4-thiazolidinedione Ia affords the benzoylated ribosylurea III on reaction with aqueous ammonia, the hydroxyethylurea derivative IVa with 2-aminoethanol, the semicarbazide derivative Va with hydrazine hydrate, the ribosylhydroxyurea derivative VIa on reaction with hydroxylamine hydrochloride and triethylamine, the benzoyl derivative of ribosylbiuret VII with O-methylisourea hydrochloride and triethylamine, and (analogously) ribosylisothiobiuret VIII with S-methylisothiourea. Methanolysis of the benzoyl derivative of hydroxyethylurea IVa with sodium methoxide affords the unprotected riboside IVb. Ribosylhydroxyurea VIb is formed on debenzoylation of compound VIa with methanolic ammonia. Acetylation of compound VIb furnishes the pentaacetyl derivative VIc.
Participation of 19-ester groups in the cleavage of 2α,3α- and 5α,6α-steroid epoxides. A case of competition between participation and external nucleophile attack
Authors: Kočovský Pavel , Černý Václav
Published: October 2011

Acid cleavage of the acetoxy epoxide IIIa with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the diol Va or the bromohydrin VIa, and the cyclic ether VIII. The latter compound arises by participation of ether oxygen of the ester group. On reaction with perchloric acid the epoxide IVa gave the diol XIIIa as a product of a normal reaction and the isomeric diol Xa as a product arising by intramolecular participation of the carbonyl oxygen of the 19-acetoxy group. Participation of the 19-ester group is confirmed by the formation of the cyclic carbonate XI when the 19-carbonate IVb is treated analogously. On reaction with hydrobromic acid, the epoxide IVa gave solely the bromohydrin XIVa as a product of the normal reaction course. Discussed is the similarity of these reactions with electrophilic additions to the related 19-acetoxy olefins I and II, the mechanism, the difference in behavior of both epoxides III and IV, the dependence of the product ratio on the nucleophility of the attacking species, and the competition between participation of an ambident neighboring group and an external nucleophile attack.
Sorption of iodide ions on ferric oxide
Authors: Beneš Jaroslav
Published: October 2011

The effect of the crystal structure, shape, and dispersity of the ferric oxide particles on the kinetics and extent of the iodide ion sorption was investigated. The dependences of the sorption on the pH and on the liquid-to-solid ratio as well as the sorption isotherm were determined. The reversibility of the sorption of the iodide ions on ferric oxide and the occurrence of a single species of the iodine sorbed were established.
Radical addition of lactones to 1-alkenes initiated by cupric oxide
Authors: Hájek Milan , Špirková Božena , Málek Jaroslav
Published: October 2011

γ-Butyrolactone and γ-valerolactone react with 1-alkenes such as 1-octene and 1-decene, in the presence of cupric oxide as initiator to form the corresponding 2-n-alkyl-γ-butyrolactone and 2-n-alkyl-γ-valerolactone. Yields of these 1 : 1 adducts vary between 41 and 82% and depend on the lactone to 1-alkene molar ratio and on the procedure used for preparation of the metal oxide. The most efficient is the cupric oxide obtained by oxidation of copper powder in a stream of oxygen at 300 °C or by a similar oxidation of a CuO-Cu2O-Cu mixture resulting from cupric oxide during the radical addition reaction.
Distribution of dibenzyl sulfoxide between the aqueous and organic phases
Authors: Vláčil František , Khanh Huynh Dang
Published: October 2011

