bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Thiophene Hydrodesulfurization on A Co‐Mo/AlaOs Catalyst
Authors: Patrov L. A. , Vladov Ch. D. , Shopov D. M.
Published: September 2010

The kinetics of hydrodesulfurization of thiophene on an industrial Co‐Mo/Al aOs catalyst has been studied at atmospheric pressure in a flow circulation system in the temperature interval 325‐425°C. A reaction scheme and kinetic model, including four stoichiometrically independent routes, have been suggested, which describe the experimental data with good accuracy.
Reinvestigation of the Substitution Products of 8‐Azatheophilline
Authors: L'abbé Gerrit , Persoons Marie‐Anne , Toppet Suzanne
Published: September 2010

The structure of the substitution products of 8‐azatheophylline can be elucidated easily by an inspection of the C‐3a and C‐7a absorptions in the 13C NMR spectra. On the basis of this criterion a number of published structures are revised.
Functionalization of Isophorone Involving Polychlorination. Part II: Chlorination of Isophorone in the 2‐ and 6‐Position Involving Addition of Chlorine to the Double Bond. Enol Allyl Rearrangements and Base‐Induced Substitution of the 6‐Chloro Atom
Authors: De Buyck L. , Bostoen R. , Lecluse M. , De Pooter H. , Schamp N.
Published: September 2010

Using trans‐2, 3‐dichloro‐3, 5, 5‐trimethylcyclohexanone (2) as an intermediate, isophorone (1) was converted into the 2‐chloro derivative 6 (85–93%), the 2, 6‐dichloro derivative 5 (65‐75%) and the 2, 6, 6‐trichloroderivative 10 (60–70%) isolated overall yields from 1). The 2, 2, 3‐trichlorocyclohexanone 7 and the 2, 2, 3, 6‐tetrachloroketones 19 and 20 underwent enol allyl rearrangement with dehydrochlorination. The preparation of 6‐acetoxy‐2‐chloroisophorone (8) (70%) is described as an example of rapid base‐induced nucleophilic substitution of 5.
Chimie des Radioprotecteurs: II. Synthèse de Nouveaux Acides S‐(Aminoethyl‐2) Phosphorothioiques Substitues
Authors: Lion Claude , Boukou‐Poba Jean‐Paul , Saumtally Imran
Published: September 2010

A new method for the synthesis of biologically interesting substituted S (2‐aminoethyl) phosphorothioic acids H2NCR1R 2‐CR3R4SPO3H2 is described. It employs the sequence : olefine R1R2CCR3R4 ‐α‐bromoazide N3R1R2C‐CBrR3R4‐aziridine R1R2 C‐CR3R4 or α‐bromamine H2 H2NR1R2C‐CBrR3R4 reacting with sodium thiophosphate. This method is particulary efficient when the intermediate α‐bronoazide is reduced by triphenylphosphine or trimethylphosphite. The overall yield is around 30 to 50%.
N‐(1‐Halogenoalkyl)Heteroaryliumsalze ‐ Synthese und Reaktionen
Authors: Anders Ernst , Tropsch Jürgen G.
Published: September 2010

The first synthesis of the title compounds 4 is described. These salts are products of a chemoselective three component reaction (eq. 1). By means of various nucleophiles, compounds 4 are transformed into the substituted products 6 (eq. 2).
Method for Determination of Atomic Pseudopotentials for C, Si, Ge and Sn
Authors: van Hooste H. , Roelandt F. F. , van de Vondel D. F. , van Der Kelen G. P.
Published: September 2010

A systematic non‐empirical method is developed to determine atomic pseudo‐potentials for C, Si, Ge and Sn.

