bluuebunny/crossref_metadata_2025 huggingface dataset:
Immobilization of some hydrolases on polymethacrylate by the method of reactive esters
Authors: Kučera Jiří , Kmínková Milena
Published: January 2014

The immobilization of chymotrypsin (EC 3.4.4.5), papain (EC 3.4.4.10), α-amylase (EC 3.2.1.1), amyloglucosidase (EC 3.2.1.3), and of a technical pectolytic enzyme on various reactive polymethacrylate esters (Ostion KM) was examined and compared with the immobilization of the same enzymes on carboxymethyl-cellulose. There is no difference in the individual reactive esters (2,4-dinitrophenyl, N-hydroxysuccinimidyl, ethyl-1-hydroxyacetyl) when enzymes reacting fast (papain, chymotrypsin) are immobilized. The ethyl-1-hydroxyacetyl ester of the support is most suitable for slowly reacting enzymes. The reaction does not proceed at pH-values lower than 7.5. The specific activity of immobilized amylolytic and pectolytic enzymes decreases with the increasing pH because of inactivation of the enzyme.
Electronic absorption spectrum and π-electronic structure of cryptocyanine
Authors: Titz Miloš , Novák Antonín , Řehák Viktor
Published: January 2014

Absorption, fluorescence excitation and APF spectra of cryptocyanine have been measured. Dipole moment of the respective S1 excited state has been estimated from shifts of the marked maximum of the first absorption band in various solvents. On the basis of quantum-chemical calculations carried out by the PPP method in the approximation of quasi-real geometry we have received the optimum model of π-electronic structure of the cryptocyanine molecule and therefrom the theoretical electronic singlet spectrum inclusive character of the S0 - S1 transition.
Electronic aspects of the chlorination of 2,4-dichloropentane as a model for the study of the chlorination of poly(vinyl chloride)
Authors: Bárta Miroslav , Lukáš Rudolf , Kolínský Miloslav
Published: January 2014

The semiempirical quantum chemical method CNDO/2 was used in the calculation of the electronic structure of TT and GG conformers of d,1-2,4-dichloropentane and TG' conformer of meso-2,4-dichloropentane. Relative stability of their model conformations was determined and compared with data of 1H-NMR spectroscopy. The TT conformer of d,l-2,4-dichloropentane was found to possess the highest stability. The chlorination mechanism of 2,4-dichloropentane was discussed using the knowledge of the total electron densities on atoms, frontier orbital electron densities and interatomic bond indices. The INDO method was employed to calculate the spin densities of stereoisomers of 2,4-dichloropentane. Results thus obtained led to a conclusion that the reactivity of monocarbon groups in the chlorination of 2,4-dichloropentane decreased in the order CH3-> -CH2-> -CHCl-.
The optically active 3-ferrocenylalanine and its application in peptide chemistry
Authors: Pospíšek Jan , Toma Štefan , Frič Ivo , Bláha Karel
Published: January 2014

Racemic 3-ferrocenylalanine was resolved in enantiomers using brucine. The absolute configuration was estimated by ozonolytic degradation of the N-trifluoroacetyl derivative of the (-)-enantiomer yielding D-aspartic acid. Diastereoisomeric cyclo(D-ferrocenylalanyl-L-prolyl) and cyclo-(L-3-ferrocenylalanyl-L-prolyl) were synthesized using conventional methods of peptide synthesis. Circular dichroism spectra of these cyclodipeptides are discussed and compared with spectra of the corresponding diastereoisomeric cyclodipeptides containing phenylalanine.
The gass-side mass transfer coefficient and the interfacial area under the turbulent flow over the packing of parallel expanded metal sheets
Authors: Lacina Jan , Brož Zdeněk , Kolář Václav
Published: January 2014

Specific interfacial area has been computed from experimental values of the gas-side volume mass transfer coefficient, kga, and the theoretically derived expressions for gas-side mas transfer coefficient per unit area of interfacial surface, kg. The results have been compared with the specific interfacial area determined experimentally using the chemical method.
Effect of temperature on chiroptical and conformational properties of acyclic ketoses
Authors: Bystrický Slavomír , Sticzay Tibor , Tvaroška Igor
Published: January 2014

Conformational mobility of tetruloses, 2-pentuloses, D-3-pentulose and 4-deoxy-L-pentulose was studied by measuring temperature dependences of CD spectra in the region +40°C to -140°C in a methanol-ethanol (1:4) mixture. The changes in spectra reflect the population of rotamers around bonds to the carbonyl chromophore. The most stable conformers were determined by PCILO quantum chemical calculation.
Carbamates and ureas derived from 11-amino-6,11-dihydrodibenzo[b,e]thiepin; Synthesis and pharmacological screening
Authors: Valenta Vladimír , Bartošová Marie , Protiva Miroslav
Published: January 2014

A series of N-substituted carbamates V-XIII was prepared by reactions of 6,11-dihydrodibenzo[b,e]thiepin-11-ol (I) with carbamates H2NCOOR in acetic acid. Whereas the Leuckart reaction of dibenzo[b,e]thiepin-11(6H)-one yielded 9-formamido-10-methylene-9,10-dihydroanthracene (XVIII), a satisfactory method for preparing the amine III was found in heating the carbamate V with 2-aminoethanol to 170°C. Reactions of the amine III with isocyanates gave most of the disubstituted ureas XX-XXV. The expected anticonvulsant activity was found only in high doses with compounds IX, XII, XV, XX, XXI and XXXIII.
Oxynemorensine, an alkaloid from Senecio nemorensis L., var. subdecurrens GRISEB
Authors: Klásek Antonín , Sedmera Petr , Vokoun Jindřich , Boeva Anna , Dvoráčková Svatava , Šantavý František
Published: January 2014

