bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal and molecular structure of potassium p-nitrophenolate monohydrate: Substituent effect on geometry of the ring in p-substituted nitrobenzene derivatives
Authors: Krygowski T. M. , Turowska-Tyrk I.
Published: February 2010

The crystal and molecular structure of potassium p-nitrophenolate monohydrate has been determined by X-ray diffraction methods giving R = 0.050. The through resonance effect between -O- and -NO2 groups resulted in a significant deformation of the ring geometry. Application of the HOSE model yielded in determination of the resonance structure contributions and offered an argument against the classical view of the through resonance effect: percentage contribution of quinoid form with full charge transfer from -O- to -NO2 was found to be the least significant of all four possible quinoid structures. Contributions of quinoid and benzenoid structures plotted against σ+ or σp constants for 14 p-systems give a reasonable linear dependence. Application of the additive scheme of substituent effect to the same series of compounds proved a strong reasonance effect from electron donating substituents and a much weaker one (and constant in the whole series) from the nitro group.
Significance test of refractive index of solvent in evaluation of effect of medium on rates of quaternization reactions of methyl iodide with amines
Authors: Nevěčná Taťjana , Bekárek Vojtěch
Published: February 2010

The rate constants have been measured of the reactions of methyl iodide with triethylamine (I) and tributylamine (III) at 293 K in twelve aprotic solvents, methyl iodide with tripropylamine (II) at 293, 313, 323, and 333 K in fifteen solvents differing greatly in their dipole moments, relative permittivities, and refractive indexes, and diiodomethane with tripropylamine in diiodomethane at 293 K (k1 = 2.1 10-5 s-1). The aprotic solvents predominantly affect the activation entropy which for the reaction of II varies from -200 J mol-1 s-1 (in cyclohexane) to -108 J mol-1 s-1 (in diiodomethane). The activation enthalpy of the reaction of methyl iodide with tripropylamine (II) is only little affected by aprotic solvents, a significant increase in activation enthalpy has been observed in the case of amphiprotic solvents. The evaluation of effect of medium on the rate constants of the above-mentioned reactions by means of the Kirkwood functions of relative permittivity and refractive index has shown a significant contribution of the refractive index of solvent which is comparable with the effect of relative permittivity.
Transmission of substituent effects in N-(p-substituted phenyl)-phthalimides
Authors: Holík Miroslav , Matějková Božena
Published: February 2010

Chemical shifts of benzene part of the title compounds have been correlated with substituent chemical shifts (SCS) increments a for 1H and z for 13C NMR spectra. These correlations gave pieces of information not only about the through-conjugation of substituents but also about the change of the twist about the central N-C bond with the change of substituent in the para-position. In such a way the electronic effects of substituents have been studied together with the effects due to conformational changes which manifest themselves with the change in the van der Waals repulsion and/or diamagnetic anisotropy of double bond. Chemical shifts in phthalimide part of molecule have been related to the electronic effect of distant substituent after separation of the main source of variation from random error by principal component analysis.
The quantification of protein bioactivity, Phage T4 lysozymes substituted at residue 86
Authors: Charton Marvin
Published: February 2010

Data taken from the literature for the activity of mutant Phage T4 lysozymes substituted at residue 86 were correlated with the intermolecular force (IMF) equation with very good results. The activity determined was the relative amount of enzyme required to give a cleared area with a radius of 7.00 mm in the lysoplate assay of Becktel and Baase. The best regression equation obtained shows hydrogen bonding to be the major factor in determining activity, with dispersion forces next in importance and steric effects least. No dependence on side chain charge was observed. The results support the utility of the IMF equation as a quantitative model of protein bioactivity.
Use of QSAR in design of antiinflammatory fluorinated arylalkanoic acids
Authors: Kuchař Miroslav , Grimová Jaroslava , Rejholec Václav , Tomková Hana , Jelínková Magda , Holubek Jiří
Published: February 2010

A series of 3-fluro-4-alkoxyphenylalkanoic acids III was synthetized and their antiinflammatory activity and fibrinolytic capacity was evaluated. The suitable fluorinated derivative with better pharmacological profile than 3-chloro-4-benzyloxyphenylacetic acid (benzofenac) was selected. Experimental, biological activities of acids III were compared with those calculated by introducing the physico-chemical parameters into the formerly derived regression equations. Good coincidence was found out, as well as similarity of the regression derived for the original series of acids extended by the acids III. Lipophilicity of the acids under study was evaluated by partition thin-layer chromatography; the values of log P of benzyloxy derivatives IIIc-IIIf were lower than tabulated values - probably due to the intramolecular hydrophobic interactions of aromatic nuclei.
Antimycobacterial thiobenzanilides
Authors: Waisser Karel , Houngbedji Nestor , Macháček Miloš , Sekera Miroslav , Urban Josef , Odlerová Želmíra
Published: February 2010

A group of 30 thiobenzanilides active against Mycobacterium kansasii have been synthesized and their 1H NMR and UV spectra and RM values (TLC on silica gel impregnated with methylsilicone oil) have been measured. From the correlation between the chemical shifts of the thioamide proton in the 1H NMR spectra and the Hammett constants it can be concluded that the substituents in both aromatic rings uniformly affect the electron density of the thioamide group. The antimycobacterial activity is probably connected with local molecular parameters and can be considered to be approximately additive with respect to both parts of the molecule.
Studies of the interface between mercury and solutions tetraalkylammonium salts in N,N'-dimethylformamide
Authors: Arévalo M. Carmen , Pastor Elena , González Sergio , Arévalo Augustín
Published: February 2010

The interface Hg/solution of tetraalkylammonium salts in N,N'-DMF was studied by using impedance and chronocoulometric measurements. The Cd-E and R-E curves were determined and maxima are noted at fairly negative potentials which are attributed to a change in orientation of the cations at the interface. The Q-t curves support this assumption revealing the existence of slow surface process at these potentials.
Temperature-programmed hydrogenation of surface carbonaceous deposits on a Ni/SiO2 methanation catalyst
Authors: Stuchlý Vladimír , Klusáček Karel
Published: February 2010