Each angular momentum dependent sub‐pseudopotential contains two Gaussian functions. The total pseudopotential is determined in correlation with the specific valence basis sets used in molecular calculations and needs the construction of the valence pseudo‐orbitals.
Déplacements Homolytiques Intramoléculaires : 15 ‐ Additions Radicalaires A des Peroxydes β‐Éthyléniques
Authors: Montaudon E. , Agorrody M. , Rakotomanana F. , Maillard B.
Published: September 2010

Free radical additions of cyclohexane, tetrahydrofuran, methyl propanoate, acetonitrile, dichloromethane to allyl t‐butyl peroxide, t‐butyl 2‐methyl prop‐2‐enyl peroxide, t‐butyl 2,2‐dimethyl prop‐2‐enyl peroxide and t‐butyl 3‐methyl but‐2‐enyl peroxide have been studied. Every step of the induced decomposition has been analyzed in terms of steric and polar effects, but no one itself could explain the observed results.
Anomalous Reactivity of Methylidenemalonates in the Prilezhaev Reaction. Evidence For A 1,3‐Dipolar Mechanism
Authors: De Cock Christian J. C. , Keyser Jean‐Luc De , Poupaert Jacques H. , Dumont Pierre
Published: September 2010

Methylidenemalonates are converted into the corresponding oxiranes in 81–97 % yield when treated with m‐chloroperbenzoic acid in solution in refluxing dichloromethane (Prilezhaev reaction). Results suggest that Prilezhaev's epoxidation of methylidenemalonates proceed via a 1,3‐dipolar addition process in sharp contrast with the behaviour of acrylates.
Syntheses des Benzimidazolo [1,2‐a] Benzimidazoles A Partir des Benzodiazepine‐1,5Ones‐2
Authors: Achour Reddouane , Zniber Rachid
Published: September 2010

Some [1,2‐a] benzimidazolo benzimidazoles have been synthesized from 2‐benzimidazolone substituted in 1,3 positions, product obtained by the warmth of 1,5‐benzodiazepin 2‐one, product which proceeds of the 1,3 sigmatropic transposition of the heterocycle.

The products have been characterized by the spectrale data (1H n. m. r., i. r. and mass spectrum) and analysis.
Synthesis of Topsentin‐A, A Bisindole Alkaloid of the Marine Sponge Topsentia genitrix
Authors: Braekman J. C. , Daloze D. , Stoller C.
Published: September 2010

The synthesis of topsentin‐A, a bisindole alkaloid isolated from the maring sponge Topsentia genitrix, has been achieved starting from 3‐acetylindole.
Reinvestigation of the Reactions of N‐Phenylhydrazones With Isothiocyanates
Authors: L'abbé Gerrit , Allewaert Kathy
Published: September 2010

The reactions of N‐phenylhydrazones with phenyl isothiocyanate in dimethylformamide containing sodium hydride yield C=N adducts 4 instead of the previously reported2 C=S adducts 3.
New Developments in Hydrotreating Catalysis : Characterization and Optimization of Niw/A12O3 Catalysts
Authors: Breysse M. , Bachelier J. , Bonnelle J. P. , Cattenot M. , Cornet D. , Décamp T. , Duchet J. C. , Durand R. , Engelhard P. , Frety R. , Gachet C. , Genested P. , Grimblot J. , Gueguen C. , Kasztelan S. , Lacroix M. , Lavalley J. C. , Leclercq C. , Moreau C. , De Mourgues L. , Olivé J. L. , Payen E. , Portefaix J. L. , Toulhoat H. , Vrinat M.
Published: September 2010

Alumina supported NiW catalysts with components concentrations varying in a wide range were systematically studied in order to optimize a catalyst for further industrial uses.

The genesis of the active phase was examined by using several physicochemical techniques and the catalytic properties were determined in different reactions characteristic of the hydrotreating process i. e. dibenzothiophene and thiophene HDS, biphenyl and pyridine hydrogenation as well as piperidine HDN. The promoting effect of Ni is always observed but the synergy is greatly dependent on the nature of the molecule to be treated. In addition to these activity determinations, the differences in behaviour towards sulfiding conditions and relationships with probe molecules adsorptions suggest that hydrogenation and hydrogenolysis reactions take place on different catalytic sites. The nature of these sites is discussed in terms of the mixed phase model.

