bluuebunny/crossref_metadata_2025 huggingface dataset:
Laterite as a catalyst for the hydrotreatment of heavy Oil. II. Influence of chemical and thermal treatments on the HDS and HDM activity
Authors: Yunes S. , Thakur D. S. , Grange P. , Delmon B.
Published: September 2010

Effects of thermal treatment and iron extraction by the dithionate method (DCB) on the pore size distribution of laterite, and influence of iron and molybdenum impregnation on hydrodesulfurization (HDS) and hydrodemetallization (HDM) of natural DAO Morishal feedstock, were investigated. Thermal treatment up to 400°C noticeably improves pore size distribution and surface area. Higher temperatures drastically decrease the specific surface area, although the total pore volume remains constant. Iron extraction of laterite calcined at 550°C decreases HDS activity, but improves HDM activity. On the contrary, iron and molybdenum impregnation noticeably increases HDS activity and does not improve the HDM function.
A convenient preparation of 3H‐1,3‐Oxazol‐2‐One and its N‐formyl derivative
Authors: Tavernier Dirk , van Damme Sabine , Ricquier Patrick , Anteunis Marc J. O.
Published: September 2010

The electrochemical hydroxylation of 1,3‐oxazolidin‐2‐one to 4‐hydroxy‐1,3‐oxazolidin‐2‐one is reported; a substantial side product is the symmetrical ether derived from the hydroxycompound. An improved synthesis of 3H‐1,3‐oxazol‐2‐one has been developed; nothing more is involved than boiling the readily available 4‐methoxy‐1,3‐oxazolidin‐2‐one with an excess of acetic acid and one equivalent of acetic anhydride, evaporation of the solvents and recrystallization of the residue. The mechanism of the reaction is discussed. In a reinvestigation of the known conversion, by acetic anhydride, of 4‐methoxy‐1,3‐oxazolidin‐2‐one to N‐acetyl‐1,3‐oxazol‐2‐one, we have uncovered the formation of two 3,4′‐bioxazole side products [3‐(2‐oxo‐1,3‐oxazolidin‐4‐yl) 1,3‐oxazol‐2‐one and its N‐acetyl derivative], especially in the presence of added acids. We have found that N‐formyl‐1,3‐oxazol‐2‐one can be made in good yield by treatment of 3H‐1,3‐oxazol‐2‐one with a mixture of formic acid and acetic anhydride (“acetic formic anhydride”) in the presence of 4‐(N, N‐dimethylamino)pyridine; the formation of an intermediate phosphonate derived from 3H‐1,3‐oxazol‐2‐one, as described in the literature synthesis of N‐formyl‐1,3‐oxazolone, is superfluous.
Ft‐Ir study of the interaction between N, N,1,9‐tetramethylguanine and the Li+ Ion. Comparison with protonation
Authors: Parmentier J. , De Taeye J. , Zeegers‐Huyskens Th.
Published: September 2010

The interaction between N, N, 1, 9‐tetramethylguanine and the Li+ ion is investigated in acetonitrile and in the solid state by FT‐IR spectrophotometry. The spectroscopic results are in agreement with the ab initio calculations of Del Bene which predict a structure where Li+ is bonded to the N7 and O6 atoms. In contrast, protonation takes place on the N7 atom. The comparison of results for other carbonyl systems allows to establish a correlation between the calculated elongation of the carbonyl bond and the frequency variation of the °C = O vibration.
Nucleophilic substitutions on 2‐Chloro‐3‐Nitroquinoxaline
Authors: Nasielski‐Hinkens R. , Kaisin M. , Grandjean D. , Loos M. , Nasielski J.
Published: September 2010

Piperidine, cyclohexylamine, methoxide ion and para‐thiocresolate ion react with 2‐chloro‐3‐nitroquinoxaline 1 by selectively substituting the nitro group, in contrast to the behavior of most ortho‐chloronitroaromatics which loose halide when subjected to nucleophilic substitution reactions. This inversion is interpreted as being due to the lack of activation of the 2‐position by the nitro group in the 3‐position because of the low value of the π‐bond index between these two vertices. It is also suggested that the substitution by neutral reagents such as amines is strongly influenced by stabilizing interactions between the negatively charged nitro group and the ammonium moiety in the σ complex; this built‐in solvation may be responsible for inversions in the chemoselectivity between chloro and nitro nucleofugicities.
Three new norditerpenes with an isopimarane skeleton from vellozia variabilis
Authors: Pinto Angelo C. , Ribeiro Núbia Moura , Brito Lavínia , Tinant Bernard , Declercq Jean Paul
Published: September 2010