Hydrogenation of surface carbonaceous deposits from CO disproportionation or methanation on a high-weight loading commercial Ni/SiO2 catalyst was investigated by temperature-programmed surface reaction (TPSR). Two types of surface carbon (Cα and Cβ)were hydrogenated following the CO disproportionation. Adsorbed carbon monoxide was probably hydrogenated after CO methanation. Hydrogenation of Cα proceeded substantially faster than hydrogenation of Cβ and faster than hydrogenation of preadsorbed CO. Significantly lower activation energy was estimated for hydrogenation of Cα than for hydrogenation of CO (50 vs 90 kJ/mol). An approach for analysis of the data from a temperature-programmed experiment is given.
Extraction of scandium with tetraphenyl imidodiphosphate and its sulfur analogues, and the radiation stability of the reagent
Authors: Navrátil Oldřich , Herrmann Eckhard , Grossmann Gisbert , Teplý Jiří
Published: February 2010

Solvent extraction of scandium from perchloric or hydrochloric acid aqueous systems into benzene solutions of tetraphenyl imidodiphosphate, (PhO)2P(O)NHP(O)(PhO)2 (HA), and its sulfur analogues containing the P(O)NHP(S) or P(S)NHP(S) groups was studied. Behaving as weak acids in the aqueous phase, the reagents form complex extractable compounds ScA3 with scandium. The extraction constants were measured and found lower for the sulfur analogues than for the oxygen reagent. The configuration changes induced in the reagent by gamma irradiation from a 60Co source were studied by examining the extraction of scandium with it and by 31P NMR measurements. Whereas the changes in the solid reagent are not very marked and appear only at doses in excess of 800 kGy, the reagent dissolved in benzene exhibits configuration changes even on the application of doses at the 10 kGy level. This fact is related to the presence of benzene and dissolved oxygen in the system.
The polarographic and voltammetric determination of 2,6-dichloro-4-nitro-2'-acetylamino-4'-diethylaminoazobenzene
Authors: Barek Jiří , Civišová Dagmar , Ghosh Ashutosh , Zima Jiří
Published: February 2010

The polarographic reduction of the title azo dye has been studied, a mechanism has been proposed and optimal conditions have been found for its analytical use. The detection limit using a classical dropping mercury electrode was 2 . 10-7 mol l-1 for TAST polarography and 1 . 10-8 mol l-1 for differential pulse polarography. Using a hanging mercury drop electrode, the detection limit was 9 . 10-9 mol l-1 for fast scan differential pulse voltammetry and 1 . 10-8 mol l-1 for linear scan voltammetry. Adsorption accumulation of the test substance on the surface of the hanging mercury drop electrode led to a further decrease in the detection limit to 1 . 10-9 mol l-1 for fast scan differential pulse voltammetry and 7 . 10-10 mol l-1 for linear scan voltammetry.
The coulometric titration of the derivatives of N,N-dimethyl-4-aminoazobenzene by generated trivalent titanium
Authors: Barek Jiří , Kvapilová Helena , Pastor Tibor , Zima Jiří
Published: February 2010

Conditions for the coulometric generation of titanium(III) ions in buffer medium in the presence of sodium citrate were found on the basis of a study of the electrochemical behaviour of the Ti(III)/Ti(IV) system. A current efficiency of 100% was attained in acetic acid solution (c = 1 mol l-1) containing citric acid (c = 0.2 mol l-1) and titanium (IV) chloride (c = 0.1 mol l-1), with pH adjusted to 6 using sodium hydroxide, in the current density range 0.5 to 10 mA/cm2 using a mercury electrode and 1 to 2 mA/ cm2 using a paraffin-impregnated spectrographic carbon electrode. It was found that methanol does not affect the current efficiency at contents of up to 33% (v/v) and conditions were found for the coulometric titration of small amounts (0.2-2 mg) of some genotoxic derivatives of N,N-dimethyl-4-aminoazobenzene.
The crystal and molecular structure of scandium formate
Authors: Hašek Jindřich , Ondráček Jan , Karen Pavel , Bauer Jaroslav
Published: February 2010

The structure of Sc(HCOO)3 was refined up to R = 0.046. The substance crystallizes in the monoclinic system, space group P21/c, a = 10.340(2), b = 6.631(1), c = 9.027(2) Å, β = 98.11(2)°, Z = 4. Scandium atoms are placed in the two symmetrically non-equivalent centres of symmetry thus forming alternating layers parallel to the plane of b,c. All formate oxygens are coordinated to Sc atoms thus forming a three-dimensional net with octahedral coordination of both independent Sc atoms. C-H bonds are oriented in between the nearest oxygens of neighbouring formate groups, but only one contact is sufficiently short to be denoted as the C-H···O hydrogen bond. IR and Raman spectra seem to confirm the differences between formate anions.
Structure determination of N,N'-diphenylacetamidinium oxalate
Authors: Kratochvíl Bohumil , Novotný Jiří , Smrčková Svatava , Krechl Jiří
Published: February 2010

The structure of N,N'-diphenylacetamidinium oxalate was solved by direct methods and refined anisotropically to R = 0.036 for 1 551 unique observed reflections. The compound (C16H16N2O4) crystallizes in the P21/c space group with the lattice parameters a = 17.672(2), b = 8.263(3), c = 10.771(2) Å, β = 104.64(1)°, Z = 4. Intra- and intermolecular hydrogen bonds between amidinium nitrogens and oxalate oxygens of the N-H···O and O-H···O types form infinite chains parallel to the [010] direction in the structure. Mutual interactions between the chains are mediated by the van der Waals forces. Planes of the phenyl rings bisect at the dihedral angle of 55.8(1)°. In contrast to similar model structures benzamidinium pyruvate, benzamidinium bromoacetate and p-methylbenzamidinium formate monohydrate, the structure of N,N'-diphenylacetamidinium oxalate does not exhibit the amidine-carboxyl interaction through two parallel intramolecular N-H···O bonds.
N-substituted tricyclic isoquinoline hydantoins
Authors: Niopas Ioannis , Smail Gordon A.
Published: February 2010

