bluuebunny/crossref_metadata_2025 huggingface dataset:
Flame ionization detector response to coeluting hydrocarbons and carbon disulphide and its application to the determination of the sum of C6-C11 alkanes and cycloalkanes in air
Authors: Koval Martin
Published: March 2011

The flame ionisation detector response to C6-C11 aliphatic hydrocarbon solutions in carbon disulphide in the concentration range between 1.3-9.5 mg ml-1 retained lineary despite the excess of solvent entering the detector simultaneously with the analyte. Pure carbon disulphide exhibited a small positive detector response which did not interfere in calibration procedure and which, under certain GC conditions, inverted to negative values. This response was not proportional to the injected volume and was strongly influenced by the column temperature and/or bleed. On the basis of these findings, a method compatible with the widely used charcoal tube carbon disulphide desorption procedure was developed and evaluated. It consists of static desorption of the sum of aliphatic alkanes and cycloalkanes from the activated charcoal after which an internal standard is added to the supernatant eluate. The resulting carbon disulphide solution is analysed on a highly polar stationary phase 1,2,3-tris(2-cyanoethoxy)propane where the solvent and the analyte coelute in a single peak, the height of which is practically proportional to the sum of alkanes and cycloalkanes present. This also makes determinations of other substances present in the sample more simple. The field test of the proposed method yielded values comparable in precision and accuracy with a control infrared spectrophotometric method.
Photoacoustic spectrum of a nickel oxide-alumina co-precipitated aerogel catalyst
Authors: Řeřicha Roman
Published: March 2011

The near UV and visible spectrum of a NiO-Al2O3 aerogel hydrogenation catalyst (bulk weight of about 50 mg/cm3; 23 wt.% of Ni) was measured using photoacoustic detection. Within the 300-900 nm region, the sample (about 5 mg) showed a single band at 310 ± 5 nm. The band is assigned to an electron transfer from oxygen ligands to Ni2+ ions incorporated in the lattice of the co-precipitated aerogel. The absorption spectra of the sample in the near and middle infrared regions (900-10 000 nm) obtained by classical transmission technique are presented for comparison.
Effect of cation on the kinetics and mechanism of the reaction of copper single crystal in alkali hydroxide solutions
Authors: Sušinka Petr , Miadoková Milica
Published: March 2011

The effect of the metal (Li, Na, K) on the kinetics and mechanism of the reaction of a copper single crystal in alkali hydroxide solutions was studied on the faces corresponding to the (100), (110), and (111) planes, with a special attention to the (100) plane. The differences in the kinetic behaviour are discussed in terms of the hydratability of the cations as well as of the physico-chemical characteristics of the hydroxide solutions, particularly their viscosity and the solubility of oxygen in them. Of the electrochemical parameters examined, only the E0 value is affected by the cation.
Hold-up and flooding in a vibrating plate extractor
Authors: Heyberger Aleš , Sovová Helena , Procházka Jaroslav
Published: March 2011

The mean volumetric hold-up of the dispersed phase and the limiting flow rates of phases in five sizes of experimental vibrating plate extractors VPE were measured and the results compared with the relations of Richardson and Zaki, Míšek and Ishii and Zuber for the relative phase velocity. The experiments were performed with the system toluene-water, toluene dispersed. All the relations were found to describe the dependence of hold-up on flow rates very well. They also allowed a satisfactory estimation of the limiting phase velocities. Within the range of the experimental conditions the characteristic velocity as well as the limiting phase velocities could be approximated by linear functions of the frequency of vibrations. For the columns studied no influence of column size on limiting velocities was detected. The deviations of individual columns from geometrical similarity, however, brought about an appreciable effect both on the hold-up and on the flooding rates. This phenomenon has been explained in terms of longitudinal hold-up profiles, the shape of which depends on the boundary conditions in the particular column. This explanation was corroborated by case studies using a polydisperse mathematical model which show that even in the presence of hold-up profiles the effect of phase velocities on the mean hold-up can be correlated by means of the investigated relations with constant parameters and that the parameters depend on the hold-up profiles form.
The effects of lipophilicity on the inhibition of denaturation of serum albumin and on the activation of fibrinolysis observed with a series of benzyloxyarylaliphatic acids
Authors: Kuchař Miroslav , Rejholec Václav , Roubal Zdeněk , Matoušová Oluše
Published: March 2011

Activation of fibrinolysis and inhibition of denaturation of serum albumin by a series of substituted benzyloxyarylaliphatic acids have been measured and analyzed in relation to the physico-chemical parameters of these acids. The lipophilicity of the benzyloxy derivatives was characterized both by the tabulated parameters π and by experimental data obtained by TLC. Regression analysis has revealed that the derivatives manifest higher lipophilicities in both the activation of fibrinolysis and the inhibition of denaturation, and that these lipophilicities are better described by the tabulated data than by experimental values. Taking into account the earlier results of regression analysis of erythrocyte membrane stabilization and antiinflammatory activity it can be judged that the role of lipophilicities of these substances is influenced by the nature of their interaction with the biological system.
Prediction and representation of ternary excess enthalpy data
Authors: Prchal Miloslav , Dohnal Vladimír , Veselý František
Published: March 2011

A survey of relations making it possible to predict ternary HE,s from binary data and of relations for representation of the concentration dependence of ternary HE,s is presented in this part. Altogether 13 prediction and 26 correlation relations (including some proposed recently) were tested using a thoroughly selected set of nine ternary systems. Relevant recommendations are given on the basis of the results obtained.
Dibenzo[b,f]thiepin-10-carbonitrile, its 10,11-dihydro derivative, some transformation products and related compounds
Authors: Šindelář Karel , Holubek Jiří , Ryska Miroslav , Svátek Emil , Urban Jiří , Grimová Jaroslava , Červená Irena , Hrubantová Marta , Protiva Miroslav
Published: March 2011

