bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cobalt(II), Nickel(II), copper(II) and zinc(II) complexes of thiazolidine
Authors: Louloudi M. , Kovala‐Demertzi D. , Hadjiliadis N. 
Published: September 2010

AbstractThe reactions of thiazolidine with anhydrous metal halides of Co (II), Cu(II), Zn(II) and NiCl2.6H2O were studied in ethanolic solutions. Complexes of the type MLX2 (M=Ni (II), X=Cl, M=Cu (II), X=Cl, Br), ML2X2 (M=Co(II), X=Cl, Br, M=Cu(II), X=Cl, M=Zn(II), X=Cl), ML3X2 (M=Ni(II), X=Br, M=Co(II), X=Br) were isolated and characterized from these studies, with elemental analysis, conductivity and magnetic susceptibility measurements, 1H NMR, IR and ESR spectra. Thiazolidine acts as a monodentate ligand in all cases and coordinates through its nitrogen atom with Co(II) and Cu(II) and through sulfur with Ni(II) and Zn(II). Possible structures of the isolated complexes were also proposed, based on the above data.
Analyse Polarographique Et Spectrophotométrique Des Réactions De Déprotonation Et Des Modifications Subsequentes D'Aromaticité En Milieu Acide
Authors: Lejeune R. , Thunus L. 
Published: September 2010

AbstractFormer publications showed important modifications to occur in polarographic and spectrophotometric curves when the pH of the solution changes. This may be assigned to perprotonation or to rearomatisation of pyridine derivatives. The authors investigate this problem and make an attempt to resolve it qualitatively and quantitatively.
Carbon‐, alumina‐, and silica‐supported iron sulfide catalysts
Authors: Groot C. K. , van De Gender P. J. G. D. , Niedžwiedž W. S. , van Der Kraan A. M. , De Beer V. H. J. , Prins R. 
Published: September 2010

AbstractIron sulfide catalysts supported on various carbon materials, on alumina and on silica were compared for their thiophene hydrodesulfurization (HDS) activity measured in a flow micro reactor at atmospheric pressure. The iron content was varied from 0.2–5.0 iron atoms per nm2 support surface area. Mössbauer spectroscopy and X‐ray photoelectron spectroscopy (XPS) were used to characterize the nature and dispersion of the iron phases present in oxidic and sulfided catalysts.Within the surface loading range studied, carbon‐supported iron sulfide catalysts are much more active for thiophene HDS than the alumina‐ and silica‐supported ones. The activity of sulfided iron on alumina catalysts was found to be even lower than expected on the basis of data obtained earlier for other (supported) transition metal sulfides. This is most likely caused by an incomplete sulfidation. Among the various carbon supports employed, activated carbons, despite their high degree of micro porosity are more suitable than carbon blacks and carbon black composites.Based on a comparison of the effective Debye temperature derived from Mössbauer data with dispersions also obtained from Mössbauer measurements on oxidic catalyst precursors, the interaction between the iron‐containing phase and the various carbon supports is described in a qualitative way.
Crystal structure of 5‐Phenyl‐ [1, 2, 3] triazolo [1, 5‐b] [1, 2, 4] triazine‐3‐carboxamide. Evidence for the dimroth‐rearrangement of [1, 2, 3] triazolo‐[5, 1‐c] [1, 2, 4] triazines into [1, 2, 3] triazolo [1, 5‐b] [1, 2, 4] Triazines
Authors: L'Abbé Gerrit , Meutermans Wim , van Meervelt Luc , King Geoffrey S. D. , Lenstra Albert T. H. 
Published: September 2010