Mannich condensation of the 1,3-dioxo-5H-10,10a-dihydroimidazo[1,5-b]isoquinoline (Ia) and 5-ethoxy-10-bromo-1,3-dioxo-5H-imidazo[1,5-b]isoquinoline (IVa) with secondary amines gave a series of N-2-aminomethyl isoquinoline hydantoins IIa-IIg and IVb, respectively. Alkylation of Ia with N,N-dialkylaminoethyl chlorides and ethyl chloroacetate afforded the N-dialkylaminoethyl and N-ethoxycarbonylmethyl derivatives Va, Vb and IIh. The N-2-hydroxymethyl and N-2-amino isoquinoline hydantoins IIj and If were also prepared.
Synthesis and reactions of condensed furan derivatives
Authors: Krutošíková Alžbeta
Published: February 2010

Synthesis of heterocyclic compounds containing a fused furan ring was studied. Substitution, addition and cycloaddition reactions of furo[3,2-b]pyrroles and their condensed derivatives involving the interesting transformations of furo[3,2-b]pyrrole system are presented.
Molecular connectivity indices revisited
Authors: Kunz Milan
Published: February 2010

It is shown that the product νiνj of degrees ν of vertices ij, incident with the edge ij, is the number of paths of length 1, 2, and 3 in which the edge is in the center. The unified connectivity index χm = Σ(νiνj)m, where the sum is made over all edges, with m = 1, is the sum of the number of edges, the Platt number and the polarity number. And it is identical with the half sum of the cube A3 of the adjacency matrix A. The Randić index χ-1/2 of regular graphs does not depend on their connectivity.
Additive-multiplicative description of extrathermodynamic relations: Application to solvent effect
Authors: Pytela Oldřich
Published: February 2010

The paper is focused on evaluation of significance of the additive-multiplicative model of extrathermodynamic relations (linear free energy relationships) as compared with the additive model. Application of the method of conjugated deviations to a data matrix describing manifestations of solvent effects in 367 processes in solutions (6 334 data) has shown that introduction of cross-terms into the additive model is statistically significant for a model with two and particularly three parameters. At the same time the calculation has provided a new set of statistical parameters for description of solvent effect with application of the additive-multiplicative model. Compared with an analogous set designated for the additive model, the new parameters show a lower mutual correlation, retaining the same nature of the properties described, i.e. polarity-acidity (PAC parameter), polarity-basicity (PBC), and polarity-polarizability (PPC).
A new classification of solvents based on chemometric empirical scale of parameters
Authors: Pytela Oldřich
Published: February 2010

The paper presents a classification of 51 solvents based on clustering in three-dimensional space formed by the empirical scale of PAC, PBC, and PPC parameters designed for interpretation of solvent effect on a model with cross-terms. For the classification used are the clustering methods of the nearest neighbour, of the furthest neighbour, of average bond, and the centroid method. As a result, the solvents have been divided into 8 classes denoted as: I - nonpolar-inert solvents (aliphatic hydrocarbons), IIp - nonpolar-polarizable (aromatic hydrocarbons, tetrachloromethane, carbon disulphide), IIb - nonpolar-basic (ethers, triethylamine), IIIp - little polar-polarizable (aliphatic halogen derivatives, substituted benzenes with heteroatom-containing substituents), IIIb - little polar-basic (cyclic ethers, ketones, esters, pyridine), IVa - polar-aprotic (acetanhydride, dialkylamides, acetonitrile, nitromethane, dimethyl sulfoxide, sulfolane), IVp - polar-protic (alcohols, acetic acid), and V - exceptional solvents (water, formamide, glycol, hexamethylphosphoric triamide). The information content of the individual parameters used for the classification has been determined. The classification is based primarily on solvent polarity/acidity (PAC), less on polarity/basicity (PBC), and the least on polarity/polarizability (PPC). Causal relation between chemical structure of solvent and its effect on the process taking place therein has been established.
Preferential cis-olefin formation: A striking resemblance between alkali-alkoxide and alumina promoted eliminations in low polar solvents
Authors: Závada Jiří , Pánková Magdalena
Published: February 2010

Olefin-isomer distribution has been investigated in the Woelm alumina promoted elimination from a series of 2-decyl and 5-decyl derivatives (X = F, Cl, Br, I, OTs) in ether. From the observed effect of leaving group it has been inferred that the heterogeneous reaction is a concerted process. A comparison has been made with corresponding results from homogeneous, alkali-alkoxide promoted eliminations in low polar solvents. A striking similarity in steric course between the two reactions has been noted and explained in terms of acid-base co-catalysis.
The structure of products of coupling of arenediazonium salts with 3-aminocrotononitrile derivatives
Authors: Elnagdi Mohamed Hilmy , Sadek Kamal Usef , Taha Nadia Mohamed , Yassin Youssef Mahfous
Published: February 2010

The structure of products of coupling arenediazonium salts with 3-aminocrotononitrile derivatives is reported. The spectral data as well as the chemical behaviour of coupling products indicated that it is the hydrazone in (E)-form.
Preparation of N-protected α-amino alcohols by acetoxyborohydride reduction of N-protected α-amino acid esters
Authors: Souček Milan , Urban Ján , Šaman David
Published: February 2010

N-Protected α-amino alcohols were prepared by reduction of N-protected α-amino acid esters by sodium acetoxyborohydride in dioxane at elevated temperature. The reductions proceed with excellent yields and without racemisation. Reduction of the carbamate protecting groups was not observed.
Conformation of ring A in triterpenoid and 4,4-dimethylsteroid 3-ketones. Chemical shifts of methyl protons and lanthanide and benzene induced shifts
Authors: Klinot Jiří , Buděšínský Miloš , Světlý Jarmil
Published: February 2010