From S. nemorensis L., var. subdecurrens GRISEB. there were isolated the previously obtained alkaloids nemorensine (I), retroisosenine (II), bulgarsenine (III) and, in addition, the alkaloid oxynemorensine which was assigned the structure VIII on the basis of the interpretation of the 1H-NMR, 13C-NMR, mass spectra, and on that of the identification of the products of hydrolysis and reduction. Furthermore, the isolation of the cis-nemorensic acid (V) as well as that of the unsaturated acid IV, and the transformation of bulgarsenine (III) to nemorensine (I) were described.
Alpha- and beta-amylase immobilized by a covalent binding to hydroxyalkyl methacrylate gels
Authors: Babor Karol , Rexová-Benková Lubomíra
Published: January 2014

Insoluble active preparation of alpha- and beta-amylase were prepared by a covalent binding of enzymes to hydroxyalkyl methacrylate gel (various kinds of Spheron type) activated with cyanogen bromide. The amount of the bound enzyme, its amylolytic activity on individual substrates, storage and heat stabilities, and pH-optimum were determined.
Removing of phenol from waste waters by oxidation to melanin with mushroom polyphenoloxidase
Authors: Vedralová Eliška , Pechan Zdeněk , Duchoň Jiří
Published: January 2014

Phenol can be removed from cokery effluents by oxidation to melanin on the action of mushroom polyphenoloxidase. Under optimum conditions - pH 8.8, temperature 30°C - 98% phenol can be removed in this manner within 48 h.
Spectrophotometric study of the reaction of dyes of the alizarin green series with indium(III) ions in the presence of cationic tensides
Authors: Son Nguyen Truong , Ružička Eduard
Published: January 2014

The reactions of four dyes of the alizarin green series with indium(III) ions were studied. In weakly acid media of pH 4-6.5, binary InL and InL2 complexes are formed in solution. In the presence of cationic tensides containing cetyltrimethylammonium and cetyl pyridinium, defined ternary complexes, InL3S6, are formed in the solution. The conditional stability constants of the binary In-L complexes and the equilibrium constants of the studied complexing ternary systems were calculated and a procedure for the photometric and chelometric determination of indium was proposed.
Alkaline hydrolysis of pivalic esters of ethylene glycol in water-acetone solutions
Authors: Ševčík Stanislav , Kubín Miroslav , Štamberg Jiří
Published: January 2014

The paper reports alkaline hydrolysis of ethylene dipivalate and 2-hydroxyethyl pivalates as compounds modelling the structural unit and crosslinking site of hydrophilic gels, i.e. copolymers of 2-hydroxyethyl methacrylate and ethylene dimethacrylate. The kinetics of hydrolysis was investigated in water-acetone solutions containing respectively 50, 75, 80, 85 and 90% by vol. (related to 20°C) of acetone at 20, 30, 40, and 50°C. It was demonstrated that, owing to steric hindrance, the preferential hydrolysis of monoester was more pronounced in the case of pivalic esters of ethylene glycol compared with acetic esters of ethylene glycol. The results are discussed in connection with the selectivity of the alkaline hydrolysis of ester bonds in "pendant" parts of structural units in hydrophylic methacrylate gels.
Synthesis of trisubstituted ethylenes of the furan series based on 5-methoxycarbonyl-2-furfuryl trichloromethyl sulfone
Authors: Jurášek Adolf , Kováč Jaroslav , Belko Rudolf
Published: January 2014

Condensation of 5-methoxycarbonyl-2-furfuryl trichloromethyl sulfone with 4-X-benzaldehydes (X = H, OH, OCH3, N(CH3)2, Cl, I, CN) or 5-Y-2-furaldehydes (Y = H, NO2) in acetic acid in the presence of ammonium acetate and piperidine afforded the corresponding 1-(5-methoxycarbonyl-2-furyl)-1-trichloromethylsulfonyl-2-arylethylenes (IIa-IIj). Structure of these new compounds is discussed on the basis of their UV, 1H-NMR and IR spectra.
The conversion of 5-nitrofurfuryl derivatives into 5-aminofurfurylidenemalonodinitrile
Authors: Považanec František , Kováč Jaroslav , Hesek Dušan
Published: January 2014

The reaction of 5-nitrofurfuryl bromide or 5-nitrofurfuryl iodide with sodium azide and malonodinitrile afforded 5-aminofurfurylidenemalonodinitrile. The intermediate of the reaction is 5-nitrofurfuryl azide which decomposes to give 5-nitrofurfurylideneamine. Its reaction with malonodinitrile gives 5-nitrofurfurylidenemalonodinitrile which reacts further with sodium azide and malonodinitrile to give 5-aminofurfurylidenemalonodinitrile.
Alkaloids from Papaver rupifragum BOISS. et REUT.
Authors: Slavíková Leonora , Slavík Jiří
Published: January 2014

The following alkaloids were isolated from Papaver rupifragum BOISS. et REUT.: rhoeadine, protopine, rhoeagenine, magnoflorine and very small amounts of coptisine, cryptopine and (-)-stylopine. The presence of isorhoeadine, allocryptopine, corytuberine, papaverrubine A, B, C, D and E and corysamine was also detected.
First passage time for the state of exact chemical equilibrium
Authors: Šolc Milan
Published: January 2014

The establishment of chemical equilibrium in a system with a reversible first order reaction is characterized in terms of the distribution of first passage times for the state of exact chemical equilibrium. The mean first passage time of this state is a linear function of the logarithm of the total number of particles in the system. The equilibrium fluctuations of composition in the system are characterized by the distribution of the recurrence times for the state of exact chemical equilibrium. The mean recurrence time is inversely proportional to the square root of the total number of particles in the system.
Study of some properties of dithiocarbamates derived from heterocyclic amines
Authors: Kúdela Štefan , Garaj Ján , Hofbauerová Helena , Kettmann Viktor
Published: January 2014

Some physicochemical properties of sodium pentamethylenedithiocarbamate and complexes with Cu(II), Ni(II), and Fe(III) were studied. The bands in the electronic and IR absorption spectra were measured and characterized, and the possibility of coulometric determination of NaS2CN(CH2)5.2 H2O was examined. The conditions for spectrophotometric determination of trace quantities of Cu(II), Ni(II), and Fe(III) as dithiocarbamate complexes were established and the stability constants of the complexes were determined.
Oxydation des N,N-dimethyl-4-amino-4'-hydroxyazobenzols mit verbindungen des dreiwertigen mangans
Authors: Barek Jiří , Berka Antonín , Borek Vladimír
Published: January 2014

without abstract
ν(C-F) in some organosilicon compounds
Authors: Jakoubková Marie , Papoušková Zlata , Chvalovský Václav
Published: January 2014