The distribution of dibenzyl sulfoxide (DBSO) between toluene or tetrachloromethane and aqueous solution of nitric, hydrochloric, or perchloric acid was investigated for different acid concentrations. The solubility of DBSO in the two solvents was established (0.0555 mol l-1 in toluene, 0.0121 mol l-1 in tetrachloromethane at 20 °C) and its distribution constants KD were determined for the systems toluene-water and CCl4-water (133.7 and 27.4, respectively, at 20 °C). Employing the dependence of the distribution ratio of DBSO on the Hammett function for nitric and perchloric acids solutions (1-6M) and taking into account the extraction of the solvates of these acids as described previously, the value of the DBSO protonation constant was calculated to be KH1 (B + H+ ##e BH+) = 1.00 . 10-2, and more accurate values of the extraction constants of the nitric acid solvates were obtained, Kex1 (HNO3 . B) 1.1 . 10-3 and Kex2 ((HNO3)2 . B) 4.3 . 10-5. Owing to the lower solubility of DBSO in water as well as in acid solutions as compared with aliphatic or cyclic sulfoxides and also with tri-n-butylphosphate, solution of DBSO in toluene suits better as the stationary phase for extraction chromatography of metal salts.
Some chemical reactions of sulfur hexafluoride with silicon containing species stimulated by cw CO2 laser radiation
Authors: Pola Josef , Engst Pavel , Horák Milan
Published: October 2011

The CO2 cw laser induced interaction of sulfur hexafluoride with chlorine, silicon tetrachloride, trichlorosilane, and methyltrichlorosilane in a glass reaction vessel has been investigated. The reaction of SF6 with glass surface yielding silicon tetrafluoride and thionyl fluoride was observed. It is inhibited by the products and its rate increases with growing initial pressure (0.6-5.3 kPa) of SF6. Presumed vibrationally excited or dissociated SF6 undergoes the same reaction in the presence of chlorine and silicon tetrachloride, too. The reaction is suppressed by the addition of trichlorosilane and methyltrichlorosilane; in these cases SiF4, SiCl4 and HCl, or SiF4, SiCl4, HCl, acetylene and carbon disulfide are formed. The products indicate a non-sensitizing action of SF6 and a specific reaction channel for the formation of CS2 not attainable by pyrolysis.
Transient response of the 1-st order dynamic system with fluctuating parameters
Authors: Herles Vladimír , Čermák Jan , Havlíček Antonín
Published: October 2011

The paper deals with the analysis of the dynamic behavior of the 1st order system with two random parameters. The theoretical results have been compared with experiments on flow model of a stirred tank reactor.
Products of the acid hydrolysis of 7-chloro-1,3-dihydro-3-hydroxy-5-phenyl-2H-1,4-benzodiazepin-2-one (oxazepam)
Authors: Gasparič Jiří , Zimák Jiří , Sedmera Petr , Breberová Zdeňka , Volke Jiří
Published: October 2011

The acid hydrolysis of oxazepam (Ib) was studied. Under various reaction conditions 6-chloro-4-phenylquinazoline-2-carbaldehyde (V) and the compounds VI and VIII were identified among the products besides the expected 2-amino-5-chlorobenzophenone (IVb).
Structure of neutral oligosaccharides from the enzyme hydrolysate of polysaccharide of peach gum (Prunus persica (L.) BATSCH)
Authors: Kardošová Alžbeta , Rosík Jozef , Kubala Jozef , Kováčik Vladimír
Published: October 2011

Structures of two neutral oligosaccharides from the enzyme hydrolysate of the polysaccharide of peach gum were determined by mass spectrometry and gas chromatography. Tetrasaccharide III was proved to be O-β-D-galactopyranosyl-(1 → 6)-O-β-D-galactopyranosyl-(1 → 3)-O-β-D-galactopyranosyl-(1 → 6)-D-galactose and the disaccharide IV 3-O-α-D-mannopyranosyl-D-galactose.
Extraction of americium with benzyldibutylamine from nitrate solutions
Authors: Jedináková Věra , Cibulková Jana , Kuča Libor
Published: October 2011

The extraction of Am(III) with benzyldibutylamine from nitrate medium was examined in dependence on the concentration of nitric acid, kind and concentration of the salting-out agent in the aqueous phase, and on the solvent. Am(III) is extracted into the organic phase in the form of {(R3NH+)α, Am(NO3)52-}. The IR spectra of the organic phase are discussed and confronted with the results of the chemical analysis of the organic phase. The extraction of Am(III) and of lanthanoids was found to be considerably higher than that of some products of corrosion and nuclear fission (Cs, Sr, Zr, Fe), which is documented by the high values of the separation factors.
Catalytic hydrogenation of binary and ternary mixtures of unsaturated substances in the liquid phase on platinum
Authors: Červený Libor , Junová Radka , Růžička Vlastimil
Published: October 2011