The selected most active catalyst for performing HDN reactions was studied for real feedstock conversion. Its activity is compared to the properties of conventional nickel molybdenum and nickel tungsten catalysts.
A Comparative Study of the Influence of the Preparation on the Activity of NiMo and NiW Hydrodesulfurization (Hds) Catalysts
Authors: Ledoux Marc J. , Hantzer S. , Guille J.
Published: September 2010

This article deals with the correlation between preparation and HDS activity for NiMo and NiW catalysts. For NiMo catalysts, the successive impregnation or coimpregnation of molybdenum and nickel salts give the same activity. A TPR analysis shows that the nature of the oxidic surface is identical on the two catalysts. On the contrary, for NiW, the successive impregnation leads to inactive catalysts; only a coimpregnation procedure with a very careful control of the pH gives active catalysts. The TPR diagrams are now different. A probable nickel tungsten bronze is formed after calcination of an intermediate “polymer” isolated from the solution used for the coimpregnation process.
Hydrodesulphurization and Hydrodenitrogenation Over Promoted‐Molybdenum Sepiolite Catalysts
Authors: Mendioroz S. , Palacios J. M. , Fierro J. L. G. , Agudo A. López
Published: September 2010

The hydrodesulphurization (HDS) and hydrodenitrogenation (HDN) activities of Mo‐sepiolite catalysts promoted by Ni, Co, Zn and Fe, containing 5.2 wt % MoO3 and 2.0 wt % of promoter, have been measured in a high pressure tricklebed reactor. The catalysts have been characterized by X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy, surface acidity, and extraction by ammonia. Activity for HDS was found to be higher than for HDN. Both HDS and HDN activities were dependent on the nature of promoter and of the preparation method. The observed differences in HDS activity may be related to differences in the distribution of promoter, whereas HDN activity seems to be also governed by the hydrogenating property of the promoter and by the surface acidity of the catalyst.
Prediction of the Hydrodesulfurization (Hds) Performances of Catalysts Under Operating Conditions Relevant to Industrial Practice
Authors: Gosselink J. W. , Stork W. H. J.
Published: September 2010

Catalysts for the catalytic HDS process are still being improved, for instance by optimization of the particle geometry. They are generally tested in small‐scale trickle‐flow equipment, with heavy gas oil (HGO) serving as the feedstock. An analysis of this test procedure has shown that the most important factors which determine the HGO‐HDS performance are the intrinsic HGO‐HDS activity  and the diffusion of the sulfur compounds through the catalyst pores. A study of the applicability of the dynamic oxygen chemisorption (DOC) technique has shown that  can be estimated from the DOC capacity (DOCC). However, there are some limitations: the ‐DOCC correlations are restricted to narrowly defined groups of catalysts and  must not exceed a critical level M, which is group‐dependent. The effect of pore diffusion can be described very precisely by a simple but physically substantiated multi‐component HDS computer model, which makes use of a statistical function for the distribution of the rate constants k over the individual sulfur compounds and assumes that they all have the same effective diffusion coefficient . It is illustrated by way of an example that the model, in combination with DOC, is able, on the basis of the measured HGO‐HDS performance of one catalyst geometry, to predict very accurately the performances of other geometries.
Reactivity of H2S and H2S/H2 Mixture With Molybdenum Oxide Thin Films Epitaxied on CoO (100) : Characterization by Rheed and Auger Spectroscopy
Authors: Steinbrunn A. , Bordignon M.
Published: September 2010

Molybdenum‐Cobalt composite oxide films were prepared by the evaporation of molybdenum trioxide on a fresh cleaved CoO (100) surface (Thickness = 10 Å).

The MoO3‐CoO interface has been characterized simultaneously by reflexion high electron diffraction (RHEED) and Auger Electron Spectroscopy (AES). The thin film structure and composition depend on the annealing temperature.

After a 300°C treatment, metallic cobalt islands nucleate at the interface thin film ‐ CoO (100) and crystallize with the cubic FCC symmetry. After a 700°C treatment cobalt molybdate (a CoMoO4) islands grow. The metastable crystallites are epitaxied on CoO (100).