Three new γ‐lactone norditerpenes with an isopimarane skeleton were isolated from roots, stem and leaf sheaths of Vellozia variabilis. X‐ray diffraction analysis established the structure of one of these norditerpenes. The other two were elucidated through spectroscopic data and chemical correlation.
Electronic stabilized four‐membered tin cycles. Molecular structure of bis‐μ‐sulfido‐bis{1,4‐Diethyl‐1,4‐Diaza‐8‐Stannatricyclo [3. 2. 3.1,804,8]Undecane}
Authors: Schollmeyer D. , Kalbitz J. , Hartung H. , Tzschach A. , Jurkschat K.
Published: September 2010

The synthesis of the intramolecular penta and hexa‐coordinated tin compounds [MeN(CH2CH2CH2)2SnS]2 3, and [(CH2N(Et)CH2CH2CH2)2 SnS]2 5, is described and their 1H, 13C and 119Sn NMR data are reported. 5 crystallizes in the monoclinic space group P21/C with the unit cell dimensions a =8.977(2), b = 13.053(2), c = 13.310(1) Å, β = 103.54(2)ρ, V 1516.3(5) Å3, ρ= 1.529 g/cm3, Z=2. The structure was refined to a final R value of 0.058 for 1.774 observed independent reflections. The tin atoms are hexa‐coordinated by 2 C, 2 S and 2 N. The intramolecular Sn‐N distances amount to 2.766 and 2.859 Å.
Bicyclic imidazolidinones as potential antibiotics
Authors: Marchand‐Brynaert Jacqueline , Vanlierde Huguette , Ghosez Léon
Published: September 2010

The bicyclic imidazolidinones 5 topologically related to the penicillin family, are susceptible to form a stable carbamate with serine‐ D, D‐peptidases. A series of N‐7 acylated or sulfonylated (2R, 5R)‐ 3,3‐dimethyl‐8‐oxo‐4‐thia‐7, 1‐diazabicyclo[3.3.0]octane‐2‐carboxylates 12–21 have been prepared. None of these novel penicillin analogs exhibited antibacterial activity.
Electrochemical behaviour of the Ni(II) ion in soda‐lime‐silica melts
Authors: Claes P. , Tilquin J. Y. , Glibert J.
Published: September 2010

Determination of the oxidation state of solutes in glass‐forming melts can be made in situ using electrochemical techniques. Nevertheless accurate voltammetric measurements are perturbed by the simultaneous influence of broader voltamperometric signals and high residual currents. The aim of this investigation was to test various voltammetric methods as well as chronopotentiometry, chronoamperometry and AC impedance plots in order to analyze the electrochemical behavior of a given solute. The Ni(II) entity was selected, its reduction wave being well‐defined. Experiments were carried out over the temperature range from 1148 to 1473 K.
Spectroscopic and Thermodynamic Investigation of Molecular Complexes of 1,2,3,4‐Tetrachloro‐Bicyclo [4,2,0] Octa‐1,3,5‐Triene‐7,8‐Dione with π‐Electron Donors In Solution
Authors: Nagy Ottó B. , Szpakowska Mariola , Hevesi Làszló , Nagy Jà nos B.
Published: September 2010

The title compound (Q) forms readily molecular complexes with various π‐donor molecules in 1,2‐dichloroethane solutions. It is shown that the intermolecular charge transfer occurs between the highest occupied molecular orbital of the donors (D) and two closely spaced unoccupied orbitals of the acceptor Q. The complexes are of composition 1:1. They are rather weak having only slightly ionic intermolecular bonds. The studied complexes obey all the relationships valid for weak molecular complexes from which the unknown electron affinities of Q(EA1=0.916 eV and EA2=0.724 eV) and ionization potential of fluorene (ID=7.82 eV) could be determined. The LCDA MO theory is also fully borne out by the experimental data. It turns out that the new acceptor compares favourably with analogous halogenated oxygen containing π‐electron acceptors.
Monitoring of Deprotection Reactions of Cyclic Somatostatin Analogues by Fast Atom Bombardment Mass Spectrometry
Authors: Elseviers M. , Jaspers H. , Laus G. , Tourwé D. , van Binst G.
Published: September 2010

The removal of t‐butyloxycarbonyl‐, benzyloxycarbonyl‐and O‐benzyl group from protected somatostatin analogues by hydrogenolysis and acidolysis was monitored by FAB‐mass spectrometry. Sideproducts can be identified and the optimum deprotection conditions can be determined using a minimal amount of peptide.
Application De La Methodologie De La Recherche Experimentale A La Synthese Du Methylene‐2 Vinylcyclopentane Par Cyclodimerisation Du Butadiene A L'Aide De Complexes Du Nickel
Authors: Masotti Henriette , Peiffer Gilbert , Siv Chhan , Joblet Elisabeth , Luu Roger Phan Tan
Published: September 2010