Hydrogenation of olefinic substrates in binary and ternary mixtures using 5% Pt on silica gel as the catalyst was studied in normal conditions in the liquid phase with methanol or cyclohexane or in solvent-free systems. The effect of the solvent concentration on the selectivity of hydrogenation of the unsaturated alcohol-olefin binary mixtures was investigated. In ternary systems of unsaturated substrates, the effect of each of the substrates on the selectivity of hydrogenation of the remaining two substances was examined. Another system was found in which a jump change of the hydrogenation selectivity occurred on the vanishing of the fastest reacting substance.
Hydrogen bonding, configuration and conformation of substituted α-oxo oximes and hydrazones
Authors: Exner Otto , Smolíková Jorga , Jehlička Václav , Shawali Ahmad S.
Published: October 2011

Substituted 2-bromo-1-phenylglyoxal 2-phenylhydrazones IIIa-f exist in tetrachloromethane or benzene solutions prevailingly in E-configuration and in conformation A with an intramolecular hydrogen bond. The latter was evidenced by the N-H valence frequency at 3 290 cm-1 and by 1H NMR shifts with reference to derivatives without a carbonyl group - α-chlorobenzaldehyde phenylhydrazones V. From dipole moments of IIIa-d, measured in benzene solution, the contribution of the hydrogen bond (μH) was evaluated to 17 . 10-30 C m. This quantity is twice larger than in any other reported compound but the direction of the vector is as usual: approximately from H to N. In structurally similar derivatives of hydroxylamine, substituted 2-phenylglyoxylhydroximoyl chlorides IVa-d, no intramolecular hydrogen bond was detected; the dipole moments found were interpreted in terms of the Z-configuration and the prevailing conformation G.
Arylhydrazones of 5-nitrofurfuryl dichloromethyl sulfone
Authors: Jurášek Adolf , Kováč Jaroslav , Bencková Mária
Published: October 2011

X-Phenylhydrazones of α-dichloromethylsulfonyl-5-nitro-2-furaldehydes (X = H, 4-CH3, 4-OCH3, 4-Cl, 4-Br, 4-COOC2H5, 4-COOH, 4-NO2, 3-NO2) were prepared by condensation of aryldiazonium salts with 5-nitrofurfuryl dichloromethyl sulfone in ethanolic sodium acetate. IR, UV and 1H NMR spectra of the synthesized substances were interpreted.
Oxydation von Zitronesaure mit Hexaaquamangan(III)-ionen im nichtkoplexen Perchlorsauremedium
Authors: Babek Jiří , Berka Antonín , Pokorná Alena
Published: October 2011

Article without abstract
Synthesis and chiroptical properties of (-)-(1R)-3-azatricyclo[5,4,0,04,9]undecan-2-one - A lactam with non-planar cis-amide group
Authors: Tichý Miloš , Maloň Petr , Frič Ivo , Bláha Karel
Published: October 2011

The title compound (-)-II was prepared starting from (-)-(2S)-endo-bicyclo[2,2,2]oct-5-ene-2-carboxylic acid ((-)-III). Parameters of the dichroic bands obtained in solvents of various polarity indicate the presence of a non-planar amide group in (-)-II. This amide group is of an opposite chirality and deviates less from planarity than the amide group in (-)-(3S)-4-azatricyclo[4,4,0,03,8]decan-5-one (I). Comparison of the calculated ORD curves with the experimental ones shows that molecular chirality of the σ-skeleton does not participate directly in the dichroic absorption of the amide group.
Addition of primary alcohols to perfluoro-1,3-butadiene
Authors: Dědek Václav , Kováč Milan
Published: October 2011

