bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of 2-allyl-2-ethylsuccinic anhydride
Authors: Hájíček Josef , Trojánek Jan
Published: August 2011

The paper describes a synthesis of 2-allyl-2-ethylsuccinic anhydride (I), starting from ethyl cyanoacetate, with the Wolff rearrangement of diazo ketone XVI as the key step. The unsuccessful attempts at the synthesis are also described. The mechanism leading to an anomalous product of the reaction between cyanohydrine VI and sodium ethylcyanoacetate, viz. ethyl 2-cyano-3-methyl-5-oxoheptanoate (VIII), is also discussed.
1-[3-(2-Alkoxyphenoxy)-3-phenylpropyl]piperazines and some related compounds
Authors: Valenta Vladimír , Bartošová Marie , Protiva Miroslav
Published: August 2011

Amino alcohols VIIIa-c, prepared by reduction of the Mannich bases VIa-c, were transformed by treatment with thionyl chloride to the chloro derivatives IXa-c which were subjected to substitution reactions with the sodium salts of guaiacol, 2-ethoxyphenol and 2-benzyloxyphenol giving the title compounds IIIb,c, IVb,c and Va-c. N,N-Dimethyl-3-(2-benzyloxyphenoxy)-3-phenylpropylamine (Va) was partially demethylated by treatment with ethyl chloroformate and by the following alkaline hydrolysis to the secondary amine XI. Amines III-V and XI in high doses exhibit central excitation but do not show antireserpine activity; they have several structurally less specific effects (hypotensive, local anaesthetic, spasmolytic).
CNDO/S CI calculation of spin-orbit coupling and intersystem crossing in photochemical biradical formation reaction
Authors: Minaev Boris F. , Kižner David M.
Published: August 2011

The CNDO/S CI method has been employed to calculate potential curves for singlet and triplet states along reaction path for photolysis of cyclopentanone (dissociation of the C-C bond and biradical formation). Spin-orbit coupling between these two states and the probability of intersystem crossing (ISC) in Landau-Zener approximation were calculated. This probability has proved enough to compete with nuclear spin induced ISC process. In this way some peculiarities of chemically induced dynamic nuclear polarization in formation of products via biradicals can be qualitatively understood.
Study of potential curves by UHF type methods. Potential curve of F2 molecule
Authors: Klimo Viliam , Tiňo Jozef
Published: August 2011

The potential curve of the F2 molecule was described with the use of the RHF, UHF, RMP2, UMP2, and PUHF methods and compared with the experimental one. Thus, the peculiarities of the various methods were revealed. The results suggest the direction of a further development of UHF type methods which would ensure a correct description of the given curve.
13C, 29Si, 115Sn, 117Sn and 119Sn NMR spectra of some triphenyl derivatives of elements of IVB group
Authors: Lyčka Antonín , Šnobl Dobroslav , Handlíř Karel , Holeček Jaroslav , Nádvorník Milan
Published: August 2011

13C, 29Si and Sn NMR spectra of ten compounds type (C6H5)3XY, four compounds type ((C6H5)3XO)2CrO2 and - for comparison - two compounds type (CH3CH2CH2CH2)3SnY and ((CH3CH2CH2CH2)3SnO)2CrO2 (X are elements of IVB group) have been measured in deuteriochloroform. The respective chemical shifts, absolute values of coupling constants nJ(119Sn13C) and 2J(119Sn117Sn) are given.
Fluorinated 3-diethylaminopropenoates and their reactions
Authors: Svoboda Jiří , Paleta Oldřich , Liška František , Dědek Václav
Published: August 2011

The reaction of diethylamine with methyl trifluoropropenoate (I), methyl 2-chloro-3,3-difluoropropenoate (II), methyl 3,3-difluoropropenoate III) and methyl 3-chloro-2,3-difluoropropenoate (IV) affords halogenated 3-diethylaminopropenoates V-VII via the vinylic substitution of fluorine or chlorine atoms. When hydrolyzed the latter give methyl N,N-diethylcarbamoylacetates X-XII. On addition of 1-butanol and 2,2,3,3-tetrafluoropropanol to aminopropenoates V-VII fluorinated 3-alkoxy-3-diethylaminopropenoates XIII-XVI were prepared which when hydrolyzed eliminate the diethylamino group under formation of alkyl methylpropanedioates XX to XXIII. Heating of aminoethers XIII-XVI at 150 °C gives 1-fluorobutane or 1,1,2,2,3-pentafluoropropane, respectively. These fluoro derivatives are also formed on heating of the mentioned alcohols with 3-diethylaminopropenoates V-VII. During the thermal decomposition of methyl 2-chloro-3-diethylamino-3-fluoro-3-(2,2,3,3-tetrafluoropropoxy)propanoate (XV) 3-chloro-1,1,2,2-tetrafluoropropane was formed as a by-product. The substitution of the hydroxyl group with fluorine is discussed from the point of view of preparative application.
Distribution of 4-O-methyl-D-glucuronic acid units in xylan of the bark of white willow (Salix alba L.)
Authors: Toman Rudolf , Kohn Rudolf , Malovíková Anna , Rosík Jozef
Published: August 2011

Homogeneous, water soluble 4-O-methyl-D-glucurono-D-xylan was isolated from the bark of white willow (Salix alba L.). The equivalent weight of the polymer was found to be 990, i.e. each sixth unit of D-xylose on average was substituted by 4-O-methyl-D-glucuronic acid. The single-ion activity coefficient of calcium counterions γCa2+ was estimated in a molecular disperse solution of calcium 4-O-methyl-D-glucurono-D-xylan. The mean distance of adjacent carboxyl groups, b = 1.1 nm, was obtained from the experimentally determined value γCa2+ = 0.39 using the relation γCa2+ = f(b). Comparison of the value b = 1.1 nm with the D-xylose unit length (0.50 nm) and the calculated value of the equivalent weight indicated the presence of blocks with a close arrangement of uronic acids in the D-xylan chain. In this case, as it follows from the conformation of the macromolecule, at least each second D-xylose on average bears the side monomeric 4-O-methyl-α-D-glucuronic acid unit at C(2). Blocks with a high concentration of uronic acid alternate with approximately three times greater blocks of unsubstituted, or very little substituted D-xylose units.
Terpenoid derivatives of 4-hydroxypropiophenone as juvenoids and juvenogens I.
Authors: Kahovcová Jitka , Romaňuk Miroslav
Published: August 2011