Reactions of 10-bromodibenzo[b,f]thiepin (IIIa), its 2-chloro derivative IIIb and 2,8-dichloro derivative IIIc with cuprous cyanide in boiling dimethylformamide gave the carbonitriles Iabc out of which the first two were reduced with sodium borohydride to the 10,11-dihydro derivatives IVab; the amides VIIab were obtained as by-products. Alkaline hydrolysis of the nitriles IVab or their mixtures with the amides VIIab afforded the acids VIIIab. By the addition of 3-dimethylaminopropylmagnesium chloride to the nitrile Ia cis and trans-11-(3-dimethylaminopropyl)-10,11-dihydrodibenzo[b,f]thiepin-10-carbonitriles (XVIII) were obtained. Alkylation of the nitrile IVa with 2-dimethylaminoethyl chloride and 3-dimethylaminopropyl chloride resulted in the 10-(dimethylaminoalkyl) derivatives XX and XXI. A reaction of the crude cyano alcohol XXIII with phosphorus tribromide afforded the 2-bromoethyl derivative XXIV as a by-product only. The main product was the hydrobromide of the spirocyclic imidate XXX which affords by acid hydrolysis the spirocyclic lactone XXXI. An analogous sequence proceeding via the ether XXVI and the alcohol XXVII leads to the 10-(3-bromopropyl) derivative XXVIII as the main product. An attempt at preparing the same substance by alkylation of the nitrile IVa with 1,3-dibromopropane gave stereoisomeric dinitriles XXXII. At high doses the amides VIIab reveal an anticonvulsant effect, the acids VIIIab antiinflammatory actions, the basic nitrile cis-XVIII antireserpine activity and the basic nitriles XX and XXI a central depressant and pseudo-analgesic activity in addition to further peripheral and cardiovascular effects.
Alternative syntheses of steroidal maleimides
Authors: Drašar Pavel , Pouzar Vladimír , Černý Ivan , Havel Miroslav
Published: March 2011

The described synthesis starts from the α-keto esters VIII and XVI which afford the maleimides X and XVIII via products of condensation with carbamoylmethylenetriphenylphosphorane (IX and XVII). In this way, the steroidal maleimides X and XVIII (structurally similar to the cardenolides), derived from 17β-androstanyl-(2-maleimide) and 21-nor-pregnanyl-(2-maleimide) were prepared. Other routes for their preparation have been studied.
The crystal and molecular structure of the complex of zinc(II) with di-μ-diallyldithiocarbamate-bis(diallyldithiocarbamate)
Authors: Kellö Eleonóra , Vrábel Viktor , Kettmann Viktor , Garaj Ján
Published: March 2011

The structure of {Zn[S2CN(C3H5)2]2}2 was solved by X-ray structural analysis. The heavy atom method was used in interpretation of the structure. The dimeric compound crystallizes in the triclinic system with a space group of P1 and lattice parameters of a = 0.8218(2), b = 0.9462(6), c = 1.2942(9) nm, α = 77.70(5), β = 77.46(4), γ = 78.25(4)°. The experimentally determined density value for Z = 2 is 1.42 Mg m-3 and the calculated value is 1.44 Mg m-3. In the dimeric molecule each Zn atom is coordinated by five sulfur atoms at distances of Zn-S1 0.2346, Zn-S2 0.2339, Zn-S3 0.2468, Zn-S4 0.2846, Zn-S'4 0.2387 nm in a deformed trigonal bipyramid. The coordination number of Zn can be expressed as 3 + 1 + 1. The distance between two zinc atoms is 0.3580 nm.
Synthesis of oligodeoxyribonucleotides from 3'-O-formyl-(N-acyl)-2'-deoxyribonucleosides using o-chlorophenylphosphoditriazolide and/or methyl phosphodichloridite. Removal of methyl group from phosphotriester by the action of aqueous pyridine
Authors: Večerková Hana , Smrt Jiří
Published: March 2011

d-GGAATTCC (XI) was prepared by phosphomonotriazolide method in solution. Synthesis of oligodeoxyribonucleotides by phosphite method in solution using methyl phosphodichloridite was studied. Preparation of P-methyl esters of protected d-CA (XVII), d-CAT (XIX), d-TT (XXI) and d-ATT (XXIII) is described. The removal of methyl group from methyl containing phosphotriester by the action of aqueous pyridine is described.
Vasopressin analogues modified in positions 2, 3 and 8. Synthesis and biological effects
Authors: Bláha Ivo , Konopinska Danuta , Zaoral Milan
Published: March 2011

Four vasopressin analogues, modified in positions 2, 3 and 8 were prepared by solid phase as well as solution synthesis. Analogues, containing a D-amino acid in position 3, exhibit a low but markedly specific antidiuretic activity. Analogues with a D-substituent in position 2 show a more specific pressor activity.
3-(4-Methylpiperazino)dibenzo[b,f]-1,2,4-triazolo[4,3-d]-1,4-thiazepine and its 6-chloro and 12-chloro derivatives; Synthesis and pharmacology
Authors: Polívka Zdeněk , Holubek Jiří , Svátek Emil , Dlabač Antonín , Půček Dušan , Šedivý Zdeněk , Protiva Miroslav
Published: March 2011

Dibenzo[b,f]-1,4-thiazepin-11(10H)-ones IIa-IIc reacted with phosphorus pentasulfide in pyridine under the formation of the thiones IIIa-IIIc which were transformed by treatment with hydrazine hydrate in 1-butanol to the hydrazine derivatives IVa-IVc. Reactions with triethyl orthoformate in ethanol in the presence of sulfuric acid effected cyclization to dibenzo[b,f]-1,2,4-triazolo[4,3-d]-1,4-thiazepine (Va) and its chloro derivatives Vb, Vc which were treated with bromine in a boiling mixture of chlorofom and pyridine and gave the 3-bromo derivatives VIa-VIc. The title compounds Ia-Ic were obtained by substitution reactions with an excess of boiling 1-methylpiperazine. An attempt at preparing an analogous 14H-dibenzo[b,g]-1,2,4-triazolo[4,3-d]-1,4-thiazocine derivative was discontinued in the stage of reaction of the thione X with hydrazine hydrate which resulted in the azine XI. Compounds Ia-Ic on intravenous administration are highly toxic and inactive in tests for CNS effects; compound Ic showed a clear anticholinergic activity.
Synthesis of two 1-substituted 8-bromo-6-(2-chlorophenyl)-4H-s-triazolo[4,3-a]-1,4-benzodiazepines
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: March 2011

