bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of hydrogenation of petroleum asphaltenes
Authors: Šebor Gustav , Reynoso Salvador , Hájek Milan , Weisser Otto , Mostecký Jiří
Published: August 2011

Isolated petroleum asphaltenes were subjected to model thermal and catalytic hydrogenation experiments in the temperature region 300-450° C. The course of hydrogenation of the asphaltenes studied is discussed based on 1H-NMR type analysis of the starting material and the hydrogenation products.
Antraquinone-triazine derivatives of polysaccharides. Relation between structure and affinity to lactate dehydrogenase
Authors: Gemeiner Peter , Mislovičová Danica , Zemek Jiří , Kuniak Ľudovít
Published: August 2011

The inhibition effects (I50) of a series of dyes (Cibacrom Blue 3G-A, Procion Blue MX-R, Remazo Brilliant Blue and Ostazin Brilliant Red S5-B) covalently linked to dextran T 70 were the criterion of the relationship between the structure of antraquinone-triazine compounds and their affinity to rabbit muscle lactate dehydrogenase (LDH). The I50 values indicate a substantial importance of the terminal benzenesulfonane moiety in the structure of Cibacron Blue. Also the degree of substitution of polysaccharide plays an important role in the affinity; its influence upon I50 can be expressed for Cibacron Blue-Dextrans T 70 by an equation of line. The influence of the structure of the polysaccharide constituent on the affinity of Cibacron Blue-(α-glucans) towards LDH is discussed, as well.
Synthesis of 2-substituted 5-arylidenethiazolin-4-ones from α,β-unsaturated acyl isothiocyanates
Authors: Kutschy Peter , Dzurilla Milan , Kristian Pavol , Kutschyová Kvetoslava
Published: August 2011

α,β-Unsaturated acyl isothiocyanates react with N-methylaniline to give thioureas which, when treated with bromine in chloroform, afford benzothiazoline derivatives. Under the same reaction conditions primary amines, diethylamine, piperidine and morpholine furnish 2-substituted 5-arylidenethiazolin-4-ones. Their structure was corroborated by an independent synthesis and on the basis of spectral (IR, 1H-NMR and mass) evidence.
A modified route to intermediates in partial syntheses of digitoxigenin and xysmalogenin
Authors: Kočovský Pavel , Černý Václav
Published: August 2011

3β-Hydroxy-5,14-pregnadien-20-one (X) was prepared via 6β-methoxy-3α,5-cyclo-5α-pregn-14-en-20-one (VII). The compound X and its acetate XI are known intermediates in partial syntheses of digitoxigenin and xysmalogenin, respectively. In the present paper, conversion of X into the cardenolide XVII is also described.
EPR study of reduction of vanadyl tetrasulphophthalocyanine by ascorbic acid
Authors: Wagnerová Dana M. , Stopka Pavel , Rein Horst , Friedrich Jörg
Published: August 2011

Based on the EPR spectra, vanadyl tetrasulphophthalocyanine (VOTSP) was found to be reduced by ascorbic acid in alkaline medium to the vanadium(III) complex. The hyperfine structure of the spectra indicates that after re-oxidation, the equilibrium between the dimeric and the monomeric forms of VOTSP is shifted in favour of the latter as compared with the initial state, obviously owing to the formation of adducts of VOTSP with the oxidation products of ascorbic acid. The formation of the adducts prevents dimerization.
Hydrodynamics and mass transfer in turbulent liquid film flow involving the inlet portion
Authors: Kholpanov L. P. , Malyusov V. A. , Zhavoronkov N. M.
Published: August 2011

Relationship for mass transfer coefficient in turbulent liquid film flow involving the inlet section have been derived theoretically. It was found that previously published experimental results were well explained by this theory.
Information content of analytical signals of instrumental methods
Authors: Eckschlager Karel
Published: August 2011

Instrumental analytical methods are studied from the point of view of the information content of the signal, whose intensity or both position and intensity are sources of relevant information. The information content is expressed with the aid of the divergence measure in units defined by the unit isoinform. If both the intensity and the position of the signal are sources of information, it is assumed that they are mutually independent or that the measurement of the signal intensity is carried out with accuracy which depends on the signal position.
Reactions of cumyloxyl radicals with tetrakis(allyloxymethyl)methane
Authors: Chodák Ivan , Bakoš Dušan , Zimányová Edita
Published: August 2011

GLC Analysis of decomposition products of dicumyl peroxide has been used for determination of relative rate constant of hydrogen transfer of cumyloxyl radicals with tetrakis(allyloxymethyl)-methane. This constant is 15 times higher than that with 2,2,4-trimethylpentane. In the reaction an only small portion of the oxyl radicals (up to 15% of total amount) is consumed by addition to allyl groups of the monomer even when a great excess of the latter is present in the reaction mixture.
Dipole moments and conformation of peroxy esters
Authors: Plesničar Božo , Exner Otto
Published: August 2011

Dipole moments of sixteen substituted peroxybenzoic esters III, IV were measured in benzene solution and interpreted in terms of the conformation around the O-O bond. The dipole moment of the CO3R group is different for R = methyl and R = tert-butyl, viz. 9.0 and 10.4 . 10-30 C m, respectively. Its solution into components was carried out making reference to the dipole moments of substituted benzoic esters as model compounds. As a result the dihedral angle τ = C-O-O-C was estimated to 160-180° in the case of tert-butyl peroxy esters IV and to 110-150° in the case of methyl peroxy esters III. The mesomeric dipole moment expressing the conjugation within the ester group was estimated to 0.8 or 1.5 . 10-30 C m for methyl or tert-butyl esters, respectively.
Electrochemical reduction of para-substituted 2-acyl-5-phenylfuranes in dimethylformamide
Authors: Černák Jozef , Tomanovič František , Staško Andrej , Oleinikova Anna Fedosyevna , Kováč Jaroslav
Published: August 2011

para Substituted chloro, bromo, and nitro derivatives of 2-acyl-5-phenylfurane are reduced polarographically in a one-electron wave to the corresponding anion radicals, which were studied by the EPR method. The reduction of nitro derivatives, studied by the Kalousek switch, is reversible and leads to a stable anion radical with an unpaired electron center on the nitrogen nucleus; the reduction of the halogen derivatives is only partly reversible and leads to unstable ketyl radicals. The bromo derivatives give polarographic maxima typical for concurrent reactions.
Reactions of 3-cyano-1-methylquinolinium methyl sulphate with some C-acids and with p-nitroaniline
Authors: Kocián Oldřich , Ferles Miloslav
Published: August 2011

