bluuebunny/crossref_metadata_2025 huggingface dataset:
Unsupported MoS2 and WS2 Model Catalysts: Influence of Textural Properties on Hydrodesulfurization and Hydrogenation Activities
Authors: Fréty R. , Breysse M. , Lacroix M. , Vrinat M.
Published: September 2010

Unsupported MoS2 (WS2) were prepared by decomposition of ammonium thio‐salts, under a flow of H2 + 15 % H2S at 673 K.

Samples with surface area ranging from 5 to 80 m2g−1 were tested in hydro‐desulfurization of dibenzothiophene and hydrogenation of biphenyl, at moderate temperature (523 ‐ 573 K) and medium high pressure (pT = 22.5 105Pa) conditions.

The activity, measured at the pseudo steady state, expressed in mole g−1 sec−1 was found directly proportional to the surface area of the tested catalysts, for both reactions and both types of catalysts.

Therefore the preceding reactions appear as “texture insensitive” for both WS2 and MoS2 catalysts.
Unsupported Ni‐mo Sulfide Catalysts: Relation Between the HDS and Hydrogenation Activities and Some Structural Properties
Authors: Gachet C. , Paulus R. , De Mourgues L. , Durand C. , Toulhoat H.
Published: September 2010

A series of unsupported sulfide catalysts containing nickel and molybdenum (with variable atomic ratio a Ni/Ni + Mo) was prepared using a variant of the H.S.P. method which promotes an “intimate contact” between the metallic ions. These catalysts show good activities in the dibenzothiophene hydrodesulfurization (under atmospheric or high pressure) and in the biphenyl hydrogenation. For the two reactions, the maximum of synergy is observed for a about 0.7.

X‐ray diffraction shows that for a < 0.3, only the MoS2 type phase is detected (before and after catalytic test). For higher values of a, nickel sulfide initially present under the NiS2 and NiSβ phases form, is converted into the Ni3S2 phase by catalytic working.

The variations, in terms of a, of the specific area, of the stoichiometric ratio S/Ni + Mo' of the c parameter of the MoS2 type phase, of the TPR spectra shape, show the existence of a mixed phase “Mo ‐ Ni ‐ S” of the same crystallo‐graphic type than MoS2. The presence of this phase would induce an increase of the HDS and hydrogenation properties of the catalyst without explaining the position of the synergy maximum.
IR and AEM Evidence for the Edge Location of the Promoter Atoms in Co‐Mo‐S Type Structures
Authors: Topsøe Nan‐Yu , Topsøe Henrik , Sørensen Ole , Clausen Bjerne S. , Candia Roberto
Published: September 2010

In the present paper, we will discuss recent results which show that the catalytically active Co‐Mo‐S or Ni‐Mo‐S structures consist of Co or Ni atoms at the edges of MoS2. The evidence has been observed by ir studies of NO adsorption and analytical electron microscopy (AEM) investigation of alumina supported and unsupported Co‐Mo and Ni‐Mo hydrodesulfurization catalysts. These studies have also been extended to catalysts sulfided at elevated temperatures. By combining the ir and AEM results with results from Mössbauer emission spectroscopy (MES) and EXAFS, it is found that in order to achieve a large promotion of the HDS activity one must have both a high coverage of the MoS2edges and a high MoS2edge dispersion. It is seen that one advantage of using alumina supports is the possibility of preparing MoS2with high edge dispersion.
Temperature Programmed Sulfiding of CoO/MoO3/γ‐Al2O3 Catalysts
Authors: Scheffer B. , De Jonge J. C. M. , Arnoldy P. , Moulijn J. A.
Published: September 2010

The sulfiding of CoO/MoO3/γ‐Al2O3 catalysts was studied by a technique called Temperature Programmed Sulfiding (TPS). Cobalt loading, calcination temperature and pretreatment were varied.

CoO/MoO3/γ‐Al2O3 catalysts sulfide at lower temperatures than model compounds such as CoO, MoO3 and CoMoO4 because of the higher dispersion in the catalysts. Sulfiding of Mo in CoO/MoO3/γ‐Al2O3 catalysts is dominated by O‐S exchange, reduction of Mo is due to Mo‐S bond rupture followed by reduction of elemental sulfur, in the same way as occurs in MoO3/γ‐Al2O3 catalysts.

For Co in CoO/MoO3/γ‐Al2O3 catalysts the sulfiding pattern depends strongly on the calcination temperature: low calcination temperatures (785 K) lead to catalysts which show sulfiding of Co species in the same temperature range as Mo, and an increase in the reduction rate of elemental sulfur formed by reduction of Mo oxysulfides.

Sulfiding of CoO/MoO3/γ‐Al2O3 leads to Co species which are stabilized and more disperse than those in sulfided CoO/MoO/γ‐Al2O3 catalysts. Calcination temperatures higher than 785 K cause a decrease of the amount of easily sulfidable Co species, and an increase in the amount of Co which sulfides at high temperature (1000 K).

As was found for MoO3/γ‐Al2O3 and CoO/γ‐Al2O3 catalysts the “water content” of CoO/MoO/γ‐Al2O3 catalysts has an influence on the sulfiding patterns: “wet” catalysts (containing up to 6% water) with low Co loading sulfide at lower temperature than dried catalysts. Sulfiding (in TPS) proceeds at a higher rate than reduction by H2 (in TPR).
Effect of Sulfiding Temperature on Activity and Structures of CO‐MO/AL2O3 Catalysts. ii
Authors: Candia Roberto , Sørensen Ole , Villadsen JØRgen , Topsøe Nan‐Yu , Clausen Bjerne S. , Topsøe Henrik
Published: September 2010