The cyclodimerisation reaction of butadiene leading to methylene‐2‐vinylcyclopentane catalysed by zerovalentnickel in presence of Threophos ligand has been optimised using the experimental research methodology. Thus, we obtain the cyclodimer with 70% of selectivity for a conversion rate of 90% and this in the following conditions: temperature 80°C; time 6 hours; [ligand]/[Ni0]=1; [butadiene]/[Ni0]=80; [methanol]/[Ni0]=50.
Thermal Reactions of Arylamidoximes
Authors: Da Costa Leite Lúcia F. C. , Srivastava Rajendra M. , Cavalcanti Alexandre P.
Published: September 2010

The effect of heat on arylamidoximes, la‐g, has been examined. When acetic acid was used as solvent, amidoximes, la‐g, provided three products, viz., 3,5‐bis‐aryl‐1,2,4‐oxadiazoles, 2a‐g, 3‐aryl‐5‐methyl‐1,2,4‐oxadiazoles, 3a‐g, and a small quantity of an unknown polar compound. Heating arylamidoximes at controlled temperature without acetic acid furnished bis‐aryloxadiazoles, 2a‐g. An insight has been obtained about the mechanism of formation of 2 from 1.
Face Selectivity of the Diels‐Alder Reaction of Thebaine‐Like Morphinandienes, A Computational Approach (Chemistry of Opium Alkaloids, Part XXXI)
Authors: Linders J. T. M. , Maat L.
Published: September 2010

Molecular mechanics {MMP2(85)} have been employed for the calculation of the geometry of morphinan‐6,8‐dienes.

The X‐ray structure of desoxycodeine‐A, a morphinan‐5,7‐diene, and of other morphinans were well‐reproduced by the minimization program. The conformations of 4,5α‐epoxymorphinan‐6,8‐dienes and their 4‐hydroxy analogues show considerable differences, which account for the observed face selectivity in the Diels‐Alder cycloaddition.
Effect of the Anionic Ligand on the Equilibrium Between Mononuclear and Binuclear Complexes of Copper(II) Carboxylates in Pyridine‐Chlorobenzene Solutions
Authors: Szpakowska M. , Radecka Ł.
Published: September 2010

The electronic and EPR spectra of Cu(RCO2)2 [R=(CH3)2CH‐, C2H5‐, (CH3)3C‐] have been measured in pyridine‐chlorobenzene solvent mixtures. The results have been interpreted in terms of equilibrium between mononuclear and binuclear forms of copper(II) carboxylate complexes with pyridine. The dimerization constant, Kc, and ϵb ϵm values for bi‐ and mononuclear complexes have been determined in various mixed solvent compositions. The Kc values decrease with the basicity of the carboxylate ligand. The observed tendency is opposite to that obtained for Cu(II) carboxylate complexes with α‐methyl‐substituted pyridines. The axial position of pyridine ligands in the elongated octahedron structure of mononuclear forms seems to be responsible for this correlation. It appears also that detailed comparison of physico‐chemical properties of different copper complexes is possible only when the geometric structures of the species in equilibrium are identical. Furthermore, steric effect dominates the behaviour of complexes studied in binary solvent mixtures.
Acid Catalyzed Heterolysis of a Pyrazol α‐Chloroacetanilide Derivative with Alkyl‐Amidonitrogen Fission
Authors: Rouchaud Jean , Metsue Marc , Gustin Fabrice , Moulart Claude , Herin Marc
Published: September 2010

The base‐catalyzed hydrolysis of 2‐chloro‐N‐(2,6‐dimethylphenyl)‐N‐(1H‐pyrazol‐1‐ylmethyl)‐acetamide (1) generated 2‐hydroxy‐N‐(2,6‐dimethylphenyl)‐N‐(1H‐pyrazol‐1‐ylmethyl)‐acetamide (2). The acid‐catalyzed hydrolysis of compound 1 generated after a short time 2‐chloro‐N‐(2,6‐dimethyl)‐acetamide (3) and pyrazol (5); after a longer period of time, 4,4′‐methylenebis‐(2,6‐dimethylbenzenamine) (4) and pyrazol (5) were formed; compound 4 was formed by condensation of the non isolated intermediates 2,6‐dimethylaniline and formaldehyde. Thus the base‐catalyzed hydrolysis of compound 1 did not cleave the amide; the acid‐catalyzed one first cleaved the N‐amido‐alkyl bond; then, the N‐amido‐acyl bond, the hydrolysis products condensing simultaneously together to give the unexpected compound 4.
Exchange Reactions of Substituted Benzaldehyde Hydrazones
Authors: Hearn Michael J. , Sy Karen Grace
Published: September 2010

Hydrazones IV, derived from substituted benzaldehydes and N‐aminophthalimide, experience an exchange reaction with one equivalent of 2,4‐dinitrophenylhydrazine under conditions free of added mineral acid to cleanly and irreversibly produce the related 2,4‐dinitrophenylhydrazones V in good yields. Although literature melting points for compounds V may vary from one reference to another, the infrared spectra (v (mull), cm−1; IV: 1770, 1710; V: 3280, 1615, 1580, 1510) of starting materials and products in the exchange process are strikingly different and permit ready characterization.
Cyclization of A Linear Precursor of Virginiamycin S1 (VS1) Mediated by Woodward's Reagent K
Authors: Sharma N. K. , Anteunis M. J. O.
Published: September 2010