Addition of methanol or ethanol to perfluoro-1,3-butadiene (I), catalysed with sodium alkoxide, afforded a mixture of the corresponding alkyl 4-alkoxy-3,4,4-trifluoro-2-butenoate VIb or VIa, dialkyl 2-fluorofumarate VIIb or VIIa, and dialkyl 2-alkoxy-2-butene-dioate IXb or IXa, in the overall yield 83% or 93%. The addition of propanol to the diene I in the presence of sodium propoxide gave dipropyl fluorofumarate (VIIc) as the sole product in 92% yield.. The course of the addition is suggested and discussed. The compound VIa was transformed into ethyl 3,4-diethoxy-4,4-difluoro-2-butenoate (VIIIa), diethyl 2-fluorofumarate (VIIa), diethyl 2,3-dibromo-2-fluorosuccinate (XI) and ethyl 3-amino-4-ethoxy-4,4-difluoro-2-butenoate (XIII). The compound VIIa afforded the succinate XI, diethyl 2,2-diethoxysuccinate (X) and 2-amino-2-butenediamide (XIV). Diethyl 2-ethoxy-2-butenedioate (IXa) was converted to diethyl 2,3-dibromo-2-ethoxysuccinate (XII) and the succinate X. The 1H- and 19F-NMR spectra afforded information about the structure of the prepared compounds.
Kinetics of oxidation of bivalent iron by chlorate
Authors: Mádlo Karel
Published: October 2011

Kinetics of Fe(II) oxidation by chlorate was studied in homogeneous systems (pH 1, HCLO4 and in heterogeneous systems involving precipitate of Fe(III) hydrolysis products (pH 1 to 5.5). The stoichiometry ( 6 Fe2+ : 1 ClO-3 : 6H+) as well as the rate equation (-d[Fe2+]/dt = kexp/.[Fe2+][ClO-3]) is the same in the two cases. Also the differences in the experimental activation energies and entropies for the two pH regions are insignificant. The [OH-]/[Fe3+] ratio passes a maximum during the spontaneous change of pH (pH0 5), whereas if the pH is maintained constant (pH 5) the ratio increases monotonically throughout the whole time interval followed. The balance of the Fe2+ and Fe3+ showed that part of the Fe2+ ( 10-3 mol l-1) was present during the reaction in the precipitate of the Fe(III) hydrolysis products, while part of the Fe3+ (5 . 10-3 mol l-1) existed outside this precipitate; the latter dropped by approximately two orders of magnitude only several tens of hours after the finishing of the Fe(II) oxidation.
Mass spectrometry for analysis of monohydric phenols
Authors: Buryan Petr , Kubelka Vladislav , Mitera Jiří , Macák Jiří
Published: October 2011

Mass spectrometry behaviour of monohydric phenols is discussed, and so far unpublished mass spectra of 32 monohydric C9 to C18 are given.
Preparation of oligomycin-sensitive ATPase enriched submitochondrial fraction from beef heart mitochondria
Authors: Svoboda Petr , Drahota Zdeněk
Published: October 2011

A simple method for purification of oligomycin-sensitive ATPase from beef heart mitochondria is described. The isolation procedure is based on short term solubilization of mitochondrial membrane in deoxycholate and 1M-KCl followed by sequential precipitation of hydrofobic proteins and isopycnic centrifugation of crude particulate enzyme on sucrose density gradient. The oligomycin-sesitive ATPase preparation has a specific activity 15-20μmol P/min/mg protein and contains 5% of the total mitochondrial protein which can be separated by SDS-polyacrylamide gel electrophoresis into 13 protein components of relative molecular weight from 6 000 - 65 000 daltons, respectively.
Atropodiastereoisomerism and pseudoassymetry with axial chirality of ligands in bis(2-methyl-1-naphthyl)methanols
Authors: Červinka Otakar , Bláha Karel , Fábryová Anna , Fink R. , Van der Helm Dick , Pořádek Jaroslav
Published: October 2011

On reduction of bis(2-methyl-1-naphthyl) ketone (I) with lithium aluminium hydride alcohol VI was formed which isomerized into alcohol VII. Both alcohols, the configuration of which were proved using 1H-NMR spectra and X-ray diffraction, represent the first example of compounds having a centrum of pseudoassymetry and axial chirality of ligands.
Synthesis of conjugates of 1-(carboxymethyl)cytosine and 1-(5-O-carboxymethyl-β-D-arabinofuranosyl)cytosine with proteins
Authors: Pischel Helmut , Holý Antonín , Wagner Günther
Published: October 2011