2-Amino-5-bromo-2'-chlorobenzophenone (VII) afforded by a reaction with phthalimidoacetyl chloride the phthalimido derivative VIII which was transformed by hydrazinolysis to 7-bromo-5-(2-chlorophenyl)-1,3-dihydro-1,4-benzodiazepin-2-one (II). A reaction with phosphorus pentasulfide in pyridine gave the thiolactam IX which reacted with hydrazides of acetic and methylthioacetic acid in boiling 1-butanol and gave the title compounds V and VI. Compound V is very potent in pharmacological tests for anticonvulsant, central depressant and discoordinating activity in mice; compound VI is somewhat weaker.
(5R,8S,10R)-6-Alkyl-8-ergolinecarboxylic acids and some of their derivatives
Authors: Černý Antonín , Zikán Viktor , Vlčková Drahuše , Beneš Jan , Holubek Jiří , Řežábek Karel , Aušková Marie , Křepelka Jiří
Published: March 2011

(5R,8S,10R)-6-Methyl-8-methoxycarbonylergoline (VIIb) was converted via Ib and IIb into its 6-analogues IIIb-VIb, which, in turn, were converted into acids IIIa-VIa and hydrazides IIIc-VIc. Some of the esters prepared, mainly IVb, had inhibitory effects on the secretion of prolactin in rats.
Elimination reaction of angular hydroxymethyl groups of 20(29)-lupene derivatives
Authors: Vystrčil Alois , Křeček Václav , Buděšínský Miloš
Published: March 2011

Solvolysis of 28-p-toluenesulfonyloxy-20(29)-lupene derivatives IV-VII proceeds with isomerization of the isopropenyl side chain to the isopropylidene chain and expansion of the ring E to a six-membered ring, containing trisubstituted double bond; for „anhydrobetulin" and its derivatives formulae VIII-XI with homoconjugated double bonds are suggested. Formation of a conjugated diene system is hindered by steric interactions of the isopropylidene chain with the ring C (with C(12)). Only the trisubstituted double bond in the dienes VIII and X undergoes catalytic reduction, the hydrogen approaching from the α-side (XII-XVI) as demonstrated by the Cotton effect of trinorketone XXI and its 20,20-dibromo derivative XXIII.
Another antibiotic from the basidiomycete Oudemansiella mucida
Authors: Vondráček Miloslav , Vondráčková Jitka , Sedmera Petr , Musílek Vladimír
Published: March 2011

The structure III was assigned on the basis of spectroscopic measurements to an another antifungal antibiotic isolated from the mycelial culture of the fungus Oudemansiella mucida.
Alkali vapor pressures over some simple silicate melts
Authors: Piacente Vincenzo , Matoušek Josef
Published: March 2011

Mass spectrometric analysis of gaseous phase above Na2O.4 SiO2; K2O.4 SiO2 and Na2O.K2O.8 SiO2 melts was used to identify the species observed and to determine their partial pressure values. The principal species observed were the corresponding alkaline species and oxygen. The temperature dependence of sodium and kalium partial pressures was established and corresponding vaporization enthalpy values were calculated by second law treatment of those vapor data. The average value of sodium vaporization enthalpy in binary melt amounts of ΔHT0 = 315 ± 10 kJ mol-1 being in a good agreement with the data published previously. The vaporization enthalpy of potassium ΔHT0 = 142 ± 8 kJ mol-1 is considerably lower with comparison to sodium and does not change if potassium evaporates from binary K2O.4 SiO2 or ternary Na2O.K2O.8 SiO2 melts respectively.
Preparation of optically active 3-cyclopentyl-3-methyl-2-azetidinone
Authors: Hauer Jan , Šebenda Jan
Published: March 2011

The resolution of 2-cyclopentyl-2-cyanopropanoic acid gave its enantiomers, which by esterification and hydrogenation were transformed into (+) and (-)-methyl-(3-amino-2-cyclopentyl-2-methyl)propanoate. Their cyclization yielded both enantiomers of 3-cyclopentyl-3-methyl-2-azetidinone.
Kinetics of reaction of 1-chloro-2,4,6-trinitrobenzene with enolate ions of 2,4-pentanedione and methyl 3-oxobutanoate
Authors: Macháček Vladimír , Andrle Jaroslav , Štěrba Vojeslav
Published: March 2011

Reaction of 1-chloro-2,4,6-trinitrobenzene (I) with anions of 2,4-pentanedione (II) and methyl 3-oxobutanoate (III) produces 3-(2,4,6-trinitrophenyl)-2,4-pentanedione (IV) and methyl 2-(2,4,6-trinitrophenyl)-3-oxobutanoate (V), respectively, besides 2,4,6-trinitrophenol (VI). Amount of 2,4,6-trinitrophenol decreases with increasing amount of dimethyl sulphoxide and 2,4-pentanedione in methanol. A mechanism of formation of 2,4,6-trinitrophenol is suggested. Rate constant of formation of 3-(2,4,6-trinitrophenyl)-2,4-pentanedione in methanol-dimethyl sulphoxide mixtures increases with increasing content of dimethyl sulphoxide and decreases with increasing LiCl concentration. In methanol, 1-chloro-2,4,6-trinitrobenzene reacts with anion of 2,4-pentanedione about 20x slower than with anion of methyl 3-oxobutanoate.
Substituent effect on wave numbers of C=O valence vibrations in ferrocene derivatives
Authors: Perjéssy Alexander , Toma Štefan
Published: March 2011