The changes, which take place in the structural and catalytic properties of Co‐Mo/Al2O3 catalysts sulfided at different temperatures, have been elucidated by means of high resolution electron microscopy (HREM), ir, XRD, and chemisorption of oxygen. It was observed that high temperature sulfiding induces a growth in the Co‐Mo‐S crystals which are MoS2‐like with Co occupying edge positions. For all the catalysts, Co‐Mo‐S was found to be the most important feature in determining the HDS activity and it was found that the changes, which occur with the HDS activity, can be explained in terms of the changes in the total MoS2 edge area and its Co coverage. When saturation edge coverage is exceeded, segregation of excess Co in the form of Co9S8 takes place. Differences in the hydrogenation activity can be explained in terms of variations in the relative number of promoted vs. unpromoted MoS2 edge sites. Upon increasing the sulfiding temperature, the nature of the Co‐Mo‐S structure changes from a low temperature form (Type I Co‐Mo‐S) to a high temperature form (Type II Co‐Mo‐S). It is suggested that support interactions are less important for Type II Co‐Mo‐S than for Type I.
Influence of Sulfidation Temperature on the Dispersion and Activity of Cobalt‐Molybdenum Catalysts Supported on γ‐Alumina
Authors: Prada Silvy R. , Beuken J. M. , Bertrand P. , Hodnett B. K. , Delannay F. , Delmon B.
Published: September 2010

A commercial cobalt‐molybdenum catalyst supported on γ‐alumina was activated by reduction‐sulfidation under 15% H2S in H2 in the temperature range 573 to 1073K. Optimum hydrodesulfurization activity was achieved after activation between 673 and 803K. At lower temperatures lower activity was observed and X‐ray photoelectron spectroscopy indicated that this was due to incomplete sulfidation of cobalt and molybdenum. Sintering of the supported phase, which occured after activation above 800K, was measured by high resolution electron microscopy, ion scattering spectroscopy and dynamic oxygen chemisorption. The hydrodesulfurization activity varied in the same proportion as the surface area of the MoS2‐like crystallites. It was concluded that the number of active sites per unit surface area of supported phase and the intrinsic activity of these sites for hydrodesulfurization did not change during activation above 800K.
Kinetic Models for the Hydrogenolysis of Thiophene. A Comparison of Hougen‐Watson Models with Fixed and Interconverting Sites for Hydrogenolysis and Hydrogenation
Authors: van Parys I. , Froment G. F. , Delmon B.
Published: September 2010

A Hougen‐Watson model with interconverting sites (H.W.‐I.S.) has been formulated to account for the influence of H2 and H2S on the number of active sites. The model assumes that the ratio of the concentration of active sites for hydrogenolysis and hydrogenation depends upon the ratio of the partial pressures of H2 and H2S. Compared to the Hougen‐Watson model with a fixed number of active sites (H.W.‐F.S.), this H.W.‐I.S. model is less satisfactory for low partial pressures of H2S. For higher Ps/PH ratios, however, the H.W.‐I.S. model can compete with the H.W.‐F.S. model. These results suggest that only a fraction of the adsorbed sulfur is converted into an active site for hydrogenation and that most of the adsorbed sulfur is desorbed as H2S, leaving an active site for hydrogenolysis on the catalyst surface.
Étude de la Relaxation Diélectrique du Dmso
Authors: Elie Volf
Published: September 2010

Au cours de ce travail nous avons étudié la dispersion diélectrique du DMSO entre 1 et 15 360 megaHz et ceci pour des températures comprises entre 20 et 60°C.

Le DMSO présente une dispersion diélectrique proche d'un corps possédant une faible répartition des temps de relaxation, et le type de représentation est celui d'un diagramme de Cole et Cole avec des coefficients de dispersion inférieurs à 0,02.

Les temps de relaxation diélectrique sont de l'ordre de 10−11s et les calculs de ΔH, ΔF, ΔS de rotation dipolaire confirme que le DMSO est un liquide peu associé avec un facteur de correlation de Kirkwood proche de 1,10.
Kinetics Study of Adsorption of CO2 on ZNCO2O4
Authors: Reyes Patricio A. , Plaza De Los Reyes Jorge F.
Published: September 2010

The kinetics of chemisorption of CO2 on ZnCo2O4 in a temperature range 373–423K, and pressure varying from 5 to 21 mmHg has been studied.

A kinetic law that could fit adequately the experimental data was investigated, being this the Elovich equation. The activation energy, determined by Arrhenius law, was also calculated.
Dipolar Study of Complexes Between Trialkylamines and Several Molecules of Carboxylic Acids
Authors: Kapuku F. , Huyskens P. L.
Published: September 2010

The dipole moment μ of carboxylic acid‐trialkylamine adducts containing more than one acid molecule in cyclohexane solutions and in the pure acid is significantly larger than the moment of the one:one complex μab. This is due to a larger value of the proton transfer constant for these complexes. At a given dielectric constant (ϵ = 3 and ϵ = 4), the increase of the proton transfer constant is especially important going from the ab to the a2b complexes, the further increase of the constant when adding still more acid molecules being rather small. This is also observed for the volume contraction of the binary mixtures carboxylic acids‐trialkylamine.

The proton transfer constant of the aib complexes also depends on the dielectric constant of the medium and on the nature of the base but seems to remain approximately the same for all the acids considered. At ϵ = 3, K° is of the order of 0.58 for the complexes with triethylamine and 0.67 for tributylamine. At ϵ = 4, the figures are 0.76 and 0.87.
Charge Transfer Complexes of Nitrones, III1 π‐π Molecular Complexes of 2H‐Pyrrole‐N‐Oxides and One Isoindole‐N‐Oxide
Authors: Nour El‐Din Ahmed M. , Döpp Dietrich
Published: September 2010

Molecular complexes between four 2H‐pyrrole‐N‐oxides as well as one isoin‐dole‐N‐oxide and 2,3‐dichloro‐5, 6‐dicyanobenzoquinone, tetracyanoethylene and tetracyanoquinodimethane in dichloromethane at 25°C have been studied spectro‐photometrically in the visible region. Stability constants and transition energies of the charge transfer complexes have been determined. At higher temperature (35°C) decomposition of the complexes has been observed. The ionization potentials of the donors were calculated from the energy of charge transfer transitions. The results show a strong positional effect and addivity effect of the substitution and conjugation with the azomethine‐N‐oxide group.
Acétonylation Aromatique Homolytique
Authors: Gardrat C.
Published: September 2010