Using the reactions modifying the chemical structure of 4-(3,7-dimethyl-2,6-octadienyloxy)propiophenone and 4-(3,7-dimethyl-2-octenyloxy)propiophenone a number of potential juvenoids and juvenogens were synthetized.
Alkaloids of Buxus sempervirens var rotundifolia BAILLON
Authors: Thien Huong Le thi , Votický Zdeno , Paulík Vladimír
Published: August 2011

Twenty one alkaloids were isolated from the leaves of Buxus sempervirens var rotundifolia BAILLON. Buxaminol-B, cyclobuxine-D, cyclovirobuxine-D, cycloprotobuxine-C, buxamine-E, buxtauine-M and buxpiine-K were those already known. New alkaloids, the constitution and configuration of which were inferred from physical data and corroborated by interconversion and correlation, were denominated buxithienine-M and cyclobuxophylline-O. The remaining bases were characterized by physico-chemical constant and/or spectral data.
A discussion on equations of phase equilibrium between two regular binary phases
Authors: Vřešťál Jan
Published: August 2011

The conditions of the existence of extreme on the concentration dependences of absolute temperature (x are mole fractions) T = Tα(xkα) and T = Tβ(xkβ) denoting equilibrium between two binary regular solutions are generally developed under two assumptions: 1) Free enthalpy change of pure components k = i, j at transition from phase α to β is a linear function of temperature. 2) Concentration dependence of excess free enthalpy (identical with enthalpy) of solutions α and β, respectively, is described in regular model by one concentration and temperature independent parameter for each individual phase.
Mass transfer into the liquid in turbulent flow at high Schmidt numbers. Theoretical solution
Authors: Vašák František , Kolář Václav , Brož Zdeněk
Published: August 2011

Theoretical relation is derived describing the mass transfer into the liquid in turbulent flow with steady velocity profile, at high Schmidt numbers Sc ≥ 103 in the concentration entrance section. Graphical dependences describing the effect of parameters of the model on mass transfer coefficients are presented and discussed. It is demonstrated that for the limiting cases the derived theoretical solution transforms into familiar relations (asymptotes).
Preparation of polymers and reactive prepolymers by the aminolysis of acylbis(hexanelactams)
Authors: Stehlíček Jaroslav , Šebenda Jan
Published: August 2011

The aminolysis of N,N'-isophthaloyl and N,N'-terephthaloyl-bis(6-hexanelactam) with aliphatic diamines was used in the preparation of semiaromatic polyamides, in the extension of polymer chains and in the preparation of N,N'-[poly(oxyethylene)di(carbamoylbenzoyl)]bis(6-hexanelactams) under mild conditions (50-80 °C).
Cycloheptatriene dimers: New precursors of diamantane
Authors: Tureček František , Hanuš Vladimír , Sedmera Petr , Antropiusová Helena , Mach Karel
Published: August 2011

Dimerization of cycloheptatriene, catalyzed by titanium complexes, afforded pentacyclo[8.4.0.03,7.04,14.06,11]tetradeca-8,12-diene (I) (10%) and pentacyclo[7.5.0.02,8.05,14.07,11]tetradeca-3,12-diene (II) (90%). Structure of both dimers and their derivatives was determined by means of 1H NMR, 13C NMR and mass spectra. On heating, the diene II was converted into the more stable isomer I. On hydrogenation and further catalytic isomerization, both I and II gave diamantane in high yield.
13C NMR spectra of azachalcones
Authors: Liptaj Tibor , Mlynárik Vladimír , Remko Milan , Ďurinda Ján , Heger Jozef
Published: August 2011

13C NMR spectral parameters were obtained for chalcone and fourteen its aza- and diazaanalogues. Relative conformation of the carbonyl group with respect to the double bond was studied using changes in 3J(C(1')-Hα) and PCILO method. PCILO calculations together with experimental results show that with 2'-, 3'-, and 4'-azachalcones the s-cis isomer is the most stable form. Whereas the molecule of 2'-azachalcone is planar or nearly planar, in 3'- and 4'-azachalcones the carbonyl group and the olefinic bond planes make angle of 45°.
Reactions of ethyl 4-bromo-3-(2-furyl)-2-butenoate with nitrogen nucleophiles
Authors: Špirková Katarína , Kováč Jaroslav , Horsák Ivan , Dandárová Miloslava
Published: August 2011

Nucleophilic substitution reactions of ethyl 4-bromo-3-(2-furyl)-2-butenoate with nitrogen nucleophiles are described. UV, IR, and 1H NMR spectra of the prepared substances have been interpreted.
Reduction of 2-, 3- and 4-methylquinolines, 2-, 3- and 4-quinolylmethanols and corresponding quinolinecarboxaldehydes with triethylammonium formate
Authors: Ferles Miloslav , Kocián Oldřich
Published: August 2011

Reduction of the compounds mentioned in the title with triethylammonium formate gave 1-formyl-C-methyl-1,2,3,4-tetrahydroquinolines IIa-IIc. On reduction of derivatives substituted in the position 3 and 4 (Ib, Ic, Ie, If, Ih, Ii) the products of 1,2-addition are also formed i.e. IIIa, IIIb, and on reduction of 3-quinolylmethanol (Ie) and 3-quinolinecarboxaldehyde (Ih) the products of 1,4-addition, i.e. IVa, IVb also result. Alcohol If and aldehyde Ii also give the product of the reduction of the functional groups, i.e. 4-methylquinoline (Ic). When 3-quinolylmethanol (Ie) was prepared by reduction of aldehyde Ih with sodium borohydride 1,2,3,4-tetrahydro-3-quinolylmethanol (IIe) was also isolated.
Alkaloids from Papaver litwinowii FEDDE ex BORNM.
Authors: Slavík Jiří , Slavíková Leonora
Published: August 2011