1-(Carboxymethyl)cytosine (Ia), 1-(5-O-carboxymethyl-β-D-arabinofuranosyl)cytosine (IIa) and 5'-O-carboxylmethylcytidine (IIIa) were transformed by treatment with acetic anhydride and 4-dimethylaminopyridine to the peracetyl derivatives Ib-IIIb. These products reacted with p-nitrophenol in the presence of N, N'-dicyclohexylcarbodiimide to give the activated esters Ic-IIIc which on reaction with ammonia, dimethylamine or 2-aminoethanol afforded the corresponding carboxamides Id-IIId, IIe,f. Reactions of Ic and IIc with human serum albumin and bovine γ-globulin at pH 9.2, followed by hydrolysis of the N- or O-acetyl groups at pH 9.5, gave 50% up to 64% yields of the respective conjugates Ig, IIg and Ih, IIh.
Reversible thermal denaturation of immobilized chymotrypsinogen
Authors: Brynda Eduard , Bleha Miroslav
Published: October 2011

The reversible thermal denaturation of chymotrypsinogen A bound to the insoluble poly(2-hydroxyethyl methacrylate) Spheron matrix was investigated by the fluorescence method. The applicability of fluorescence data in the calculation of the thermodynamic parameters of denaturation was tested. Equilibrium data were obtained for immobilized chymotrypsinogen and chymotrypsinogen in solution at various pH in the range 2-6. The binding to Spheron shifts the thermodynamic equlibrium in favour of the denaturated state. An increase in pH above 3 did not affect the denaturation of immobilized chymotrypsinogen. The denaturation is controlled by the first-order kinetics. The rate constants and magnitudes of changes of free energy, enthalpy and entropy were calculated for the transition from the native state into the activated state, and from denaturated state into the activated state. The temperature dependence of the rate constants for the denaturation of immobilized chymotrypsinogen is qualitatively different from for chymotrypsinogen in solution. The results were interpreted as effects of the physical interaction between the denaturated protein and polymeric matrix.
Reduction of 3-substituted quinolines with triethylammonium formate
Authors: Ferles Miloslav , Kocián Oldřich
Published: October 2011

Reduction of 3-substituted quinoline derivatives, containing electron donating substituents (Ia-Id), as well as of the quaternary salts VIb and VIc, with triethylammonium formate afforded mainly the corresponding 1-formyl-1,2,3,4-tetrahydroquinolines II or their 1-methyl derivatives. Analogous reductions of quinoline derivatives, containing electron withdrawing groups (e.g. Im) gave 1,4-dihydroquinolines IV in addition to 1,2,3,4-tetrahydroquinoline derivatives. Quaternary salts of 3-substituted derivatives with electron withdrawing substituents (e.g. VId) were reduced exclusively to 1-alkyl-1,4-dihydroquinolines IV.
The reaction of polymers of 2,3-epoxypropyl methacrylate with N-(benzyloxycarbonyl) glycine and glycine tert-butyl ester
Authors: Kellner Vladimír , Čoupek Jiří , Kálal Jaroslav
Published: October 2011

The reaction of the epoxy groups of polymers of 2,3-epoxypropyl methacrylate with N-(benzyloxycarbonyl) glycine in N,N-dimethylformamide and the reaction with glycine tert-butyl ester in benzene in the presence of 4-nitrophenol at 80°C were investigated. The rate constants were calculated for the reaction with N-(benzyloxycarbonyl) glycine. The reaction of macroporous gels of 2,3-epoxypropyl methacrylate-ethylene dimethacrylate with N-(benzyloxycarbonyl) glycine was studied.
Acetolysis of 4β-methanesulphonyloxy-6β,7aβ-cyclo-B-homo-5α-cholestane
Authors: Kohout Ladislav , Fajkoš Jan
Published: October 2011

Synthesis of 4β-methanesulphonyloxy-6β,7aβ-cyclo-B-homo-5α-cholestane is described. During its acetolysis a kind of conjugative stabilization of the carbocation formed was observed. The mechanism of the reaction is discussed.
Evaluation of the temperature responses in colorimetric measurements of chemisorption enthalpies on metal films
Authors: Smutek Miloš , Černý Slavoj
Published: October 2011