Cyclization of a model linear hexapeptide (VS1 linear peptide, 1) was achieved by using N‐ethyl‐5‐phenylisoxazolium‐3′‐Sulfonate (Woodward's Reagent K). Yields of the resulting cyclic product 2 were quite low (∼ 15%) in various solvents. The yield in CH2Cl2 increased substantially when the reaction was carried out under free air instead of N2 atmosphere.
Synthèse De Dérivés Oxo De La Benzoselenazine‐1,3
Authors: Mbuyi M. , Christiaens L. , Renson M.
Published: September 2010

Synthesis of 1,3‐benzoselenazine derivatives is attempted via cyclization of o‐methylselenobenzoylformamidines, via ring‐expansion of 1,2‐benzisoselenazolin‐3‐ones and via N‐ethoxy‐carbonyl o‐bromoselenobenzaldimine. This research succeeded in the synthesis of 2,3‐dihydro‐4H‐1,3‐benzoselenazine‐2,4‐dione and 2,3‐dihydro‐4H‐1,3‐benzoselenazine‐4‐one.
Étude De La Réactivité Du Bis‐[Phényl‐4 Oxo‐2 Benzodiazépine‐1,5 YL‐1]‐1,1' Méthane
Authors: Achour Reddouane , Essassi El Mokhtar , Salem Moussa , Zniber Rachid
Published: September 2010

Study of the reactivity of Bis‐1,1'‐[4‐phenyl 2‐oxo 1,5‐benzodiazepine 1‐yl]methane allowed us to throw into relief different reactive site of this type of molecule.
TG/XRD/Sem Study of the Conversion of Gibbsite to (Pseudo) Boehmite
Authors: Decleer Jos G.M.
Published: September 2010

The conversion of gibbsite to (pseudo) boehmite has been studied by thermogravimetry, X‐ray diffractometry and scanning electron microscopy, supplemented by density and surface area measurements. As a reference for desired product properties, commercial pseudoboehmite, laboratory synthesized pseudoboehmite and autoclaved boehmite have also been studied. Three kinds of heating processes have been applied: in an oven, in a steam flow and under vacuum. All experiments were carried out at 220°C. Prolonged heating under vacuum resulted in a complete conversion of gibbsite to (pseudo) boehmite. The product still differs too much from commercial pseudoboehmite to be a valuable alternative. Also taking into account the manufacturing implications of vacuum heating, this process seems hardly feasible on a large scale.
Synthesis and Study of Rh(III), Pd(II), Pt(II), Ag(I) and Au(III) Complexes of 1‐Methyl‐3, 4‐Diphenylpyrazole
Authors: Kovala‐Demertzi Dimitra , Perlepes Spiros P. , Lazaras George
Published: September 2010

The new complexes [RhLCl3]x, mer‐[RhL3Cl3], (LH)2[MCl4] (M=Pd,Pt), cis‐[ML2Cl2] (M=Pd,Pt) trans‐[PdL2Cl2], [AgL2](NO3), (LH)[AuCl4] and [AuLCl3], where L=1‐methyl‐3, 4‐diphenylpyrazole, have been isolated. Several synthetic routes were investigated. The complexes were characterized by elemental analyses, conductivity measurements, X‐ray powder patterns, thermal methods, magnetic susceptibilities and spectral (IR and far‐IR, Raman, ligand field, 1 H‐NMR) studies. Pseudooctahedral stereochemistries for the Rh(III) complexes and square planar structures for the Pd(II), Pt(II) and Au(III) compounds are assigned in the solid state. The Ag(I) complex exhibits a linear twofold coordination with [AgL2]+ cations and uncoordinated nitrates. The unsubstituted N(2) atom (the “pyridine” nitrogen) of L is the donor atom to the metal ions or the protonation site.
Influence of Several Factors on the Determination of Manganese Using Electrothermal Atomic Absorption Spectrometry
Authors: Stobbaerts R. F. J. , Deelstra H. A.
Published: September 2010

The influence of instrumental parameters on the determination of Mn using EAAS is investigated and the interference of several acids, cations and anions determined. When NaCl or KCl is present an interference suppressor, such as L‐ascorbic acid, has to be added. The contamination resulting from dust particles in the laboratory or from a mixer is found to be negligible. Using NBS samples several destruction techniques are investigated and comparison is made with results obtained by FAAS.
Polyimides: Synthèse, Caractérisation Et Applications
Authors: Grenier‐Loustalot Marie‐Florence
Published: September 2010

13C high resolution liquid and solid (CP MAS) states NMR spectroscopy has been coupled with DSC, Xray diffraction, infrared Fourier transform spectroscopy techniques to study the mechanisms, kinetics, solid state structures and conformation of several polyimides.