From Papaver litwinowii FEDDE ex BORNM. aporheine ((+)-roemerine) was isolated as the dominant alkaloid in addition to minor alkaloids aporheine methohydroxide, corytuberine, hordenine, (-)-mecambrine, cryptopine, protopine and coptisine. The presence of small amounts of allocryptopine, corydine, isocorydine, scoulerine, corysamine and papaverrubine A, C, D and traces of E(?) was also proved. Corytuberine was now isolated from P. dubium L. as well.
Photoinduced decomposition of aryldiazonium salts
Authors: Jirkovský Jaromír , Fojtík Anton , Becker Heinz Georg Osmar
Published: August 2011

Flash photolysis of 1,4-benzoquinone (10-3 mol l-1) in an acetonitrile/water mixture (16 : 9 v/v) leads in the presence of 2,4,6-tri-tert-butylphenol (5 . 10-2 mol l-1) to semiquinone- and phenoxy radicals. In this paper the reactivity of semiquinone with benzenediazonium tetrafluoroborate and six of its para substituted derivatives was studied. A significant effect of the substituents on the reaction rate was observed and the direct electron transfer from semiquinone to the diazonium salt was found to be the rate determining step. Different reactivity of the acid-base forms of semiquinone leads, depending on the pH, to rate constant changes within a range of five orders of magnitude.
Mass transfer into the liquid in turbulent flow at high Schmidt numbers. Dissolution of benzoic acid into aqueous solutions of glycerol from internal surface of the pipe
Authors: Vašák František , Kolář Václav , Brož Zdeněk
Published: August 2011

Theoretical relation derived in the last study for calculation of the mass transfer coefficient in the region of not fully developed concentration profile at high Schmidt numbers has been verified experimentally. This experimental study has been devoted to measurements of the rate of benzoic acid dissolution into aqueous solutions of glycerol from the internal surface of the pipe of circular cross section in the range 933 ⪬ Sc ⪬ 225 000 and 5 000 ⪬ Re ⪬ 50 000. It has been possible to explain on basis of the theoretical model, the differences between the data of various authors and to obtain a unified description of the phenomena.
Saturation of activated carbon with hexachloroplatinic acid
Authors: Machek Vladimír , Hanika Jiří , Sporka Karel , Růžička Vlastimil
Published: August 2011

The course of saturation of activated carbon with hexachloroplatinic acid was studied in dependence on the solvent of the active component; the solvent was found to have a marked effect on the rate of saturation as well as on the attained concentration of chloroplatinic acid on the support. The effects of the saturation temperature and of the solvent type on the shape of the adsorption isotherm of chloroplatinic acid on the support were also investigated.
Mechanism of anionic coordination dimerization of isoprene
Authors: Bartoň Jan , Volka Karel , Kašpar Miroslav , Růžička Vlastimil
Published: August 2011

The mechanism of controlled anionic coordination dimerization of isoprene (i.e. 2-methyl-1,3-butadiene) in the system tetrahydrofuran-isoprene-alkali metal-dialkylamine was investigated by using absorption spectrophotometry in the range of visible radiation and gas chromatography. The effect of the alkali metal (Li, Na, K) and dialkylamine (dicyclohexylamine, N-isopropylcyclohexylamine, N-methylisopropylamine) on the absorption spectra was tested. By comparing chromatographic and spectrophotometric data, the absorption bands in the range of visible radiation were identified with the existence of π-complexes between oligomeric forms of isoprene and alkali metal dialkylamide.
Terpenoid derivatives of 4-hydroxypropiophenone as juvenoids and juvenogens. II
Authors: Kahovcová Jitka , Romaňuk Miroslav
Published: August 2011

A series of potential juvenoids and juvenogens was prepared by modifying the structure of 4-(3,7-dimethyl-2,6-octadienyloxy)propiophenone and 4-(3,7-dimethyl-2-octenyloxy)propiophenone.
Basic crystallographic data of anhydrous hexaamidocyclotriphosphazene and its monohydrate
Authors: Kouřil Milan , Žák Zdirad
Published: August 2011

Powder photographs of (PN(NH2)2)3 and (PN(NH2)2)3.H2O were indexed based on the lattice parameters obtained from the single crystal data, and the parameters were refined by using the least-squares method. The space groups belonging to the two crystalline substances are Pcba (Z = 8) and P1 (P1) (Z = 2), respectively.
The liquids temperature and supercooling ability of the calcium nitrate-dimethyl sulphoxide-water system
Authors: Pacák Petr , Sláma Ivo
Published: August 2011

The liquids temperatures have been measured for the system Ca(NO3)2-dimethyl sulphoxide-H2O over a concentration range of 0-28 mol% Ca(NO3)2 and 0-100 mol% dimethyl sulphoxide. Comparison is made between the aqueous and the nonaqueous system, and the supercooling ability of both systems is discussed.
Effect of mass transfer on the selectivity of consecutive reactions in a gas-liquid system
Authors: Kondelík Petr , Pašek Josef
Published: August 2011

A mathematical model of a gas-liquid discontinuous reactor was analyzed to find the range of conditions in which the selectivity of consecutive competitive reaction can be expected to decrease on account of mass transfer. The prediction obtained from the mathematical model was tested on a model reaction of addition of chlorine to 1,5-cyclooctadiene.
Thiol derivatives of cellulose as supports for the immobilization of non-thiol enzymes
Authors: Gemeiner Peter , Zemek Jiří
Published: August 2011