IR absorption spectra of compounds of the type (CH3)3MCH2F (M = C, Si), (CH3)3MCH2Cl (M = C, Si, Ge, Sn), (CH3)3SiCH2X (X = Br, I), (CH3)3Si(CH2)2Cl, Cl3Si(CH2)2X (X = F, Cl) and (CH3)3Si(CH2)3X (X = F, Cl) have been measured and interpreted.. Solvent effects on ν(C-F) around 1 000 cm -1 have been investigated.
The oxygen basicity strengthening effect in peroxides
Authors: Pola Josef , Chvalovský Václav
Published: January 2014

The hydrogen-bonding ability of peroxides R3MOOM'R'3 having M = C, Si and Ge with phenol in CCl4 is analyzed. The oxygen basicity of the R3MOOM'R'3 with M = C and Si is indicated to be increased over the ability of the electronic effect of R3C- and R3Si- groups probably due to the interaction between lone electron pairs located at the oxygen atoms.
Synthesis of a series of positionally isomeric methyl O-(α- and β-D-xylopyranosyl)-β-D-xylopyranosides
Authors: Kováč Pavol
Published: January 2014

Crystalline α- and β-(1(r)2, 1(r)3 and 1(r)4)-linked methyl β-D-xylobiosides have been obtained by procedures based on condensation of 2,3,4-tri-O-acetyl-α-D-xylopyranosyl bromide with positionally isomeric methyl di-O-acetyl-β-D-xylopyranosides, followed by deacetylation. Per-O-acetates of the isomeric methyl β-D-xylobiosides were also obtained crystalline. The β-linked disaccharide methyl glycosides, methylated on a preparative scale, gave crystalline fully methylated products.
Nucleophilic substitution reaction of methyl 2-bromoethyl-3-(2-furyl)propenoate with amines
Authors: Žvak Vladimír , Kováč Jaroslav , Kríž Miroslav
Published: January 2014

Nucleophilic replacement of bromine in methyl 2-bromomethyl-3-(2-furyl)propenoate by amines (piperidine, morpholine, N-methylaniline, diethylamine and tert-butylamine) was studied. In all cases only products of direct substitution of bromine were obtained; this shows that a 2-furyl group in γ-position of an allylic system plays a decisive role in the change of mechanism, characteristic for keto allylic mobile systems.
Synthesis and properties of 5-phenoxyfurancarboxylic acids
Authors: Knoppová Viera , Beňo Anton , Kováč Jaroslav
Published: January 2014

Furancarboxylic acids were prepared by oxidation with Ag2O of the corresponding 5-(X-phenoxy)-2-furaldehydes (X = 4-OCH3, 4-SCH3, 3-NHCOCH3, 4-Cl, 4-Br, 4-COOC2H5, 3-NO2, and 4-NO2. The appearing pKa values of the synthesized acids were determined by potentiometric titration. The transfer effect of the substituents through the oxygen bridge is discussed and the transfer coefficient is compared with π' values of other linking groups in the furan series.
Quaternary alkaloids of some species of the Papaveraceae family
Authors: Slavík Jiří , Picka Karel , Slavíková Leonora , Táborská Eva , Věžník František
Published: January 2014

Quaternary alkaloids of the following species of Papaveraceae were studied. From Hunnemannia fumariaefolia SWEET cyclanoline, escholidine and alkaloid HF3 were isolated, from Papaver atlanticum BALL magnoflorine, from P. caucasicum MARSCH.-BIEB., P. dubium L. and P. litwinowii FEDDE ex BORNM. aporheine methohydroxide, and from P. pseudo-orientale (FEDDE) MEDW. a new alkaloid, isothebaine methohydroxide were isolated. In P. confine JORD. magnoflorine was found and in two chemotypes of P. rhoeas L. β-stylopine methohydroxide and aporheine methohydroxide could be proved.
Investigation of drug-protein interactions and the drug-carrier concept by the use of branched polypeptides as model systems. Synthesis and characterization of the model peptides
Authors: Hudecz Ferenc , Szekerke Mária
Published: January 2014

Synthesis of branched polypeptides with a new design of variations in surface topography is described. The side chains of the poly(Lys-(DL-Alam)) were elongated by single amino acids (L-Tyr, L-Glu, L-His, L-Leu, L-Pro, L-Phe) or short polymers (L-, D-Glu, L-Tyr, L-, D-, DL-Lys). Single amino acids were coupled, via the azide, active ester or N-carboxy anhydride method, oligomers were grafted by the polymerisation of N-carboxy anhydride derivatives. The resulting polypeptides were characterised by amino acid analysis, identification of the N-terminal residue of the chain ends, determination of the sedimentation coefficient and molecular weight estimation, based on sedimentation experiments and thin layer gel chromatography.
Kinetics of inhibition of acetylcholinesterase by 9-hydrazino-1,2,3,4-tetrahydroacridine and 9-amino-10-methyl-1,2,3,4-tetrahydroacridinium in vitro
Authors: Patočka Jiří , Bajgar Jiří , Bielavský Jiří
Published: January 2014