Treatment of monosubstituted benzene derivatives with acetone and manganese (III) acetate in acetic acid gave rise to products of homolytic aromatic substitution in fairly good yields and high purity except for toluene, Isomer distribution, relative rates and partial rate factors were determined for toluene, anisole, chlorobenzene, bromobenzene and benzonitrile. A Hammett plot of the logarithm of the partial rate factors for meta and para positions vs. σ‐constants gave a slope ρ of −1.74 ± 0.40 (confidence interval at the level 95°). When using σ+‐constants the slope becomes ρ+ = −1.25 ± 0.36. The negative values of ρ and ρ+ indicated that the acetonyl radical has an appreciable electrophilic character.
N‐Nitrosamines from the Reaction of Sulfamoyl Chlorides with Sodium Nitrite
Authors: Warner John C. , Nakajima Masayuki , Anselme Jean‐Pierre
Published: September 2010

N,N‐Dialkylsulfamoyl chlorides react smoothly with sodium nitrite in acetonitrile to afford the corresponding N‐nitrosamines in nearly quantitative yields.
Petrosin‐A and ‐B, Two New Bis‐Quinolizidine Alkaloids from the Sponge Petrosia Seriata(1)
Authors: Braekman J. C. , Daloze D. , Defay N. , Zimmermann D.
Published: September 2010

This paper describes the structure determinations of two new ichthyotoxic bis‐quinolizidine alkaloids from the marine sponge Petrosia seriata. The structural elucidations are mostly based on homonuclear 2D‐1H NMR experiments.
Nitration of Phenols by Clay‐Supported Ferric Nitrate
Authors: Cornlis A. , Laszlo P. , Pennetreau P.
Published: September 2010

“Clayfen”, a reactive form of ferric nitrate stabilized by adsorption unto an acidic K 10 clay, is an efficient and selective nitrating agent of phenols, under very mild conditions. It leads specifically to mononitration, with high regioselectivities. These characteristics, coupled with its low cost, ease of preparation and the simplicity of experimental procedures, make “clayfen” an attractive nitrating reagent.
N.M.R. Study of Molecular Interactions between Xenon and Crown Ethers
Authors: Claessens M. , Fabre O. , Zimmermann D. , Reisse J.
Published: September 2010

129Xe N.M.R. has been used to investigate intermolecular interactions between xenon and different crown ethers. Chemical shifts of this isotope measured in chloroform solutions containing various amounts of glymes and crown ethers show that the behaviour of the cyclic molecules is qualitatively very different from their linear analogues. Experimental data are interpreted in the frame of a 2− and 3‐site model developed for linear and cyclic ethers respectively. Our results support the existence of a loosely bound host‐guest pair between xenon and crown ethers characterized by an equilibrium constant K which appears to be independent of the ring size of the crown ether molecules.
Iridoids. Asymmetric Synthesis Via Enantiomeric Separation of the Mono Methylester of 2, 3‐DI‐Endo‐Hydroxycarbonyl‐5‐Norbornene
Authors: Storme P. , Quaeghebeur L. , Vandewalle M.
Published: September 2010

Enantiomeric separation of racemic mono methylester of the known 2, 3‐di‐endo‐hydroxycarbonyl‐5‐norbornene (2) is possible via the ephedrine salts. Both enantiomers can be converted into 2, R‐endo‐methoxycarbonyl‐3, S‐endo‐hydroxymethyl‐5‐norbornene (−)−4, which is a suitable intermediate for asymmetric synthesis of iridoids.
Intramolecular Diels‐Alder Reaction with Furan‐Diene. 1. A Novel Entry to the BCD‐Ring System of 11‐Ketosteroids
Authors: van Royen Luc A. , Mijngheer Roelant , De Clercq Pierre J.
Published: September 2010

A novel approach for the synthesis of the BCD‐ring system in steroids is described. The sequence centers about the intramolecular Diels‐Alder reaction of furan 15, which, depending on the reaction conditions, leads predominantly to adduct 26 (kinetic control) or 27 (thermodynamic control). The precursor 15 is obtained from enol ether 2, prepared via dissolved metal reduction of 5. Only in reduced adduct 34 is the oxygen bridge opened without concomitant epimerization at C‐14. The synthesis of other dienophiles (17, 19, 22 and 25) and their Diels‐Alder reactivity is discussed.
The Oxidation State of Cobalt and Its Coordination State in 3‐(4,5‐Dimethyl‐2‐Thiazolylazo)‐2,6‐Diaminopyridine Chelate
Authors: Gallo B. , Santiago C. , Arnaiz A. R.
Published: September 2010

3‐(4,5‐dimethyl‐2‐thiazolylazo)‐2,6‐diaminopyridine has been synthesized for the first time in our laboratory. It forms a stable coloured complex with cobalt, which is a sensitive reagent for the spectrophotometric determination.

The stability constant and the extraction behavior of the chelate, and its metal‐to‐ligand ratio have been determined previously. In the present work the CoL2n+ complex is characterized in the solid state by means of EPR, IR and UV/visible spectroscopy, and measurement of the magnetic susceptibility. Elemental analysis has also been performed.
X‐ray Diffraction Study of (±)‐5α‐ [2′‐Hydroxy‐l'‐Methoxycarbonyl‐2'‐(3″,4″,5″‐Trimethoxyphenyl) Ethyl)‐4α‐(3″‐4″‐Methylenedioxyphenyl)‐2α‐Phenyl‐1,3‐Dioxane
Authors: Piccinni‐Leopardi C. , Declercq J. P. , Germain G. , van Meerssche M. , van Der Eycken J. , De Clercq P. , Vandewalle M.
Published: September 2010

C30H32O10, monoclinic, P21/c, a = 12.932(5), b = 9.670(6), c = 23.276(13)Å, β = 103.87(4), ν = 2825.9(25)Å3, Mr = 552.58, Z = 4, Dx = 1.30 mg cm−3. The structure was solved by direct methods (MULTAN 80) and refined (SHELX 76) to a final R value of 0.056 for 2344 observed reflections.