The action of malononitrile, ethyl cyanoacetate, dibenzoylmethane and/or p-nitroaniline on compound I in the presence of sodium methoxide gives rise to derivatives of 3-cyano-1-methyl-1,4-dihydroquinoline, II and III
Kinetic and spectral studies on 5-phenoxy-2-furaldehydes and their condensation products
Authors: Knoppová Viera , Dandárová Miloslava , Kováč Jaroslav
Published: August 2011

The base-catalyzed reaction of 5-(4- or 3-phenoxy)-2-furaldehydes (X = 4-OCH3, 4-CH3, 4-Cl, 4-NO2, 3-NO2, 4-Br, 4-COOC2H5, 3-NHCOCH3, 4-SCH3) with malonodinitrile in ethanol gave the corresponding condensation products. The course of the reaction has been monitored kinetically. The kinetics of the nucleophilic substitution reaction at the position 5 of the furan ring of the obtained 2-cyano-3-(5-X-phenoxy-2-furyl)acrylonitriles with secondary cyclic amines (piperidine, morpholine, pyrrolidine) has been studied. The effect of X across the oxygen bridge upon the reaction site is discussed from the point of view of kinetics of the reaction. 1H-NMR spectra of the starting aldehydes and of the formed condensation products have been measured.
Synthesis and properties of styryl derivatives of 2-furaldehyde
Authors: Knoppová Viera , Jurášek Adolf , Dandárová Miloslava , Kováč Jaroslav
Published: August 2011

Reaction of 4-X-benzyltriphenylphosphonium halides with 2-furaldehyde and subsequent Vilsmeier formylation gave 5-(4-X-styryl)-2-furaldehydes ( X = H, Cl, Br, CN, NO2, CH3, and COOCH3). The UV, IR and 1H-NMR spectra of the prepared substances are discussed and it is demonstrated that the compounds are (E) isomers. The UV spectra of 5-styryl-2-furaldehyde have been compared with those of its benzene analogue.
Decyclizing phosphodiesterases associated with plasma membranes of the chick chorioalantois
Authors: Pristašová Svetlana , Rosenbergová Marta , Holý Antonín
Published: August 2011

Two different enzymatic activities hydrolyzing 2',3'-cyclic phosphates of purine and pyrimidine ribonucleosides to give 2'- or 3'-ribonucleotides have been detected in plasma membranes of the chick chorioalantois. The enzymes differ in their temperature optima: At lower temperatures, cleavage to the 2'-isomers predominates.
Relation of the temperature derivative of internal and cohesive energies of vaporization to the difference of heat capacities of liquids and gases
Authors: Svoboda Václav , Uchytilová Věra , Majer Vladimír , Pick Jiří
Published: August 2011

Methods of Calculating the difference of heat capacities of liquids and gases at constant volume are discussed. The known methods of calculation are confronted with the method proposed in this work. It starts from the relations describing the mutual dependence of the temperature derivative of internal and cohesive energies of vaporization to the difference of the heat capacities of liquids and gases at constant volume.
Use of the Padé approximants for calculating the second virial coefficient
Authors: Boublík Tomáš , Vosmanský Jan
Published: August 2011

The expansions in reduced temperature, occurring in relations for the second virial coefficient of the power-law potentials were expressed by the Pade approximant. For the Kihara potential it is proved that the functions F1(T*), F2(T*) and F3(T*) and consequently the whole virial coefficient can bee expressed for reduced temperatures T* 0.6 with a good accuracy by means of a simple Pade approximant. To describe quantum effects on the second virial coefficient of low-molecular gases at low temperatures a simple approximant was formulated on the basis of the Wigner-Kirkwood expansion allowing to correlate data on the second virial coefficient even in the temperature range where the use of the Wigner-Kirkwood expansion already fails.
The shape and velocity of interface during the growth of a new phase
Authors: Vodák František
Published: August 2011

The growth of a new phase in a one-component system is investigated. The relation between the shape and the velocity of a growing interface is formulated. Explicit dependences of this velocity on transport phenomena across and along the interface are derived by methods of the nonequilibrium thermodynamics of the discontinuity surface. Some special cases are discussed.
Oxidation scheme of symmetrically disulphonated naphthidines with cerium(IV) sulphate
Authors: Komers Karel
Published: August 2011

The author derived theoretical dependences of preasymptotic slopes of the currentless E-t curves (potential of an indicator redox electrode against time) on the number of equivalents, n, of added oxidation agent, assuming a reaction scheme of two consecutive concurrent second-order reactions involving the formation of intermediate products ( a side reaction of the starting compound with the final oxidation product leading to an adduct, which undergoes consecutive bimolecular oxidations leading again to the final product). The dependences enable to determine the type of the relatively stable intermediate products and the ratios of the rate constants. The theory was applied to the oxidation of four symmetrically disulphonated naphthidines with cerium(IV) sulphate in aqueous sulphuric acid and the results were substantiated spectrophotometrically
Mechanism of the oxidation of styrene by palladium salts
Authors: Vojtko Ján , Kaszonyi Alexander , Čihová Milina , Hrušovský Mikuláš
Published: August 2011

The oxidation of styrene by palladium salts in excess of HCl has been investigated in homogenous phase, using methanol as solvent. The degree of styrene conversion was followed polarographically. It was found that the reaction rate can be expressed by the rate equation corresponding to the transformation of a mononuclear complex with styrene coordinated to PdCl2-4, the kinetic term of which has the following form: w =k1[styrene][PdCl2-4]/[H3O+][Cl-]2.
Proton, carbon-13, and fluorine-19 NMR study of N-arylpyridinium salts: Attempted calculations of the σ1 and σR0 values for N-pyridinium substituents
Authors: Claramunt Rosa Maria , Elguero José
Published: August 2011