The kinetics was studied of the inhibition of solubilized rat brain acetylcholinesterase by 9-hydrazino-1,2,3,4-terahydroacridine (THH) and 9-amino-10-methyl-1,2,3,4-tetrahydroacridinium (QTHA); the inhibitory effect was compared with the effect of tacrine (9-amino-1,2,3,4-tetrahydroacridine, THA). It was observed that THH is a reversible, noncompetitive inhibitor of rat brain acetylcholinesterase (Ki = 0.16 μM) and that it binds, similarly to THA, to the hydrophobic domain of the active center of acetylcholinesterase thus simultaneously inhibiting the formation of complex ES2 with acetylcholine as substrate. This eliminates the inhibition of acetylcholinesterase by an excess of substrate. QTHA is a mixed, competitive-non-competitive inhibitor characterized by KI comp = 5.3 μM and Ki noncomp = 0.08 μM. QTHA binds to an entirely different site of the active surface of acetylcholinesterase than THA and THH. This binding site is most likely the so-called β-anionic or also peripheric anionic site to which, e.g. atropine is also bound. Both inhibitors studied form with acetylcholinesterase a reversible, enzymatically inactive complex in which one inhibitor molecule is bonded to each active center of the enzyme.
Periodic longitudinal flows of pseudoplastic materials
Authors: Wein Ondřej , Sobolík Václav
Published: January 2014

A model is studied in the full range of all operational parameters of the unsteady plane flow of a power-law liquid induced by periodically variable pressure drop and oscillatory motion of the walls of a plane duct. Using the theory of similariry criteria of the asymptotic behaviour are formulated in four qualitatively different rheodynamic regimes. Corresponding asymptotic expressions are found for the degree of mechanical liquidization by the action of oscillatory shear stress superimposed on the principal steady state component. Theoretical results are illustrated using a set of experimental data on the gravitational flow along a vertical oscillating sheet.
An analytical equation derived from a perturbation theory to calculate Henry's constants for square well mixtures
Authors: Guerrero M. I. , Ponce L. , Monfort J. P.
Published: January 2014

An analytic form for Henry's constant is derived and applied to several systems. The derivation is based on the use of Leonard-Henderson-Barker perturbation theory for a square well pair potential assuming the Ponce-Renon analytical solution of the square well fluid. Computed values of Henry's constants for CH4-Ar, CH4-N2, CH4-He, CH4-H2, C2H6-N2 and C2H6-CH4 mixtures are compared with experiment. The agreement is quite satisfactory, with mean relative deviations between 2.5 and 8 per cent. Heats of solutions are also computed and compared with experiment.
Hydrolysis kinetics and mechanism of N'-(3-N-methylcarbamoyloxyphenyl)-N,N-dimethylformamidine
Authors: Čegan Alexandr , Šlosar Jaroslav , Večeřa Miroslav
Published: January 2014

Hydrolysis of N' -(3-N-methylcarbamoyloxyphenyl)-N,N-dimethylformamidine (I) has been studied in mixture water-dioxane (4 : 1) at pH 1 to 13. The hydrolysis rates of methylcarbamoyl and dimethylformamidine groups are comparable within pH range 4 to 10, and they differ by as much as several orders of magnitude in pH ranges 1-3 and 11-13. The hydrolysis products of the whole pH range have been determined by paper chromatography, and reaction mechanism has been suggested on the basis of the measured hydrolysis rate constants.Effects of protonation and hydratation of dimethylformamidine group on the hydrolysis rate of the methylcarbamoyl group is discussed.
Polarographic study of hydrolysis of [8-lysine]vasopressin and its derivatives with blood serum of pregnant women
Authors: Chavko Mikuláš , Bartík Michal , Kasafírek Evžen
Published: January 2014

A polarographic study of the hydrolysis of [8-lysine]vasopressin and some hormonogens of the vasopressin series with the blood serum of women in the last week of pregnancy was studied. The dependence of hydrolysis on pH (pH optimum: 7.4-7.50, substrate concentration (Km 1.2 . 10-5M), pH stability and thermal stability were determined. The rate of hydrolysis of individual vasopressin analogues decreases in the order: [8-lysine]vasopressin > Nα-glycyl-prolyl[8-lysine]-vasopressin > Nα-leucyl-[8-lysine]vasopressin > Nα-alanyl-[8-lysine]vasopressin > Nα-phenyl alanyl-[8-lysine]vasopressin > Nα-diglycyl-[8-lysine]vasopressin > Nα-prolyl-[8-lysine]vasopressin > Nα-triglycyl-[8-lysine]vasopressin > Nα-sarcosyl-glycyl-[8-lysine]vasopressin. The degree of hydrolysis gradually increases to a multiple with the length of the pregnancy in consequence of the presence of oxytocine. However, vasopressin is also hydrolysed to a small extent with the enzymes from the blood sera of non-pregnant women. Under similar analytical conditions oxytocin was not hydrolysed with the sera of non-pregnant women and therefore oxytocin is a more suitable substrate than vasopressin for polarographic determination of serum oxytocinase.
C-Terminal amino acid sequence of chicken pepsinogen and its homology with sequences of other acid proteases
Authors: Baudyš Miroslav , Keilová Helena , Kostka Vladimír
Published: January 2014

To determine the primary structure of the C-terminal part of the molecule of chicken pepsinogen the tryptic, chymotryptic and thermolytic digest of the protein were investigated and peptides derived from this region were sought. These peptides permitted the following 21-residue C-terminal sequence to be determined: ...Ile-Arg-Glu-Tyr-Tyr-Val-Ile-Phe-Asp-Arg-Ala-Asn-Asn-Lys-Val-Gly-Leu-Ser-Pro-Leu-Ser.COOH. A comparison of this structure with the C-terminal sequential regions of the other acid proteases shows a high degree of homology between chicken pepsinogen and these proteases (e.g., the degree of homology with respect to hog pepsinogen and calf prochymosin is about 66%). Additional tryptic peptides, derived from the N-terminal part of the zymogen molecule whose amino acid sequence has been reported before, were also obtained in this study. This sequence was extended by two residues using an overlapping peptide. An ancillary result of this study was the isolation of tryptic peptides derived from other regions of the zymogen molecule.
Liquid-vapour and liquid-liquid equilibria in the tetrahydrofuran(1)-n-hexane(2)-water(3) system
Authors: Lampa Jiří , Matouš Jaroslav , Novák Josef P. , Pick Jiří
Published: January 2014