The dioxane ring has a chair conformation. On this ring, two substituents, the phenyl and the methylenedioxyphenyl groups, are in equatorial positions while the substituted ethyl fragment is axial.
A Note on the Crystal Structure of 9,10‐ Anthraquinone
Authors: Lenstra A. T. H. , van Loock J. F. J.
Published: September 2010

C14H8O2; Mr = 208.1, monoclinic, P21/c, a = 3.956(3), b = 7.866(3), c = 15.766(4) Å, α = 102.7(3)°, Z = 2, V = 478.5 Å3, F(000) = 216, Dx = 1.445 Mg m−3, Mo‐radiation, λ = 0.71073 Å, μ = 0.104 mm−1, crystal size 0.15 × 0.2 × 0.15mm., R = 0.106, Rw = 0.102 for 718 reflections with I > 3 σ (I) out of 1024 independent measurements at room temperature. The redetermination confirms geometrical features given by previous investigations. The poor fit between observations and model could be shown not to be caused by extinction effects.
Étude de la Décarbonylation du 1‐Acétylimidazole et du 1‐Acétylpyrazole Ionises
Authors: Maquestiau A. , Tommasetti A. , Pedregal‐Freire C. , Elguero J. , Flammang R.
Published: September 2010

Collisionally activated dissociations (CAD) spectra have been used to investigate the structures of ions produced by decarbonylation of 1‐acetylimidazole [1] and acetylpyrazole [12] ionized by electron impact. The results are best explained by the formation of non classical methylene‐azolium ions. The loss of carbon dioxide from l‐methoxycarbonylimidazole [7] does not produce these ions but instead leads to ionized C‐methyl‐2(or 4)H‐imidazole. A mixture of structures is produced by electron impact induced fragmentation (loss of C2H4) of 1‐(2‐hydroxypropyl)imidazole [9]
Condensation des Organomagnésiens sur les Chlorures D'Acide Dans le Tetrahydrofuranne a Basse Température
Authors: Dubois Jacques‐Emile , Lion Claude , Arouisse Abdelmajid
Published: September 2010

La condensation des organomagnésiens sur les chlorures d'acide substitués dans le THF à basse température permet la synthèse de cétones difficiles à obtenir par d'autres méthodes, en évitant la réaction parasite observée lors de la catalyse de cette réaction par CuCl dans l'éther. Appliquée à des chlorures d'acide et des organomagnésiens insaturés, la méthode permet également l'accès satisfaisant à des cétones éthyléniques comme l'Artémisia cétone.
Isolation of Stilbene Derivatives in the Bromination of 1,2‐Diaryl‐Ethylamides
Authors: Domínguez E. , Lata E. , Iriondo C. , Villa M. J.
Published: September 2010

The bromination reaction of the 1,2‐diaryl‐ethylamides (la‐d) afforded the expected bronoamides, together with two stilbene derivatives as by‐products: the (E)‐1‐(2‐bromo‐4,5‐dimethoxyphenyl)‐2‐(3,4‐dimethoxyphenyl)‐ethylene (3) and the (E)‐1,2‐bis(2‐bromo‐4,5‐dimethoxyphenyl)ethylene (4).
Hydrotreatment of Petroleum Residua Using Oceanic Manganese Nodules in a Trickle Bed Reactor
Authors: Dodet Claude , Noville Francis , Crine Michel , Marchot Pierre , Pirard Jean‐Paul
Published: September 2010

Oceanic polymetallic nodules could be used as a catalyst and an absorbent for hydrotreatment of petroleum residua in a trickle bed reactor because of their particular composition and porous texture. A kinetic study of this reaction has been undertaken in a micro‐pilot unit using operating conditions similar to those encountered in industrial reactors. Sulphur content, distillation characteristics and viscosity of the outlet liquid product were investigated. The effect of the main operating parameters (pressure, temperature and mass flow rates) has been determined.
A Thermostated Diafiltration Mini‐Apparatus For the Determination of Binding Parameters of Low Molecular Weight Ligands With Macromolecules
Authors: Claeyssens M. , van Tilbeurgh H. , De Bruyne C. K.
Published: September 2010

A thermostated diafiltration apparatus (1–2 ml) is described. A more rigorous control of cell‐volume and temperature during equilibrium binding experiments by forced‐flow ultrafiltration is obtained. Because the apparatus induces two reservoirs with appropriate valves, leakage of macromolecular receptor at the start of the binding experiment, which is frequently a problem with commercial ultrafilters, can be controlled. The apparatus is first operated in the dialysis mode and the binding experiment is started by switching to the ligand containing reservoir. The construction of the filtrate‐collecting system overcomes the problem of variable void‐volume a and allows the apparatus to be used in other equilibrium dialysis modes.
On the Amidation of 17‐Deacetyl‐Vinblastine With the Ethylesters of Some Aminoacids
Authors: Bhushana Rao K. S. P. , Collard M. P. , Trouet A. , De Bruyn A. , Verzele M. , Noiret A. , Dejonghe J. P. , Hannart J.
Published: September 2010

We describe the synthesis of amides between 17‐deacetylvinblastine (1) and the ether esters of valine (2), leucine (3), isoleucine (4), tryptophane (5) and valine‐tryptophane (6).
A Preliminary Study About the Production by the Pultrusion Technique of a Fiber Reinforced Plastic (Frp) Tension Member For Use In Dielectric Composite Optical Fibre Communication Cable
Authors: Kiekens P.
Published: September 2010

The replacement of traditional coaxial copper cables for telecommunication networks by optical fibre cables requires the introduction of tension members to strengthen the cable. The production of these tension or strength members by pultrusion is discussed. The choice of reinforcing fibre and protecting matrix resin for the composite tension member is also treated. An optimal combination of these raw materials will lead to a pultruded strength member with outstanding properties for use in optical fibre cable.
Revisited Conformational Aspects of Pro and Hyp Pyrrolidine Rings In Bicyclic Peptide Systems
Authors: Sleeckx J. J. M. , Anteunis M. J. O.
Published: September 2010

Pyrrolidine ring conformational aspects in some bicyclic Pro and Hyp derivatives (DKP and Hydantoin) are analyzed from 1H nmr data using a generalised Karplus equation as developed by Haasnoot e.a. (3, 4). Previously published data are corroborated, but those for c/Pro, Hyp/ and c/Pro‐β‐Pro/ have been refined and re‐interpreted.
Stéréochimie De L'Électroréduction De Bromocyclopropanes. IV. Nouvel Exemple De L'Influence De La Composition De L'Électrolyte Sur La Stéréosélectivité De La Réaction
Authors: Hazard R. , Jaouannet S. , Tallec A.
Published: September 2010

The stereochemistry of the electroreduction of the two geometrical isomers of methyl 1‐bromocyclopropane 1,2‐dicarboxylate has been investigated:

‐ for the trans isomer, electrolysis carried out in the presence of NH4+ ions give rise to a 90% retention ratio while 90% of inversion is attained when Bu4N+ cations are present.