AbstractThe diazotization of 5‐amino‐4‐carbamoyl‐1‐(α‐styryl)‐1, 2, 3‐triazole (1) yields 5‐phenyl‐[1, 2, 3] triazolo [1, 5‐b] [1, 2, 4] triazine‐3‐carboxamide (3) as a result of a rearrangement of the initially formed 7‐phenyl‐[1, 2, 3] triazolo‐[5, 1‐c] [1, 2, 4] triazine‐3‐carboxamide (2). Its crystal structure (C11H8N6O, a = 5.037(6), b = 26.901(4), c = 8.074(2) Å, β = 97.66 (5)*, space group P21/c, Z = 4) has been determined by single‐crystal X‐Ray diffraction techniques and refined to R = 0.039.
Conformational features of four model tripeptides having Piv‐Pro‐MeXaa‐NMe2 sequences
Authors: van Der Auwera C. , Borremans F. , Anteunis M. J. O. 
Published: September 2010

AbstractWe have looked to spectral features of four model tripeptides 1–4 which all, except one (2), are hydrolysed within 24 h in Tfa. It has previously been demonstrated that the observed endopeptolysis1 requires a cis‐peptide bond between the first and second residue. Within H nmr spectroscopic confidence level, no cis‐peptide isomeric states however could be detected except to a slight extent in DMSO‐d6 (less than 8%), but only so for 1, 3 and 4. It is therefrom clear that the resistance of 2 against hydrolysis is best explained by the fact that trans → cis isomerization is very much hampered.
Nouvelles Méthodes De Déshalogénation Et De Formation D'Alkyltriméthyl‐Acétals De Cétène Par Action De iPr2NLi Sur Quelques α‐Bromoesters
Authors: Lion Claude , Lebbar Kadija , Paul Jean , Poba Boukou 
Published: September 2010

AbstractA previously described method consisting in reacting LDA with α‐bromoketones has been extended to α‐bromoesters. Deshalogenation (after hydrolysis) and formation of ketene alkyltrimethylsilyl acetals (after SiMe3Cl addition) occur and show the generality of the method.
Flash‐vacuum pyrolysis of nitroarylbenzotriazoles. A tandem mass spectrometry study
Authors: Maquestiau Andre , Flammang‐Barbieux Monique , Flammang Robert , Chen Lin‐Zhi 
Published: September 2010

AbstractTandem mass spectrometry (MS/MS) has been applied to investigate the behaviour of 1‐(2‐nitrophenyl)benzotriazole [8] upon flash‐vacuum pyrolysis (FVP) conditions. Above 500°, 8 is pyrolyzed to give a mixture of 1‐nitrocarbazole [11], 1‐hydroxycarbazole [12] and carbazole [13] Under similar conditions, 2‐(2‐nitrophenyl) benzotriazole [9] appears to be more stable; it is however partially isomerized into 8 at high temperatures. Aza analogs of 8, like 1‐(2‐nitro‐4‐pyridyl) benzotriazole [10] also loose nitrogen above 500° to give a mixture of 1‐nitro‐3‐azacarbazole [19], 1‐hydroxy‐3‐azacarbazole [16] and 3‐azacarbazole [17].
Déplacements Homolytiques Intramoléculaires ‐ 16 ‐ Décomposition Des Peroxydes Et Peresters Insatures Par Les Radicaux Cyclohexyle Issus De Derives Peroxydiques De L'Acide Cyclohexanecarboxylique
Authors: Bourgeois M. J. , Montaudon E. , Maillard B. 
Published: September 2010

AbstractThermolyses of dicyclohexyl carbonyl peroxide have been performed in organic solutions of t‐butyl pent‐4‐enyl peroxide or t‐butyl perpent‐4‐enoate in order to study the induced decomposition by cyclohexyl radicals of these peroxides. Induced decomposition of cyclohexylcarbonyl pent‐4‐enoyl peroxide and pent‐4‐enyl cyclohexylpercarboxylate has also been studied. In the decomposition of these compounds, SH1 reaction of an acyloxy radical is involved which is, to our knowledge, the first example of such reaction with a perester.
The reaction of benzyltriphenylarsonium ylides with aldehydes. A note about the mechanism of the wittig reaction
Authors: Broos René , Anteunis Marc J. O. 
Published: September 2010