Chemical data were obtained on model compounds and applied for polymers synthetised by polycondensation or chain extension and crosslinking.

We have shown that solid state 13C NMR and IRFT were able to detect chemical structure differences caused by different cure schedules.
Poly(p‐Thiophénylene) Et Ses Copolymères Synthèses Et Mécanismes Réactionnels
Authors: Fradet Alain
Published: September 2010

Poly(p‐thiophenylene (PPS) can be synthesized following some very different reaction paths: electrophilic substitution, nucleophilic substitution or electrooxidation. The most popular route involves high temperature nucleophilic substitution of 1,4‐dihalo benzene by sodium sulfide in dipolar aprotic solvents like NMP. The mechanism of this reaction has not yet been clearly established. Several mechanisms have been put forward: SNAr and single electron transfer chain processes with the formation of either radical cations or radical anions as reactive intermediates. They are reviewed and discussed. To obtain more information on the mechanism, the reactivity of halogen in ZϕX with X=halogen has been investigated. Depending on the nature of Z, large differences of reactivity were found and are discussed in relation to the proposed mechanisms.
Les Polysiloxanes: Développements Récents
Authors: Leempoel Patrick , Parbhoo Bhukan
Published: September 2010

Polysiloxanes are characterized by an inorganic backbone made from siloxy units, substituted by hydrocarbon groups. They can be classified in cyclic, branched and linear polymers. The latter constitute the most important class and are extensively used due to the numerous substitution options of the hydrocarbon chains by terminal or pendant organic groups, functional or not. The presence of such groups opens up all the doors of organic chemistry and these new molecules are used in many different area such as High Technology or for the synthesis of silicone‐organic copolymers.
Synthesis and Characterization of New Macrocyclic Imine‐Carbinolamine Complexes of Nickel(II)
Authors: Amer S. A. , El‐Hefnawy G. B. , Seleim G. W. , Desseyn H. O.
Published: September 2010

Reaction of 2,3‐diformylfurane and ethylenediamine in ethanol in the presence of nickel(II) acetate gives an imine‐carbinolamine macrocyclic complex whilst its reaction with propylenediamine gives a diimine macrocyclic complex. The imine‐carbinolamine macrocyclic complex can also be prepared by reaction of 2,3‐diformylthiophene and ethylenediamine in ethanol in the presence of nickel(II) acetate. Attempts to prepare macrocyclic compounds of 2,3‐diformylthiophene and propylenediamine were unsuccessful. On the basis of various physical properties, the complexes can be described as four coordinate, square planar structures for imine‐carbinolamine macrocyclic complexes and six co‐ordinate, pseudo‐octahedral structure for the diimine. Simple reactions led to the isolation of isothiocyanate and perchlorate derivatives including neutral complexes having axially coordinated isothiocyanate and perchlorate.
Utilisation Du Permanganate Impregne Sur Alumine Pour L'Oxydation Des Alcools En Composes Carbonyles
Authors: Thuy Vu Moc , Maitte Pierre
Published: September 2010

Permanganate adsorbed on alumina is a suitable reagent for oxidation of alcohols to carbonyl compounds.
Synthesis, Physical Properties and Spectroscopy of Pd(II) Complexes With CH3OOCCSNH2
Authors: Jacobs Patrick , Dimitrou Katerina , Perlepes Spiros P. , Plakatouras John , Desseyn Herman O.
Published: September 2010

The new complexes trans‐[Pd(HL)2Cl2] 0.5 H2O, trans‐[Pd(HL)2X2] (X=Br, I, SCN). [Pd(HL)(ONO2)2]. cis‐[Pd(HL2)X2] (X=NCS, ONO2) and [Pd(HL)4]X2 (X=Cl, ClO4), where HL=H2NCSC′OOCH3, have been prepared. The complex trans‐[Pt(HL)2Cl2] was also isolated for comparison reasons. The complexes were characterized by elemental analyses, conductivity measurements, X‐ray powder patterns, TG/DTG studies and spectral (1H‐NMR electronic, IR and far‐IR, Raman) studies. The vibrational analysis of the complexes is also given using deuterium isotopic substitutions. Monomeric square planar structures are assigned for the 1:2 and 1:4 complexes in the solid state: the 1:1 nitrato complex is a polymer containing both monodentate and bidentate bridging nitrato groups. The thioamide sulfur atom of HL is the donor atom to Pd(II) and Pt(II). The thiocyanate ions are coordinated through sulfur in the trans complex and through nitrogen in the cis product. This differentiation in the mode of thiocyanate bonding is discussed.
Syntheses of Chiral C=N Dienophiles: Sulfonyloxyimino‐Malononitrile and Alkyl Sulfonyloxyiminocyanoacetates
Authors: Blanco José M. , Caamaño Olga , Eirin Ana , Fernandez Franco , Medina Lucía
Published: September 2010