The synthesis and NMR study of fourteen N-arylpyridinium salts have been done. Chemical shifts and coupling constants (1H-1H, 1H-13C, 1H-19F, and 13C-19F) have been measured in hexadeuteriodimethyl sulphoxide. Conformation about the phenylpyridinium bond is discussed. The electronic properties of the three pyridinium substituents ( pyridinium, 2,4,6-trimethylpyridinium, and 2,4,6-triphenylpyridinium) have been determined (Hammet and Taft's σ values) and compared with those of the trimethylammonium substituent.
Synthesis of 3-(2-alkoxyphenoxy)-2-methyl (or phenyl)propylamines as potential antidepressants
Authors: Šindelář Karel , Holubek Jiří , Metyš Jan , Bartošová Marie , Protiva Miroslav
Published: August 2011

Reactions of potassium salts of 2-methoxy-, 2-ethoxy- and 2-benzyloxyphenol with 2-methyl-3-dimethylaminopropyl chloride and 3-dimethylamino-2phenylpropyl chloride in boiling 2-butanone in the presence of potassium iodide gave the title compounds IV-VI which were partially demethylated by treatment with ethyl chloroformate in boiling benzene and by the following alkaline hydrolysis of the crude intermediates. In series a (3-aryloxy-2-methylpropylamines) the demethylation proceeded normally under the formation of the methylamino compounds VIIa-IXa; in series b (3-aryloxy-2-phenylpropylamines), however, the treatment with ethyl chloroformate effected a double cleavage resulting, after the alkaline hydrolysis, in N-methyl-2-phenylallylamine (XIII).The pharmacological testing did not confirm the expected thymoleptic effects of the compounds (IVa, VIIa); on the other hand, the benzyl ethers IXa and especially VIb exhibited strong antiarrhythmic activity.
Amino acid sequence of cyanogen bromide fragments CB4 and CB6 of hog pepsin
Authors: Morávek Ladislav
Published: August 2011

By the analyses of chymotryptic, and thermolytic peptides the amino acid sequence was determined of cyanogen bromide fragment CB4 representing the region of the pepsin chain between the N-terminus and methonine-residue I: Ile-Gly-Asp-Glu-Pro-Leu-Glu-Asn-Tyr-Leu-Asp-Thr-Glu-Tyr-Phe-Gly-Thr-Ile-Gly-Ile-Gly-Thr-Pro-Ala-Gln-Asp-Phe-Thr-Val-Ile-Phe-Asp-Thr-Gly-Ser-Ser-Asn-Leu-Trp-Val-Pro-Ser-Val-Tyr-Cys-Ser-Ser-Leu-Ala-Cys-Ser-Asp-His-Asn- + Gln-Phe-Asn-Pro-Asp-Asp-Ser-Ser-Thr-Phe-Glu-Ala-Thr-Ser-Gln-Glu-Leu-Ser-Ile-Thr-Tyr-Gly- + Thr-Gly-Ser-Met. The serine residue (Ser) in position 68 of pepsin is phosphorylated. By sequential analysis of chymotryptic, tryptic, and thermolytic peptides the amino acid sequence was determined of cyanogen bromide fragment CB6 representing the region between methionine residues II and III in the pepsin chain: Asp-Gly-Glu-Thr-Ile-Ala-Cys-Ser-Gly-Gly-Cys-Gln-Ala- + Ile-Val-Asp-Thr-Gly-Thr-Ser-Leu-Leu-Thr-Gly-Pro-Thr-Ser-Ala-Ile-Ala-Asn-Ile-Gln-Ser-Asp- + Ile-Gly-Ala-Ser-Glu-Asn-Ser-Asp-Gly-Glu-Met. The aspartic acid residue (Asp) in position 16 of this fragment is identical with the residue reacting with diazo inhibitors which forms a part of the active center of the enzyme. Both half-cystine residues of fragment CB4 and fragment CB6 are linked to one another by a disulfide bond in native pepsin.
Amino acid sequence of cyanogen bromide fragment CB3 of hog pepsin
Authors: Morávek Ladislav , Kostka Vladimír
Published: August 2011

On the basis of the knowlidge of thermolytic, chymotryptic and substilisin peptides the amino acid sequence was determined of cyanogen bromide fragment CB3 representing the region between methionine residues I and II of pepsin: Thr-Gly-Ile-Leu-Gly-Tyr-Asp-Thr-Val-Gln-Val-Gly-Gly-Ile-Ser-Asp-Thr-Asn-Gln-Ile-Phe-Gly-Leu-Ser-Glu-Thr-Glu-Pro-Gly-Ser-Phe-Leu-Tyr-Tyr-Ala-Pro-Phe-Asp-Gly-Ile-Leu-Gly-Leu-Ala-Tyr-Pro-Ser-Ile-Ser-Ala-Ser-Gly-Ala-Thr-Pro-Val-Phe-Asp-Asn-Leu-Trp-Asp-Gln-Gly-Leu-Val-Ser-Gln-Asp-Leu-Phe-Ser-Val-Tyr-Leu-Ser-Ser-Asn-Asp-Asp-Ser-Gly-Ser-Val-Val-Leu-Leu-Gly-Gly-Ile-Asp-Ser-Ser-Tyr-Tyr-Thr-Gly-Ser-Leu-Asn-Trp-Val-Pro-Val-Ser-Val-Glu-Gly-Tyr-Trp-Gln-Ile-Thr-Leu-Asp-Ser-Ile-Thr-Met.
Synthesis of the uracil analog of thuringiensin and its inhibitory effect on DNA-dependent RNA polymerase of Escherichia coli
Authors: Kalvoda Ladislav , Horská Květa , Šebesta Karel
Published: August 2011