An analysis was performed of various estimates of the adiabatic temperature Ttot that corresponds to the total heat liberated by a gas dose adsorbed on a metal film in the calorimeter for measurement of chemisorption enthalpies. Besides the two common procedures consisting either in the construction of the adiabatic temperature-time curve or in the extrapolation of the single-exponential cooling part of the actual temperature-time curve to zero time, we have examined estimates of Ttot by extrapolating the cooling exponential to the mid-point between zero time and the temperature maximum (t = tmax/2). Model calculations have shown the merit of the latter extrapolation, particularly in the cases of slow heat evolution. This has been verified on the data measured in the chemisorption of methane and ethane on molybdenum films. Extrapolation to tmax/2 has turned out to be a simple and reasonably reliable procedure for handling the data obtained in film calorimeters.
Kinetic isotherms of cyclohexane on active carbon supersorbon
Authors: Sedláček Zdeněk
Published: October 2011

The kinetic isotherm makes it possible to compute the value of diffusion coefficient and, from its temperature dependence, to calculate the activation energy of the adsorbate transfer in the adsorbent pores. The data of kinetic isotherms have been taken over from our previous paper. On the basis of comparison of the activation energy with the isosteric heats and with enthalpy of vaporization we can judge of a probable mechanism of transfer.
The use of mixing calorimeter for measuring heat capacities of liquids
Authors: Veselý František , Zábranský Milan , Svoboda Václav , Pick Jiří
Published: October 2011

Molar heat capacities of benzene, cyclohexane, tetrachlormethane and ethanol at temperatures 25, 35 and 45°C and of 1-propanol at a temperature of 25°C were measured in a mixing calorimeter described previously. The results are in good agreement with the best literature values. The error of measurements did not exceed 0.3%.
Temperature dependence of heats of vaporization, saturated vapour pressures and cohesive energies of secondary amines
Authors: Pětroš Libor , Majer Vladimír , Koubek Josef , Svoboda Václav , Pick Jiří
Published: October 2011

The temperature dependence of heats of vaporization of methylisopropylamine, ethylisopropylamine, propylisopropylamine, diisopropylamine, butylisopropylamine, ethylbutylamine and dibutylamine has been measured. Further, the dependence of saturated vapour pressures on temperature has been measured for methylisopropylamine, ethylisopropylamine, propylisopropylamine, butylisopropylamine, diisopropylamine and ethylbutylamine. The densities of the liquid phase at 25°C have been determined for methylisopropylamine, ethylisopropylamine, propylisopropylamine, butylisopropylamine and ethylbutylamine. The cohesive energies at several temperatures have been computed from the experimental data for all the substances of the set.
Synthesis of 7-chloro-5-(6,7,8,9-tetrahydro-5H-benzocyclohepten-2-yl)-2-methylamino-3H-1,4-benzodiazepine 4-oxide and of some related compounds
Authors: Vejdělek Zdeněk , Rajšner Miroslav , Svátek Emil , Holubek Jiří , Protiva Miroslav
Published: October 2011

The base catalyzed condensation of 4-chloronitrobenzene with 2-(cyanomethyl)-6,7,8,9-tetrahydro-5H-benzocycloheptene afforded the 2,1-benzisoxazole derivative VIa which was reduced with iron in acetic acid to the 2-aminophenone VIIa. Its oxime IXa was treated with chloroacetyl chloride in acetic acid and gave the 4-substituted 6-chloro-2-chloromethylquinazoline 3-oxide (Xa). The treatment with methylamine in methanol led to the substitution reaction with a simultaneous ring elargement and the title compound IVa was formed. A similar reaction with 1-methylpiperazine proceeded without rearrangement resulting in the quinazoline XIa. The object of further experiments was the preparation of the lactam Va, the norpethidine derivative XV and some new approaches to intermediates useful in the synthesis of 5-(2-chlorophenyl)-7ethyl-1,3-dihydrothieno[2,3-e]-1,4-diazepin-2-ones.
Photolytic and thermal annealing of radical anions gamma-irradiated monocarboxylic acids
Authors: Mach Karel , Janovský Igor , Vacek Karel
Published: October 2011

