bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthèse et Étude de l'Ouverture du Cycle de Sélénoloisothiazoles Bicycliques
Authors: Onyamboko N. V. , Renson M. , Paulmier C. 
Published: September 2010

AbstractCondensed selenophenes on the one hand, and isothiazoles or isoselenazoles on the other hand, show a ring opening by organolithium compounds. We studied here the competition of ring opening in two isomers of the bicyclic unsubstituted system, selenoloisothiazole. Synthesis of these unknown isomers, namely selenolo[3,2‐d] and [2,3‐d] isothiazoles, and of the corresponding selenolo[2, 3‐d] isoselenazole, is described.
Solvent Effect Upon Dipole Moment and Proton Transfer Equilibrium in Ortho Mannich Bases
Authors: Pawelka Z. , Rospenk M. , Sobczyk L. 
Published: September 2010

AbstractThe dipole moments of ortho Mannich bases containing intramolecular OH…N hydrogen bonds were determined in solvents of various electric permittivity. The dipole moment of 2‐(N,N‐diethylaminomethyl)‐3,4,6‐trichlorophenol does not depend on the solvent polarity and simultaneously no contribution of the proton transfer form was detected in ultraviolet‐visible spectra. The dipole moments of 2‐(N,N‐diethylaminomethyl)‐3,4,5,6‐tetrachlorophenol and 2‐(N,N‐diethylaminomethyl)‐4‐nitronaphtol‐1 increase distinctly with the solvent polarity. The dipole moment enhancement can be quantitatively correlated with the displacement of the OH…N ⇄ O−…H‐N+ equilibrium towards the more polar proton transfer form. The solvent influence on the free energy of the proton transfer process, ΔGPT is discussed in terms of various effects.
The Effect of Some Additives on the Aggregation of Dyes
Authors: Abd El Wahed M. G. , Abd El Kader A. K. , Killa H. M. 
Published: September 2010

AbstractThe effect of additives such as ethanol, urea and KCI on the aggregation behaviour of C. I. acid red 13 and H. acid azonitrobenzotriazol dyes has been studied polarographically. The influence of surface active substances such as albegal B, uniperol O as well as levapon AN was also investigated. The thermo‐dynamic parameters ΔG, ΔH and ΔS were calculated using van't Hoff's equation. The results indicate that the electroreduction process proceeds irreversibly and is diffusion controlled.
Accuracy in Single‐Crystal X‐ray Diffractometry: Software Checks of Scan Angle, Mechanical and Electrical Stability of the Diffractometer from Intensity Profiles
Authors: Verbruggen M. , Lenstra A. T. H. 
Published: September 2010

AbstractSoftware tests checking the diffractometer stability and the correctness of instrument settings are developed. Using averaged reflection profiles systematic underestimates of the scan angle can be detected and their effect on the background corrected with the help of α1/α2 splittings. Mechanical instabilities of the apparatus cause the center of a reflection profile to deviate from the expected value. Factors are described influencing the expected center, its spread and the accuracy of the experimental center. Mechanical errors appear to be rare. Statistical criteria are given to detect and correct background detector channels suspect of being effected by electrical instabilities. We estimate that in our experimental environment 1‐2% of all detector channels are likely to be enlarged by (external?) electrical error sources. A least‐squares analysis of Al2O3 shows that a correction of suspected backgrounds results in a 5% decrease of Σ|Δ|2 and a 1% increase of Σ|F0|.
X‐Ray Structure of 2‐Acetoxy‐1‐(4‐Nitrophenyl) Ethanone C10H9NO5
Authors: Tinant B. , Declercq J. P. , Exner O. 
Published: September 2010

AbstractMr = 223.18, monoclinic, P21/c, a = 9.004 (2), b = 12.552 (2), c = 9.416 (3) Å, β = 102.18 (2)°, V = 1040.1 (3) Å3, Z = 4, Dx = 1.43 g. cm−3, CuKα, λ = 1.5418 Å, μ = 10.13 cm−1, F(000) = 464, T = 291K, R = 0.044 for 1200 observed reflections. The two moieties of the molecule are planar and the dihedral angle between them is 79°.
Crystal Structure and Conformation of Short Linear Peptides: Part VI: L‐Alanyl‐L‐Prolyl‐Glycine Monohydrate
Authors: Wu S. , Declercq J. P. , Tinant B. , van Meerssche M. 
Published: September 2010

AbstractC10K17N3O4, H2O, Mr = 261.28, orthorhombic, P212121, a = 6.716(1), b = 11.780(1), c = 16.248(1)Å, V = 1285.6(2)Å3, Z = 4, Dx = 1.35 g. cm−3, CuKα, λ = 1.5418 Å, μ = 9.28 cm−1, F(000) = 560, T = 291K, R = 0.063 for 2447 observed reflections. The molecule (hereafter APG) adopts a collagen‐like conformation at Pro residue with (φ2, Ψ2) values of (‐66.6°, 156.9°) and an extended form at the two terminal residues. The pyrrolidine ring is disordered with two positions for C(6) its conformation is C2‐Cγ‐endo for the major component (75%) end C2‐Cγ‐exo for the minor one (25%). The geometry and the main‐chain conformation are both in excellent agreement with those found in the tripeptide L‐Leu‐L‐Pro‐Gly monohydrate (hereafter LPG)(1,2) It seems that the atoms further than Cγ of the Leu side chain do not affect significantly the conformation of peptide backbone in this case. The twofold screw axis in the LPG crystal structure corresponds to that of the APG in the a direction.
The Effect of Added Electrolytes on Amphiphilics in Aqueous Solution: Data Motiving a Differentiation Between the Action of Anions and Cations
Authors: Vijlder Michel De 
Published: September 2010