AbstractThe products and stereochemistry of the reaction of the benzyltriphenylarsonium ylide with benzaldehyde and acetaldehyde both in the presence of lithium salts and under salt‐free conditions are studied by H NMR at 360 MHz. The stereochemistry is discussed in view of recent developments in the mechanistic interpretation of the Wittig and Johnson‐Corey‐Chaykovsky reaction.
New cardenolide glycosides from the defence glands of chrysolinina beetles (coleoptera: Chrysomelidae)
Authors: van Oycke S. , Randoux T. , Braekman J. C. , Daloze D. , Pasteels J. M. 
Published: September 2010

AbstractThe composition of the defence secretions of six species of chrysomelid beetles (Chrysolina polita, C. americana, C. grossa, C. herbacea, C. fastuosa, and Oreina gloriosa) belonging to the sub‐tribe Chrysolinina has been investigated. Two known cardenolide aglycones, sarmentogenin (1) and oleandrigenin (23), and fourteen new cardiac glycosides (7–20) have been isolated and their structure established by spectral and chemical methods. Three of the glycosides (18, 19, and 20) are based on a new cardenolide aglycone, namely Δ11‐digitoxigenin. All the new glycosides but 17 contain monosaccharides (e. g. lyxose, ribose, allose) which are rarely encountered in secondary metabolites.Ethanolamine was shown to be present in the secretions of the six species examined, as well as in C. hyperici and in C. coerulans. In the latter, ethanolamine is accompanied by its N‐(γ‐glutamyl) derivative.
Pisa: A new model for the estimation of intermolecular interaction energies in the liquid state
Authors: Dejaegere A. , Claessens M. , Bardiaux M. , Reisse J. 
Published: September 2010

AbstractWe propose a new model for the estimation of intermolecular interaction energies in the liquid state. This model, which we call PISA, is especially devoted to the calculation of the London‐Pauli contribution. The model has been tested on a large ensemble of pure liquids and the results compare well with those obtained by molecular dynamics and Monte‐Carlo simulations. The advantages of PISA are its simplicity and rapidity.
Regioselective synthesis of Alkyl‐methoxyoxiranes from α‐alkyl‐α, α', α'‐trichlorocyclanones and methanolic sodium methoxide
Authors: De Buyck L. , Bauwens S. , Schamp N. 
Published: September 2010

Abstractα‐Alkyl‐α, α', α'‐trichlorocyclohexanones 3 and 4 and the cyclopentanone 7 react with methanolic sodium methoxide to afford exclusively the stable methoxyoxiranes 5, 6 resp. 8. These results are in line with the selectivity observed earlier with methoxyoxirane formation from 9. The trichloroketones 3 and 4 were prepared from the cyclohexanols 1 and 2 by chlorination in dimethylformamide.
Conformational study by 1H NMR of the |D‐MePhe4|‐epimer of virginiamycin S1
Authors: Zhang W. , Anteunis M. J. O. , Borremans F. 
Published: September 2010

AbstractThe conformation in CDCl3 of the synthetic 4‐epimer of the natural synergimycin factor B (Virginiamycin S1) has been obtained from 2D H NMR spectroscopic data using NOE and different COSY techniques. The characteristics of the three NH protons have also been determined (temperature shift dependence, dilution and deuterium exchange). Conformations of the two diastereomeric depsipeptides are strikingly similar with respect to the backbone and cis/trans peptide bond configurations. This results for VS‐epi4 in a rather unexpected type of β bend for the [3–6] sequence, reinforced by the same intramolecular hydrogen bridge bonding mechanism [Pro3CO → NHPhg6] as for the natural isomer. The aromatic side chain of D‐MePhe4 however stacks over the preceding Pro3‐residue instead of over the succeeding 4‐oxo‐Pec5 as is the case in VS1. The outer surface of the 2–5 region remains pronouncedly lipophilic. The conformational mobility of the cyclic residues seems to be greater in VS‐epi4. Some other orientational differences may reside in the [5–1]‐region e. g. at NH (Thr1‐) and the carbonyl grouping of the 4‐oxo‐Pec1 residue.
Stable nitroxides with delocalized positive charge
Authors: Drâgutan I. , Câldâraru H. , Balaban A. T. , Mehlhorn R. J. 
Published: September 2010