Thiosulfate derivatives, which can be reduced with mercaptoacetic acid, are suitable intermediates for the preparation of thiol derivatives of polymers. Thiosulfate derivatives of cellulose were prepared via chlorodeoxy- or via 3-chloro-2-hydroxy-propylcellulose, while mercaptodeoxycellulose prepared via chlorodeoxy derivative had more convenient properties for the immobilization of non-thiol enzymes (acetylcholine esterase, butyrylcholine esterase and trypsin). Before immobilization SH groups were introduced into choline esterases by i) reduction of the cystine residues, ii) reaction with methyl 4-mercaptobutyrimidate, and the isothiocyanate groups were introduced into trypsin on reaction with 3-isothiocyanatopropyl 1-isocyanate. The immobilization of the enzymes treated in this way was carried out under the conditions of the oxidation of thiol groups (i), thiol-disulfide exchange reaction (ii), or an addition nucleophilic reaction of isothiocyanates with thiols. In contrast to the proteolytic activity of the immobilized trypsin the esterolytic activity of immobilized choline esterases attained satisfactory values.
Intramolecular binding of calcium ions to L-guluronan and D-galacturonan
Authors: Kohn Rudolf , Malovíková Anna
Published: August 2011

The values of activity coefficients γCa2+, determined earlier in solutions of calcium oligoguluronates and oligogalacturonates of various polymerization degree n, were interpreted. Values γCa2+ corresponding to an intramolecular Ca2+ bond to a polymeric chain of L-guluronan and D-galacturonan were obtained by extrapolation of functions γCa2+ = f(1/n) and γCa2+ = f((n-2)/n) to lim n → ##h. The γCa2+ values were compared with those determined in solutions of calcium salts of O-acetyl derivatives of pectic acid and D-mannuronan. In molecular disperse solutions the Ca2+ ions are bound to L-guluronan and D-galacturonan by an electrostatic bond. The course of the above-mentioned functions leads to the conclusion that both terminal uronic acid units in polyuronates under study bind Ca2+ ions less firmly than do the inner units in the macromolecule chain. The linear course of the function γCa2+ = f((n-2)/n) for L-guluronan proves the additivity of contribution of the terminal and inner uronic acid units to the total activity of Ca2+ counterions bound to L-guluronan.
Conformational dependence of solvation energy of phosphates
Authors: Bleha Tomáš , Mlýnek Ján , Tvaroška Igor
Published: August 2011

Conformational dependence of solvation energy has been calculated for dimethyl phosphate, its monoanion and ion pair with the proton considering rotation about P-O bonds in the molecules. The solvent (water) effect has been expressed using the continuous model according to Sinanoglu. Contribution of individual terms (electrostatic, dispersion and cavity) of the solvation energy in the stabilization of individual conformers has been analyzed. Some of methodical problems of the calculation of solvation energy have been discussed and particularly the inevitability of reliable determination of torsional dependence of molecular volume has been stressed. A comparison of the three molecules has shown that different character of the solvation energy dependences is due to the electrostatic term and is connected with orientation of the group dipole moment of the central PO2 group in the individual molecules.
Kinetics of oxidation of 2,4-pentanedione with Ce(IV) ions in relation to Belousov-Zhabotinskii reaction
Authors: Treindl Ľudovít , Kaplán Peter
Published: August 2011

Oxidation of 2,4-pentanedione with Ce(IV) ions in a solution of sulphuric acid is an inner-sphere reaction which proceeds via an intermediary complex. The reaction is of the first order with respect to both reactants, it is catalysed with H3O+ ions, and its rate diminishes with increasing concentrations of HSO4- and Ce(III) ions. According to the proposed mechanism, the rate-determining reaction step is an intramolecular redox step of the intermediary complex. The modified Belousov-Zhabotinskii reaction with 2,4-pentanedione as substrate is interesting in that oscillations with an increasing amplitude are formed after an induction period even in the absence of stirring.
Calcium selenites
Authors: Ebert Miroslav , Havlíček David
Published: August 2011

The following selenites were studied by the solubility method, thermal analysis, powder X-ray diagrams, and IR molecular spectroscopy: CaSeO3.H2O, CaSeO3 (two crystalline modifications), Ca(HSeO3)2.H2O, CaSe2O5, and Ca2S3O8 (hitherto unknown). Exact conditions for the preparation of the selenites and their bonding relations are given.
Synthesis of B-alkyl derivatives of o-carborane by alkylation under electrophilic conditions; Scope and limitation
Authors: Plešek Jaromír , Plzák Zbyněk , Stuchlík Jiří , Heřmánek Stanislav
Published: August 2011

The reaction of o-carborane with 13 alkylation agents in CS2 over AlCl3 using different ratios of reactants was investigated. Alkylation succeeded with CH3X, C2H5X and i-C3H7X whereas other used agents failed. Only i-C3H7Br alkylated in nitromethane. A rich mixture resulted even with o-carborane: RX 1 : 1 ratio. In the presence of H2SO4 o-carborane was isopropylated with i-C3H7OH, no other alcohols or olefins reacted. Alkyls enter stepwise B-9(12) > B-8(10) > B-4(5,7,11) positions, facilitating always the introduction of further alkyl into the skeleton. On ethylation, the most ethylated product was 4,5,7,8,9,10,12-(C2H5)7-1,2-C2B10H5. Seven B-alkyl and polyalkyl derivatives were isolated as individua. With C6H5Br-AlCl3 no reaction occurred at 27 °C, while only a transfer of Br into 9-position was observed at 127 °C. Possible mechanisms of B-substitution under electrophilic conditions are discussed.
Extraction study of hafnium complexes with aliphatic hydroxy acids
Authors: Hála Jiří , Londýn Petr
Published: August 2011