After a 900°C treatment, the thin film consists of flat two‐dimensional crystallites with the following structures √5 × √5 R 26°, P (2 × 2), P (2 × 1), P (3 × 1) R 45°, P (4 × 2) R 45°.

The sulphurization by H2S of the deposited thin film (300–400°C) is much slower than that of the CoO substrate (Pressure range : 0.1–15 Pa). The reaction products are epitaxied crystallites of Co9S8 and islands of amorphous MoS2.
Electrophoretic study of RuO2/γ‐Al2O3 samples used in the water gas shift reaction
Authors: Moya S. A. , Mansilla A. , Gil Llambías F. J.
Published: September 2010

RuCl3 supported on γ‐Al2O3 and calcined in air at 550°C generates an active catalytic phase for the water‐gas‐shift‐reaction, at 100–140°C and atmospheric pressure. Both apparent surface coverage of alumina by RuCl3, as measured by electrophoresis, and activity occur simultaneously with metal deposited on the samples.
AlPO4 supported on polymer beads as catalysts in the esterification of carboxylic acids
Authors: Fernadez C. , Marinas J. M. , Sinisterra J. V.
Published: September 2010

Some new AlPO4 supported on polymer beads are described. These solids are effective catalysts in the esterification of carboxylic acids in mild conditions. The yields obtained are similar to those obtained with pure AlPO4 but at low temperatures. The influence of the chemical and textural properties of the supported polymer catalysts in the yield is studied.
Crystal structure and conformation of short linear peptides part IX : L‐Tyrosyl‐L‐tyrosyl‐l‐tyrosine hemihydrochloride trihydrate
Authors: Wu S. , Declercq J. P. , Tinant B. , van Meerssche M.
Published: September 2010

C27H29N3O7.l/2HCl.3H2O, Mr = 579.84, orthorhombic, P22121, a = 9.816(3), b = 12.365(14), c = 23.394(25)Å, V = 2839(4)Å3, Z = 4, Dx = 1.36gcm−3, Dm = 1.35gcm−3 (by flotation in dichloromethane/chloroform), CuKα, λ = 1.5418 Å, μ = 13.01 cm−1, F(000) = 1228, T = 291K, R = 0.084 for 1788 observed reflections. The conformational angles of the middle residue are somewhat similar to those corresponding to the parallel β‐sheet structure with ϕ2 =−107°, ϕ2 = 123°, but no β‐type interchain H‐bond is formed. The(X1, X21) values for three Tyr residues are respectively, (−65°, −56°), (−166°, 89°) and (−58°, 76°). The X21 value of −56° is the smallest one reported so far for Tyr residues in peptides.
Titanium (O) Reagents; 4. A selective and efficient reduction of nitropyridine derivatives
Authors: Malinowski Marek
Published: September 2010

Following the successful applications of a titanium (O) slurry in the deoxygenation of aromatic N‐oxides, we attempted to achieve this method for the reduction of a nitro‐ group in pyridine derivatives. In general, only aminopyridine derivatives were formed in 85‐98% yield.

The advantage of this excellent reducing agent consists in mild reaction conditions and high yields of products, as well as in the selectivity of the reaction.
Use of selective noe measurements. A note of warning on the assignment of stereochemistry of 1‐substituted 3‐aryltetrahydroisoquinolines
Authors: Badía D. , Domínguez E. , Laborra C.
Published: September 2010

The stereochemistry of the 1‐methyl‐3‐aryltetrahydroisoquinoline (2) was previously misassigned. Application of NOE difference spectroscopy has shown that its correct configuration is the trans‐methyl‐3‐ (3, 4‐dimethoxyphenyl) ‐5‐bromo‐7‐methoxy‐8‐hydroxy‐1, 2, 3, 4‐tetrahydroisoquinoline.
Cobalt(II), Nickel(II), copper(II) and zinc(II) complexes of thiazolidine
Authors: Louloudi M. , Kovala‐Demertzi D. , Hadjiliadis N.
Published: September 2010