AbstractThe synthesis of several cationic stable free radicals with different positive charge characteristics, obtained by the reaction of spin labelled primary amines with 2,4,6‐trisubstituted pyrylium perchlorates, is presented.
Convenient synthesis of spin labelled amines
Authors: Drăguţan Ileana , Drăguţan Valerian , Mehlhorn Rolf J. 
Published: September 2010

AbstractA one‐step procedure of general use for the synthesis of spin labelled amines is described and a labelled pyridinium perchlorate derived from 3‐(aminomethyl)‐2,2,5,5‐tetramethyl‐2,5‐dihydropyrrole‐l‐oxyl is characterized.
Solvent Extraction Studies of Molybdenum (VI), Cobalt (II) and Copper (II) with Tri‐N‐Octylamine and Thiocyanate Ion
Authors: Salama S. B. , Aziz H. A. , Ashry A. H. 
Published: September 2010

AbstractThe extraction of the thiocyanate complexes of molybdenum (VI), cobalt (II) and copper (II) with tri‐n‐octylamine, yielding orange‐red, blue and yellowish green complexes respectively has been investigated as a function of the acidity of the aqueous phase and of the thiocyanate and amine concentrations. Under proper operating conditions extraction yields of 95% can be obtained. The molybdenum complex has an absorption maximum at 470 nm with a molar absorptivity of 2.6 · 104 dm3 mol−1 cm−1 in cyclohexane, while the cobalt complex has an absorption maximum at 622 nm with a molar absorptivity of 2.5 · 103 dm3 mol−1 cm−1 in dichlorethane. The copper complex in chloroform has no maximum absorption. The separation of copper from molybdenum has successfully been accomplished.
2D‐NMR Study of Petrosins: Revised Structure for Petrosin‐A
Authors: Braekman J. C. , Daloze D. , Cimino G. , Trivellone E. 
Published: September 2010

AbstractA 2D‐NMR study of petrosin, petrosin‐A and petrosin‐B has been performed. All the hydrogen and carbon atoms resonances of the three molecules have been assigned. As a result, structure 2 that was previously proposed for petrosin‐A has been revised to 4.
The synthesis and properties of 1,4‐diketo‐pyrrolo[3,4‐C]pyrroles
Authors: Iqbal A. , Jost M. , Kirchmayr R. , Pfenninger J. , Rochat A. , Wallquist O. 
Published: September 2010

AbstractSyntheses and mechanistic aspects of formation of 1,4‐Diketopyrrolo[3,4‐c]pyrroles (DPP) are discussed. The chemical reactivity of this novel class of heterocycles is illustrated by specific electrophilic aromatic and N‐substitution reactions, as well as by nucleophilic transformations of the bicyclic lactam carbonyl group. X‐ray structural analysis of the diphenyl‐DPP molecule reveals significant intermolecular hydrogen bonding and π‐π interactions in the solid state.
Stereoelectronically‐programmed molecular ‘lego’ sets
Authors: Ellwood Paul , Mathlas John P. , Fraser Stoddart J. , Kohnke Franz H. 
Published: September 2010

AbstractThe observation that the syn‐isomer 1 of 1,4:5,8‐diepoxy‐1,4,5,8‐tetrahydroanthracene becomes involved in a series of highly diastereoselective Diels‐Alder reactions with 2,3,5,6‐tetramethylene‐7‐oxabicyclo[2.2.1]heptane 2 to form, in excellent overall yield, the novel macropolycyclic compound 6 ‐ a potential precursor of [12]beltene 7, [12]collarene 8, [12]cyclacene 9, and the perhydro[12]cyclacene derivative 10 ‐ is interpreted in terms of the stereoelectronic characteristics of the dienophilic components of 1 and the diene components of 2, and obvious steric factors, combining to favour one particular stereochemistry out of eight possibilities for the transition states involving each of the four different cycloaddition steps.
New binuclear heterocyclic ligands sharing an α‐diimine moiety and their ruthenium(II) tris‐chelates
Authors: Orellana Guillermo , Alvarez‐Ibarra Carlos , Quiroga Maria Luz 
Published: September 2010