Hafnium complexes with glycolic, lactic, malic, tartaric and citric acids were studied in perchlorate medium (1.0-3.0 mol l-1 HClO4) by using the competitive extraction method. In the hydroxy acid concentration region 0.01-1.0 or 2.0 mol l-1, complexes with the hafnium-to-ligand ratios 1 : 1 and 1 : 2 (in the case of lactic and malic acids also 1 : 3) were identified and their stability constants determined. One proton is split off during the formation in acidic medium, a five-membered chelate ring being formed with the Hf(IV) cation bonded to the non-dissociated hydroxy group of the ligand.
13C NMR study of substituted quinone methides. 2- and 2,6-substituted fuchsones
Authors: Lyčka Antonín , Šnobl Dobroslav , Koutek Bohumír , Pavlíčková Libuše , Souček Milan
Published: August 2011

Carbon-13 chemical shifts and 1J(CH) coupling constants for 11 fuchsones of the types I and II in deuteriochloroform are reported. The assignments are based on an analysis of proton coupled and proton decoupled spectra and on the analogy to chemical shifts of some structuraly related compounds. Satisfactory Swain-Lupton F and R correlations which were found for most of 13C chemical shifts afforded values for percent resonance contributions to transmission of substituent effects as follows, C(1), 19%; C(3), 71%; C(7), 43%. Some alternative correlations for other similar systems e.g. quinones and tropones are also given.
3-(s-Hydrindacen-4-yl)propylamines and 4-(s-hydrindacen-4-yl)butylamines; Synthesis and pharmacological screening
Authors: Vejdělek Zdeněk , Bartošová Marie , Protiva Miroslav
Published: August 2011

4-Chloromethyl-s-hydrindacene (VIIa) was transformed via the malonic acid derivatives VIIIa and IXa to the acid Xb which afforded in four steps the homological acid Xc. Reactions of chlorides of both acids (XIbc ) with dimethylamine, 1-methylpiperazine and 1-(2-hydroxyethyl)piperazine led to the amides XIIbc-XIVbc which were reduced with lithium aluminium hydride to the title compounds IVcd-VIcd. The amines obtained show central neuroleptic effects only in subtoxic doses; they are also potent local anaesthetics and have significant spasmolytic activity of the neurotropic as well as musculotropic type.
Potential metabolites of tricyclic neuroleptics: 3,7-Dimethoxy and 7,8-dimethoxy derivatives of 10-(4-methylpiperazino)-10,11-dihydrodibenzo[b,f]thiepin
Authors: Protiva Miroslav , Šindelář Karel , Šedivý Zdeněk , Holubek Jiří , Bartošová Marie
Published: August 2011

Reaction of 2-iodo-4-methoxybenzoic acid with 3-methoxythiophenol resulted in the acid II which was transformed via the alcohol III and the nitrile IV to [4-methoxy-2-(3-methoxyphenylthio)phenyl]acetic acid (V). Reaction of (2-iodophenyl)acetic acid with 3,4-dimethoxythiophenol gave the isomeric [2-(3,4-dimethoxyphenylthio)phenyl]acetic acid (XI). Acids V and XI afforded by cyclization the ketones VIa and VIb which were converted by reactions with 1-methylpiperazine and titanium tetrachloride to the enamines IXa and IXb. Reduction of these enamines with diborane led to the title compounds. Attempts to reduce the enamines with zinc in acetic acid resulted in hydrogenolysis, the main products being 2,3-dimethoxy- and 3,7-dimethoxy-10,11-dihydrodibenzo[b,f]thiepin (Xab).
Synthesis of 5,6-cyclopropanocholestane derivatives with an oxygen function in position 7
Authors: Kohout Ladislav
Published: August 2011

Synthesis of the all four possible isomeric 7-hydroxy-5,6-cyclopropanocholestane derivatives is described starting from 5-cholesten-7-one and using Simmons-Smith methylenation.
Hydrogenation of 12-oxo-5β-chol-9(11)-enates on platinum
Authors: Kasal Alexander
Published: August 2011

Methyl 12-oxo-5β-chol-9(11)-enates with various substituents in the position 3 were prepared and the conditions were found under which hydrogenation of the supposedly resistent double bond to 9α-cholanates takes place. Under these conditions the products of deoxygenation in the position 12, and in the case of the hydrogenation of 3-oxo derivatives the products of deoxygenation in the position 3, were isolated as side-products of this reaction. The rate of the last mentioned reaction is a function of the excess of the catalyst.
Prolonged antidiuretic action of vasopressin analogues in relation to their primary structure
Authors: Škopková Jana , Hrbas Pavel , Slaninová Jiřina , Barth Tomislav
Published: August 2011

The effectiveness of vasopressin analogues with prolonged antidiuretic action was related to their primary structure. Prolonged action was primarily due to the absence of the amino group of cysteine in position 1 of the peptide chain. The carba substitution of the disulphide bridge and introduction of basic homologous amino acids into position 8 contributed in differing degrees to the prolonged action of the analogues. [8-L-Norarginine]deamino vasopressin was the most potent of the analogues compared; its action was 10 times more prolonged than that of dDAVP.
Haemoglobin stabilization during lyophilization with saccharides. Perturbation effect of polyethylene glycols
Authors: Přistoupil Tomáš I. , Ulrych Stanislav , Kramlová Marie
Published: August 2011

The stabilizing effect of glucose and sucrose upon haemoglobin molecules against oxidation during lyophilization was perturbated by the presence of fluid or greasy polyethylene glycols (m.w. 300-600 daltons) but not of the rigid ones (m.w. 1 500-6 000 daltons). The results corroborate the idea of a simple mechanical nature of haemoglobin stabilization under study.
Decomposition of hydrogen peroxide on nickel oxide-manganese sesquioxide two-component catalysts and effect of ionizing radiation on them
Authors: Múčka Viliam
Published: August 2011