Wave numbers of C=O valence vibrations of 83 ferrocene derivatives have been measured in tetrachloromethane. For a series of 154 compounds containing ferrocene skeleton linear correlation has been found between wave numbers of C=O vibration and X+(R) constants of structural fragments in the sense of modified and extended Seth-Paul-Van Duyse equation. Validity has been verified of the recently derived empirical relation for calculation of the X+(R) constants of complex structural fragments from values of constants of substituents and transmission factors for simple structural groupings. The transmission factors γ and π' for 1,3- and 1,1'-ferrocene system have been found to be well applicable to calculation of constants of structural fragments containing ferrocene skeleton.
Reactions of carbonyl isothiocyanates with nucleophilic bifunctional reagents
Authors: Uher Michal , Berkeš Dušan , Leško Ján , Floch Ľubomír
Published: March 2011

Reactions of benzoyl-, 2-furoyl-, acetyl-, and trichloroacetyl isothiocyanates with 1,2-diaminobenzene, 2-aminophenol, 5,6-diamino-1,3-dimethyluracil and 2,3-diaminopyridine were investigated. Formation of the individual products and their IR, UV and electron impact mass spectra are discussed.
Hydroxylation of 6-substituted 2,7-dioxabicyclo[3.2.0]hept-3-enes. The synthesis of analogs of 3-deoxy-DL-streptose
Authors: Kozluk Tadeusz , Zamojski Alexander
Published: March 2011

Hydroxylation of 6-substituted 2,7-dioxabicyclo[3.2.0]hept-3-enes (I, XIV and XV) with m-chloroperoxybenzoic acid occurs mainly from the exo side and leads to the corresponding 3-m-chlorobenzoates of trans-3,4-diols (VI, XVIII and XXII). Hydroxylation of substrates XIV and XV with potassium permanganate leads to 3-deoxy-3-C-formyl-DL-arabino-aldofuranoses. Epimerization at the formyl group-bearing carbon atom occurs during the reorganization of dihydroxylated dioxabicycloheptanes in basic medium.
Solubility in the K2H2P2O7-K3HP2O7-K3H2P3O10-K4HP3O10-H2O system at 0 °C
Authors: Ebert Miroslav , Lukeš Ivan , Eysseltová Jitka , Nassler Jindřich
Published: March 2011

The solubility in the K2H2P2O7-K3HP2O7-K3H2P3O10-K4HP3O10-H2O system has been studied at 0 °C. The results are discussed in terms of the possible application of the substances as components of multicomponent liquid fertilizers of the PK type.
Chemical transformations of nitromethyl group in 3,5-dicyano-1,4,4,6-tetramethyl-2-nitromethyl-1,4-dihydropyridine
Authors: Kurfürst Antonín , Kuthan Josef
Published: March 2011

Chemical transformations have been studied of nitromethyl group in 3,5-dicyano-1,4,4,6-tetramethyl-2-nitromethyl-1,4-dihydropyridine (I) brought about by action of acetic acid and/or acetic anhydride, diazomethane, and phosphorus trichloride and giving also the products VIII and IX of intramolecular reaction with the neighbouring cyano group. Spectral characteristics of the synthetized compounds and their splitting by electron impact in mass spectrometer are given, and mechanism of the individual transformations is discussed.
Cycloadditions of N,N'-dicyclohexylcarbodiimide to 2-phenylethenyl isothiocyanates
Authors: Hritzová Oľga , Kniežo Ladislav
Published: March 2011

2-Phenylethenyl- and 2-(4-nitrophenyl)ethenyl isothiocyanates undergo a 2 + 2 cycloaddition with N,N'-cyclohexylcarbodiimide to form 1,3-thiazetedine derivatives; this reaction takes place at the C=S bond of the isothiocyanate group. The olefinic C=C bond was not involved.
Case studies of some atoms-in-molecules formulations
Authors: Polák Rudolf , Vojtík Jan
Published: March 2011

Four versions (Hermitian, non-Hermitian, Schmidt- and symmetrically orthogonalized) of the atoms-in-molecules method are applied to calculate potential energy curves of the H2, HeH and HF species. By comparing the results of various approaches among themselves and to external accurate data, conclusions are drawn concerning the reliability of the individual solutions.
Heat and mass transfer in rectification of binary mixtures at turbulent vapour flow
Authors: Kolář Václav , Červenka Jan
Published: March 2011

Theoretical analysis of the heat and mass transfer mechanism in rectification of binary mixtures was made at the use of earlier obtained relations for the heat and mass transfer coefficients. Theoretical results were applied to the mixture methanol-water and have revealed that the effect of simultaneous heat transfer on mass transfer is insignificant and is little affected by both the reflux ratio and hydrodynamic conditions.
An ab initio MO study of conformation structure of nicotinamide and its derivatives
Authors: Böhm Stanislav , Kuthan Josef
Published: March 2011

Conformation of nicotinamide (I), 3-carbamoylpyridinium (IIa), 1-methyl-3-carbamoylpyridinium (IIb), and 1-methyl-1,4-dihydronicotinamide (IIIa) has been studied in the rigid rotor approximation on the basis of non-empirical STO-3G wave functions. The rotation barriers decrease in the order: IIIa > I ~ IIb > IIa. When confronted with semiempirical calculations, the conformation curves of molecular energy show a better qualitative similarity to the EHT than to NDDO and particularly to CNDO/2 curves. Relation of the calculated characteristics to experimental findings is discussed.
Binding of cadmium and copper(II) ions to oligogalacturonic acids
Authors: Kohn Rudolf , Heinrichová Kveta , Malovíková Anna
Published: March 2011