Abstract‐ A number of chelating heterocyclic ligands which include pyridine, pyrazine, 1,3‐heteroazole, and/or 1,2,4‐heterodiazole moieties, have been prepared and characterized in order to tune the excited state properties of the corresponding Ru(II) complexes. The detailed study on the binuclear heterocycles by using uv, 1H‐ and 13C‐nmr spectroscopy, as well as mass spectrometry, is also provided. The synthesis and spectral data (uv, ir, 1H‐ and 13C‐nmr) of the ruthenium(II) tris‐chelates is also included.
Nuclear magnetic resonance study of the sodium salt of mutalomycin, a structural analog of lonomycin
Authors: Zhang Weiguo , Anteunis Marc J. O. , Borremans Frans A. M. 
Published: September 2010

AbstractThe complete assignment of the proton NMR spectrum of the sodium salt of mutalomycin in chloroform was obtained by applying homo‐ and heteronuclear shift correlation techniques. From the observed chemical shifts and coupling constants the conformation of the title compound is discussed, in relation to its structural analog lonomycin A.
Synthèse De Spermine Et De Spermidine Sélectivement Substituées Sur Les Fonctions Amines Secondaires
Authors: Garrigues Bernard , Vidaud Lionel 
Published: September 2010

AbstractProtection of the primary amino group of various polyamines followed by alkylation or benzoylation at the secondary amino group and finally removal of the protecting group leads to the N‐methyl (23, Scheme 3), N‐benzoyl (11, Scheme 1) (ethylenetriamine, N‐benzoyl spermidine (22, Scheme 3), N, N′‐methyl (27, Scheme 4)‐ethyl (28, Scheme 4),‐propyl (16, Scheme 2) ‐benzoyl (15, Scheme 2) spermine.
Fundamental questions about entropy II. The combinatorial entropy of mixing in liquids
Authors: Huyskens P. L. , Siegel G. G. 
Published: September 2010

AbstractIn liquid mixtures a molecule A is separated on the average from the nearest molecule of the same kind by XA−1/2 −1 molecules of a different kind, according to the relation of Einstein and Smoluchowski. In this direction (between a molecule and its nearest neighbour of the same kind) which continuously changes but which has a physical meaning, there exist thus XA−1/2 standardized possibilities of exchange with the other molecules. This is a characteristic of the stationary wave function of each A molecule in the liquid and intervenes in the counting of the standardized possibilities <WA>. In this direction the number of places available for one A can thus be calibrated by molecules of a different kind. In the other directions the places in the standardized domain <DomA> have to be calibrated by the volume of A itself. This leads to a value of XA−1/2 ϕA−1/2 for <WAcomb>, the standardized number of places available for one A in the mixture. The combinatorial entropy of mixing derived from this value is intermediate between the Flory‐Huggins expression and the classical one. Experimental evidence for the correctness of this new equation can be found in the predicted solubilities of solid n‐alkanes in liquid n‐alkanes.
Laterite as a catalyst for the hydrotreatment of heavy Oil. I. Identification and characterization of a venezuelan laterite
Authors: Yunes S. , Herbillon A. , Grange P. , Delmon B. 
Published: September 2010

AbstractThe use of laterite as a hydrotreating catalyst has been recently initiated. For this purpose, a careful characterization of the laterite was necessary. Chemical analysis and several physico‐chemical techniques, e. g. XRD, TGA/DTA, IR, show that the laterite studied here consists of aluminous goethite. hematite, gibbsite and titanium oxide. It has also shown a substitution of 22–24% mole of AlOOH in the goethite lattice.
Application of experimental design methodology to the study of the synthesis of nucleosides
Authors: Elguero J. , Goya P. , Martinez A. 
Published: September 2010