The 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

Former 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

Iron 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

The 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

We 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

A 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

Tandem 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

Thermolyses 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

The 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

The 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

We 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

α‐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

The 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

The 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

A 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

The 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

A 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

Syntheses 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

The 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

‐ 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

The 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

Protection 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

In 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 . 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  have to be calibrated by the volume of A itself. This leads to a value of XA−1/2 ϕA−1/2 for , 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

The 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

A 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

The 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

A 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

In 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

Taking 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

Methylmethoxyacetate (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.
The structure of molluscan haemocyanins and their homology with tyrosinases
Authors: Préaux Gisèle , Gielens Constant , Witters Raphaël , Lontie René
Published: September 2010

Haemocyanins, proteins with binuclear copper sites, are dioxygen carriers in four classes of molluscs: gastropods, cephalopods, polyplacophorans (the chitons), and bivalves (in the latter class only in a limited number of primitive species). They show typical quaternary structures and dissociation patterns in the analytical ultracentrifuge and in the electron microscope.

The subunit (Mr 450 000) of the βC‐haemocyanin of the gastropod Helix pomatia is composed of eight functional units, which have been separated by chromatography after limited proteolysis. The two types of subunits (Mr 450 000) of the αD‐ and αN‐Hc components are also constituted of eight functional units like the subunit (Mr 390 000) of the haemocyanin of the cephalopod Sepia. The subunit (Mr 350 000) of the haemocyanin of the cephalopod Octopus is composed of only seven functional units.

The amino‐acid sequences of a functional unit of Helix and of Octopus haemocyanin show a homology with the CUB site of arthropodan haemocyanins near the ligands of copper, but not with their CUA site. There is a striking homology near the potential copper ligands for both the CUA, and the CUB sites of molluscan haemocyanins with those of tyrosinases from the bacterium Streptomyces to man.
Spin delocalisation in heterocyclic captodative radicals1,2
Authors: Nootens C. , Merényi R. , Janousek Z. , Viehe H. G.
Published: September 2010

The open chain and heterocyclic precursors of 12 captodative radicals 1–4 were prepared in order to perform their ESR spectroscopic evaluation. Each of them contains a ketone as a captor substituent and an amino, a thioether or an ether substituent as a dative group. Spectral comparison shows the influence of geometry since 5‐membered cd‐radicals with thio‐groups are more delocalised than their 6‐membered or open chain analogues. Interestingly, when cyclic conjugation becomes possible because of an additional double bond such as in 4b, no marked difference of spin delocalisation is observed in comparison with dihydroanalogue 2b. As the dative substituent changes from CH3N‐ to S‐ and to O‐ (in 2b‐2d) the delocalisation decreases and the participation of the corresponding carbonyl group increases.
Similarites De Comportement Et Formes Locales La Topologie Reflet De La Topographie
Authors: Dubois J. E. , Doucet J. P. , Panaye A.
Published: September 2010

In DARC PELCO topological correlations, each site contribution is individualized, and interaction terms are accurately identified, Topological filiations underlying such approaches very often reflect topographical filiations. We establish that a simplified conformational analysis justifies and assesses the predictive potency of this PELCO model by structural interpolation. Its interpretative ability is based on analysis of the more important site valuations and possibly on interaction terms. Identifying the favored conformers allows us to build actual topographical correlations on the same principle of site evaluation. For instance, gauche or anti carbons provide different contributions to 13C shifts or ΔH comb. values in the alcane series. Further interpretative refinements are available. For instance, in hydrophobicity of amines, alcohols and ethers, each site contribution is evaluated in terms of inductive effect, lone pair accessibility and ability to form hydrogen bonds.
Effet D'Un Champ Magnetique Sur L'Ecoulement Des Oxydes De L'Azote NO Et NO2 Dans Un Milieu Granuleux Effect of a magnetic field on the flow of nitrogen oxydes NO and NO2, through a granulous medium
Authors: Gire Alain , Lomaglio Madame Germaine , Theobald Jean Gérard
Published: September 2010