The object of this work is the isobaric vapour-liquid equilibrium (at 101.32 kPa) and the liquid-liquid equilibrium (at 30 and 50°C) in the ternary tetrahydrofuran-n-hexane-water system. Further, the isobaric vapour-liquid equilibrium (at 101.32 kPa) in the binary tetrahydrofuran-n-hexane and tetrahydrofuran-water systems has been established. The experimental data obtained have been fitted to the Redlich-Kister equation. The constants of the correlation relation determined from the data on the vapour-liquid equilibria have been proved to provide an adequate description of the liquid-liquid equilibrium.
Kinetics and mechanism of the redox reaction of thallic sulphate with acroleine
Authors: Treindl Ľudovít , Melicherčík Milan
Published: January 2014

The stoichiometry, kinetics and mechanism of the redox reaction of thallic sulphate with acroleine in aqueous sulphuric acid or in aqueous dioxane solutions were studied. The acroleine molecule is oxidised with Tl(III) ions in two consecutive one-electron steps to glyceraldehyde. The corresponding rate equation is -d[Tl(III)]/dt = k[Tl(III)]n [A], where n = 0-2. The zeroth reaction order with respect to thallic ions is attributed to a slow enolization of the hydrated acroleine, which is the rate-determining step preceding the redox reaction proper.
Kinetics of a monomolecular reaction between n components
Authors: Jakeš Jaromír
Published: January 2014

The reaction kinetics has been investigated of a general monomolecular reaction between n components, where reactions between some components are reversible and between others irreversible. The reacting components may be divided into groups so that all the components inside one group may change reversibly into each other, while reactions between components of different groups are irreversible. The reaction kinetics for each reversible group may be found similarly to the case where all the reactions are reversible; solutions for the individual reversible groups may be used to obtain solution for the whole system. A solution was also found to a difficult case in which matrices have multiple eigenvalues for irreversible consecutive reactions, namely, for a general case of degeneracy. Formulas are given for the calculation of derivatives of concentrations of the individual components with respect to parameters. The equations thus derived were applied to the reaction kinetics of a polymeranalogous reaction (e.g., hydrolysis of polyacrylonitrile).
Quantum chemical study of sulfonium ylides: Structure, charge distribution and dipole moments
Authors: Král Vladimír , Arnold Zdeněk , Jehlička Václav , Exner Otto
Published: January 2014

The geometry, charge distribution and dipole moments of parent sulfonium ylide - dimethylsulfoniomethylide (I) - and a series of stabilized sulfonium ylides, including 2-dimethylsulfuranylidene-1,3-cyclopentanedione (VI) prepared in this study, was investigated using the CNDO/2, PCILO and ab initio methods. Values of dipole moments, calculated by quantum chemical methods (CNDO/2 with sp and spd bases, ab initio with the STO-3G basis) as well as by the method of empirical bond moments, are compared with the experimental values determined in dioxane or benzene. Dipole moments of several related ammonium ylides were also studied.
Hydrolysis kinetics and mechanism of acyl-1,3-diphenyltriazenes
Authors: Pytela Oldřich , Večeřa Miroslav , Vetešník Pavel
Published: January 2014

The hydrolysis rate constants of 3-(N-methylcarbamoyl)-1,3-diphenyltriazene (I), 3-(N-phenylcarbamoyl)-1,3-diphenyltriazene (II) and 3-acetyl-1,3-diphenyltriazene (III) have been determined in aqueous media within pH 0 to 14, Ho to 3 and H- to 15. The hydrolysis at pH < 2 and pH > 11 show specific acid and base catalysis, respectively, whereas within pH 2 to 11 non-catalyzed hydrolysis takes place. Activation parameters of the non-catalyzed and catalyzed hydrolysis have been determined. Quantum-chemical calculation of 3-carbamoyltriazene (IV) has been carried out by the MINDO/2 method. Hydrolysis mechanism of the studied compounds is suggested for the non-catalyzed, specific acid catalyzed and specific base catalyzed hydrolysis.
Synthesis of the amino-terminal decapeptide of human calcitonin, in which the disulfide bond is replaced by a thioether group
Authors: Procházka Zdenko , Jošt Karel
Published: January 2014

A fully protected amino-terminal decapeptide Ib with the sequence of human calcitonin, in which the S-S bridge was replaced by the S-CH2 group (a so-called 7-carba-analogue), was synthetized mainly by the stepwise method. The cyclization of the linear decapeptide was performed by means of active ester.
Nature of stationary points on CNDO/2 energy hypersurfaces of van der Waals molecules formed by polar molecules
Authors: Hobza Pavel , Pancíř Jiří , Zahradník Rudolf
Published: January 2014

An attempt was made to find a complete set of stationary points on CNDO/2 energy hypersurface for five molecular complexes. Diagonalization of Hessian matrices served for analysis of the nature of stationary points which permits to distinguish between relative minima and saddle points. The total number of stationary points and real minima of the individual complexes is indicated in parentheses: (HF)2 (8, 1); (H2O)2 (7, 3); (LiF)2 (2, 1); (CH3OH)2 (6, 4) and CH3OH...HF (2, 1). CNDO/2 structural characteristics are compared with experimental values and with results of nonempirical calculations.
Structure and the properties of 18α,19βH-ursane derivatives with a lactone bridge to ring E
Authors: Klinotová Eva , Skorkovská Hana , Protiva Jiří , Vystrčil Alois
Published: January 2014

Oxidation of ketolactone II in alkaline medium led predominantly to hydroxy acid VI with an oxabicycloheptane arrangement of the E ring. Further oxidation of hydroxy acid VI with lead tetraacetate or the pyrolysis of its diacetate, VII, gave ketone XV which on further oxidation gave either lactone XVIII or XXIV, depending on conditions. The structure of both lactones was confirmed by reduction to tetrol XIX or pentol XXV, from lactone XXIV diketone XXXI was also obtained.
Heats of mixing prediction of binary solutions of homologues based on the solution of groups concept
Authors: Dohnal Vladimír , Holub Robert , Pick Jiří
Published: January 2014