Chemical shifts of signals due to methyl groups in position 10β (in CDCl3) and 4α and 4β (in C6D6) in 1H NMR spectra of pentacyclic triterpene 3-oxo derivatives (V, VIII, IX, and XII) are suitable for estimation of chair-boat equilibrium in the ring A. Benzene and lanthanide induced shifts of 4α and 4β-methyl protons were also used for this purpose. The results obtained with 2α-methyl-3-ketones (III, X) and 2β-methyl-3-ketones (IV, XI) as the respective chair and boat models agree well with those derived from other physical data (about 40% boat). The same methods were applied to 4,4-dimethylsteroid 3-ketones XV-XVII.
Open-ring models of hetero-cannabinoids: Synthesis of 2-(alkylthio)-5-(2-aminoethyl)hydroquinone derivatives
Authors: Šindelář Karel , Holubek Jiří , Svátek Emil , Schlanger Jiří , Dlabač Antonín , Valchář Martin , Hrubantová Marta , Protiva Miroslav
Published: February 2010

2,5-Dimethoxythiophenol was S-alkylated with pentyl bromide and heptyl bromide, the sulfides IVa,b were chloromethylated and the products were transformed to the nitriles VIIa,b. Reduction with aluminium hydride gave the amines XIIIa,b which were transformed to N-methyl- and N,N-dimethyl derivatives XVa,b and XVIa,b. Alkylation of the nitriles VIIa,b with 2-propyl bromide and the following reduction with aluminium hydride led under simultaneous partial demethylation to monophenolic amines XVIIIa,b. Methylation of these amines gave the N-(monomethyl) compound XIXa and the N,N-dimethyl compound XXb. The complete O-demethylation of XXb with boron tribromide or iodotrimethylsilane gave the hydroquinone XXI in the form of the corresponding salt (hydrobromide, hydroiodide). Compound XIIIb (hydrogen maleate VUFB-16 519) exhibited interesting antireserpine activity in two tests and may be considered a potential antidepressant.
Potential neuroleptics of the orthopramide series; Synthesis of N-(3-(tert.amino)propyl)-5-sulfamoyl-2-methoxybenzamides
Authors: Valenta Vladimír , Vlková Marie , Holubek Jiří , Svátek Emil , Metyšová Jiřina , Protiva Miroslav
Published: February 2010

Heating ethyl 5-sulfamoyl-2-methoxybenzoate with a series of twelve 3-(tert.amino)propylamines (IIIa-IIIl) afforded the title compounds IIa-IIl which were transformed to salts and subjected to pharmacological screening as potential neuroleptics of the sulpiride series. Only compounds IId (hydrogen oxalate, VUFB-15 453) and IIg (methanesulfonate, VUFB-15 397) showed indications of the desired psychotropic activity.
Properties and reactivity of first and second row hydrides. Introductory remarks, isomerizations, and inversion barriers of the AH2, AH3, AH4 and related systems
Authors: Zahradník Rudolf , Havlas Zdeněk , Hess B. Andes , Hobza Pavel
Published: February 2010

In this paper and in the following parts of this series chemical reactivity and physical characteristics of hydrides of the first (LiH, BeH2, BH3, CH4, NH3, H2O, HF) and second (NaH, MgH2, AlH3, SiH4, PH3, H2S, HCl) row atoms of the Periodic System are discussed in terms of nonempirical quantum chemical characteristics. Semiquantitative features and tendencies rather than quantitative aspects of reactivity are investigated, which permits one to use rather modest theoretical methods. Besides the members of the mentioned series also radicals, ions, and radical ions thereof will be treated. In this part isomerizations of ìunnaturalî ionic hydrides (cations derived from electron-deficient and anions derived from electron-rich hydrides, e.g., LiH(+). and LiH2(+) or HF(-)., H2F(-)) are studied. One or two van der Waals ions derived from all these systems represent thermodynamically rather stable forms. Relations between structure and inversion barriers have been studied for bent triatomic (C2v), pyramidal tetraatomic (C3v) and tetrahedral pentaatomic (Td) molecules and ions. Inversion barriers increase when passing from the first-row C2v and C3v hydrides to higher-row analogues; both decrease (e.g., CH4 → SiH4) as well as increase (e.g., BH4(-) → AlH4(-)) were calculated for transitions of Td hydrides.
Potential-pH diagrams for the systems Ir-H2O-Cl-, Pt-H2O-Cl-, and Pd-H2O-Cl- at 25 °C
Authors: Loučka Tomáš , Ternbach Zdenko
Published: February 2010

On the basis of available thermodynamic data, potential-pH diagrams have been calculated for the systems Ir-H2O-Cl-, Pt-H2O-Cl-, and Pd-H2O-Cl- in a 264 g/l NaCl aqueous solution at 25 °C.
Crystal and molecular structure of potassium [Δ,Λ-racemic-(1-phenylethylenediamine-N,N,N',N'-tetraacetato)cobaltate(III)] sesquihydrate
Authors: Kettmann Viktor , Kalina Marián E. , Lučanský Ján , Strašák Milan
Published: February 2010

The crystal and molecular structure of the title compound was determined by X-ray analysis. It crystallizes in the orthorhombic system, space group Ccc2, with cell parameters a = 3.773(3), b = 1.404(11), c = 0.6962(6) nm, V = 3.687 nm3, and Z = 8. The main factors determining stereochemistry of the complex are intramolecular hydrophobic stacking interaction between the methylene hydrogens of the out-of-plane R1 ring and the aromatic ring of the phenyl group, and the nonbonding van der Waals interactions between the methylene hydrogens of the central ethylenediamine (E), in-plane glycinate (G) and R rings as well as of the hydrogens of the phenyl group. The observed stereospecific coordination is due to an energy preference for the equatorially located phenyl group on the E ring.
4-Aminoethylene derivatives of 2-methylbenzotriazole
Authors: Milata Viktor , Ilavský Dušan , Goljer Igor , Leško Ján , Chahinian Marc , Henry-Basch Erica
Published: February 2010