We show, using a molecular beam method, that the flow of the gas nitric oxyd can be affected by a magnetic field, in relation with the angular momentum of the molecule.
Hydrogenolysis of Ethane on RH Powder. Application of the Landing Site Model
Authors: Crucq A. , Degols L. , Frennet A. , Lienard G.
Published: September 2010

The kinetics of ethane hydrogenolysis catalysed by Rh powder is studied in a very wide range of experimental conditions: 10 torr < PH2 < 1400 torr; 147°C < T < 245°C; 10torr < PC2H6 < 500torr. The results are compared with previously published results obtained under transient conditions on the same metal at much lower temperature (0°C < T< 80°C) and pressure (P < 0,01 torr) that allowed to propose the reaction mechanism. With this mechanism, using the landing site model and published data on hydrogen adsorption, the kinetic parameters, orders and activation energy, are calculated and shown to be in good agreement with experimental values.
1,3‐Dimethylindole: NMR Spectroscopy and Reactivity Towards Ethyl Carbonate in the Presence of Buthyl Lithium
Authors: Avendaño Carmen , De Diego Carmen , Elguero José
Published: September 2010

We report the reactivity of the 2‐lithium derivative of 1,3‐dimethylindole 1 with ethyl carbonate to prepare tris‐(1,3‐dimethyl‐2‐indolyl)methanol 2. A strong concentration dependence in CDCl3 for H‐2 and N‐methyl protons resonances of 1 is described.
Unsymmetrically Substituted Deoxybenzoins: An Improved Preparative Route
Authors: Badía D. , Domínguez E. , Galarza J. , Lete E. , Martínez De Marigorta E. , Villa M. J.
Published: September 2010

A regioselective synthesis of unsymmetrically substituted deoxybenzoins via α‐aminonitriles, establishing the advantage of the use of N,N‐dimethylaminonitriles over the corresponding N,N‐diethylamino derivatives, is reported.
Regio Et Stereochimie De La Cycloaddition D'Une Diarylnitrilimine Sur les Phenyl‐1 N‐Alkyl Dihydro‐1,2 Isoquinoleines Resultats Preliminaires
Authors: Kitane Saïd , Sebban Abdelfatah , Vebrel Joël , Laude Bernard
Published: September 2010

The cycloaddition of a diarylnitrilimine on 1‐phenyl‐N‐alkyl‐1,2‐dihydro‐isoquinolines is regiospecific. The approach of the dipole occurs on the two sides of the dipolarophile except when the size of the N‐alkyl substituent imposes a specific anti approach of the N‐alkyl group.
Introduction D'Un Systeme “Cage” Derive De L'Adamantane Dans Les Acides Carboxyliques, Par Alkylation En Catalyse Par Transfert De Phase Et Par Une Methode Non Catalytique
Authors: Hedayatullah Mir
Published: September 2010

The syntheses of new carboxylic esters of general type RCO2‐CH2CO‐Ad (Ad=1‐adamantyl), where R may be aliphatic or aromatic, have been achieved in high yield by reaction of the corresponding acides with an appropriate derivative of adamantane under phase‐transfer conditions or by a noncatalytic procedure. The influence of the lipophilicity of the catalyst on the course of the alkylation of benzoic acide is discussed.
Synthesis of Anionic and Hydrophobic Derivatives of Ethidium Bromide as Potential New Trypanocydes
Authors: Loccufier J. , Schacht E.
Published: September 2010

This paper describes the synthesis of anionic and hydrophobic derivatives of 3,8‐diamino‐5‐ethyl‐6‐phenyl phenantridium bromide (ethidium bromide, homidium). Evidence for regioselective acylation is provided.
Stereochimie De La Reaction Du β‐Cyclocitral Avec Les Organozinciques Issus Des γ‐Bromosenecioates De Trimethylsilyle
Authors: Bellassoued M. , El Borgi A. , Gaudemar M.
Published: September 2010