The binding of Cu2+ and Cd2+ ions to potassium oligogalacturonates of polymerization degree DP 1 to 9 was investigated by ion-specific electrodes and by the metallochromic indicator method. The interaction was evaluated on the basis of degree of association β of cations (M2+) with carboxyl groups of the compounds examined and the single-ion activity coefficients of counterions γM2+. The results were compared with values corresponding to an electrostatic bond of Ca2+ ions to these oligomers. The Cd2+, and especially Cu2+ ions were bound in a considerable measure already to mono- and oligogalacturonates of a low polymerization degree very probably by a chelate bond. Precipitation of Cu- and Cd-oligogalacturonates takes place at a polymerization degree DP 5 and 8, respectively. Interpretation of results by the multiple equilibria theory evidenced that the Cu2+ ions were stoichiometrically bound to mono- and oligogalacturonates (one cation to two carboxyl groups) similarly, as with polymeric D-galacturonan. The results revise the early conception concerning the formation of a positively charged complex of Cu2+ ions (similarly also of Cd2+ and Pb2+ ions) with monogalacturonic acid of (MA)+ type, where A- is the anion of uronic acid. The results are a contribution to the elucidation of the elimination mechanism of these toxic cations from human body involving the oligomeric fragments of pectin as products of its enzymic degradation in the digestive tract.
Equilibrium constants of pyridoxal 5'-phosphate Schiff bases - A polarographic study
Authors: Llor Juan , Bonal Javier , Cortijo Manuel
Published: March 2011

The equilibrium constant for the formation of the Schiff base between pyridoxal 5'-phosphate and n-hexylamine has been evaluated from polarographic measurements. The pH dependence of the equilibrium constant has been investigated at constant ionic strength. The values thus obtained for the equilibrium constant compare well with those computed from the pK of the several ionic forms of pyridoxal 5'-phosphate, its Schiff base and the amine present in the solution.
The determination of acetone using mass spectrometry after acid hydrolysis of polymer acetals
Authors: Hudeček Slavko , Otoupalová Jaroslava , Ryska Miroslav , Světlík Jan , Čefelín Pavel
Published: March 2011

A mass spectrometric method for the determination of acetone in the presence of polymers has been suggested. Perdeuterated acetone was used as the internal standard. The method was employed in a quantitative determination of (2,2-dimethyl-1,3-dioxolane-4-yl) methyl methacrylate units in copolymers with methyl methacrylate and in the determination of copolymerization parameters.
Preparation and pharmacological properties of 4,5-secopregnane-3,20-dione and its derivatives
Authors: Kasal Alexander , Stárka Luboš , Hampl Richard , Kohout Ladislav
Published: March 2011

20β-Benzoyloxy-4-pregnen-3-one was oxidized to seco acid VI which was deoxygenated in the position 5 and converted to methyl ketone XI. This substance was oxidized directly to 4,5-secodihydroprogesterone and also converted to 17α-acetoxy derivative XXI via the corresponding monoketal XV. Compounds XIV and XXI do not display a gestagenic activity or an antiandrogenic activity either.
Electrophilic addition to the 5,6-double bond in A-nor-3,5-secosteroids
Authors: Kohout Ladislav , Kasal Alexander
Published: March 2011

The stereochemistry of epoxidation, Simmons-Smith methylenation and addition of bromine and hypobromous acid to 5,6-unsaturated A-nor-3,5-secosteroids was studied. The additions proceed from both sides of the molecule and, the β-oriented positively charged intermediate is regularly cleaved under participation by the substituent at C(3) to the corresponding oxa derivative II or to the lactones VI and XI. Cleavage of the cyclopropano derivative XVI with thallium(III) acetate was accompanied by Westphalen rearrangement and lead to the 5-membered lactone XXI. The structures of the products were established by spectral and chemical means and the mechanisms of reactions observed are discussed.
Synthesis of 17β-steroidal 4-(2-butenolides)
Authors: Černý Ivan , Pouzar Vladimír , Drašar Pavel , Havel Miroslav
Published: March 2011

Derivatives of 5-androsten-3β-ol with 2-butenolide ring in position 17β were prepared by addition of lithium salt of protected propargyl alcohol to 17β-carbaldehyde IV, hydrogenation of the formed isomeric acetylenes over P-2 nickel and oxidative cyclization of the obtained olefinic 20,24-diols IX and X. Stereochemistry of the desired lactones XII and XIII was determined by CD spectroscopy. The 17β-(2-furyl) derivative XI was formed as the cyclization side-product. The 3β-hydroxyl was protected by a methoxymethyl group which allowed a selective removal of tetrahydropyranyl group during the synthesis.
Synthon approach and graph grammar
Authors: Kvasnička Vladimír
Published: March 2011

The Corey's synthon approach is formalized by a special type of graph grammar. The graph language induced by this grammar is composed of all possible graphs (molecules) that can be constructed from the so-called starting graphs. The retro-synthetic analysis is treated as the parser which provides an answer to the question „is a graph element of the given language?".
Saturated vapour pressures of the ternary system urea-ammonium nitrate-water
Authors: Hejtmánková Jiřina , Bartovská Lidmila , Šišková Marie , Jäger Lubomír
Published: March 2011

Saturated vapour pressures of the ternary liquid solutions of urea and ammonium nitrate in water were investigated by the isopiestic method at 15, 25 and 35 °C. The measurements were carried out within the concentrations that are measurable by means of the NaCl standard solutions (i.e. up to the NaCl molality 6 mol/kg). The experimental data are correlated in terms of isotonic solutions of the urea-water and ammonium nitrate-water binary systems.
To the question whether higher associates exist in the vapour phase of acetic acid
Authors: Malijevská Ivona
Published: March 2011

Equilibrium constants for higher associates in an ideal-gas associating mixture are correlated from existing data on the P-V-T behaviour of acetic acid. Further, a model of real-gas dimerizing mixture is tested on the basis of estimated critical properties for monomer and dimer of fatty acids.
Medium-pressure liquid chromatography of platinum metal ions on Spheron DEAE
Authors: Vláčil František , Vinš Ivan , Malíček Oldřich
Published: March 2011