High yield syntheses of one chiral sulfonyloxyiminomalononitrile and four alkyl sulfonyloxyiminocyanoacetate derivatives (3a‐e), to be used in asymmetric hetero‐Diels‐Alder additions, are described.
Synthesis of 2′‐Chloro‐2′,3′‐Dideoxy‐2′,3′‐Didehydro Nucleosides
Authors: van Aerschot A. , Herdewijn P.
Published: September 2010

Treatment of O2,2′‐anhydrouridine with triphenylmethyl chloride in pyridine at 80°C gives mainly the 2′‐chlorinated nucleoside 3. Reaction of 2′‐chloro‐3′‐0‐trifluoromethane‐sulfonyl‐5′‐0‐trityl‐2′‐deoxyuridine (4) with NaOH led exclusively to the elimination product 5, opening the way to 2‐chloro substituted glycero‐pent‐2‐enofuranosyl nucleosides.
2,3′‐Difluoro‐and 3′‐Azido‐2′‐Fluoro Substituted Dideoxypyrimidines as Potential Anti‐HIV Agents
Authors: van Aerschot A. , Herdewijn P.
Published: September 2010

2′‐Deoxy‐2′‐fluorouridine (2) was obtained by reaction of the arabinofuranosyl nucleoside 1 with diethylaminosulfur trifluoride followed by detritylation. After inversion of the configuration at the 3′‐position, 4 was used as starting material for the preparation of the 2′,3′‐disubstituted derivatives 6, 7, 8 and 10.
Réactivité des β‐enaminoesters cycliques derives de la quinoxaline
Authors: Essassi El Mokhtar , Ferfra Souad , Salem Moussa , Zniber Rachid
Published: September 2010

Action of alkylant agent in phase transfer catalysis conditions on 3‐ (ethoxy carbonyl methylene)2‐oxo quinoxalines have been studied. Reaction of bromination following by nucleophile substitution reaction in presence of potassium cyanure, sodium azoture and sodium nitrite have been examinated.
Spectrométrie de masse de triazolides et de leurs produits de transformation par pyrolyse‐éclair sous vide
Authors: Maquestiau André , Abdelouahab Fouad Bachir Ben , Flammang Robert
Published: September 2010

Besides the formation of acylium ions, the molecular ions of 1‐acyl‐1,2,4‐triazoles substituted (R) at position 3 lose competitively ketene and carbon monoxide after electron impact ionization, but the ketene loss dominates largely if R is a strong electron‐donating substituent. This supports the occurrence of an ion‐molecule complex which incorporates a substituted triazole and ionized ketene before the decarbonylation (methylene transfer) or the ketene elimination (hydrogen transfer).

Flash‐vacuum pyrolysis (FVP) of these triazolides yields oxazoles with specific substitution at positions 2 (R) and 5 which implies an irreversible sigmatropic [1,5(1,2)] transformation. Oxazole formation dominates largely a competitive ketene loss if the triazolides bear a strong electron‐donating substituent like N(CH3)2; this kind of substitution does not however allow the migration of groups like CO2CH3 and CONH2 which have a lower migratory aptitude.

The fragmentation of the ionized oxazoles is highly dependent upon the nature of the substituent at position 5 (methyl or phenyl) and is directed by ring cleavages, mainly of the 1,2‐bond. Moreover, compounds bearing a N(CH3)2 group undergo a complex rearrangement which eliminates (C, H3, N) from the molecular ions (for the oxazoles) or from the fragment ions [M‐C2H2O]−+ (for the azolides).
Heteropoly Acid‐Catalyzed Reactions of Terpenes I. Direct Hydration of Camphene
Authors: Schwegler M. A. , van Bekkum H.
Published: September 2010

The heteropoly acids 12‐tungstophosphoric and 12‐tungstosilicic acid are excellent catalysts in the homogeneous hydration of camphene to isoborneol. The effects of a number of reaction variables are reported.
Nouveaux décontaminants. Destruction chimique totale, rapide et douce d'insecticides et de toxiques de guerre par les peracides
Authors: Lion C. , Charvy C. , Hedayatullah Mir , Bauer P. , Sentenac‐Roumanou H. , Despagne B. , Delmas G.
Published: September 2010

Peroxyacids RCOOOH (R = n C7H15 to n C13H27) are very good decontamination reagents. Paraoxon (O,O‐diethyl O‐p nitrophenyl phosphate, VX [O‐ethyl S (2‐diisopropylaminoethyl)methylphos‐phorothiolate] and HD (2,2′‐dichlorodiethylsulfide) react for example, with perdodecanoïc acid, completely in a few seconds. The reaction rate is enhanced by micellar catalysis.
Improving the One‐Electron States of ab initio GTO Calculations in Momentum Space. Tests on two‐Electron Systems: H−, He and Li−+
Authors: Delhalle Joseph , Fripiat Joseph G. , Defranceschi Mireille
Published: September 2010