AbstractThe sequences of electrolyte effectiveness in altering the behaviour of two still closely related azo dye homologues Benzyl Orange (C6H5‐CH2‐NH‐C6H4‐N‐N‐C6H4SO3−) and Orange IV (C6H5‐NH‐C6H4‐N‐N‐C6H4SO3−), obtained from spectrometric measurements, are different.The extension of earlier data 1,2,3 on the effect of electrolytes with various anions affirms the differentiating action of anions and cations: anions do specifically influence the ordening of the water structure while cations differ in their ion pair formation tendency. Both processus induce a self‐association of the dyes3.
Crystal Structure and Conformation of Short Linear Peptides: Part VIII: L‐Leucyl‐L‐Tryptophanyl‐L‐Leucine Hydrochloride Dihydrate
Authors: Wu S. , Declercq J. P. , Tinant B. , van Meerssche M. 
Published: September 2010

AbstractC23H35N4O4 +Cl−.2H2O, Mr = 503.08, orthorhombic, C2221, a = 21.661(4), b = 22.820(4), c = 12.568(2)Å, V = 6212(2)Å3, Z = 8, Dx = 1.08 g. cm−3, CuKα, λ = 1.5418 Å, μ = 14.12 cm−1, F(000) = 2160, T = 291K, R = 0.078 for 3133 observed reflections. The molecule assumes a poly‐Gly‐II type conformation with (ϕ2,Ψ2) values of (‐75°,‐135°). The two C atoms of the methyl groups of Leu(2) side chain are disordered with two positions for each (56%,44%). The side chain of Leu(1) and the minor component of Leu(2) have the similar conformation characterized by (X1, X21, X22) angles of (‐71°,‐56°,‐179°) and of (‐77°,‐33°,174°) respectively, close to one of the most frequently observed ones (‐60°,‐60°, 180°) (1). The corresponding values of the major conformation of Leu(2) are unusual (‐77°,44°,142°). The Trp side chain takes an energically defavorable conformation (X1 = 63°, X21 = ‐15°, X22 = 164°) with the indole ring almost parallel to the CαCβCγ plane instead of being perpendicular to it(2).
Electrochemical and Photochemical Preparation of N‐Acylated a‐Methoxy‐Phenethylamine. Failure to Conversion into Phenylalanine
Authors: Callens R. , Anteunis M. J. O. , De Witte M. 
Published: September 2010

AbstractAnodic oxidation of N‐methoxycarbonyl phenetylamine in MeOH at pH 9 proceeds quantitatively although only 45% conversion can ba reached in a simple undivided electrocall as the result of the formation of an obstructing precipitate. Treatment of several N‐acyl‐a‐methoxy derivatives with cyanide results in elimination instead of substitution. The preparation of Phe from the above‐mentioned synthons therefore was unsuccessfull.
Décomposition des Esters de la N‐Hydroxythiopyridone‐2. Synthèse de Quelques Nouveaux Halogènures Secondaires et Tertiaires Encombres
Authors: Stofer Edwond , Lion Claude 
Published: September 2010

AbstractHindered α,α‐disubstituted and α,α,α‐trisubstituted acyl chlorides give with N‐hydroxy‐2‐thiopyridone, the corresponding ester. The decomposition of this compound in tetrachlorotethane or in bromotrichloromethane as solvent and halogen atom source results in the formation of new very hindered secondary R1R2CHX (R1 = iPr or tBu; R2 = iPr or tBu; X = Cl or Br) and tertiary R1R2R3CX (R1 = R2 = R3 = iPr; R1= tBu, R2= iPr, R3= et or Me, X = Cl) alkylhalides.
Kinetics of Thiophene Hydrodesulfurization on A Co‐Mo/AlaOs Catalyst
Authors: Patrov L. A. , Vladov Ch. D. , Shopov D. M. 
Published: September 2010

AbstractThe 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

AbstractThe 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

AbstractUsing 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractFree 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

AbstractMethylidenemalonates 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

AbstractSome [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

AbstractThe 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

AbstractThe 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

AbstractAlumina 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

AbstractThis 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

AbstractThe 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

AbstractCatalysts 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 <k> 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 <k> can be estimated from the DOC capacity (DOCC). However, there are some limitations: the <k>‐DOCC correlations are restricted to narrowly defined groups of catalysts and <k> must not exceed a critical level <k>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 <D>. 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

AbstractMolybdenum‐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

AbstractRuCl3 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

AbstractSome 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

AbstractC27H29N3O7.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

AbstractFollowing 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

AbstractThe 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.