‐ preferential inversion of configuration always occurs for the reduction of the cis isomer and stereospecificity (i.e. 100% inversion) is achieved in the presence of Bu4N+ cations.

These results are compared with those observed in the study of electroreduction of cis methyl 1‐bromo 2‐methoxymethyl cyclopropane 1,2‐dicarboxylate.
Molecular Structure Analysis of Minaprine Analogs: 3‐Morpholinoethylthio‐4‐Methyl‐6‐Phenyl‐Pyridazine, C17H21N3OS
Authors: van Der Brempt C. , Evrard G. , Durant F.
Published: September 2010

Mr=315.1, triclinic, P, a=11.162(3), b=10.793(3), c=9.142(4) A, α=103.05 (1), β=98.72(1), γ=126.42(1)º, V=804.0 λ3, Z=2, Dx=1.30 g.cm−3, Cu K+, λ=1.54178 λ, μ=17.18 cm−1, F(0,0,0)=336, T=293 K, final Rw=0.038 for 2559 observed [I 2.5σ(I)] reflections. The sulfur atom is sp2 hybridized and participates to the electronic delocalisation in the pyridazinic ring.
Spectres Rmn‐1H Et −13C Des Acides Mercapto‐2 Pyridinecarboxylique‐4, Mercapto‐4 Pyridinecarboxylique‐2 Et De Leurs Dérivés Méthyles Correspondants
Authors: Gelbcke M. , Grimée R. , Lejeune R. , Thunus L.
Published: September 2010

Proton and carbon‐13 chemical shifts and coupling constants of 2‐mercapto‐4‐pyridinecarboxylic acid, 4‐mercapto‐2‐pyridinecarboxylic acid and their seven respective methylated derivatives are reported. Substituent effects are discussed.
Carbon Monoxide Hydrogenation on the Reduced Nickel‐Titanium Crystal System
Authors: Malinowski M. , Makowski R. , Muranyi R.
Published: September 2010

The catalytic Ni‐Ti system was studied in the Fischer‐Tropsch reaction in a flow microreactor system under normal pressure. Nickel‐titanium was used as a crystal system reduced in a flow of hydrogen. No support was used. The influence of the titanium on the yield of higher hydrocarbons was observed
Rearrangement of 2‐Acyl‐2‐Chloro‐1, 3‐Cyclohexanediones into 2‐Acylresorcinols and 2‐Acyl‐4‐Chloro‐1, 3‐Cyclohexanediones
Authors: De Buyck L. , Seynaeve D. , De Kimpe N. , Verhé R. , Schamp N.
Published: September 2010

2‐Acetylresorcinol was prepared in 80–881 yield from 2‐acetyl‐1, 3‐cyclohexanedione by 2‐chlorination (excess of NCS in boiling carbon tetrachloride or one equivalent of molecular chlorine in the cold solvent) followed by aromatization in a heated dry solution of hydrogen chloride in dimethylformamide. The scope of the method was extended to the preparation of 2‐propionyl‐and 2‐isobutyrylresorcinol (resp. 791 and 661 yield). Application of the method on 2‐acyl‐5, 5‐dimethyl‐1, 3‐cyclohexanediones (acyl=acetyl, propionyl, n‐butyryl, i‐butyryl) afforded the corresponding 2‐acyl‐4‐chlorodimedone derivatives in 40–771 yields
Polarographic Study of Schiff Bases Derived From 2‐Pyrrolecarboxaldehyde and 2‐Thiophenecarboxaldehyde
Authors: Capitán F. , Molina F. , Espinosa P. , Capitán‐Vallvey L. F.
Published: September 2010

Polarographic behaviour of Schiff bases derived from 2‐pyrrolecarboxaldehyde and 2‐thiophenecarboxaldehyde has been investigated in 50%, dioxane‐water medium in pH range 4 to 10. The experimental conditions for the study were so chosen that no appreciable hydrolysis of the Schiff bases occurred during the recording of polarograms. Schiff bases gave two well separated monoelectronic waves in the pH range studied, which shifted to more negative potentials as the pH was increased. Dependence of diffusion current on concentration of depolarizer and height of mercury reservoir suggest that both the waves are diffusion controlled.

On the basis of the polarographic and cyclic voltammetry data an overall electrode reaction is given.
Characterisation and Elimination of the Interfering Effects of the Foreign Species In Flame Atomic Absorption Spectrophotometric Analysis of Thallium
Authors: Mostafa M. A. , Kabil M. A.
Published: September 2010

The interfering effects of some foreign species in flame atomic absorption spectrophotometric analysis of thallium is discussed. The elimination of these interfering effects using either potassium cyanide or n‐butylamine is done. The mechanism of their releasing effect is illustrated. The inhibition release titration method has been used in studying the interfering effects.
Extraction‐Photometric Determination of Oxalate in Urine With Furohydroxamic Acid (Fha)
Authors: Martínez‐Vidal J. L. , González‐Pradas E. , Villafranca M. , Salinas F.
Published: September 2010

Furohydroxamic acid reacts with V(V) and oxalate anion to give a mixed ligand complex of stoichiometry 2:1:1, that it is extracted in toluenic solution of Adogen 464. The ionic pair extracted follows the Beer law between 4 and 13 ppm of oxalate at 633 nm (ε=4,300 L mol−1 cm−1). The determination of oxalate in urine is achieved.
Solution Conformation of Cyclic Dipeptides of Pipecolic and Thiapipecolic Acid Combined With Glycine and Sarcosine
Authors: Reyniers FrançOise S. , Borremans Frans A. M. , Anteunis Marc J. O.
Published: September 2010

From 1 H NMR parameters we demonstrate that the cyclic dipeptides derived from L‐pipecolic acid and L‐γ‐thiapipecolic acid with glycine or sarcosine are negatively buckled. The degree of folding of the diketopiperazine ring increases in the γ‐thia‐analog. The evaluation of the effect of changing the solvent from chloroform to methanol, and of N‐methylation of the Gly residue, on the buckle of the DKP ring is attempted.
Réaction De L'Indazole Avec Le Chlorure De Trityle: Identification Par Rmn Du Proton Des Isomères 1‐, 2‐Et 3‐Substitues
Authors: Claramunt Rosa Maria , Elguero José , Fruchier Alain
Published: September 2010