N-Methylation of 4(7)-nitrobenzotriazole (I) afforded a mixture of three isomers; one of them, 4-nitro-2-methylbenzotriazole (II) could easily be isolated. Catalytical hydrogenation of II led to the corresponding amine which in turn, afforded products of nucleophilic substitution IVa-IVi on reaction with alkoxymethylene derivatives IIIa-IIIi. Thermal cyclocondensation of IVi yielded 7-ethoxycarbonyl-6,9-dihydro-6-oxo-2-methyl-2H-triazolo[4,5-h]quinoline (V). The structure of all products was deduced from the IR, UV, 1H and 13C NMR spectral data.
Potential antidepressants: 1-(2-(Methoxy- and hydroxyphenylthio)phenyl)-2-propylamines
Authors: Urban Jiří , Šedivý Zdeněk , Holubek Jiří , Svátek Emil , Ryska Miroslav , Koruna Ivan , Dlabač Antonín , Valchář Martin , Metyšová Jiřina , Polívka Zdeněk , Šindelář Karel , Pomykáček Josef , Hrubantová Marta , Protiva Miroslav
Published: February 2010

2-(Methoxyphenylthio)benzaldehydes Xa-Xd were reacted with nitroethane in boiling acetic acid to give the corresponding 1-aryl-2-nitropropenes XIIa-XIId; benzonitriles XIIIa and XIIIc and benzaldoximes XXIc and XXId were isolated as by-products. Chromatographed compounds XIIa-XIId were reduced with lithium aluminium hydride to the primary amines VIIa-VIId, and formylated by heating with ethyl formate to the formamides XIVa, XIVc, and XIVd. Reduction of the formamides with lithium aluminium hydride afforded the secondary amines VIIIa, VIIIc, and VIIId, and methylation of the primary amines with formic acid and formaldehyde gave the tertiary amines IXa, IXc, and IXd. Compound VIIIa was prepared also by an alternative route starting from the nitrile XIIIa and proceeding via XIXa and XIVa. Some of the methoxylated amines were demethylated either by heating with pyridine hydrochloride or by treatment with boron tribromide to the title compounds IVa, IVc, Vc, Vd, VIa, and VIc. The amines prepared were transformed to salts for characterization and for pharmacological testing. Compound VIIIa (hydrogen oxalate V⁄FB-15 475) showed clearly the character of a potential antidepressant.
Comments on the Antonow and interfacial interaction rules
Authors: Kloubek Jan
Published: February 2010

Results presented for the aliphatic hydrocarbon-water interface show that the recent hypothesis of the free energy minimization called interfacial interaction rule, which was suggested as a theoretical base of the Antonow rule, cannot be generally valid.
The effect of random and systematic errors of the equilibrium distribution concentrations on the number of stages of countercurrent extraction with various consumption of solvent
Authors: Dojčanský Ján , Bafrncová Soňa , Surový Július
Published: February 2010

On using five hypothetical systems differing in the extent of mutual solubility of components, tie-line slope, and type of binodal curve, the effect is evaluated of random and systematic errors in the liquid-liquid equilibrium distribution concentrations on the accuracy of calculated number of theoretical stages of isothermal countercurrent extraction under different operating conditions.
13C and 119Sn NMR spectra of diphenyl- and dibenzyltin(IV) compounds and their complexes
Authors: Holeček Jaroslav , Lyčka Antonín , Handlíř Karel , Nádvorník Milan
Published: February 2010

13C and 119Sn NMR spectra of diphenyl- and dibenzyltin(IV) compounds have been studied in solutions of coordinating and non-coordinating solvents. Regions of values of the δ(119Sn) chemical shifts have been determined which characterize individual types of coordination of the central tin atom. The values of 13C NMR spectral parameters, the δ(13C) chemical shifts and nJ(119Sn, 13C) coupling constants, have been used to describe the real shapes of coordination sphere of the central tin atom and to discuss the internal structure of the organic substituents and of the nature of their bonding linkage to the tin atom.
8-Acyl-7-phenylbicyclo[2.2.2]-2,6-diones by rearrangement of 3-acyloxy-5-(2-phenylethenyl)-2-cyclohexen-1-ones. 1H and 13C NMR spectral evidence of their structure
Authors: Hrnčiar Pavel , Liptay Tibor , Šraga Ján
Published: February 2010

3-Acyloxy-5-(2-phenylethenyl)-2-cyclohexen-1-ones II were prepared by O-acylation of 5-(2-phenylethenyl)-1,3-cycloxanedione (I). Treatment of II with AlCl3 resulted in rearrangement of the acyl group to the double bond of the phenylethenyl grouping followed by cyclization to 8-acyl-7-phenylbicyclo[2.2.2]octane-2,6-diones III. Their structure was evidenced by analysis of the 1H and 13C NMR spectral data.
Titanium-mediated Dieckmann condensation
Authors: Pátek Marcel
Published: February 2010

The Dieckmann condensation of alkyl 2-(N-methyl-N-(alkoxycarbonylmethyl)sulfamoyl)-benzoates Ia and Ib with titanium tetrachloride-tert-amine or butyltitanium ate complex III affords alkyl 4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxides IIa and IIb which are the piroxicam intermediates.
Derivatives of 5α-androstan-3α- and 3β-ol with acrylate side chain
Authors: Pouzar Vladimír , Chodounská Hana , Sameš Dalibor , Drašar Pavel , Havel Miroslav
Published: February 2010

Hydroxy derivatives I, II, III, XVII and XX were oxidized to give the respective aldehydes IV, V, VI, XVIII and XXI which were further converted by Wittig-Horner reaction into unsaturated methyl and ethyl esters. Removal of the acetal protecting group in position 3 afforded methylesters X, XXIV and XXXVI and ethyl esters XIV, XXV and XXXVII. Compounds XXIV, XXV, XXXVI and XXXVII were converted into the corresponding hemisuccinates XXVIII, XXIX, XL and XLI and β-D-glucosides XXXII, XXXIII, XLIV and XLV.
Potential antidepressant and anti-inflammatory agents: 4-(2-Propylthio)acetophenone oximes and 4-(2-propylthio)phenylalkanoic acids
Authors: Jílek Jiří , Šindelář Karel , Grimová Jaroslava , Maturová Eva , Holubek Jiří , Svátek Emil , Metyšová Jiřina , Metyš Jan , Hrubantová Marta , Protiva Miroslav
Published: February 2010