The catalytic and some physico-chemical properties were studied of nickel oxide-manganese sesquioxide two-component catalysts with various proportions of the constituents. Decomposition of hydrogen peroxide in aqueous solution with the initial concentration 1.2 mol l-1 served as testing reaction. The catalyst components affect each other; the effect, being highest in the region of 20-30 mol.% manganese sesquioxide, brings about an enhanced dispersity of the system, with the result of increased surface area, increased amount of overstoichiometric oxygen and deficit in chemical analysis. Furthermore, the mutual component influencing appears in the specific catalytic activity of the system and in the amount of overstoichiometric oxygen per unit surface area, which is highest at 85 mol.% Mn2O3. A model of the mechanism is suggested for the reaction under study, based on the concept of bivalent catalytic centres, assuming that during the reaction, the high valency manganese species are gradually reduced as far as divalent manganese; this accounts for the occurrence of the observed two or three stages of hydrogen peroxide decomposition. Neither the mechanism of interaction of the two oxides nor the mechanism of the hydrogen peroxide decomposition changes on prior gamma irradiation of the catalyst. However, the irradiation affects markedly the catalytic activity of the system, the effect for catalyst of different composition being qualitatively different. Within the suggested concept of the reaction mechanism, the observed changes can be interpreted in terms of formation of non-eqilibrium charge carriers (electrons) resulting from the ionization both in the surface layer and in the catalyst bulk; after stabilization on the surface, the carriers may serve as adsorption centres for chemisorption of oxygen or may recombine with the catalytic centres of the reaction under study.
Decomposition of hydrogen peroxide on nickel oxide-molybdenum trioxide two-component catalysts and effect of gamma radiation and neutrons on them
Authors: Múčka Viliam
Published: August 2011

Decomposition of hydrogen peroxide in aqueous solution was studied on nickel oxide-molybdenum trioxide two-component catalysts with various proportions of the constituents covering the entire region of 0-100% of one component. The systems were found to comprise the two oxides and, in the region of 18-92 mol.% MoO3, a small quantity of nickel molybdate, which, however, does not affect appreciably their catalytic activity. A change in the kinetics of the reaction was found in its initial stage, which is probably associated with surface reduction of Mo6+ ions (major catalytic centres) to ions in lower oxidation state (minor centres) whose surface concentration determines the catalytic activity. The nickel oxide present probably accelerates this process, obviously occuring also during the ageing of the catalysts. In the regions of very low contents of one component the catalytic activity is determined by that of the major constituent, but is appreciably affected by the admixture oxide. In the range of 15 mol.% MoO3 both oxides contribute significantly to the catalytic activity; the activity is rather high, which is explained in terms of the concept of bivalent catalytic centres. In addition to the minor centres constituted by Ni3+ and probably also Mo5+ ions, determining the catalytic activity of the system, catalytic centres of another kind also take part in the reaction; these may be associated with structure defects on the catalyst surface. The greatest part play these centres in catalysts with roughly equal proportions of the two constituents. Neither the mutual influencing of the two components of the system nor the mechanism of the testing reaction alters on prior irradiation of the system by gamma radiation or by neutrons. The irradiation, however has a negative effect on the catalytic activity of the sample with 2.7 mol.% MoO3, both kinds of catalytic centres (of charge and structure nature, respectively) being probably affected. In the case of catalyst with 76.2 mol.% MoO3, radiation of both kinds induces increase in the catalytic activity; this is probably due to the establishment of a new equilibrium of the charge defects acting as catalytic centres in the reaction in question.
Hydrogen peroxide decomposition on a non-irradiated and gamma pre-irradiated NiO-U3O8 catalyst
Authors: Múčka Viliam
Published: August 2011

This paper deals with some physico-chemical properties of a two component catalyst NiO-U3O8, prepared with varying ratio of both components. Special interest was given to the catalytic properties - tested by decomposition of aqueous solution of hydrogen peroxide. The study presented evidence of mutual charge interaction between both components of the catalyst. This enables one to explain the observed behaviour of the studied system on the basis of the principle of bivalent sites. A pre-irradiation of a catalyst by gamma rays leads to significant increase of the oxidation states of both catalyst components.
Conformational structure of ethylene glycol dibenzoate. Vibrational and NMR spectra
Authors: Schneider Bohdan , Sedláček Pavel , Štokr Jan , Doskočilová Danica , Lövy Jan
Published: August 2011

It was found that three crystalline forms of ethylene glycol dibenzoate can be prepared. Infrared and Raman spectra of these three forms, as well as of the glassy and liquid states, were measured. From 3JHH coupling constants obtained by analysis of the 13C satellite band of the -CH2- group in 1H NMR spectra, and from the 3JCH coupling constants of the -CO.O.CH2- fragment obtained by analysis of the carbonyl band in 13C NMR spectra it was found that in the liquid state the -CH2-CH2- group exists predominantly in the gauche conformational structure, and the bonds C-O-C-C assume predominantly a trans orientation. The results of the analysis of NMR and vibrational spectra were used for the structural interpretation of conformationally sensitive bands in vibrational spectra of ethylene glycol dibenzoate.
A re-examination of the Eötvös equation
Authors: Exner Otto
Published: August 2011

The Eotvos equation (1) was re-examined from a purely empirical standpoint on a restricted but carefully selected set of compounds; the main intention was to test how an empirical equation of several variables can be verified by experiments. At a fixed temperature Eq. (1) is able to predict one of the three experimental quantities - surface tension, density, critical temperature - from the remaining two with a fair precision, but the range of validity as to the structure is rather restricted. At variable temperature and for a given compound, Eq. (1) describes the temperature dependence of surface tension provided the temperature dependence of density is known; however, the precision is low and a simpler and a more effective equation can be derived. If both temperature and structure are varied, Eq. (1) infers relationships of very low precision or even clearly invalid.
Reesterification of ethyl acetate by propanol catalysed by glycidyl methacrylate copolymers containing sulphonic acid groups
Authors: Setínek Karel
Published: August 2011