An analog of thuringiensin (II), containing uracil instead of adenine, was synthetized by the method employed for thuringiensin. Similarly to the parent substance this analog inhibits the DNA-dependent RNA polymerase of Escherichia coli, simultaneously competing with the natural substrate, i.e. UTP. The inhibition constant (Ki = 30 μm) shows that the uracil analog of thuringiensin is an inhibitor of RNA polymerase roughly as efficient as thuringiensin.
Analysis of adsorption kinetics on zeolites at non isothermal conditions and analysis of the kinetics curves
Authors: Bezus Arkadij , Zikánová Arlette , Smutek Miloš , Kočiřík Milan
Published: August 2011

Adsorption kinetic curves were numerically simulated for the case of simultaneous mass and heat transfer. Proposed and discussed are different methods of model testing, experimental curves fitting and of evaluation of the diffusion and heat transfer coefficients from experimental kinetic curves.
Syntheses and properties of substituted icosahedral carborane thiols
Authors: Plešek Jaromír , Heřmánek Stanislav
Published: August 2011

Syntheses of twelve C-SH and eight B-SH carborane thiols of the formula HS,X-C2B10H10 (X = H, Hlg, CH3) and some of their properties ( pKa, RF, 1H-, 11B-NMR) are described. All compounds are crystalline. For C-SH compounds a new convenient route was elaborated. B-SH compounds were prepared directly from substituted carborane, sulfur and AlCl3.
Effects of salts on the kinetics of oxidation of alkenes by thallic salts in aqueous solutions
Authors: Strašák Milan , Majer Jaroslav
Published: August 2011

The kinetics of oxidation of alkenes by thallic sulphate in aqueous solutions, involving the two reaction steps-the hydroxythallation and the dethallation - was studied, and the effect of salts on the kinetics was examined; this made it possible to specify more precisely the reaction mechanism and to suggest a qualitative model of the reaction coordinate. It was found that in homogeneous as well as in heterogeneous reaction conditions, the reaction can be accelerated appreciably by adding tetraalkylammonium salts. These salts not only operate as catalysts of the phase transfer, but also exert a significant kinetic effect, which can be explained with a simplification in terms of a stabilization of the transition state of the reaction.
Reactions of Ge(IV) with aminocarboxylic and aminohydroxylic chelones
Authors: Mikanová Eva , Mikešová Milena , Bartušek Miloš
Published: August 2011

Reactions of GeO2 with eight chelones were studied in dilute aqueous solutions by using the potentiometric neutralization titration method. The equilibrium formation constants were determined for the Ge(OH)Y- and Ge(OH)(HY) complexes with EDTA, Ge(OH)2Z- complex with NTA, and Ge(OH)(OH2) complex with TEA. The conditions for formation of Ge(IV) chelates with chelones are discussed.
The atomic absorption spectrometry of molybdenum in the presence of sulphonated aromatic compounds
Authors: Komárek Josef , Mahr Vít , Sommer Lumír
Published: August 2011

The effect of sulphonated aromatic compounds on the atomization of molybdenum in acetylene-air and nitrous oxide-acetylene flames was studied. The absorbance signal is increased in the presence of these compounds only in acetylene-nitrous oxide flames and in the presence of potassium or sodium salts. Otherwise, the absorbance is decreased. The probable mechanism of the effect of sulphonated aromatic groups during the atomization of molybdenum is discussed. The determination in the presence of 0.1M 5-sulphosalicylic acid and 9.5 mg ml-1 KCl is without interference and has high sensitivity.
CNDO/2 study of interaction of 1-methyl-1,4-dihydronicotinamide and acetaldehyde
Authors: Krechl Jiří , Kuthan Josef
Published: August 2011

The CNDO/2 method has been used for evaluation of energy relations between some configurations of 1-methyl-1,4-dihydronicotinamide (I) - acetaldehyde (II) supermolecule. Stabilization energies have been estimated for formation of the configuration type A,B and C, the energetically most favourable situation corresponding to the formulas IIIa and IIIb. Characters of some MO's and CNDO/2 and INDO electron distributions are discussed with respect to biochemical aspects of the interaction of NADH and acetaldehyde.
Stable 2H-pyran derivatives accessible by cyclocondensation of p-substituted benzoylacetonitriles
Authors: Kuthan Josef , Paleček Jaroslav , Valihrach Jiří
Published: August 2011

The 2H-pyrans IIa-f can be prepared by thermal cyclocondensation of the ketonitriles Ia-f. The alternative structure III of the compounds obtained has been excluded unambiguously on the basis of spectral data. The compounds VII to XI have been isolated as byproducts of the said cyclocondensation of the compound Ia in acetic acid with catalysis of ammonium acetate. Probable course of the reaction investigated is discussed.
Polymorphism of cow colostrum proteinase inhibitor
Authors: Jonáková Věra , Čechová Dana , Mach Otakar
Published: August 2011

Cow colostrum contains three isoinhibitors A, B, and C, which are glycoproteins. In this study isoinhibitor A was isolated and characterized and the structure of its protein moiety compared with the known protein structures of isoinhibitors B and C. It was found that the primary structure of isoinhibitor A is identical with the primary structure of isoinhibitor B except that the C-terminus of its molecule is shorter by five amino acid residues. Four discrete chromatographic forms (I-IV) with different isoelectric points (pI 3.8 - I, 4.0 - II, 4.3 - III, and 4.5 - IV) were isolated by chromatography on SE-Sephadex, Form I is identical with isoinhibitor A. Forms II, III, and IV are represented by mixtures of isoinhibitors A, B, and C with a heterogeneous carbohydrate moiety which affects the total net charge of the individual inhibitor forms.
Determination of heats of vaporization and some other thermodynamic quantities for three fluorinated halogen ethanes
Authors: Majer Vladimír , Svoboda Václav , Pošta Antonín , Pick Jiří
Published: August 2011

Some thermodynamic properties were investigated for three fluorinated halogen ethanes: 1-bromo-2-chloro-1,1,2-trifluoroethane, 1,2-dibromotetrafluroethane and 1,2-dibromo-1-chlorotrifluoroethane. The temperature dependence of heats of vaporization, saturated vapour pressures, densities and refractive indices was measured at two temperatures. On the basis of the experimental quantities obtained, the standard heats of vaporization and the cohesive and internal energies of vaporization in their dependence on temperature were determined.
The effect of phenyl substituents on elimination stereochemistry: A mechanistic manifold in alkoxide promoted decomposition of 1-phenyl-1-propyltrimethylammonium ion
Authors: Machková Zuzana , Závada Jiří
Published: August 2011