4-(2-Propylthio)acetophenone oxime (IV) was reacted with 2-aminoethyl chloride and 3-dimethylaminopropyl chloride to give the O-(aminoalkyl)oximes V and VI which are analogues of the antidepressant agent fluvoxamine (I). Kindler-Willgerodt reaction of 4-(2-propylthio)acetophenone (III) gave the thiomorpholide VII which was hydrolyzed to the acid IX. Friedel-Crafts reaction of (2-propylthio)benzene with ethoxalyl chloride afforded ethyl 4-(2-propylthio)benzoylformate (X) which was transformed by reaction with methylmagnesium iodide, by the following hydrolysis and reduction with hydroiodic acid to 2-(4-(2-propylthio)phenyl)propionic acid (XII), a thia isostere of the anti-inflammatory and analgesic agent ibuprofen (II); acid XII was also obtained by reaction of 2-(4-mercaptophenyl)propionic acid (XVII) with 2-bromopropane and by the following hydrolysis. The acids IX and XII were converted to the amides XIII-XV. The fluvoxamine analogue V (V⁄FB-16 650) showed some pharmacological properties of potential antidepressants. The acids IX and XII (V⁄FB-16 603) have comparable anti-inflammatory activity with that of ibuprofen (II); in addition, XII has lower acute toxicity and higher analgetic activity than ibuprofen.
Synthesis and antibacterial activity of some 1-aryl-1,4-dihydro-4-oxocinnoline-3-carboxylic acids
Authors: Rádl Stanislav , Moural Jaroslav , Bendová Radoslava
Published: February 2010

The coupling reaction of corresponding benzene diazonium chlorides with benzoyl acetates IIIa-IIIc yielded intermediates IVa-IVe. Their intramolecular nucleophilic cyclization provided 1-aryl-1,4-dihydro-4-oxocinnoline-3-carboxylates Va-Ve. Compounds Va, Vb, Vd, and Ve were hydrolyzed to acids VIa-VIc. Treatment of these acids with the respective cyclic amines yielded compounds VIIa-VIIg which were converted to their hydrochlorides. All compounds prepared were tested for their antimicrobial activity in vitro.
The empirical conformational surface of the co(ethylenediamine) ring
Authors: Pavelčík František , Luptáková Eva
Published: February 2010

The conformational surface of the Co(en) chelate ring was studied by the method of structural correlation. The reduction of dimensionality of the conformation problem was achieved by employing the pseudorotation concept. The empirical potential surface was obtained by statistical treatment of 743 independent conformations from the Cambridge Structural Database. The theoretical potential surface was obtained by molecular mechanics. The minimal-energy conformation is gauche with the Co atom on the two-fold axis. Conformational flexibility also includes an envelope conformation with the N atom bent out of the plane. The transition between the mirror-image symmetrical conformations can occur by a pseudorotation pathway and is accompanied by increased planarity of the ring. The transition state is an envelope conformation with an out-plane Co atom.
Studies of association in solution from permitivity measurements: Statistical problems
Authors: Exner Otto
Published: February 2010

Association of a solute can be followed by permittivity measurement which allows us in principle to calculate the equilibrium constant K and dipole moments of the monomer μM and dimer μD. However, the procedures used in the literature are unsatisfactory from the statistical point of view and the published values are mostly completely wrong. In all known examples their errors were badly underestimated. Using a correct statistical approach several examples have been now reevaluated. It is practically impossible to calculate reliably all three parameters from permittivity data of common accuracy. Better results are obtained if either μM or K can be determined in an independent way. A symmetrical structure of the dimer is preferable in several cases (acetic acid, 2-pyrrolidinenone) contrary to the previous claims.
Influence of nonideality of a ternary solvent on its extraction characteristics
Authors: Ovečková Jana , Graczová Elena , Surový Július
Published: February 2010

Limiting selectivities and capacities for various compositions of the mixed solvent ethylene glycol (EG)-diethylene glycol (DEG)-N-methylpyrrolidone (NMP) with respect to toluene have been calculated from limiting activity coefficients of toluene and heptane. The calculations were made for both the ideal and real behaviour of the mixed solvent. The limiting activity coefficients of the model hydrocarbons toluene and heptane in the mixed solvent were calculated from experimentally determined binary coefficients of the Redlich-Kister equation, Wilson's equation as modified by Novak and co-workers, and the NRTL equation.
Vibrational spectra of aquadioxotetra; peroxodivanadates(V) M2[V2O2(O2)4(H2O)]·xH2O (M = N(CH3)4, Cs)
Authors: Schwendt Peter , Sýkora Milan
Published: February 2010

The infrared and Raman spectra of M2[V2O2(O2)4(H2O)]·xH2O and M2[V2O2(O2)4(D2O)]·xD2O (M = N(CH3)4, Cs) were measured. In the region of the vanadium-oxygen stretching vibrations, the spectra were interpreted based on normal coordinate analysis, employing empirical correlations between the bond lengths and force constants.
Oxidation of 1- and 2-acetylnaphthalenes by iodate - a kinetic study
Authors: Manikyamba Prerepa
Published: February 2010

Kinetics of oxidation of 1- and 2-acetylnaphthalenes by iodate in the presence of sulphuric acid in aqueous methanol has been studied. The reaction is first order with respect to both [iodate] and [acetylnaphthalene]. Solvent effect indicates a cation-dipole type of interaction in the rate limiting step. A mechanism is proposed with a slow attack of IO2+ on enol form of acetylnaphthalene forming an intermediate carbonium ion, which ultimately gives corresponding ω-hydroxyacetylnaphthalene. The higher reactivity of 2-acetyl isomer is attributed to the greater stability of the corresponding carbonium ion than that of 1-acetyl isomer.
Synthesis of 20-iodoeicosanoic and 20-[125I]-iodoeicosanoic acids
Authors: Protiva Jiří , Pecka Jaroslav , Urban Jiří , Zima Jiří
Published: February 2010