A study of a one‐step iteration method expressed in momentum space to improve properties calculated at the Hartree‐Fock level is presented. The results obtained for two‐electron atoms H−, He and Li−+ show substantial and consistent improvement in their 1s ground‐state orbital initially expressed as a linear combination of four gaussian functions.
Synthèse dans la chimie des phenanthridines. III. Préparation de quelques modèles d'acides ω‐(diamino ‐3,8 phenanthridinyl‐6) carboxyliques
Authors: Lion C. , Boukou‐Poba J. P. , Charvy C.
Published: September 2010

New series of ω‐(3,8‐diamino‐6‐phenanthridinyl) alkanoic acids are obtained from the acid chloride‐esters ROCO(CH2)nCOCl (n = 0,3 to 8; R = Me or Et). Reaction of these with 2‐amino‐3,8‐ dicarbethoxyaminobiphenyl leads to the expected 2‐acylamino‐3,8‐ dicarbethoxy‐aminobiphenyls which by cyclization lead to the corresponding methyl or ethyl (3,8‐dicarbe‐thoxyamino‐6‐phenanthridinyl)alkanoates. Quaternarization followed by hydrolysis has been performed to obtain some ω‐(3,8‐diamino‐6‐phenanthridinium) alkanoic acid salts.
The N‐Alkane Solvent Effect on the Dipole Moment of the Trans‐1,2‐Dibromocyclohexane
Authors: Dionísio Madalena , Almeida Luís N. , Moura‐Ramos Joaquim
Published: September 2010

Dipole moment techniques have been applied to the study of the n‐alkane environmental influence on the conformational equilibrium of trans‐1,2‐dibromocyclohexane. Both the Debye and the Onsager theories have been used in order to calculate the dipole moment from the dielectric constants of the liquid solutions, and the results have been obtained in five different n‐alkane solvents. The eventual influence of the solvent molecular order in the position of the equilibrium is discussed.
Infrared Study of Surface Properties of Alumina Supported Chromia: Nitric Oxide Adsorption
Authors: Batis H. , Younes M. K. , Ghorbel A.
Published: September 2010

Infrared study of NO adsorption on chromia/alumina catalysts gives interesting information concerning both the surface heterogeneity and the reactivity of alumina‐supported Cr ions.

On a preoxidized surface NO interacts with oxygen ligands to form nitrite and nitrate species. However in the presence of chemisorbed NH3 on oxidized catalyst the mobility of oxygen is strongly increased and can be displaced by NO molecules to form surface complexes with bands at 1715 and 1855 cm−1

On a prereduced surface, coordinatively insaturated Cr ions are created. A small fraction of these ions with one coordination vacancy adsorb weakly one NO molecule giving rise to a band at 1810 cm−1. These ions are poisoned by most strongly adsorbed NH3 as would be expected for Cr−4+ ions. Most of the Cr ions coordinate a couple of NO molecules to form stable Cr(NO)2 complexes with bands at 1725 and 1865 cm−1.
Reactions of Thiocarbonyl Ylides With Sulfur Dioxide; A Route to a Novel Heterocyclic System
Authors: Mlostoń Grzegorz
Published: September 2010

Thiocarbonyl ylides generated from Δ−3‐1,3,4‐thiadiazolines la‐c by thermal extrusion of nitrogen undergo 1,3‐dipolar cycloadditions with sulfur dioxide, giving 1,2,4‐oxadithiolane 2‐oxides 3a‐c in good yields.
Mössbauer Study of Some Polymeric Iron(II) Complexes of Halo‐Salicylhydroxamic Acids
Authors: Kane S. N. , Ali S. M. , Gupta Ajay , Khadikar P. V.
Published: September 2010

Polymeric complexes of iron (II) salicylhydroxamic acids: Fe‐SHA, Fe‐5CSHA, Fe‐3,5DCSHA along with Fe‐BHA, where SHA = salicylhydroxamic acid, 5CSHA = ‐5‐chloro salicylhydroxamic acid, 3,5DCSHA = 3,5 di‐chloro salicylhydroxamic acid and BHA = Benzohydroxamic acid, have been prepared, characterized by elemental and spectral analysis and identified by the electronic spectra as ML2.2H2O, where L stands for the salicylhydroxamic acid moiety and M stands for Fe(II). Various Mössbauer parameters obtained at room temperature, change with respect to the kinds of chelating agent which may be attributed to the effect of substitution in the salicylhydroxamic acid moiety. Quadrupole splitting and isomer shift values have been explained in terms of restricted rotation between C6H5‐°C‐ bond due to the π‐electron system in the benzene nucleus.
Transport of Amino Acids Methyl Esters by a Bicyclic Crown Ether
Authors: Janus Stephan , Kraïmi Khalil , Sonveaux Etienne
Published: September 2010