The first example of substitution on position 3 of indazole by an alkylating agent is described. It takes place, together with substitution in position 1 and 2, when indazole is allowed to react with trityl chloride. The three isomers were characterized by their proton nmr spectra at 360 MHz.
Synthesis of New Aziridime‐Carboxamide‐, Thioamide‐, Amidime‐Derivatives and Their Reaction With Phosgene
Authors: Lambert C. , Merényi R. , Caillaux B. , Viehe H. G.
Published: September 2010

The reactions of primary amines with α‐chloroacrylamide 2, thioamide 3 or amidinium salts 8 give the corresponding aziridines, which themselves are used for the synthesis of new heterocyclic systems when treated with phosgene.
Chemistry of 2‐Diphenylphosphoryl Ketene Thioacetals
Authors: Schaumann Ernst , Fittkau Stefan
Published: September 2010

Carbanions of diphenylphosphane oxides add to carbon disulfide to give, after alkylation, the title compounds 4. In the reaction with the allylphosphane oxide 5, exclusive γ‐attack is observed to yield dienes 6B. An exploratory study of the reactivity of 4 shows that reduction to thioacetal 7 and hydrolysis to 5‐thiocarboxylates 10 are feasible. Deprotonation of phosphane oxides having a β‐sulfur substituent reveals a high tendency to thiolate elimination to give vinyl sulfides 9, resp. 15. However, reaction of thioester 10a with benzaldehyde indicates that the compounds can be used in Wittig‐Horner olefinations. Ketene thioacetal 4e gives a 1,3 methylthio shift on treatment with acid.
Macromolecular Prodrugs of Metronidazole. 1. Esterification of Hydroxyl Containing Polymers With Metronidazole Monosuccinate
Authors: Vermeersch Joan , Vandoorne Filip , Permentier Dirk , Schacht Etienne
Published: September 2010

Metronidazole was converted into the corresponding monosuccinate ester by treatment with succinic anhydride in almost quantitative yield and under mild reaction conditions. The monosuccinate derivative was subsequently coupled onto dextran, inulin and poly‐[N‐(2‐hydroxyethyl)aspartamide].
Valence Electron Density, Deformation Potential and Reactivity of α‐Al2O3 Studied By X‐Ray Diffraction
Authors: Lenstra A. T. H. , De Wolf M. , Vanhouteghem F.
Published: September 2010

The structure of α‐Al2o3 was investigated using X‐ray single crystal data. The model of the structure is shown to be stable in θ‐biased refinements. Corrections on the observed intensities adjusting negative function values for Iobs and removing the impact of thermal diffuse scattering have no effect on positional parameters and only a minor effect on thermal parameters. Transfer of electrons between valence shells proved an important characteristic of the structure, but the coupling of thermal parameter values to the choice of scattering functions prevented the determination of net atomic charges. The electronic potential due to outer‐shell electrons (dynamic deformation potential) indicates the preferred sites for attack by positive and negative ions.
Extraction and Spectrophotometric Determination of Ti(IV) Using 2‐Pyrilideniminobenzohydroxamic Acid As Chelating Agent
Authors: Salinas F. , Jiménez‐Arrabal M. , Merás I. Durán
Published: September 2010

The reaction of Ti(IV) with 2‐pyrilideniminobenzohydroxamic acid (2‐PIBHA) was studied in aqueous medium and by using an extraction in isoamyl alcohol. The stoichiometries of the complexes formed are 1:1 and 1:3 (Ti(IV):reagent) in both cases.

The extraction and spectrophotometric determination of titanium with 2‐PIBHA can be performed in a concentration range from 0.1 to 1.4 μg/ml of Ti(IV). The apparent molar absorptivity in isoamyl alcohol is 39600 1.mol−1.cm−1 at 375 nm. The relative error of the method is ± 0.64% for 25 μg of Ti(IV) in the aqueous phase (50 ml) and the extraction constant is 1.45×1013.
2‐Hydroxy‐1‐Naphthaldehyde Guanylhydrazone as an Analytical Reagent Extractive‐Spectrophotometric Determination of Iron
Authors: Salinas F. , Berzas J. J. , Eapinosa Mansilla A.
Published: September 2010

The synthesis and the analytical properties of 2‐hydroxy‐1‐naphthaldehyde guanylhydrazone are described for the first time. New methods for estimation of iron in homogeneus medium and by extraction in isoamyl alcohol have been proposed.

The extractive‐spectrophotometric determination of iron with NAG can be performed between 6.25–150 μg of iron; the molar absortivity is 5.20×103 liters mole−1.cm−1 at 575 nm, the relative error is ± 1.30% and the extraction constant is 2.17×1011 The proposed method was applied to the determination of iron in a Portland cement and in a high‐purity magnesite.
Computarized Searching Program to Identify the Primary Structure of Peptides and Proteins by Using Chemical Shifts C‐13 Data. Amino Acids
Authors: Hashem K. M. E. , A‐E‐A. Ali F.
Published: September 2010

A computer program to identify the primary structure of “unknown” peptides and proteins is described, based upon the Chemical shifts of C‐13 for 28 common amino acids. The spectra have been measured by high resolution nmr spectroscopy to be used as reference data. To facilitate the investigation procedure, the characteristic Chemical shift (s) are selected. The operation of the program and its performance in investigation of unknown spectra of three hypothetical peptides are fully illustrated after complete hydrolysis in 6N HCl. Correlation between the obtainable results proved the stability of a hydrolysis intermediate by‐product kinetically affected by the polar and steric factors of the main function group in the media.
Approche Expérimentale de la Relaxation de L'Énergie Cédée a un Solide Moléculaire par un Rayonnement Ionisant
Authors: Tilquin B.
Published: September 2010

The purpose of this work is to further clarify the subtle matrix effect on the energy transfer in alkane solid radiolysis. In this autoreview, previous results are interpreted in terms of exciton migration inhibited at the solid‐solid interfaces.
Étude de la Réactivité D'Ylideneoxazoline‐5‐Ones vis‐à‐Vis de Composés Enaminocarbonyles
Authors: Maquestiau A. , Vanden Eynde J.‐J. , Papleux P.
Published: September 2010

Reactions between 4‐ylideneoxazolin‐5‐ones and enaminocarbonyl compounds do not lead to 4,7‐dihydrooxazolopyridines. These reactions yield, by cleavage of the five‐membered ring, monocyclic derivatives whose structures are elucidated.