20-Iodoeicosanoic acid (X) was prepared in 9 steps, its carbon chain being constructed from thiophene and ethyl ester chlorides of dodecanedioic and butanedioic acids. Isotope exchange afforded 20-[125I]-iodoeicosanoic acid required for scintigraphic studies of the myocardium. Desulfuration of the thiophene precursor VIII was accompanied by formation of side products XI-XIX arising by cleavage of the thiophene C-C bonds. Desulfuration of the model compounds XX and XXI has shown that the formation of these products is general.
(8Z)-1(15),8(9)-Trinervitadien-3α-ol from Nasutitermes nigriceps termites. The revised structure for a deffense compound of Trinervitermes gratiosus termites
Authors: Valterová Irena , Buděšínský Miloš , Vrkoč Jan , Prestwich Glenn D.
Published: February 2010

The structure of (8Z)-1(15),8(9)-trinervitadien-3α-ol (IIa) was established by a detailed analysis of its NMR spectra for a trinervitane derived alcohol isolated from the species Nasutitermes nigriceps. The previously suggested structure I for the same compound isolated from Trinervitermes gratiosus is now revised.
Potential nootropic agents: Synthesis of a series of (2-oxo-1-pyrrolidinyl)acetic acid piperazides
Authors: Valenta Vladimír , Šindelář Karel , Holubek Jiří , Ryska Miroslav , Krejčí Ivan , Dlabač Antonín , Protiva Miroslav
Published: February 2010

The title compounds VI-XXIII were prepared by heating ethyl (2-oxo-1-pyrrolidinyl)acetate (II) with a series of N-monosubstituted piperazines. The propionamides XXVI and XXX were obtained by reactions of the acid chlorides IV and XXXIII with 3-(1-piperazinyl)propionamide. Compounds VI (V⁄FB-13 763) and VIII (V⁄FB-14 745) proved more active than piracetam (I) by their antiamnesic effects in rats, by antagonizing the brain-damaging effects of cycloheximide in infantile rats, and by their potentiation of the effects of anticonvulsant agents.
Preparation of (20E)-21-ethoxycarbonyl-5β-pregn-20-en-3β-yl hydrogen butanedioate
Authors: Pouzar Vladimír , Černý Ivan , Drašar Pavel , Havel Miroslav
Published: February 2010

Article without abstract
A stochastic model of decomposition of selectively excited polyatomic molecules
Authors: Šolc Milan
Published: February 2010

In the model proposed it is assumed that intramolecular processes (fluctuation of energy) corresponding to the Poisson process on the time scale occur in excited polyatomic molecules. On the scale of number of events (reorganizations, fluctuations), the probability of decomposition depends on the distance from the termination of the excitation process. This model enables the basic features of the lifetime distribution of selectively excited molecules to be derived.
A relation between excess volume and the form of the dependence of density on composition for binary liquid mixtures
Authors: Cibulka Ivan
Published: February 2010

A relation of excess volume and density is analyzed for binary liquid mixtures. It is shown that, unlike the ideal mixture, whose density is a monotonous function of composition, extremes may appear on the density curves of mixtures with non-zero excess volumes. Conditions for the existence of extremes are derived. Some examples are also given and briefly discussed.
Kinetics of electrode reaction of Eu3+/Eu2+ studied by cyclic voltammetry and tast polarography
Authors: Němec Jaroslav , Loučka Tomáš
Published: February 2010

The electrochemical behaviour of europium at the dropping mercury electrode was studied in the medium of 1M-NaClO4, 1M-NaCl, 1M-NaNO3, and 1M-Na2SO4. The curves obtained by Tast polarography and the kinetic parameters (ks, α) for the Eu3+/Eu2+ system in the medium of perchlorate and chloride solutions are in accord with the results published earlier. The kinetic parameters in nitrate and sulphate media are given for the first time. In the medium of nitrates, the electrode reaction is probably accompanied by a chemical reaction.
Belousov-Zhabotinskii oscillation reaction with glyceraldehyde
Authors: Melicherčík Milan , Treindl Łudovít
Published: February 2010

An oscillation system of Belousov-Zhabotinskii type with aldehyde as substrate is described for the first time. Oscillations of the concentration of Mn(III) ions can be followed spectrophotometrically or potentiometrically with a Pt electrode in a relatively narrow concentration range of the substrate. In contrast to the analogous reaction with malonic acid, no oscillations of the concentration of Br- ions were detected by a bromide ion selective electrode. This together with the fact that the concentration of Mn(III) ions oscillates even at relatively high bromine concentrations suggests that oscillations of the concentration of the redox catalyst Mn(II)/Mn(III) are probably controlled by organic radicals rather than by Br- ions.
Selective determination of tantalum in ores by extraction with N-phenylbenzohydroxamic acid in toluene
Authors: Aznarez José , Vidal Juan Carlos , Vaquero Cecilia
Published: February 2010

A method for tantalum(V) spectrophotometric determination in a non-aqueous phase is proposed. Tantalum(V) is extracted with N-phenylbenzohydroxamic acid into toluene from a 5M hydrochloric acid solution. The colour is then developed by addition of 4-(2-pyridylazo)-resorcinol (PAR) solution in N,N-dimethylformamide and pyridine to an aliquot of the extracted phase. The Ta(V)-PAR complex gives an absorption maximum at 547 nm with a molar absorptivity of 3.88 ± 0.04 . 104 l mol-1 cm-1. The method has been applied to the selective determination of tantalum in ores with good accuracy and precision.
Effect of triphenylphosphine on the cyclotrimerization of butadiene catalyzed by the TiCl4-EtAlCl2 system
Authors: Poláček Jindřich , Antropiusová Helena , Petrusová Lidmila , Mach Karel
Published: February 2010