Reactions of the positionally isomeric 1-phenyl-1-propyl (I) and 1-phenyl-2-propyltrimethylammonium (II) ions with CH3OK-CH3OH, t-C4H9OK-t-C4H9OH and t-C4H9OK-C6H6 systems have been investigated with aid of the deuterated analogues erythro-2-D-I, threo-2-D-I, 1-D-I and threo-1-D-II. A least five mechanistic components (anti-β-elimination, syn-β-elimination, α',β-elimination, Sommelet-Hauser rearrangement and SN2substitution) have been found to participate in the reaction of the quaternary compound I, in proportions varying greatly with base-solvent combination. The corresponding reactions of the isomeric compound _____CHYBI_CISLO_____ proceeded in a more simple manner, without the intervention of ylide pathways in the olefin as well as in the amine formation. The stereochemistry of β-elimination determined for the two phenyl-substituted 'onium compounds has been compared with that reported previously for structurally related aliphatic analogues. The anomalously low propensity for syn-elimination as well as the anomalously high values of trans/cis-olefin ratios in anti-elimination stigmatizing the presence of phenyl substituents are proposed to originate from a lack of base-approach hindrance in the reaction.
The effect of base concentration on orientation in E2 reactions: A common feature in metal alkoxide promoted olefin formation from alkyl halides and tosylates
Authors: Závada Jiří , Pánková Magdalena , Bartsch Richard A. , Cho Bong Rae
Published: August 2011

The title effect has been investigated in the reactions of three 2-butyl (X = I, Br, OTs) and four 2-decyl (X = I, Br, Cl, OTs derivatives with t-C4H9OK/t-C4H9OH, t-C4H9OK/tetrahydrofuran and t-C4H9ONa/t-C4H9OH as the base-solvent system. It has been found that a gradual increase of base concentration induces marked changes in positional as well as geometrical orientation by simultaneously increasing the 1-alkene/2-alkene and cis-2-alkene/trans-2-alkene ratios. The variations in orientation observed for the different substrates and/or base-solvent combinations are very similar. Concentration-dependent competition of dissociated and associated alkoxide species in the reaction or concentration-dependent solvation of leaving group by metal alkoxides are proposed to account for the changes in orientation.
IR spectra of some quinone methides. A study of the ortho-effect
Authors: Velek Jiří , Koutek Bohumír , Musil Lubomír , Vašíčková Soňa , Souček Milan
Published: August 2011

Experimental values of frequencies and integrated intensities of carbonyl stretching vibrations in sixteen 2- and 2,6-substituted fuchsones were correlated with electronic substituent constants σ and steric parameters . For disubstituted fuchsone derivatives the ortho-effect is additive and is adequately described by the relationship *u(C=O) = 35.6 ΣσI - 9.1 Σ* + 1 625.5 (t = 0.982) and A(C=O)1/2 = -33.2 ΣσI - 1281 Σ* + 141.1 (r = 0.942). Wavenumber and integrated intensity of the carbonyl band decrease with increasing van der Waals volume of substituents. Contribution of the steric effect to the total transmission is substantially higher (about 30%) for 2,6-disubstituted than for 2-monosubstituted fuchsones.
Semiempirical and ab initio study of the nature of the C-S bond in sulfonium ylides
Authors: Král Vladimír , Arnold Zdeněk , Havlas Zdeněk
Published: August 2011

The importance of d-orbitals for the interpretation of properties of sulfonium ylides is demonstrated on the basis of semiempirical and ab initio calculations. The calculated C-S bond length values are sensitive to inclusion of d-orbitals into the AO basis set. Even a high quality basis (4-31 G) without d-orbitals leads to C-S bond lengths which are significantly larger than the experimental ones whereas bases including d-orbitals afford satisfactory agreement. Inclusion of d-orbitals results in charge reduction on the atoms C and S and in a substantially increased order of the bond between these atoms. The decrease of total energy which results from inclusion of d-orbitals is related to (d-p)π bonding overlap between the atoms S and C.
Coupling constants nitrogen-15-nitrogen-15 and nitrogen-15-hydrogen in phenylhydrazones forming hydrogen bond
Authors: Lyčka Antonín , Šnobl Dobroslav
Published: August 2011

Absolute values of the coupling constants 1J(15N15N), 1J(15NH) of six phenylhydrazones forming hydrogen bond, 2J(15N15NH) of four, and 4J(15NH) of two phenylhydrazones have been determined. Three coupling constants 1J(15N15N) have been obtained from the nitrogen-15 monolabelled compounds by measuring the other nitrogen at natural abundance. The coupling constants 2J(15N15NH) have been measured with the nitrogen-15 doubly labelled compounds, because in the arrangement 15N14NH there exists a broadening of the proton signal due to nitrogen-14. Absolute values of the coupling constants 1J(15N15N) of the phenylhydrazones forming hydrogen bond to the ester group are smaller ( 10.8 Hz) than those of the phenylhydrazones having hydrogen bond to carbonyl group ( 11.1 Hz). The coupling constants 2J(15N15NH) have a value 2.4 ± 0.2 Hz. The value of 1J(15N15N) of 1-phenylazo-2-naphthalenol decreases with increasing content of hydrazone form. The values of 2J(15N15NH) of this compound are within 1.2 to 1.6 Hz.
Electrooxidation of 2-arylfurans
Authors: Janda Miroslav , Šrogl Jan , Dvořáková Hana , Dvořák Dalimil , Stibor Ivan
Published: August 2011