Thus, starting from 4‐arylideneoxazolin‐5‐ones, mixtures of cis and trans dihydro‐α‐pyridones are formed but, in most cases, only the cis isomers can be isolated.

Starting from 2‐phenyl‐4‐ethoxymethyleneoxazolin‐5‐one, reactions proceed, in addition, by loss of ethanol and α‐pyridones are obtained.
Application des Règles de Sélection MCD au Spectre du Cristal Dope: YAl3(BO3)4/EU3+
Authors: Görller‐Walrand C. , Vandevelde P.
Published: September 2010

The selection rules previously developed for the magnetic dipole allowed transition 5D1 ← 7Fo and the induced electric dipole allowed transition 5D2 ← 7Fo in the MCD spectrum of Eu3+ are applied and discussed with respect to the spectrum of the huntite crystal: YAl3(BO3)4/Eu3+.

The 5D1 ← 7Fo transition appears as a positive A1 signal whereas to the 5D2 ← 7Fo transition correspond two A1‐terms with opposite sign. These features confirm the hypothesis that the magnetic dipole allowed transition is symmetry independent while the induced electric dipole transition is closely related by its sign to the site symmetry of the Eu3+ ion, in this case D3.
Friedel‐Crafts Synthesis of Benzophenone with Little Lewis Acid Catalyst. Factorial Design and Mechanism
Authors: Scuotto Jean‐François , Mathieu Didier , Gallo Roger , Phan‐Tan‐Luu Roger , Metzger Jacques , Desbois Michel
Published: September 2010

A series of benzene derivatives C6H5R with R ranging from the two extremes of the σ+ scale of H.C. Brown has been acylated with little FeCl3 catalyst at reflux temperature. Under these conditions the reaction is limited to activated substrates: with benzene and deactivated aromatics the yield is below 10%. A fractional factorial design is carried out with 5 parameters: temperature, % catalyst, time, ratio aromatic/acylation reagent and nature of catalyst in the case of acylation of benzene by benzoyl chloride with a Lewis acid catalyst (AlCl3 or FeCl3). The multivariate analysis shows that the important factors are: temperature, nature and ratio of catalysts; and also that the interaction % of catalyst‐nature of catalyst and temperature‐nature of catalyst are determinant. Acylation of benzene (and deactivated aromatics) with little Lewis acid catalyst will give acceptable yields if both a moderately active catalyst (FeCl3, ZnCl2) and a high temperature of reaction are used.
Rélations et Similarité Structurales: Régularité et Interactions Modèle Topologique Pulso a Environnement Variable
Authors: Dubois J. E. , Doucet J. P. , Panaye A.
Published: September 2010

LFER correlations are justified by similarity functions developed in Taylor series. In the same formalism of Palm‐Leffler‐Wold, we present here an equation expressing similarity relations based on information extracted from a model with a variable environment (E) for a transition sO + s. This model is implemented in the PULSO topological method. Thanks to the procedure used, and called “nE/2s”, we can decompose the action of a substituent s in two terms related to the action of s on a reference environment EO and to its interaction on (E1 ‐ EO). This model complements the usual one which has a constant environment E. The LFER relations, procedure (2E/ns) used especially for monosubstitutions, source of action parameters, is hardly efficient for Multiple Substitution Effect studies (MSE) because of the difficulties involved in evaluating interactions. Both models can be used either within the framework of a population (internal treatment) or with external references. The new model, alone or in association with the first, is used to identify the nature of the interactions to be associated with Taylor derivatives.
Barrières de Rotation Adjacentes aux Doubles Liaisons Étude Structurale Théorique D'Acides Carboxyliques, Oléfines et Amides, Relaxation Tensionnelle et Déformations Valencielles des Composés Contraints
Authors: Cossé‐Barbi A. , Massat A. , Dubois J. E.
Published: September 2010

Conformations associated with alkyl groups adjacent to a double bond are studied on five series of aldehyde, ketone, carboxylic, amide and olefine compounds. The data used, spectroscopic or theoretical, are based on 14 compounds R(C‐X)Y with Y‐H,OH,Me,N (Me)2 and X‐O or CH2. The number, the relative abundance of conformers and the heigth of the rotation barriers obtained by the PCILO method are discussed for two series of compounds with neopentyl chains BuCH2(C=X)Y and triptyl groups tBu(Me)2C(C‐X)Y.

In each case, the eclipsed double bond form competes with one or two skew conformers.

For simple flexible compounds, the conformational motion is determined primarily by rotation relaxation. But for compounds with high structural constraints, the relaxation mechanism implies variations in the bond angles. The conformational flexibility is greatly increased and linked to a marked attenuation of the rotation barriers. The valency relaxation of tensions is estimated at between 20 and 30 kilocalories. When the constraints are important, they are associated with the existence of strong interactions of the two alkyl groups situated in δ position with regard to each other.
Quelques Aspects de la Chimie Theorique Contemporaine
Authors: Leroy Georges
Published: September 2010