Addition of PPh3 to the TiCl4 + n EtAlCl2 (n = 4-10) systems, which normally exhibit mostly Friedel-Crafts and polymerization activity towards butadiene, turns these systems into highly specific catalysts for the cyclotrimerization of butadiene to (Z, E, E)-1,5,9-cyclododecatriene. The effect of PPh3 lies in removal of AlCl3, which is formed in the reduction of TiCl4 with EtAlCl2 and in the disproportionation of EtAlCl2, for the AlCl3.PPh3 complex displays higher stability in comparison with the analogous complexes with ethylaluminium chlorides. The composition of the (η6-benzene)Ti(II) complexes, which are the catalytically active species, was determined by electronic absorption spectroscopy in the post-reaction mixtures.
Synthesis of some salicylic acid derivatives and determination of their acidity constants
Authors: Djurendić Evgenija A. , Surányi Terézia M. , Miljković Dušan A.
Published: February 2010

Several derivatives of salicylic acid have been synthesized by the condensation reaction of methyl salicylate with α,ω-diols and α,ω-diamines, and the acidity constants of five newly prepared derivatives have been determined in 61.10% aqueous ethanol using potentiometric titration method. In order to avoid calibration of pH-meter, the standard potential of glass electrode was determined from the titration data. The results obtained are discussed with regard to different resonance effects of the ester oxygen and the amide nitrogen atoms.
Steric effects in alkaline solvolysis of diaryl anilidophosphates
Authors: Kašpárek František , Vavčíková Kamila , Mollin Jiří , Husek Aleš
Published: February 2010

Analysis of the products of solvolysis of aryl esters of anilidophosphoric acids in water-2-propanol mixture excludes that the reaction proceeds via E1cB mechanism. Analysis of the reaction products of solvolysis of methyl-substituted compounds made it possible to evaluate the importance of the reported steric hindrance by CH3 group. The dependence of rate constants of the solvolysis on solvent system has been established.
An efficient mild acidolytic deprotection procedure for Boc/Bzl-based solid phase peptide synthesis
Authors: Dölling Rudolf , Jeschke Peter , Otto Albrecht , Eichler Jutta
Published: February 2010

Using the mild acidolytic deprotecting reagents 0.1M MSA or 0.1M TMSOTf in TFA in combination with PMB, which simultaneously accelerates the cleavage and acts as irreversible scavenger, the rate of cleavage of a model dipeptide from the appropriate Nα-Fmoc-dipeptidyl resin (polymer-bound benzyl ester, p-MBHA and BHA resin, respectively) was studied. The new deprotecting method was successfully applied to the synthesis of three Nα-halogenoacetyl modified octapeptides (I, II) and a 16-residue peptide (III). In all cases, the crude products were of the same quality as peptides obtained via the HF/10% anisole technique.
Synthesis of 1-acyl- and 1-(thioacyl)-4-benzylpiperazines as potential antidepressants
Authors: Kmoníček Vojtěch , Svátek Emil , Holubek Jiří , Ryska Miroslav , Valchář Martin , Protiva Miroslav
Published: February 2010

2-Nitro, 3-nitro- and 4-nitrobenzoyl chloride were reacted with 1-benzylpiperazine in benzene in the presence of triethylamine and gave the amides IV-VI, the first of which is considered a bioisostere of the antidepressant agent piberaline (I). 2-Dimethylamino-, 3-dimethylamino- and 4-dimethylaminobenzoic acid were treated with thionyl chloride in benzene in the presence of triethylamine or pyridine, and the acid chlorides formed were reacted in situ with 1-benzylpiperazine affording the amides VII-IX. The amides I and IV-VI were transformed by treatment with phosphorus pentasulfide in pyridine to the thioamides X-XIII. 4-(Dimethylaminomethyl)benzoic acid was reacted with 1-benzylpiperazine in dimethylformamide in the presence of N,N'-carbonyldiimidazole and afforded the amide XIV. Heating of ethyl 5-methylimidazole-4-carboxylate with 1-benzylpiperazine to 200-210 °C gave the amide XV together with the unexpected 1-benzyl-4-ethylpiperazine (XVI). The oily or crystalline bases of the amino amides or thioamides were mostly transformed to crystalline salts and characterized by spectra. Out of the compounds prepared only X (V⁄FB-17 070) and XIV (V⁄FB-17 114) showed indications of efficacy in tests which are considered indicative of antidepressant activity. Compounds VII, VIII, and X appeared to be mildly antidopaminergic - similarly like piberaline (I), and compounds IV, V, XI, XIV, and XV on the contrary showed signs of dopaminominetic activity.
A spectrophotometric assay of Indulin C - A potential new substrate for determination of lignin-degrading abilities of microorganisms
Authors: Gabriel Jiří , Homolka Ladislav , Krejčí Roman
Published: February 2010

A basic spectrophotometric study of a commercially produced sodium salt of Kraft lignin (Indulin C) was performed. The method of quantitative determination of Indulin C based on its absorbance at 276 nm has been found to be applicable. The spectra were also studied by means of derivative UV-spectrophotometry, which is recommended for theoretical studies of electronic spectral behaviour of lignins and lignin model compounds. Linear dependences were found between Indulin C concentration and the second derivative of spectrum at 250 nm and 276 nm. Both methods were used for determining the lignin degrading ability of the basidiomycete Phanerochaete chrysosporium and their suitability is discussed.
Synthesis of three analogues of tuftsin with 1-aminocyclopropane-1-carboxylic acid
Authors: Procházka Zdenko , Veretennikova Nadezhda I.
Published: February 2010

Article without abstract
Topological study of the chemisorption of N2 on (112) stepped surfaces of Pt and Ir
Authors: Pancíř Jiří , Haslingerová Ivana , Kašová Klára
Published: February 2010

Interaction of N2 molecule with stepped (112) Ir and Pt surfaces has been studied by a quantum chemical topological method. The adsorption of N2 takes place preferentially in top bound configurations. The reactivity of the N2 molecule chemisorbed on the studied (112) surfaces of Pt can be expected to be increased for electrophilic reagents, while chemisorption of N2 molecules on the studied Ir surfaces apparently does not affect their reactivity.