Electrochemical methoxylation of 2-phenylfuran (I) and 2-(4-nitrophenyl)furan (VI) proceeded anomalously, affording 5-methoxy-2-phenylfuran (XI) and 5-methoxy-2-(4-nitrophenyl)furan (XIII), respectively. 2-Phenyl-5-methylfuran (II) and methyl-2-(2-methylphenyl)-3-furoate (VIII) behaved normally giving the respective 2,5-dimethoxy-2,5-dihydrofuran derivatives XII and XIV. The suggested ECNECB mechanism of the anomalous methoxylation was confirmed by methoxylation of compound II, in which the methyl group hinders the last CB step, and also of compound VIII in which the automaticity is suppressed by forced deviation from planarity. Forced deviation from planarity was moreover studied also on 2-(4-methylphenyl)furan (III), 5-methyl-2-(2-methylphenyl)furan (IV) and 3,5-dimethyl-2-(2-methylphenyl)furan (V) as model compounds. For all the derivatives the INDO charges were calculated and correlated with the 1H- and 13C-NMR spectra. The experimental electronic spectra were correlated with the theoretical ones (INDO-S-CI). All the results obtained confirm the suggested mechanism.
Preparation and absolute configuration at C(20) of 21-nor-5α-chol-22-en-24→20-olide derivatives
Authors: Pouzar Vladimír , Havel Miroslav
Published: August 2011

Reaction of the aldehyde I with the lithium salt of 1-(2-tetrahydropyranyloxy)-2-propyne yielded the compounds II and IV. From the compound II the lactone XII was prepared via the intermediates III and X, the lactone XVIII was prepared from the substance IV via the intermediates V and XVI. The unsaturated lactones XII and XVIII were also prepared by sulfenylation and dehydrosulfenylation of the saturated lactones XIII and XIX. Based on chemical correlation and 1H-NMR spectra analyses of the compounds II and IV, the lactone XII was assigned the 20R-configuration whereas the lactone XVIII was allotted the 20S-configuration.
Preparation of conjugates of uridine with proteins by the imido ester condensation method
Authors: Pischel Helmut , Holý Antonín , Wagner Günther
Published: August 2011

Reaction of 5'-O-p-toluenesulfonyl-2',3'-O-isopropylideneuridine (I) with sodium 4-cyanophenoxide afforded 2',3'-O-isopropylidene-5'-O-(4-cyanophenyl)uridine (II) which was converted by acid hydrolysis into 5'-O-(4-cyanophenyl)uridine (IIIa). Acid-catalyzed addition of ethanol to compound IIIa gave the imido ester hydrochloride IIIb which on reaction with ammonia or ethylamine was transformed into the amidine derivatives IIIc and IIId. Compound IIIb reacted with human serum albumine or bovine gamma-globuline at pH 9.2 to give protein conjugates with uridine, bound covalently by an amidine bond (IIIe,f).
Contribution to the analysis of liquid macroflow in a cylindrical vessel with a high speed impeller
Authors: Medek Jaroslav , Fořt Ivan
Published: August 2011

In hitherto published studies the investigation of liquid macroflow in a vessel with an impeller has been concentrated mostly on the assessment of the volumetric flow rate through the impeller. Due to molecular and turbulent diffusion, however, significant exchange of mass and momentum occurs between this flow and the neighbouring charge. The extent of this induced volumetric flow rate has not been systematically investigated. This contribution attempts at the assessment of the induced, and total volumetric flow rate components in a vessel, in the plane of rotation of the lower edge of an impeller with flat inclined blades, in dependence on the blade number and the inclination angle between the blade and this plane.
Titrimetric determination of cobalt, nickel and lanthanoids in alloys for novel permanent magnets using ion selective electrodes
Authors: Kalavská Dagmar , Košturiak Adam , Kalavský Svetozár
Published: August 2011

A procedure of chelatometric determination of cobalt, nickel and lanthanoids based on back titration with Cu(II) ions using copper ion selective electrode has been developed and applied to alloys for novel type permanent magnets. In addition, a method has been worked out for direct titrimetric determination of lanthanoids with solution of fluoride ions in 75% ethanol using fluoride ion selective electrode.
Influence of structure of some azo compounds on their acid-base properties and reduction
Authors: Madajová Vlasta , Zelenský Imrich
Published: August 2011

A series of azo compounds were prepared and their acid-base equilibria in aqueous-alcoholic solutions were studied in dependence on the pH. The oxidation-reduction properties of the compounds and of their reduction products were examined polarographically and by preparative electroreduction. The effect of substituents at the azo group on the examined properties of the compounds is discussed.
Activity and selectivity of cobalt, nickel and copper catalysts for hydrogentaion of lauronitrile
Authors: Pašek Josef , Kostova Nina , Dvořák Bohumír
Published: August 2011

Cobalt and nickel metal powders possessing various specific surface areas were prepared by decomposition of their salts under hydrogen. The activity of the metals for hydrogenation of lauronitrile was found to be proportional to their specific surface areas. Oxide carriers do not affect the specific activity of the metals. The relative specific activities of the metals are in the ratio Ni : Co : Cu = 20 : 10 : 1. Pure nickel affords 2.3 times more secondary amine than cobalt; on copper catalyst, secondary amine is formed predominantly.
Kinetics of hydrogenation of cyclic butadiene oligomers on palladium catalysts. Cyclooctadiene isomers
Authors: Hanika Jiří , Svoboda Ivan , Růžička Vlastimil
Published: August 2011

Kinetics of hydrogenation of 1,3- and 1,5-cyclooctadiene and cyclooctene on palladium support catalysts (Pd/CaCO3, Pd/γ-Al2O3) were measured in heptane solutions at 300 K and atmospheric pressure of hydrogen. The kinetic constants were obtained by relating the experimental data to a kinetic model in which the partial reactions are assumed to be 1 st order.
Components of Senecio nemorensis var. subdecurens
Authors: Jizba Josef , Laudová Věra , Samek Zdeněk , Ubik Karel , Novotný Ladislav
Published: August 2011

From the root of Senecio nemorensis L. var.subdecurens Girsb. ex Pantocs. a mixture of the following compounds was isolated: sesquiterpenic hydrocarbons of mass 204 and paraffinic hydrocarbons C11 - C13, a secondary paraffinic alcohol - ginnol a mixture of triterpenic alcohols bauerenol and lupeol, a mixture of caretenoids, a mixture of phytosterols, i.e. β-sitosterol, stigmasterol, D-aromadendren-4-ol (spathulenol) (I), D-aromadendrane-4β,10α-diol (III), and nemosenin E (1β,10β-epoxy-3β-hydroxy-6β-isovaleryloxyfuroeremophilane (X).
Ribonuclease activiy associated with chick embryo chorioallantoic plasma membranes
Authors: Pristašová Svetlana , Rosenbergová Marta
Published: August 2011