Total yields of paramagnetic species, their optical bleaching and thermal annealing in acetic, propionic, a-butyric, isobutyric, and pivalic acid γ-irradiated at 77 K were followed by ESR spectroscopy. Radical anions, always found after irradiation, disappear during optical bleaching without formation of any paramagnetic product. During thermal annealing they are converted almost quantitatively into the α-radicals of the respective acid, with the exception of pivalic acid. Amounts of radical anions were estimated from the difference of integrated ESR spectra taken before and after optical bleaching. The results show that approximately equal amounts of the reduction and oxidation paramagnetic products of the γ-irradiation can be detected.
Extraction of hafnium(IV) with organophosphorus reagents from solutions of mineral acids mixtures
Authors: Navrátil Oldřich , Smola Jiří , Kolouch Rostislav
Published: October 2011

Extraction of hafnium(IV) was studied from solutions of mixtures of perchloric and nitric acids and of perchloric and hydrochloric acids for constant ionic strength, I = 2, 4, 6, or 8, and for cHf 4 . 10-4 mol l-1. The organic phase was constituted by solutions of some acidic or neutral organophosphorus reagents or of 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, or N-benzoyl-N-phenylhydroxylamine in benzene, chloroform, or n-octane. A pronounced synergic extraction of hafnium proceeds only on applying organophosphorus reagents from an aqueous phase whose acidity is not lower than 3M-(HClO4 + HNO3) or 5M-(HClO4 + HCl). The synergic effect was not affected markedly by a variation of the initial concentration of hafnium in the range 1 . 10-8 -4 .10-4 mol l-1, it lowered with increasing initial concentration of the organophosphorus reagent and decreasing concentration of the H+ ions. It is suggested that the hafnium passes into the organic phase in the form of mixed complexes, the salting-out effect of perchloric acid playing an appreciable part.
Isomerisation of β-epoxy sulfones
Authors: Poláková Jana , Paleček Miloš , Procházka Miloš
Published: October 2011

The base-catalyzed isomerisation of β-epoxy sulfones to γ-hydroxy αβ-unsaturated sulfones was shown by kinetic data, isotope effect and stereochemistry to involve an intramolecular synfacial 1-3 hydrogen migration with carbanion-like transition state.
A novel method to chemically bind thiazolidine-2,4-dione through cross-linked chitosan nanoparticles using malanodialdehyde as a cross-linker
Authors: Singh Prashant , Kumari Kamlesh , Tomar Vartika , Samim Mohd. , Patel Rajan , Mehrotra Gopal Kumar , Dubey Monica , Pandey Narendra Deo , Katyal Anju
Published: October 2011

Chitosan is a biodegradable natural polymer with great potential for pharmaceutical applications because of its biocompatibility, high charge density, nontoxicity and mucoadhesion. It has been shown that it not only improves the dissolution of poorly soluble drugs but also exerts a significant effect on fat metabolism in the body. Gel formation can be obtained by interactions of chitosans with low molecular counterions such as polyphosphates, sulfates, and cross-linkers. This gelling property of chitosan allows a wide range of applications such as the coating of pharmaceuticals and food products, gel entrapment of biochemicals, plant embryos, whole cells, microorganisms, and algae. This manuscript is an insight into the exploitation of its properties for microencapsulating drugs. Herein, we report a novel method to chemically bind thiazolidine-2,4-dione through cross-linked chitosan nanoparticles using malanodialdehyde as a new cross-linker and well characterized by FT-IR, NMR, TGA, DSC, powder X-ray diffraction, TEM, and cyclic voltametry.
Intra- and inter-molecular interactions in salicylic acid — Theoretical calculations of17O and1H chemical shielding tensors and QTAIM analysis
Authors: Esrafili Mehdi D.
Published: October 2011