In this paper we make a survey of various aspects of theoretical chemistry to which we have made some contribution. Our Localized Molecular Orbital (LHO) approach to the electronic structure and reactivity of chemical species allowed us not only to generalize the Lewis and Linnett theories of valence but also to determine the mechanism of a wide variety of organic reactions. We have also proposed a general definition of the concept of stabilization energy applying to any compound. Using this concept, we have been able to elaborate a table of standard bond energy terms, to unify various notions such as hyperconjugation, resonance, ring strain and steric repulsion energy and to carry out a critical analysis of former definitions of the stabilization energy of olefines and free radicals. Furthermore, we have shown that the enthalpy changes and, eventually, the rate constants of any physical or chemical process involving paramagnetic or charged species could be rationalized in terms of their stabilization energies. In this prospect, we have proposed an original interpretation of the persistence of some free radicals and we have made interesting predictions concerning the thermochemistry and the kinetics of various reactions involving neutral or charged reactive intermediates. Moreover we have devised a semi‐empirical method for estimating the barrier heights of atom transfer reactions. So, we have been able to systematically determine the kinetic parameters of these processes using the transition state theory with an Eckart tunnelling correction. Finally, our barrier height modelling allowed us to interpret the effect of substituents on the activation barriers of hydrogen transfer reactions leading to carbon centred free radicals. On the whole, we have tried to demonstrate the promising role theory is presumably led to play in the development of modern chemistry, owing to the joint utilization of its own tools ‐ concepts, models and formalism ‐ and the information provided as much by experimental techniques as by the ab initio methods of quantum chemistry.
The Substrate Specificity of Phospholipase A2: The Reaction of the Enzyme with 3‐Octanoyloxy‐4‐Nitrobenzoic Acid
Authors: Markowitz Michael A. , Seykora John T. , Kézdy F. J.
Published: September 2010

3‐Octanoyloxy‐4‐nitrobenzoic acid is hydrolyzed by the phospholipase A2 (D‐49) from the venom of Agkistrodon piscivorus. The hydrolytic reaction is truly catalytic, requiring the presence of calcium ion (Kd=3.3 ± 0.7mM). At pH=7.0 the value of the enzymatic rate constant is (Kcat/Km)max=175 ± 14 M−1 sec−1, comparable to that of the enzymatic hydrolysis of 3‐sn‐dibutyryl lecithin.
Regiochemistry of the Alkylation of Selenium Stabilized Allylic Anions
Authors: Hevesi L. , Nsunda K. M. , Renard M.
Published: September 2010

Selenium substituted allyl lithiums react with alkyl halides or benzaldehyde to produce alkylation products in good yield. The regiochemistry of this reaction is found to bear similarities with that of the thio‐analogs in that it depends largely on the nature of the alkylating agent and on the reaction conditions; it is further complicated by the occurrence of the allyl selenide rearrangement discovered recently.
Photolysis of m.Chloroanisole: Nature of Excited States
Authors: Vermeulen J. , Soumillon J. Ph.
Published: September 2010

The distribution of the photoproducts in the photolysis of m.chloroanisole is used as a probe for the identification of the excited states responsible for the reduction and substitution.
Electron Impact Fragmentation of Mixed and Asymmetric Benzyltin Compounds
Authors: Gielen Marcel
Published: September 2010

The mass spectra of seventeen mixed and of five asymmetric benzyltin compounds are described and analysed. The proposed fragmentation pattern is in agreement with the hypothesis of preferred Sn(IV) and Sn(II) valence states in the tin‐containing fragments, which are reached by a loss of a radical from the molecular ion, or by the loss of an alkene or alkane from a favourable valence state.
The Vibrational Analysis of the Copper Complexes with Planar Oxamides and Oxamic Acid
Authors: Desseyn Herman , Schoeters Georges
Published: September 2010

The preparation of different complexes of planar oxamides and oxamic acid with Cu(II) and Cu(III) are reported. Isotopic shifts in the i.r. spectra let us assign the most fundamental vibrations.
Conductometric Study of Ion‐Pair Equilibria of Silver Benzoate in Methanol‐Water Mixtures: A Comparison of Conductance Equations and Ion‐Pair Constants
Authors: Maniah V. , Sethuram B. , Navaneeth Rao T.
Published: September 2010

Conductivities of silver benzoate in 0–60% (w/w) methanol‐water mixtures were measured at 25°C and analysed using Fuoss‐Hsia equation in the form of Fernandez‐Prini coefficients, Shedlovsky and Fuoss‐Kraus extrapolation techniques for calculating the association parameters (ΛO and KA). A comparison of these parameters revealed that all the methods of analysis yield essentially the same ΛO values but differed in KA values. The Shedlovsky method turned out to be superior and predicted better association constants than the Fuoss‐Kraus technique.

The log KA vs 1/D plot was linear with finite intercept in accordance with the modified Denison‐Ramsey theory i.e. KA=2.934 exp (161.08/D) of ion‐pair equilibria. The association constants and ionsize parameter (a) values required by Bjerrum, Fuoss, Denison‐Ramsey and Ebeling‐Kraeft, Yokoyama Yamatera theories were also estimated and their soundness to explain the behaviour of silver benzoate in all the solvent mixtures studied, was discussed.
Neutral Chelate Lanthanide Complexes of 3‐Hydroxy Pyridine‐1‐Oxide and Nicotinic Acid‐1‐Oxide
Authors: Navaneetham N. S. , Kalyanasundaram R. , Soundararajan S.
Published: September 2010

New lanthanide neutral complexes of Nicotinic acid‐l‐oxide and 3‐hydroxy pyridine‐l‐oxide were synthesized by a novel method consisting of refluxing the mixture of the ligand (L) and lanthanide trichloroacetate in methanol. Solid complexes of the formula LnL3.2H2O where Ln=La‐Yb and Y, were isolated. Proton NMR and IR spectra for the complexes reveal the bidentate binding of both the ligands to the lanthanide ion. Electronic spectra along with the conductance data, for the complexes, indicate a coordination number of six for the lanthanide ion in the complexes of both the N‐oxide derived ligands.
Réactivité des Dihydro‐3, 4‐2H‐Benzoxazines‐1, 3 Avec les Amines Mise en Évidence D'Un Equilibre Impliquant L'Ouverture de L'Hétérocycle
Authors: Tzschoppe D. , Vebrel J. , Schwob J. M. , Roche M. , Riess G.
Published: September 2010

In the presence of primary or secondary amines 2H‐3, 4‐dihydro‐1, 3‐benzoxazines equilibrate with a ring‐opened coupling product and the corresponding Mannich base. The equilibrium conditions and the mechanism of the reaction have been verified.
Action des Organométalliques sur les Iminoéthers: Nouvelle Voie D'Accès Aux Oxazolines
Authors: Bellassoued M. , Gaudemar M. , Hajjem B. , Baccar B.
Published: September 2010

Iminoethers of type 1 have been shown to react with organometallic reagents to give oxazolines in good yield. The process of the reaction is discussed.