AbstractA factorial design has been used to study the effect of three factors on the reaction between 4‐amino‐8H‐pyrazino[2,3‐c]‐1,2,6‐thiadiazine 2,2‐dioxide and 1,2,3,5‐tetra‐O‐acetyl‐β‐D‐ribofuranose. Reaction conditions have been found in which the usually less abundant N‐8 isomer is selectively obtained.
Isolation and characterization of mutumol, 22‐acetoxy‐3β,23‐Dihydroxy‐24‐methylenelanost‐8‐ene, from the east african fungus pisolithus arhizus (Pers.) rausch
Authors: van Puyvelde Luc , De Kimpe Norbert , Vanderick François , Costa Jean , Niyotwagira Viateur , Borremans Frans , Martins José , Declercq Jean‐Paul , Schamp Niceas 
Published: September 2010

AbstractThe isolation and spectrometric characterization of mutumol, 22‐acetoxy‐3β,23‐dihydroxy‐24‐methylenelanost‐8‐ene, from the fungus Pisolithus arhizus (Pers.) Rausch is described. Besides the usual spectrometric methods, also an X‐ray crystallographic analysis and a complete 1H 500 MHz NMR analysis was performed.
Le Transfert du Proton Entre Molécules d'Eau
Authors: Peeters D. , Leroy G. 
Published: September 2010

AbstractA study of the structure and properties of some (H2O)n.H+ systems has been realized with the aim to analyze some possible mechanisms of the proton transfer. Results were obtained ab initio using the 4–31G basis set. Correlation and basis sets extensions were included for n = 1 and 2. In all cases, a conventional structure presenting three OH bonds is found for n = 1. On the other hand, an unique structure localizing the proton midway between two water molecules is obtained for n=2. These two systems are basic models for the other members of the set under investigation. Extra water molecules arrange around these model structures. The transfer of the proton may then be interpreted as a transfer from one class of structures to the other: the members of the H3O+ class being stable and rigid, while those of the H5O2+ class present a rather movable central proton and must be considered as relay structures to the transfer.
Représentation Dynamique des Objets de la Chimie
Authors: Sana M. , Leroy G. 
Published: September 2010

AbstractIn this work, we consider a frame of multirepresentation for the molecules and the supermolecules. This is an open architecture based on graphs and lists which enables the storage and the handling of the information about chemical species at different levels of fullness and accuracy. From viewpoint of systems theory, it is a conceptual framework for a set of interrelated components involving processes. This gives a simple picture for the backward inference as the shortest path in a graph where vertices are components of the multirepresentation and directed edges are interconversion processes. Moreover, this viewpoint corresponds to a dynamical frame for a chemical knowledge based system. Finally, we consider more carefully the electronic representation process; we describe it as a set of sequential rules which produces electron distribution in molecules, ions and radicals.
Apports de la Spectroscopie Mössbauer À la Détermination de la Structure des Alliages
Authors: Mahieu B. 
Published: September 2010

AbstractTaking the iron‐tin alloy as an example, it is shown that the conjunction of various techniques allows a narrower description of a crystalline structure. The positions of atoms in the lattice being known, neutron diffraction adds information about the magnetic moment orientation. Mössbauer spectroscopy improves the precision of this parameter and measures the electric field gradient that each atom is exposed to. In the case of the iron‐tin alloy a complete determination of the structure requires a quadruplation of the lattice which has been primilarly fixed by X‐ray diffraction.
Reactivity of the “capto‐dative” methylmethoxyacetate (MMA) toward radicals, studied by electron pulse radiolysis in neutral aqueous medium
Authors: Massaut B. , Tilquin B. , Hickel B. 
Published: September 2010

AbstractMethylmethoxyacetate (MMA) has been irradiated in neutral aqueous solution by pulsed electrons (Febetron 707). Spectrum of the radical formed by H atom abstraction (MMA°) has been determined. Relative velocity of the reaction of MMA with OH° has been evaluated by mean of a competition kinetic. The reactions e−soiv + MMA, MMA° + MMA° and MMA° + O2 have also been investigated.