Spheron DEAE (modified macroreticular hydroxyethylmethacrylate-ethylenedimethacrylate copolymer) was used for chromatographic separation and determination of Rh(III), Pd(II), and Pt(IV) in chloride medium. The most suitable composition of the mobile phase was looked for by studying the influence of hydrochloric acid concentration on the capacity ratios of the metal ions mentioned and on their resolution, as well as the influence of different additions to the mobile phase on the decrease of the high Pt(IV) retention. Using the photometric (UV) detection, the linear dependence was found up to following concentrations: Rh 200 mg l-1, Pd 2 g l-1, Pt 500 mg l-1. The detection limit was 23 ng Rh, 62 ng Pd and 96 ng Pt in 7 μl sample injected.The reproducibility of the determination was (as relative standard deviation for n = 3) 1-4%, relative error 0.7-7%.
Application of the ionization detector and the alkali flame ionization detector in capillary liquid chromatography
Authors: Krejčí Miloš , Rusek Miroslav , Houdková Jana
Published: March 2011

A possibility is demonstrated of the use of the flame ionization detector (FID) and the alkali metal flame ionization detector (AFID) in capillary liquid chromatography. The minimum detectable mass flow rates for the FID and the AFID were ≈10-12 and ≈10-13 g s-1, respectively. The detection time constant is about 1 s allows for operation with columns of inner diameters of 10-60 μm and lengths above 1 m. The suggested design of the detector is described. The burner allows the total effluent from the column to enter the detector. The temperature of the end of the capillary column in the burner is controllable.
Chelating ion exchangers with bonded 8-quinolinol on a glycidyl methacrylate gel
Authors: Janák Karel , Janák Jaroslav
Published: March 2011

The optimum conditions of chemical bonding of 8-quinolinol to a porous glycidyl methacrylate matrix were established with respect to the sorption capacities of the ion exchangers prepared. After its modification, the reagent was fixed either directly as 5-(4-hydroxyphenylazo)-8-quinolinol or 5-(4-aminophenylazo)8-quinolinol (or their copper(II) complexes), or indirectly, after fixing the intermediate and its diazotization, by coupling with the gel. The best results (Qa(Cu2+) = 0.24 mmol g-1) were achieved by the direct bonding of copper 5-(4-hydroxyphenylazo)-8-quinolinate in pyridine.
Effect of the amine structure on the course of linear anionic-coordination dimerization of isoprene in the presence of dialkylamine and sodium
Authors: Bartoň Jan , Hrubeš Martin , Kašpar Miroslav , Růžička Vlastimil
Published: March 2011

The effect was studied of the structure of the amine on the course of linear anionic-coordination dimerization of isoprene (2-methyl-1,3-butadiene) to β-myrcene (3-methylene-7-methyl-1,6-octadiene) in tetrahydrofuran solution in the presence of dialkylamine and sodium. The modified Taft-Pavelich equation was used to express this effect quantitatively. The selectivity of the reaction to β-myrcene was found to depend above all on the polar properties of the substituents R1, R2 of the dialkylamine use, described by the Σσ* parameter, while the reaction rate of the formation of β-myrcene depended more on their steric properties, expressed by the ΣEs parameter.
Nonisothermal control of batch reactor with reaction by digital computer. Experimental verification of the control algorithm based on mathematical model of the system
Authors: Jiráček František , Horák Josef
Published: March 2011

Two-position feedback temperature control of the mixture in a batch reactor with the strongly exothermic autocatalytic reaction is studied. The control is based on continuous measurement of reaction temperature, evaluation of its time derivative and periodical determination of conversion of the reactant. On basis of numerical solution of equations of the mathematical model of the reactor is then evaluated the highest operating temperature of the mixture at which is still secured a safe operation of the reactor and trajectories along which the given operating temperature could be reached in the shortest time period. The manipulated variable was the flow rate of heat carrier into the cooler. Sampling of the reaction temperature and two-position switching over of flow rate of the heat carrier was performed in real time by use of the digital measuring center Hewlett-Packard 3052A. In the experiments has been verified the effect of changes in reactivity of the mixture, accuracy of the mathematical reactor model and effect of additional noise in the measured reaction temperature on control safety. Results of the experiments have proved that the proposed control algorithm enables safe control of the reaction temperature also in cases when the operating reactor states are unstable at the open control loop and when the cooler has a slow response to changes in the manipulated variable.
Calculation of the rate of amalgam decomposition in a horizontal decomposer
Authors: Cezner Václav , Novák Petr , Roušar Ivo , Mejta Vladimír
Published: March 2011

The decomposition rate of the sodium or potassium amalgam in a horizontal decomposer was calculated with regard to three different forms of the amalgam surface, namely a horizontal plane, a half-spherical, and a half-ellipsoidal form. A comparison of the three models showed that the dependence of the amalgam decomposition rate on the driving force of the decomposition is in all cases analogous. In the region of low decomposition rates, all three models lead to practically the same decomposition rates.
A two-point regulator control of a chemical reactor; Cooling system with a large inertia - PD algorithm
Authors: Horák Josef , Jiráček František , Ježová Libuše
Published: March 2011

The effect has been investigated of the gain of the derivative element of a PD controller on the quality of the temperature control of an exothermal reaction mixture in a batch reactor. The investigation concerned a reactor equipped with a cooling system whose rate of response could be varied in the range of several orders of magnitude. The results have lead to the conclusion that a slow response of the coolong system is difficult to make up for by using more sophisticated control algorithms. For the slow response of the cooling system the range of gain of the controller providing for a safe temperature control is narrow leaving essentially no margin for its practical utilization. The study combined simulation on a mathematical model with experimental verification of a laboratory scale reactor cooled by a submersible retractable cooler.
Dynamic sorption and desorption of gold using Spheron DEAE as sorbent
Authors: Vláčil František , Plicková Olga
Published: March 2011