Ribonuclease activiy was found associated with plasma membranes isolated from chick embryo chorioallantoic cells. The enzyme was solubilized with buffered 1% Triton X-100 and purified 40-fold by 1-butanol extraction and gel-filtration on Sephadex G-100. The purified Rnase was found to be free of deoxyribonuclease, alkaline phosphatase and decyclizing 2',3'-phosphodiesterase activities. the enzyme is capable to degrade RNA and polycytidylic acid into acid-soluble oligonucleotides terminated in 3'-phosphate. No nucleoside monophosphates and 2',3'-cyclic nucleoside monophosphates were detected. The optimal pH of RNA and poly C hydrolysis were 7.2 and 7.8, the optimal temperatures 60 and 45°C, respectively. The purified enzyme is thermolabile, and it requires monovalent cations for the full enzyme activity.
Hydrogen and electron transfer from diphenylamine in reaction with coordinated peroxy-radicals and hydroperoxides
Authors: Cholvad Vlado , Tkáč Alexander
Published: August 2011

Reaction of diphenylamine with coordinated peroxy-radicals and various hydroperoxides (tert-butyl hydroperoxide, cumene hydroperoxide, tetraline hydroperoxide) has been studied in non-polar solvents by the EPR method. From this kinetic study the activation energies of H-transfer (105 ± 2 kJ/mol in the temperature range -40 to -10 °C) and e-transfer (97 ± 2 kJ/mol in the temperature range 10 to 50 °C) have been determined. From the activation energies it follows that, in a reaction mixture containing simultaneously a hydroperoxide and initiating peroxy-radicals, oxidation of diphenylamine goes by the both parallel mechanisms until the final concentration of nitroxyl radical reaches the value of about 1.7 . 1021 spin/l.
Existence of a solution of the balance simulation problem
Authors: Dohnal Mirko
Published: August 2011

The balance simulation problem (BSP) is one of the most frequent problems occurring in the design and intensification of integrated chemical technologies. In contrast to the simulation problem, BSP does not always have a solution. It is therefore important to know such values of the independent variables (some parameters of apparatuses and some balance quantities) for which the solution does not exist. To estimate the intervals of the independent variables for which no solution of the BSP exists, the results of a simulation under uncertainty are used.
Spectrophotometric study of the interaction of Chromazurol S and Eriochromazurol B with surface active substances - tensides
Authors: Burešová Irena , Kubáň Vlastimil , Sommer Lumír
Published: August 2011

The acid-base and optical properties of Chromazurol S and Eriochromazurol B in the presence of 1 . 10-6 - 2 . 10-2M solutions of cetylpyridinium bromide, cetyltrimethylammonium bromide and 1-ethoxycarbonylpentadecyltrimethylammonium bromide (Septonex) and 0.001-1.0% w/v solutions of octylphenolpolyethylene glycol ether (Triton X-100), polyoxyethylenemonolauryl ether (Brij 35) and lauryl sulphate sodium salt were determined by graphical and numerical interpretation of absorbance curves. The poorly soluble ion associates, which can be extracted into chloroform and which have the defined composition [LH4-nn-.n T+] or [LH3-nn-.n T+] are formed at submicellar concentration of the tenside. In regions close to the critical micellar concentration of the tenside, soluble binary complexes of the acid-base forms of the reagent are formed with tenside micelles. The conditional stability constants of the reagent acid-base equilibrium depend on the type and concentration of the tenside, on the reagent concentration, on the concentration and type of inorganic acid anions and on the ionic strength of the solution. The mechanism of interaction of the reagent with the tenside and the probable structure of the binary species are discussed.
Ternary complexes of N-carboxymethylaminoacetohydroxamic acid
Authors: Karlíček Rolf , Polášek Miroslav , Jokl Vladimír
Published: August 2011

The formation of N-carboxymethylaminoacetohydroxamic acid complexes in solutions with excess copper(II) or iron(III) ions or both of them was studied. In the presence of Cu(II), the binuclear complex Cu2H-1L+ was identified; in the ternary system, the complex CuFeH-1L+ was found. This complex formation is necessarily associated with the ligand structure >N-CH2.CO-NHOH and with a new property of hydroxamic acids of this type - detachment of two hydrogen ions from one carbohydroxamic functional group.
A calorimetric study of the interaction between n-butyllithium and some electrondonors
Authors: Kmínek Ivan , Kašpar Miroslav , Trekoval Jiří
Published: August 2011

Solvation of n-butyllithium with some ethers and amines was investigated by employing thermometric titration at the initial temperature 303 K. The highest enthalpy changes appear in the reaction of n-butyllithium with dimethoxyethane and N,N,N',N'-tetramethylethylenediamine (ΔH = -48.0 and -51.3 kJ/mol respectively), the lowest are observed in the reaction with diethyl ether and anisole (ΔH = -10.2 and -4.3 kJ/mol respectively). Anomalies in the temperature dependence of these reactions were observed for tetrahydrofuran and dimethoxyethane. The respective entropy changes were calculated for some electrondonors. The replacement of one electrondonor in the complex by another was examined thermometrically.
An investigation of the formation of complexes of n-butyllithium with some electrondonors
Authors: Kmínek Ivan , Kašpar Miroslav , Trekoval Jiří
Published: August 2011

The formation of complexes of n-butyllithium with triethyl amine, tetramethylethylenediamine, tetrahydrofuran and dimethoxyethane was investigated by using the GLC analysis of the gas phase over a solution of organometallic compounds and electrondonor and by the vapour pressure osmometry method (VPO) at 303 K in benzene. A simple general reaction scheme was proposed, involving dissociation of BuLi hexamer followed by coordination. The composition of the complex, its concentration and the equilibrium constant of coordinations were determined by GLC. These parameters were used in VPO measurements of the molecular mass of the complexes. With respect to the type of the electrondonor, the main types of the complexes contain one to four molecules of electrondonor.
Electrochemical and biological oxidation of 1,4-dihydropyridine derivatives
Authors: Kurfürst Antonín , Ludvík Jiří , Rauch Pavel , Marek Miroslav
Published: August 2011