A relation has been derived, on the basis of the solution of groups concept, for predicting partial molar excess enthalpies or activity coefficients of a system A + B' from experimental data for a related system A + B, requiring no knowledge or adjustment of group contributions. The method suggested has been employed for predicting hE of systems formed by compounds of the same homologous series. For these systems a relation has been derived between constants of the Redlich-Kister polynomial of the basal and predicted systems which makes it possible to obtain directly an easy estimate of these constants for the predicted system. The method has been tested with 20 mixtures of n-alcohols and 25 mixtures of 2-ketones. In the case that the component B' lies in the homologous series between the components A and B the method makes possible the prediction of hE with sufficient accuracy (on the average better than 8%). In the opposite case, providing that the numerical stability of the calculation is ensured, the method provides reliable results only for a slight extrapolation outside the range of components A and B.
Synthesis of macrocyclic polyether-diamides and their membrane selectivity
Authors: Petránek Jaromír , Ryba Olen
Published: January 2014

The preparation of a series of polyether-diamides with different structure of the macrocyclic chain is described. The ion-selective properties of these compounds with respect to ions of the I and II group were investigated electrochemically in poly(vinyl chloride) membranes plasticised with 2-nitro-1-octyloxybenzene. The relationship between the structure of ionophores and their membrane selectivity are discussed.
13C-NMR spectra of benzenesulphonyl derivatives
Authors: Horyna Jaroslav , Lyčka Antonín , Šnobl Dobroslav
Published: January 2014

13C-NMR chemical shifts and 1J(CH) and 3J(CH) coupling constants have been determined for a series of C6H5SO2X derivatives (X = Cl, C6H5, Ona, OCH3, OC2H5, OC6H5, NH2, NHNH2, N(CH2)5, NHC6H5) in hexadeuteriodimethyl sulphoxide solutions, and the substituent shift values of benzene nucleus have been calculated for the individual SO2X groups,. These groups, carrying partial positive charge at the sulphur atom, have electron-acceptor effects on the benzene nucleus, and increasing electron-donor character of the substituent X is connected with a proportional increase of mesomeric acceptor influence on the benzene nucleus and with increase in absolute values of 1J(CH).
Reactions and spectral properties of 2-amino-3-cyano-4,5-disubstituted furane derivatives
Authors: Prousek Josef , Jurášek Adolf , Kováč Jaroslav
Published: January 2014

Propanedinitrile reacts with acyloins I-III to give 2-amino-3-cyano-4,5-disubstituted furanes IV-VI; the latter react with formamide to give 4-amino-5,6-disubstituted furo[2,3-b]oyrimidines VII-IX. The derivative IV reacts with acetanhydride to 2-acetylamino-3-cyano-4,5-di(2-furyl)furane (X), and aminofurane VI reacts with acetanhydride to give 2-(N,N-diacetylamino)-3-cyano-4,5-diphenylfurane (XI). With aldehydes the aminofuranes IV-VI form the corresponding azomethines XII-XIV. The synthesized derivatives were identified by IR, UV, 1H-NMR and mass spectra.
1-Acyl-3-cyclooctylguanidines
Authors: Sluka Jaroslav , Šmejkal František , Buděšínský Zdeněk
Published: January 2014

On recation of cyclooctylamine with the sulfate of S-methylisothiourea cyclooctylguanidine was formed which was acylated with the methyl esters of 5-halogeno- and 3,5-dihalogeno-2-alkoxybenzoic acids. The 1-acyl-3-cyclooctylguanidine I-XVII formed were tested for their antiviral effect against the influenza virus A/NWS, A-PR8 and A2 Singapore, and further against the viruses NDV, herpes 2, vaccinia and WEE. In the in vivo test against the influenza virus A2 Singapore and herpes simplex 1-(5-bromo-2-dodecyloxybenzoyl)-3-cyclooctylguanidine is more active and less toxic than cyclooctylamine and 1-cyclooctylguanidine.
Effect of irradiation and of replacement of hydrogen by deuterium on the kinetics of hydrogenation of maleic acid on a nickel catalyst
Authors: Kudláček Rostislav , Jelínková Růžena
Published: January 2014

Liquid phase hydrogenation reaction was studied on modifying the solid catalyst by preliminary irradiation and replacing the reacting hydrogen by deuterium; the changes in the reaction rate were measured and the phenomena on the catalyst surface, particularly the change in the catalyst activity, were investigated. For the model reaction, the dependences of the reaction rate on the temperature of reduction and of the successive activation of the catalyst on the absorbed gamma dose were followed, and the dependences of the reaction rate on the reaction temperature were compared for the hydrogenation and deuteration. Isotope effect was found in the influence of the reacting medium on the catalyst property. The activity of the nickel carrier catalyst is governed by its interaction with hydrogen after the reduction, particularly by the temperature of this process.
Temperature and concentration dependence of equivalent conductivity in Ca(NO3)2-CaI2-H2O system
Authors: Novák Jindřich , Sláma Ivo
Published: January 2014

The dependence of the equivalent conductivity on the temperature and composition of the Ca(NO3)2-CaI2-H2O system was studied. The ionic fraction [I-]/([I-] + [NO-3]) was changed from 0.1 to 0.5, the mole fraction of calcium salts (assumed in anhydrous form in the presence of free water molecules) was 0.075-0.200. The equivalent conductivity was found to be a linear function of the ionic fraction at constant temperature and salt concentration.
Polarographic reduction of 3-O-methylpyridoxal 5'-phosphate
Authors: López-Cantarero Enrique , Llor Juan , Cortijo Manuel
Published: January 2014

The polarographic reduction of 3-O-methyl-pyroxidal 5'-phosphate has been studied as a function of pH. The reduction of the aldehyde group by a two electrons process occurs in all conditions studied. The rate of interconversion between the free and hydrate forms of the carbonyl group has been computed. This reaction is acid-base catalyzed. The other reactions (proton transfers) that precede the electrodic reaction are very much faster. The results are compared with those previously obtained for pyridoxal 5'-phosphate.
Electron impact mass spectra of some vicinal trans-dihalo- and trans-hydroxyhalocholestanes
Authors: Trka Antonín , Kasal Alexander
Published: January 2014