Both Z et E γ‐bromosenecioic trimethylsilyl esters react with ß‐cyclocitral in the presence of zinc and at low temperature (−40°C) to give the hydroxyacid 2 as the main product. When the reaction is carried out at reflux of THF for 30 mn, the lactone 4 is exclusively obtained. An extended heating of the reaction mixture leads to the acid 5.
Synthesis of 5‐Aryl‐ and 5‐Alkyl‐4‐Ethoxycarbonyl‐2‐Methylthio‐1,3‐Thiazoles from Dimethyl N‐(Ethoxy‐Carbonylmethyl)Iminodithiocarbonate and Dithioesters
Authors: Alonso G. , Alvarez‐Ibarra C. , Orellana G. , Quiroga M. L.
Published: September 2010

In this paper we give account of an efficient synthesis of 5‐aryl‐ and 5‐alkyl‐4‐ethoxycarbonyl‐2‐methylthio‐1,3‐thiazoles from dimethyl N‐(ethoxycarbonylmethyl)iminodithiocarbonate and dithioesters.
Sur L'Utilisation De L'Ion Chromate Comme Agent Oxydant Dans La Synthese De Composes Carbonyles A Partir De Derives Halogenes Actives
Authors: Thuy Vu Moc , Maitte Pierre
Published: September 2010

The reaction between actived alkyl halides and K2CrO4 in DMF or DMSO provides a convenient synthetic route to corresponding carbonyl compounds.
Complexes of Tetrahydrothiamine and its Phosphate Esters With Chromium(III), Iron(III), Cobalt(II), Nickel(II) and Copper(II)
Authors: Hadjiliadis Nick , Yannopoulos Athanassios , De Grave Eddie , Bau Robert
Published: September 2010

The reactions of tetrahydrothiamine (thth) and its mono‐(ththmp) and pyro‐(ththpp) phosphate esters, with metal halides of NiII, CuII, CoII, CrIII and FeIII were studied in organic solvents. Complexes of the formulae NiL(H2O)4Cl2, CuL(H2O)Cl2, CoL(H2O)3Cl2, CrL(H2O)2Cl3 and FeL(H2O)3Cl3, with L thth, ththmp and ththpp, were isolated as solid adducts. An attempt was made for their characterization, with elemental analysis, conductivity and magnetic susceptibility measurements, ir, uv‐vis and Mössbauer spectra in the case of the FeIII complexes. The N atom of the pyrimidine moiety of the ligands is proposed as a possible coordination site, in the case of NiII, CuII and CoII complexes.
Spectrophotometric and First Derivative Spectrophotometric Determination of Copper With 1‐Phenyl‐1,2‐Propanedione‐2‐Oxime‐1‐Guanylhydrazone
Authors: Salinas Francisco , Nevado Juan Jose Berzas , Valenzuela María Isabel Acedo
Published: September 2010

1‐phenyl‐1,2‐propanedione‐2‐oxime‐i‐guanylhydrazone (FPOG) reacts with copper (II) in a basic medium to form an 1:1 yellow complex having an absorption maximum at 405 nm. A detailed study of the characteristics of this complex has been carried out and a spectrophotometric method for the determination of copper (II) at the 0.2‐13.0 ppm level is proposed. Molar absorptivity at 405 nm is 5.6×103 l.mol−1. cm−1 and the relative error (P=0.05 and n=9) is 0.7%. The selectivity of the method has been increased by employing first derivative spectrophotometry. By the use of the derivative approach copper(II) can be determined in aluminium alloy and aluminium bronze.
Spectres RMN‐1H Et‐13C De Phenyl‐1‐Propanediamines‐1,2 Derives De L'Ephedrine Et De Leurs Imidazolidines
Authors: Tytgat D. , Gelbcke M.
Published: September 2010

A series of N1‐methyl‐1‐phenyl‐1,2‐propanediamines substituted at the nitrogen (N2) by alkyl groups (CH3, C2H5, i‐C3H7, t‐C4H9) and the corresponding imidazolidines from formaldehyde have been synthesized. The study of their 1H‐and 13C‐NMR spectra allowed the differentiation of the diastereoisomers in these two series.