Electrochemical oxidation of 1,4-dihydropyridines I-XII and electrochemical reduction of the nitro group of 4-(2-nitrophenyl)-1,4-dihydropyridines III, VI, IX and XII was studied using cyclic voltametry. When comparing the electrochemical and the biological oxidation of 3,5-dimethoxycarbonyl-2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine (IX, Nifedipine) and related 1,4-dihydropyridines it was found that in spite of certain common trends the oxidation of these compounds (I-XII) in the organism cannot be predicted unambiguously. Of the substances tested compounds IX and XI (3,5-diethoxycarbonyl-4-phenyl-2,6-dimethyl-1,4-dihydropyridine) were the least oxidizable by the respiratory chain, and at the same time they did not inhibit this enzyme system. In addition to this, compound IX was the least oxidizable by the microsomal system.
Delocalization and stability of o- and p-quinone methides: A HMO study
Authors: Musil Lubomír , Koutek Bohumír , Píšová Milena , Souček Milan
Published: August 2011

A series of twenty one p- and o-quinone methides has been investigated by the HMO method. Stability predictions for compounds I-XIII are based on a combination of their topological resonance energy, nucleophilic reactivity and dimerization ability. The obtained results have been verified by the synthesis of four new quinone methides IIb, Vb, VIa and VIb.
Reaction of 1-pyridyl-1,3-butanediones and 1,3-dipyridyl-1,3-propanediones
Authors: Ferles Miloslav , Kafka Stanislav , Šilhánková Alexandra , Šputová Michaela
Published: August 2011

Reduction of diketones I with zinc and formic acid gives monoketones II. Diketones Ia, IIIb, IIIc are converted with hydrazines to pyrazoles VIa, IVa, IVb, V. Methiodides VII are reduced with sodium borohydride to derivatives of 1-methyl-3-piperideine VIII-X.
The synthesis of arylpropionic acids and the quantitative relationship between the structure and the activation of fibrinolysis
Authors: Kuchař Miroslav , Brunová Bohumila , Rejholec Václav , Roubal Zdeněk , Němeček Oldřich
Published: August 2011

A number of substituted 2-arylpropionic (IV) and 3-arylpropionic (V) acids were prepared and their activity in the activation of fibrinolysis and the inhibition of heat denaturation of serum albumin was evaluated. The results were worked up using the method of regression analysis. From the regression equations obtained it may be considered that both activities are affected mainly by the lipophilicity of the aromatic substituents. The effect of the branching in the connecting chain between the carboxyl group and the aromatic ring is negligible in both activities. The linear dependence of the fibrinolytic capacity on lipophilicity is in both series of acids, IV and V, characterized by a distinct decrease in activity, following the attainment of the optimum value of lipophilicity. In the series of cinnamic acids (VI) regression equations concerning the inhibition of the denaturation of serum albumin and the activation of fibrinolysis were also calculated, showing a linear dependence of these activities on the lipophilicity of the varying substituents R and X. Summary regression equations were derived for both activities in the whole set of acids I-VI. Both the inhibition of the denaturation of serum albumin, and the activation of fibrinolysis depends on the lipophilicity of the mentioned acids exclusively. The modification of the connecting chain between the carboxyl group and the aromatic ring affects both activities primarily by the corresponding change in lipophilicity.
Potential metabolites of the neuroleptic agent octoclothepin; Synthesis of 8-chloro-2,6-dihydroxy and 8-chloro-3,6-dihydroxy derivatives of 10-(4-methylpiperazino)-10,11-dihydrodibenzo[b,f]thiepin
Authors: Protiva Miroslav , Šedivý Zdeněk , Pomykáček Josef , Svátek Emil , Holubek Jiří
Published: August 2011

[2-(4-Chloro-2-methoxyphenylthio)-5-methoxyphenyl]acetic acid (V) and [2-(4-chloro-2-methoxyphenylthio)-4-methoxyphenyl]acetic acid (XVII) were synthesized and cyclized to 8-chloro-2,6-dimethoxy (VII) and 8-chloro-3,6-dimethoxydibenzo[b,f]thiepin-10(11H)-one (XVIII). Two further steps afforded dichlorodimethoxy derivatives XI and XXII which reacted with 1-methylpiperazine and gave the 8-chloro-2,6-dimethoxy (II) and 8-chloro-3,6-dimethoxy derivative of 10-(4-methylpiperazino)-10,11-dihydrodibenzo[b,f]thiepin (IV). Demethylations with boron tribromide resulted in the title compounds I and III being new potential metabolites of the neuroleptic agent octoclothepin.
Xanthomegnin and viomellein derivatives from submerged cultures of the ascomycete Nannizzia cajetani
Authors: Sedmera Petr , Volc Jindřich , Weijer Jan , Vokoun Jindřich , Musílek Vladimír
Published: August 2011

Antibacterial metabolites isolated from a submerged culture of the ascomycete Nannizzia cajetani AJELLO grown on wort medium were spectroscopically identified as dimeric naphthoquinone derivatives xanthomegnin (I), viomellein (II), 3,4-dehydroxanthomegnin (III) and two, not previously described pigments: 3',4'-dehydroviomellein (IV) and 3,4,3',4'-bisdehydroxanthomegnin (V).
Time of persistence of a particle in selected state during reversible first-order conversion. Application to crystal growth and dissolution
Authors: Šolc Milan , Hostomský Jiří
Published: August 2011

The distribution of the total time of persistence of a particle in a state A was derived both in an exact and an approximate form on the basis of a probability model of the conversion A ##e B. The result was applied to the probability description of a change in size of one-dimensional crystals in a double crystallizer. The time change of the distribution of the crystal sizes can be described by the Fokker-Planck equation for diffusion with a diffusion coefficient proportional to the square of the sum of values of the growth and dissolution rate constants.