The dynamic sorption and desorption of gold was studied using Spheron DEAE, a macroreticular hydroxyethyl methacrylate-ethylenedimethacrylate copolymer with chemically bonded diethylaminoethyl groups, as the sorbent. Factorial experiments were designed to optimize the composition of the mobile phase (H+ and Cl- ions); as a result, hydrochloric acid was used in a concentration of 0.01 mol l-1. Thiourea solution (0.4 mol l-1) in 0.25M hydrochloric acid served as the eluent: the gold sorbed was eluted completely in seven column volumes. A column of 1 cm3 volume retained gold quantitatively from 0.5 l of solution containing the metal in a concentration of 1 mg l-1 (5 μmol l-1); the recovery of gold by elution was 99% and the degree of concentration of gold with respect to the influent was a hundred. A method is worked out for a direct photometric determination of gold in the thiourea eluates, based on the decomposition of thiourea with hydrogen peroxide.
Preparation of 3-deoxy-3-fluoro-D-mannose and corresponding hexitol
Authors: Černý Miloslav , Doležalová Jitka , Mácová Jindra , Pacák Josef , Trnka Tomáš , Buděšínský Miloš
Published: March 2011

Reaction of 1,6 : 3,4-dianhydro-β-D-altropyranose (I) with potassium fluoride in hot ethylene glycol gave 1,6-anhydro-3-deoxy-3-fluoro-β-D-mannopyranose (II). On acid catalysed hydrolysis or acetolysis of compound II 3-deoxy-3-fluoro-D-mannose (VIII) or its tetra-O-acetyl derivative VII, respectively, were obtained. Reduction of compound VIII with sodium borohydride gave 3-deoxy-3-fluoro-D-mannitol (IX). The structures of the mentioned compounds were proved by 1H NMR spectroscopy.
S-adenosyl-L-homocysteine hydrolase from mouse leukemic cells: Isolation and properties
Authors: Merta Aleš , Votruba Ivan , Veselý Jiří , Holý Antonín
Published: March 2011

S-Adenosyl-L-homocysteine hydrolase from mouse leukemic cells L1210 was purified to evident homogeneity with no concomitant enzymatic activities. The isoelectric point of the enzyme is 5.65 and the optimum temperatures for the synthesis and hydrolysis are 52 °C and 47 °C, respectively. The respective KM values for adenosine and S-adenosyl-L-homocysteine (SAH) are 3.8 and 4.4 μmol l-1. The optimum pH value for the synthesis of SAH is 6.95-7.20 and for the hydrolysis 7.15-7.80. The enzyme is competitively inhibited by 9-(S)-(2,3-dihydroxypropyl)adenine and inactivated with both enantiomers of eritadenine and 3-(adenin-9-yl)-2-hydroxypropanoic acid.
Theoretische und praktische Aspekte der Anwendung einer pseudostationären Quecksilbertropfelektrode in der anodischen Inversvoltammetrie
Authors: Scholz F. , Roloff R. , Henrion G.
Published: March 2011

Es wird gezeigt, wie eine Quecksilbertropfelektrode mit einer Tropfzeit von 20 bis 30 Minuten einfach hergestellt werden kann. Die Hydrodynamik dieser pseudostationaren Quecksilbertropfelektrode (PSDME) ist leicht berechenbar. Zur Beschreibung der Abhängigkeit des anodischen Peakstroms von der Elektrolysezeit mußte die bekannte Stromberg-Gleichung modifiziert werden. Diese modifizierte Gleichung trägt dem Tropfenwachstum Rechnung und ist experimentell verifiziert. Die mit dieser PSDME erreichten Nachweisgrenzen entsprechen den mit stationären Quecksilbertropfen (HMDE) erreichten. Für Konzentrationen oberhalb der zehnfachen 3σ-Nachweisgrenzen beträgt die relative Standardabweichung ca. 1%.
Approximation of adsorption heats of carbon monoxide on transition metals by means of an empirical model
Authors: Fusek Jiří , Štrouf Oldřich , Kuchynka Karel
Published: March 2011

The class structure of transition metals chemisorbing carbon monoxide was determined by expressing the following fundamental parameters in the form of functions: The molar heat capacity, the 1st and 2nd ionization energy, the heat of fusion, Pauling electronegativity, the electric conductivity, Debye temperature, the atomic volume of metal. Adsorption heats have been predicted for twelve transition metals.
Heptamanganese tricarbide Mn7C3
Authors: Hájek Bohumil , Karen Pavel , Brožek Vlastimil
Published: March 2011

A procedure was examined for the preparation of Mn7C3 by reaction of manganese dust with n-pentane at 850 °C and a reduced pressure. The identity of the product was confirmed by chemical and X-ray diffraction analysis; no other carbide was found to be present. The powder X-ray diffraction patterns were investigated in terms of the structure assignment either to the hexagonal P63mc or the orthorhombic Pnma symmetry. The reflection intensities fit better the latter structure, but the possibility of hexagonal indexing indicates that the octahedral structural elements do not arrange coherently during the synthesis. The composition of the products of hydrolysis is also consistent with the formula Mn7C3. The gaseous products contain hydrogen, methane, and a number of other hydrocarbons, mostly saturated, whose concentration decreases with increasing number of carbon atoms in the molecule. The concentration distribution of the hydrocarbons is discussed in terms of the radical mechanism of the hydrolysis; the data are borne out indicating that in Mn7C3 the covalent nature of the bonds is more pronounced than in salt type carbides.
Isothermal and isobaric vapour-liquid equilibrium data in the tetrachloromethane-n-butyl alcohol system
Authors: Linek Jan
Published: March 2011

Isothermal vapour-liquid equilibrium data at 65, 73 and 80 °C and isobaric ones at 101.3 kPa were measured in the tetrachloromethane-n-butyl alcohol system. A modified circulation still of the Gilespie type was used for the measurements. Under the conditions of measurements, the system exhibits positive deviations from Raoult's law and minimum boiling-point azeotropes. The experimental data were fitted to a number of correlation equations. The best correlation was reached with the Wilson equation but the regression failed in some cases. Therefore the results for the 5th order Redlich-Kister equation are presented.
Potential noncataleptic neuroleptic agents: Synthesis and pharmacology of 7-chloro-4-[4-(2-hydroxyethyl)piperazino]-4,5-dihydrothieno[2,3-b]-1-benzothiepin
Authors: Polívka Zdeněk , Valchář Martin , Protiva Miroslav
Published: March 2011