A density functional theory (DFT) study was performed to examine intra- and inter-molecular hydrogen bond (HB) properties in crystalline salicylic acid (SA). BLYP, B3LYP, and M06 functionals with 6–311++G** basis set were employed to calculate NMR chemical shielding isotropy (σiso) and anisotropy (Δσ) at the sites of the17O and1H nuclei of SA. From this study, it appears that the intra- and inter-molecular O–H···O as well as C–H···O HBs around the SA molecule in the crystal lattice have a major influence on the chemical shielding tensors and more specifically on the carbonyl17O isotropy value. The quantum theory of atoms in molecules (QTAIM) analysis was also employed to elucidate the interaction characteristics in SA H-bonded network. Based on QTAIM results, a partial covalent character is attributed to the intra- and inter-molecular O–H···O HBs in SA.
From Autonomic to Self-Self Behaviors
Authors: Bouchenak Sara , Boyer Fabienne , Claudel Benoit , De Palma Noel , Gruber Olivier , Sicard Sylvain
Published: October 2011

Autonomic computing enables computing infrastructures to perform administration tasks with minimal human intervention. This wrap-up paper describes the experience we gained with the design and use of
Jade
---an architecture-based autonomic system. The contributions of this article are, (1) to explain how
Jade
provides autonomic management of a distributed system through an architecture-based approach, (2) to explain how we extended autonomic management from traditional self behaviors such as repairing or protecting a managed system to self-self behaviors where
Jade
also fully manages itself as it manages any other distributed system, (3) to report on our experience reaching self-self behaviors for two crucial autonomic properties, repair and protection.
Smoothed Analysis of the k-Means Method
Authors: Arthur David , Manthey Bodo , Röglin Heiko
Published: October 2011

The
k
-means method is one of the most widely used clustering algorithms, drawing its popularity from its speed in practice. Recently, however, it was shown to have exponential worst-case running time. In order to close the gap between practical performance and theoretical analysis, the
k
-means method has been studied in the model of smoothed analysis. But even the smoothed analyses so far are unsatisfactory as the bounds are still super-polynomial in the number
n
of data points.

In this article, we settle the smoothed running time of the
k
-means method. We show that the smoothed number of iterations is bounded by a polynomial in
n
and 1/
σ
, where
σ
is the standard deviation of the Gaussian perturbations. This means that if an arbitrary input data set is randomly perturbed, then the
k
-means method will run in expected polynomial time on that input set.
Prolonged renal allograft survival by donor interleukin-6 deficiency: association with decreased alloantibodies and increased intragraft T regulatory cells
Authors: Wang Hao , Guan Qiunong , Lan Zhu , Li Shuyuan , Ge Wei , Chen Huifang , Nguan Christopher Y. C. , Du Caigan
Published: October 2011

Both humoral and cellular immune responses are involved in renal allograft rejection. Interleukin (IL)-6 is a regulatory cytokine for both B and Foxp3 (forkhead box P3)-expressing regulatory T (Treg) cells. This study was designed to investigate the impact of donor IL-6 production on renal allograft survival. Donor kidneys from IL-6 knockout (KO) vs. wild-type (WT) C57BL/6 mice (H-2b) were orthotopically transplanted to nephrotomized BALB/c mice (H-2d). Alloantibodies and Treg cells were examined by fluorescence-activated cell sorting analysis. Graft survival was determined by the time to graft failure. Here, we showed that a deficiency in IL-6 expression in donor kidneys significantly prolonged renal allograft survival compared with WT controls. IL-6 protein was upregulated in renal tubules and endothelium of renal allografts following rejection, which correlated with an increase in serum IL-6 compared with that in those receiving KO grafts or naive controls. The absence of graft-producing IL-6 or lower levels of serum IL-6 in the recipients receiving IL-6 KO allografts was associated with decreased circulating anti-graft alloantibodies and increased the percentage of intragraft CD4+CD25+Foxp3+Treg cells compared with those with WT allografts. In conclusion, the lack of graft-producing IL-6 significantly prolongs renal allograft survival, which is associated with reduced alloantibody production and/or increased intragraft Treg cell population, implying that targeting donor IL-6 may effectively prevent both humoral and cellular rejection of kidney transplants.