Partial mass spectra of 1α, 2β-, 2α, 3β-, 3α, 4β-, 3β, 4α-, 4β, 5α-, 5α, 6β- and 6β, 7α-dihalocholestanes and -halocholestanols are given. Applicability of mass spectrometry for structure determination of these compounds types is demonstrated. Although the differences found in the appearance of their mass spectra are often only quantitative, they are characteristic enough for reliable localization of the substitution.
The splitting of substance P by the post-proline cleaving enzyme from lamb kidneys
Authors: Hauzer Karel , Katzwinkel Siegfried , Jošt Karel , Barth Tomislav
Published: January 2014

The degradation of substance P (an undecapeptide with the following structure: Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2) by the post-proline cleaving enzyme (EC 3.4.21.-) was investigated. The peptide bond between proline and glutamine in positions 4 and 5 of substance P was hydrolyzed in the presence of the enzyme. The tetrapeptide Z-Gly-Pro-Leu-Gly-NH2 was synthesized and used for determining the enzyme activity during the purification procedure.
Liquid-vapour equilibrium in strongly associating binary system propionic acid-cyclohexane
Authors: Svítilová Marie , Malijevská Ivona , Malijevský Anatol , Pick Jiří
Published: January 2014

Equilibrium data for the propionic acid-cyclohexane system at the pressure of 101.3 kPa are presented. The activity coefficients have been obtained by the simultaneous solution of equations of the phase and the chemical equilibrium and correlated by the Wilson, HMW, NRTL and Orye equations.
Reduction of NiO-Mn2O3 mixed oxides with hydrogen and its affecting by ionizing radiation
Authors: Pospíšil Milan , Topinka Jan
Published: January 2014

Reduction of NiO-Mn2O3 mixed oxides with hydrogen was studied thermogravimetrically at 350-440°C; in the entire composition region, 0-100% of one component, total reduction with the formation of a heterogenous Ni-MnO system was observed. The character of the kinetic curves of reduction of Mn2O3 is affected by the way of preparation and heat treatment of the samples before their reduction in inert atmosphere. In the mixed oxide, nickel accelerates the reduction of manganese sesquioxide, proceeding via Mn3O4 intermediate product. The mutual interaction of the two components appears in the pronounced dependence of the reaction rate on the composition, correlable with the analogous dependence of the apparent activation energy of reduction. The extent of the interaction, morphological changes, and some physicochemical parameters depend upon the degree of dispersion of the two oxides, which is also a function of the composition. A prior irridation of the samples by gamma radiation, dose 8 . 105 Gy, or fast neutrons, fluency 6.8 . 1015 n/m2 (Dn = 28.1 Gy), brings about a substantial increase in the content of the chemisorbed oxygen, particularly in the range of excess Mn2O3. The gamma irradiation results in an acceleration of the reduction of the mixed oxides; the extent of this positive effect is a nonmonotonic function of the composition and depends markedly on the temperature. The complex influence of fast neutrons appears as a negative effect (lowering of the reduction rate) resulting from the destruction of the existing centres (the polishing effect); in dependence on the composition the effect inverts into a positive one on the generated and stabilized new centres, which affect the rate of nucleation of the nickel metal phase.
Comparison of spectrophotometric methods of determining Fe(III) using a computer-controlled SuperScanR 3 UV-VIS spectrophotometer
Authors: Gotzmannová Dagmar , Kubáň Vlastimil
Published: January 2014

Methods of the direct determination of Fe(III) with Eriochromazurol B, Chromazurol S, Eriochromcyanine R, 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol were compared using basic parameters for the spectrophotometric methods. The most useful reagents for determining Fe(III) in blood serum are Chromazurol S and PAR. The possibility of direct recording and treatment of the calibration curve using the SuperScanR 3 spectrophotometer controlled by an HP 9815A desk-top calculator is demonstrated.
CO2 laser-induced decomposition of acetone, 2,3-butanedione and cyclobutanone sensitized by sulfur hexafluoride
Authors: Pola Josef , Vítek Josef , Horák Milan , Engst Pavel
Published: January 2014

The CO2 cw laser powered homogeneous pyrolysis (LPHP) of acetone, 2,3-butanedione and cyclobutanone (all 1.3 - 4kPa) sensitized by sulphur hexafluoride (0.7-1.3kPa) was investigated. The decomposition course of the ketones is analogous to that occuring under conventional pyrolytic conditions. The decomposition rate and the product composition are affected by laser power, partial pressure of the sensitizer, and the buffer gas (helium) added. Besiedes the conventional pyrolytic products, the LPHP of acetone and 2,3-butanedione affords acetylene and that of cyclobutanone produces acetic acid. A possible reaction mechanism of the decompositions is discussed.
Kinetics of condensation of benzaldehyde and its derivatives with acetone and methyl ethyl ketone catalysed by aluminium oxide
Authors: Nondek Lubomír , Málek Jaroslav
Published: January 2014

Kinetics of condensation of benzaldehyde with excess acetone and methyl ethyl ketone in the liquid phase and in the presence of aluminium oxide as the catalyst was investigated in the range of temperatures from 60 to 160°C. The pseudo-first order kinetics for the condensation of benzaldehyde with acetone and the positive value of the Hammett reaction constant (ρ = 1.43 ± 0.08 at 90°C) found for the condensation of substituted benzaldehydes with acetone, both lead to the conclusion that the formation of 4-hydroxy-4-phenylbutan-2-one is the rate-determining step. The ρ constant decreases with increasing temperature and the estimated isokinetic temperature corresponds to 449 ± 8 K. At temperatures ranging from 60 to 90°C, the retroaldolisation of the above β-hydroxy ketone is the minor and the dehydration of the β-hydroxy ketone the major reaction; the proportion of the dehydration reaction increases with increasing polarity of the reaction medium and decreases with increasing temperature. In the benzaldehyde condensation with methyl ethyl ketone at 90-160°C, the formation of 1-phenyl-1-penten-3-one, which is catalysed by basic sites of aluminium oxide, is the favoured reaction. The apparent activation energy for the reaction producing the latter ketone is c. 11.5 kJ mol-1 larger than that for the formation of 4-phenyl-3-methyl-3-buten-2-one resulting from the condensation catalysed by acidic sites of the catalyst.
The reaction of methyl 2-cyano-3-(5-phenylsulphonyl-2-furyl)acrylate with nucleophiles
Authors: Kada Rudolf , Knoppová Viera , Kováč Jaroslav , Večeřa Zbyněk
Published: January 2014