Heating of 2,5-dichloroacetophenone with 2-thiophenethiol, potassium carbonate and copper gave 5-chloro-2-(2-thienylthio)acetophenone (V) which was subjected to the Willgerodt reaction with sulphur and morpholine. The product was a mixture of the thiomorpholide VI and oxothiomorpholide VII. After a partial separation the predominanting product VI was hydrolyzed without characterization with ethanolic potassium hydroxide to give the acid VIII. Cyclization by treatment with phosphorus pentoxide in boiling toluene gave 7-chlorothieno[2,3-b]-1-benzothiepin-4(5H)-one (X) which was reduced with sodium borohydride to the alcohol XII. A reaction with hydrogen chloride in benzene led to the chloro derivative XIII whose substitution reaction with 1-(2-hydroxyethyl)piperazine afforded the title compound IV. The product has strong central depressant and discoordinating activity, a low cataleptic efficity but in a relatively high dose it does not influence the dopamine metabolism in the rat brain.
Potential antitussives: Synthesis and pharmacology of a series of 1-[2-amino-2-(4-fluorophenyl)ethyl]-4-(2-benzoylpropyl)piperazines
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: March 2011

Compound V, obtained by a reaction of 2-chloro-4'-fluoroacetophenone with 1-(ethoxycarbonyl)piperazine, was reduced with sodium borohydride to the amino alcohol VIf. The hydrochloride of VIf was treated with thionyl chloride to give the hydrochloride of 1-[2-chloro-2-(4-fluorophenyl)ethyl]-4-(ethoxycarbonyl)piperazine (VIg). The crude VIg was subjected to substitution reactions with diethylamine, pyrrolidine, piperidine, morpholine and 1-methylpiperazine in benzene at 60 °C. The obtained aminocarbamates VIa-VIe were hydrolyzed with concentrated ethanolic potassium hydroxide and gave the amines VIIa-VIIe. Mannich reactions of the hydrochlorides of these compounds with paraformaldehyde and propiophenone (and 4-hydroxypropiophenone, respectively) resulted in the title compounds IIIa-IIIe, IVa,b and IVd,e. Only substances IIIa and IIId were found to have an antitussic activity in rats and guinea-pigs comparable to that of eprazinone (I). In higher doses they brought about central depression, ataxia and ptosis in mice and some of them adrenolytic and hypotensive effects in rats.
Electrophilic additions to 10β-vinyl cholestane derivatives
Authors: Kočovský Pavel , Starý Ivo , Tureček František , Hanuš Vladimír
Published: March 2011

Hypobromous acid addition to steroid dienes I-VI proceeds in four steps. The reaction commences by the attack on more reactive endocyclic double bond from the α-side yielding intermediary diaxial bromohydrins XXVIII, XXXIV, XL, XLIV, L and LVI via corresponding α-bromonium ions. The 10β-vinyl group of the bromohydrins then reacts with a second equivalent of the reagent forming transient 19-epimeric bromonium ions. The ions generated from I, II, V and VI are cleaved intramolecularly by the hydroxyl group, in accordance with the Markovnikov rule, giving rise to 19-epimeric dibromo epoxides XXXIa and XXXIIa, XXXVII and XXXVIII, LIIIa and LIVa, LIX and LX. By contrast, the ions generated from III and IV are cleaved in an anti-Markovnikov manner to yield dibromo epoxides XLII, XLVII and XLVIII. Products due to formation of a new C-C bond were not observed. The reaction mechanism and differences in the behaviour of the dienes I-VI are discussed.
On the comparison of the theoretical and experimental data for the kinetics of the Cope rearrangement of 1,5-hexadiene
Authors: Slanina Zdeněk
Published: March 2011

The Cope rearrangement of 1,5-hexadiene is treated as a process passing through an intermediate; this feature was verified by recent quantum-chemical studies. Relationships are derived between the characteristics of the both partial activation processes involved and the experimental data (which characterize the overall process). It is shown that proper consideration of the kinetic consequences of the existence of the intermediate might help to eliminate the recently reported large difference between the MINDO/3 activation entropy and the experimental entropy for the boat pathway for the Cope rearrangement.
Stability of tetramer α-methylstyrene dianion in tetrahydrofuran
Authors: Salajka Zdeněk , Kučera Miloslav
Published: March 2011

Solutions of carbanions of living α-methylstyrene tetramer in tetrahydrofuran exhibit limited stability even at relatively low temperatures. The rate of decay of these active centers depends upon the type of counter-ion and it decreases in the sequence Li+ < Na+ < K+. It is dependent also upon temperature, concentration and some other unrevealed factors. In dark, with Na+ as a counter-ion at 263 K and ~ C-Na+ concentration of 1.5 mmol/dm3, the initial period of a fast concentration decrease of active centers is followed by a very slow period of rate decay. At 296 K the decrease of their concentration is much faster and seems to obey a first reaction order. Rinsing the dry inner surface of glass apparatus by solutions of carbanions does not cause a decrease of their concentration. When a part of the glass apparatus is heated up to the softening point, a certain portion of carbanions is consumed.
Model compounds of poly(methyl methacrylate). Conformational structure of 2,2-dimethyl-1-methoxypropane and of the methyl ester of 3-methoxy-2,2-dimethylpropanoic acid
Authors: Schneider Bohdan , Doskočilová Danica , Štokr Jan , Lövy Jan , Přádný Martin , Ševčík Stanislav
Published: March 2011

By analysis of infrared, Raman and 13C NMR spectra of 2,2-dimethyl-1-methoxypropane and of the methyl ester of 3-methoxy-2,2-dimethylpropanoic acid, the formation of conformers generated by rotation about the CH2-OCH3 and C-CH2 bonds was studied. It was found that in both molecules, only the form with trans orientation of the C-CH2-O-CH3 bonds is present. The conformational structure of the major form of the methyl ester of 3-methoxy-2,2-dimethylpropanoic acid was proposed.