A series of differently crosslinked macroporous 2,3-epoxypropyl methacrylate-ethylenedimethacrylate copolymers with chemically bonded propylsulphonic acid groups were used as catalysts for the kinetic study of reesterification of ethyl acetate by n-propanol in the liquid phase at 52 °C and in the gas phase at 90 °C. Analysis of kinetic data by the method of nonlinear regression for a series of equations of the Langmuir-Hinshelwood type showed that kinetic equations which describe best the course of the reaction are the same as for the earlier studied sulphonated macroporous styrene-divinylbenzene copolymers. Compared types of catalysts differ, however, in the dependence of their activity on the degree of crosslinking of the copolymer used.
Kinetics and mechanism of hydrogenation of nitrobenzene by [diaquocobaloxime + amine] system
Authors: Tyrlik Stanislaw , Kwieciński Michal , Kawczyński Lech
Published: August 2011

The initial rate of nitrobenzene hydrogenation catalyzed homogeneously by cobaloximes is second order in cobalt and is inhibited by an excess of nitrobenzene. It also strongly depends upon cobaloxime : amino ratio. These observations were rationalized in terms of binuclear nitrobenzene-complexed intermediate as crucial in the catalytic cycle. This assumption was further supported by the unusual selectivity of cobaloxime system, which does not catalyze hydrogenation of ortho-substituted nitrobenzenes.
Study of properties of copper-modified platinum catalysts
Authors: Červený Libor , Paseka Ivo , Stuchlý Vladimír , Růžička Vlastimil
Published: August 2011

The properties of catalysts based on platinum black modified with copper were studied. The free platinum surface area and the amount of the surface copper were determined by potentiodynamic measurements; the isosteric heats of hydrogen adsorption were also measured. The catalysts were tested in gas phase dehydrogenation of cyclohexanol; after the reaction, and also after mere thermal exposition of the catalyst to hydrogen stream, the surface of the catalysts was re-examined.
Hydrogen solubility in organic solvents and adsorption from them on catalyst surface
Authors: Červený Libor , Vostrý Boris , Růžička Vlastimil
Published: August 2011

The effect of solvent on the adsorption of hydrogen on the surface on platinum catalyst was studied. The adsorption coefficient of hydrogen was found independent of the solvent used. The solubility of hydrogen was determined in 15 solvents.
Hydrolysis kinetics and mechanism of diaryldithiocarbamates in 20% aqueous dioxane
Authors: Mindl Jaromír , Sulzer Jiří , Večeřa Miroslav
Published: August 2011

Nine diaryldithiocarbamates have been prepared. Kinetic study of their hydrolysis has revealed that this hydrolysis proceeds by E1cB mechanism in the pH range 2 to 12. Values of activation entropies, reaction constants, Broensted coefficient, and comparison with reactivity of the corresponding N-methyl analogue have been used as criteria for the suggested mechanism. In acid media pH 2 to 0.4 and H0 -0.6 the hydrolysis follows a mechanism analogous to AAc2. Results of hydrolyses of dithiocarbamates, thiocarbamates and carbamates are compared.
Changes in human haemoglobin after its reaction with glutaraldehyde
Authors: Fričová Václava , Přistoupil Tomáš I. , Kramlová Marie , Ulrych Stanislav , Mařík Tomáš
Published: August 2011

The heterogeneity and molecular weight of human haemoglobin derivatives after their reaction with glutaraldehyde was examined. When subjected to polyacrylamide gel electrophoresis the intact and modified haemoglobin markedly differ: the former shows two fractions in the molecular weight range of 20 000 daltons whereas a series of fractions of molecular weight of 35 000-100 000 daltons are observed after the reaction with glutaraldehyde. Simultaneously the dissociation curves of oxyhaemoglobin vary as a function of glutaraldehyde concentration. The samples of modified haemoglobin show a higher affinity for oxygen than intact haemoglobin.
Process characteristics of screw impellers with a draught tube for Newtonian liquids. The power input
Authors: Seichter Pavel , Dohnal Jiří , Rieger František
Published: August 2011

An expression has been proposed for the power input of a screw impeller with a draught tube in the creeping flow regime based on the analogy with extruder screws. Experimental verification has confirmed practical utility of the expression in a wide range of geometrical parameters of the impeller and for the Reynolds number for mixing below 20. The total power input of the impeller is expressed as a sum of the input inducing the drag flow and the input to create the pressure flow. The former of the inputs may be deduced from the theory of extruders while an empirical approach based on experiment has been used to formulate an expression for the latter.
Process characteristics of screw impellers with a draught tube for Newtonian liquids. Pumping capacity of the impeller
Authors: Seichter Pavel
Published: August 2011

Velocity profiles and pumping capacity have been determined using a thermistor anemometer in a vessel equipped with a screw impeller. In region of the creeping flow of a Newtonian liquid, i.e. for Re <15, the dimensionless pumping capacity is dependent on the geometrical arrangement of the mixing system. The efficiency was assessed of individual configuration from the value energy criterion expressing the dimensionless power requirements for recirculation of a highly viscous liquid in a vessel equipped with a screw impeller.
Hydrogenation of maleic acid on nickel-magnesium oxide mixed catalysts and the isotope effect of solvent
Authors: Kudláček Rostislav , Rexová Jana
Published: August 2011

The activity of nickel-magnesium oxide mixed catalyst in liquid phase hydrogenation was investigated in dependence on the composition of the solid phase and on the preparation procedure. The isotope effect of substitution of light water by heavy water, the kinetic dependences, and the sorbed amount of the reacting maleic acid were examined with a view to deducing the reaction mechanism.
Porous electrodes for hydrogen peroxide preparation by oxygen reduction. The influence of temperature and pressure applied in preparation of the electrodes on their functional properties
Authors: Špalek Otomar , Balej Jan
Published: August 2011