In suitable solvents, methyl 2-cyano-3-(5-phenylsulphonyl-2-furyl)-acrylate reacts with nucleophiles, e.g. piperidine, pyrrolidine, morpholine, N-phenylpiperazine, N-methylpiperazine, N-benzylpiperazine, hexamethyleneimine, dimethylamine, diethylamine and sodium azide, to afford products of nucleophilic substitution of the phenylsulphonyl group at the position 5 of the furan ring. The course of the nucleophilic substitution has been monitored kinetically.
Simmons-Smith methylenation of the 4,5-double bond in 19-hydroxylated steroids
Authors: Joska Jiří , Fajkoš Jan
Published: January 2014

Simmons-Smith methylenation of 4-cholestene-3α,19-diol 19-monoacetate and of 4-cholestene-3β,19-diol 19-monoacetate has been studied and structure of the products established by spectral means.
Glass transition temperature of calcium nitrate-potassium nitrate-water system
Authors: Malá Jarmila , Sláma Ivo
Published: January 2014

The glass-formig concentration region of the calcium nitrate-potassium nitrate-water system was determined. The glass transition temperature can be in the studied region approximated by a linear function of the salt concentrations. A comparison of the properties of the studied system with the hydrated calcium nitrate and chloride mixture revealed important differences in the effect of different salts on the undercoolability of aqueous calcium nitrate solutions.
Supersaturation of solutions in crystallisers with the well stirred suspension
Authors: Nývlt Jaroslav
Published: January 2014

Relations were derived comparing the steady supersaturation in the continuous MSMPR and/or bath crystallisers with the stirred suspension having the maximum supersaturation corresponding to the boundary of metastable region at the given conditions. The derived relations include only the quantities used for the system constant BN from the corresponding crystallisation experiments. By use of supersaturation in the crystalliser obtained by the described method it is possible to evaluate the kinetic constants of nucleation and growth. However, it is not possible to expect a high accuracy of the data so obtained.
Meerwein-Ponndorf reduction of benzaldehyde over metal oxides
Authors: Nondek Lubomír , Sedláček Jiří
Published: January 2014

The Meerwein-Ponndorf reduction of benzaldehyde by 2-propanol in the liquid phase was studied in the presence of metal oxides as the catalysts. Except for aluminia, all the eight metal oxides tested were found to be nearly inactive. The activity of the aluminia-magnesia catalysts decreased with the decreasing aluminia content. No correlation was observed between the basic properties of the aluminia-magnesia catalysts and their activity in the reduction of benzaldehyde.
Influence of preparation conditions on physicochemical properties and catalytic activity of stabilized zeolites
Authors: Nováková Jana , Kubelková Ludmila , Wichterlová Blanka
Published: January 2014

Highly decationized zeolite NH4NaY, stabilized by water vapour under steaming conditions at 1030 K, was characterized by its lattice constant, sorption capacity, quantity of extralattice Al, number and character of OH groups present after dehydration in vacuum at 670 K. The catalytic activity and the effect of Lewis and Broensted type acid centers were tested by oligomeration of ethylene and propylene at 310 K and isotopic exchanges of ethylene-d4 + OH and propylene-d6 + OH at 570 K. The properties of this zeolite were compared with zeolites stabilized under selfsteaming conditions at 1040 and 820 K. Structural changes caused by the stabilization process are more pronounced with the steamed zeolite than with the selfsteamed one; in the latter case they diminish with stabilization temperature. Accordingly, the results of catalytic measurements reveal the effect of strong Broensted acid centers in the case of low-temperature selfsteamed zeolite; these centers apparently originate from remainders of the original decationized zeolite. The high-temperature self-steamed zeolite is essentially inactive, whereas the activity of the high-temperature steamed zeolite suggest the presence of catalytically active electron-acceptor centers.
Synthesis and characterization of tetrasodium salt of ethylenediphosphinetetraacetic acid, the phosphorus analogue of EDTA
Authors: Podlahová Jana , Podlaha Jaroslav
Published: January 2014

The phosphorus analogue of EDTA was prepared by alkylation of Cl2PCH2CH2PCl2 with ethyl bromozincacetate and hydrolysis of the ester formed. It was isolated as crystalline tetrasodium salt monohydrate, (NaOOCCH2)2PCH2CH2P(CH2CoONa)2 . H2O, stable on air and well soluble in water. The free acid was only obtained in solution. The structure of the new ligand was checked by spectral methods (UV, IR, and 1H, 13C and 31P-NMR). The acid behaves in solution as tetrabasic with relatively close dissociation constants in the range of pK 2.5-6.0, corresponding to protons bonded at the carboxyl groups. Unlike EDTA, the phosphorus atoms protonize only at pH 0, and, consequently, the ligand does not form zwitterions.
Isolation and characterization of a peptide derived from the active site of chicken pepsin
Authors: Keilová Helena , Kostka Vladimír , Baudyš Miroslav
Published: January 2014

A peptide was isolated from chicken pepsin which contains the aspartic acid residue reacting with diazoacetyl-D,L-norleucine methyl ester in the presence of Cu2+ -ions. The peptide is N-terminated with isoleucine and contains (besides isoleucine) valine, aspartic acid, two threonines, serine, and leucine. In concurrent experiments a peptide of the same composition was isolated from the thermolysin digest of chicken pepsin and its sequence determined as Ile-Val-Asp-Thr-Gly-Thr-Ser-Leu. Since both peptides have entirely identical amino acid composition and other characteristics, the sequenced peptide corresponds to the peptide isolated from the active site of the enzyme.