The influence of the temperature and pressure applied in preparation of porous electrodes from Teflon-bonded carbon black on the hydrogen peroxide current yield and the current density was investigated. The porous structure, the wetted surface area of carbon black, and the electric resistance of the electrode mass were examined in order to establish the factors responsible for the varying electrode activity.
Comparison of non-empirical and semiempirical SCF MO calculations of non-substituted dihydropyridines
Authors: Böhm Stanislav , Kuthan Josef
Published: August 2011

Results of ab initio MO calculations of the dihydropyridine molecules I-V are confronted with analogous CNDO/2 and MINDO/3 calculations. The molecular energies calculated by means of the 4-31 G base predict the 6pi-electron isomers I and II to be the most stable dihydropyridine forms in contrast to the STO-3G and CNDO/2 data preferring the 4pi-electron isomers III-V. The charge distributions calculated non-empirically and semiempirically show different characteristic features.
Hydrogenation of alkenes on a nickel-tungsten-alumina catalyst
Authors: Uchytil Jan , Kočová Eva , Kraus Miloš
Published: August 2011

Eleven C2 to C8 alkenes were hydrogenated on a reduced sulphided industrial nickel-tungsten catalyst. Kinetics of the reaction was investigated in detail for ethylene and data were correlated by different equations. Best fit was obtained by three equations of the Langmuir-Hinshelwood type and these were used to describe hydrogenation of the other alkenes. Logarithms of the rate constants obtained were correlated linearly with the sum of steric constants E0s of substituents of semihydrogenated state R1R2R3C-*. Also adsorption coefficients of alkenes were structure dependent, increased with molecular weight of alkene and correlated roughly with boiling points.
13C NMR study of 7,7-disubstituted quinone methides
Authors: Lyčka Antonín , Šnobl Dobroslav , Koutek Bohumír , Pavlíčková Libuše , Souček Milan
Published: August 2011

Carbon-13 chemical shift assignments for nine 7,7-disubstituted 2,6-ditert-butylquinone methides of the types III-VI are reported. The 13C shifts of the exocyclic double bond carbon atoms are extraordinarily sensitive to C(7) substitution, viz. ΔδC(7) = 82.4 ppm and ΔδC(4) = 56.7 ppm on going from the dimethylamino to the cyano substituent. In contrast, electronic properties of the substituents are only weakly expressed on the carbonyl carbon atom. Satisfactory Swain-Lupton correlations were found for C(1), C(2) and C(4) chemical shifts yielding more than 50% of resonance contribution to the total transmission of substituent effects. Intercorrelations between the exocyclic double bond carbon chemical shifts of quinone methides and of identically substituted fulvenes as well as styrenes are also presented.
Solvent effect as a criterion of solvolysis mechanism. Solvolysis of 3-acyl-1,3-diphenyltriazenes
Authors: Pytela Oldřich , Svoboda Petr , Večeřa Miroslav
Published: August 2011

Solvent dependence of hydrolysis rate constants of 3-acetyl-1,3-diphenyltriazene (I) and 3-(N-methylcarbamoyl)-1,3-diphenyltriazene (II) has been followed in the solvent mixtures ethanol-water, methanol-water, dioxane-water, and formamide-water within the mole fraction x = 0.0 to 0.5 at 25, 35 and 45 °C. A criterion has been suggested, based on sign of change of logarithm of the observed rate constant in dependence on change of the solvent composition, for evaluation of the reaction molecularity and, hence, participation of water in the hydrolysis mechanism. It has been found that water takes part as a proton donor in the transition state of hydrolysis of the substrates studied.
Ketimine-enamine tautomerism of 2-ethoxycarbonylmethylene-4-methyl-3-oxo-1,2,3,4-tetrahydroquinoxaline: A kinetic study
Authors: Toman Jaromír , Štěrba Vojeslav , Klicnar Jiří
Published: August 2011

Tautomerism of the title compound in methanol in the presence of buffers is subject to general acid and base catalysis. The rate-limiting step of the acid-catalyzed reaction consists in addition of the proton to the methine carbon atom of the enamine form, whereas that of the base catalyzed reaction consists in protonation of the formed conjugated base of the enamine. Solvent effects on the equilibrium constant of the isomerization have been measured.
1-Substitution derivatives of 4-aryl-2,3-dibromo-1-naphthol
Authors: Křepelka Jiří , Roubík Jiří , Holubek Jiří
Published: August 2011

Alkylation of 7-ethyl-4-(4-ethylphenyl)-2,3-dibromo-1-naphthol (I) with ethyl esters of ω-bromoalkanoic acids XX-XXIII in a non-aqueous medium gave the 1-substitution derivatives II, IV, VI and VIII which were hydrolyzed to the acids III, V, VII and IX. The acid III was used for syntheses of the esters X-XIII and amides XIV-XVIII. Compounds II-XVIII exhibited moderate antineoplastic effects in animals with transplanted tumours; best results were observed with the compound II.
Vasopressin and oxytocin analogs with interchanged sequence of amino acids in positions 7 and 8. synthesis and biological effects
Authors: Bláha Ivo , Krchňák Viktor , Zaoral Milan
Published: August 2011

p-Toluenesulfonyl-S-benzylcysteinyl-tyrosyl-phenylalanyl-glutaminyl-asparaginyl-S-benzylcysteinyl-NG-p-toluenesulfanylarginyl-prolyl-glycineamide (I) and S-benzylcysteinyl-tyrosyl-isoleucyl-glutaminyl-asparaginyl-S-benzylcysteinyl-leucyl-prolyl-glycine amide (III) were prepared by solid phase synthesis. After removal of the protecting groups, closure of the disulfide ring, and purification by continuous free-flow electrophoresis [arginine7, proline8]vasopressin (II) and [leucine7, proline8]oxytocin (IV) were obtained. The antidiuretic effect of II is markedly higher than its pressor effect; IV possesses c. 6% of the uterotonic and c. 10% of the galactogogous effect of oxytocin.