Racemic protonated amino acid methyl esters were efficiently transported through a dichloromethane phase using L,L‐Cbz‐bis(15‐crown‐5)DOPA‐OMe as a carrier. The enantioselectivity was however marginal. The (15‐crown‐5) rings of the carrier were essential for affinity, as Cbz‐bis(12‐crown‐4)DOPA‐OMe was not a good host.
Oxidation of Benzylamines by Alkyl Sulphoxides
Authors: Azran Jacques , Buchman Ouri , Pri‐Bar Ilan
Published: September 2010

Primary, secondary and tertiary benzylamines were oxidized to aromatic aldehydes and ketones when their HX (X = Br, I) salts were heated, under anhydrous conditions, in excess of alkyl sulphoxide. Quaternary benzylammonium salts also react, to give lower yields of carbonyl compounds. Benzylamine is being oxidized in the presence of anhydrous HX formed in situ by the reaction of alkyl halide and hydrosiloxane, but not in the presence of aqueous HX.
Diverse CO2− Radicals in γ‐ and α‐Irradiated Synthetic Calcite
Authors: Debuyst RenÉ , Bidiamambu Mawete , Dejehet Fernand
Published: September 2010

Modifications in the synthesis procedure of calcite involve statistically significant changes in the relative intensities of the EPR lines of the irradiated samples.

Of the 6 (or 8) paramagnetic centres produced by γ‐ (or α‐) irradiations, four are attributed to the CO2− radical:

The first one is an unstable anisotropic species with g1 ≃ 2.0028, g2 ≃ 2.0022, g3 ≃ 1.9971 and a hyperfine coupling of ∼2.6 gauss with 2 equivalent I = 1/2 nuclei.

The second one is a more stable species with a larger linewidth and g1 ≃ 2.0028, g2 ≃ 2.0011 and g3 ≃ 1.9972.

The third one is an isotropic species with g = 2.0007.

The last one is an axial species with g∥ = 2.0032 and g⟂ = 1.9995 solely produced by an α‐particle bombardment

.
Catalysed Quantitative Synthesis of 2,3,3‐Trichlorotetrahydrofuran
Authors: Buyck Laurent De , De Lepeleire Carine
Published: September 2010

Tetrahydrofuran was chlorinated in the presence of N,N‐dimethyloctylamine (1 mmol per mol optimal) with an excess of sulfuryl chloride at 55‐80°C. After a first stage producing trans 2,3‐trichloro THF (1) the reaction proceeded to complete conversion to 2,3,3‐trichloro THF (2) in less than 22 h.

The mechanism is discussed in terms of an inhibitory effect of hydrogen chloride and a catalytic role for anions unintentionally derived from the sulfuryl chloride.

Equilibration of 2 with the isomer 2,2,4‐trichlorobutanal (3) was observed at 130‐170°C with hydrogen chloride catalysis, at 70°C with titanium tetrachloride or zinc chloride.
Aromaticity: A new Multilinear Approach
Authors: Párkányi Cyril , Boniface Christian
Published: September 2010

Six equations obtained by multiple regression analysis were developed to characterize aromaticity of alternant and nonalternant hydrocarbons. Three equations are applicable to alternant systems, three to nonalternant systems. The quantities used in the equations are the various experimental and theoretical (HMO and SCF‐MO) data reflecting aromatic behavior of delocalized π–electron systems. The aromaticity index, AI, is given as a numerical value and the equations can be used to predict aromaticity of various compounds on a quantitative basis.
Studies on the Thermal Rearrangement of 2‐Methoxypyridine N‐Oxides to 1‐Methoxypyridin‐2‐Ones
Authors: Ballesteros Paloma , Senent Salvador , Elguero José
Published: September 2010

A study of the influence of the solvent polarity on the rearrangement of 2‐methoxypyridine N‐oxides to 1‐methoxypyridin–2‐ones suggests an ionic mechanism.
Design, Synthesis, and Properties of Macrocyclic Receptors for Tetrahedral Substrates
Authors: Collet André , Dutasta Jean‐Pierre , Lozach Bénédicte
Published: September 2010

In order to complex lipophilic molecules of tetrahedral shape, hosts made of two cyclotriveratrylene caps have been designed and named ”cryptophanes“. Cryptophanes can be synthesised in two different ways from vanillyl alcohol. In a first method, a C3‐cyclotriveratrylene of suitable structure is prepared and used as a template for intramolecular assemblage of the second cap. In a second method, much shorter, the two cyclotriveratrylene caps of the cryptophane are simultaneously built from appropriate vanillyl alcohol dimers. The complexation of halogenomethanes, aliphatic hydrocarbons, and polymethylammonium ions by certain D3‐cryptophanes has been studied. Neutral molecules such as chloroform and isobutane are comparatively strongly bound in organic solvents (1,1,2,2‐tetrachloroethane‐d2) and very strongly bound in water, whereas the tetramethylammonium cation shows an inverse behaviour. Choline and acetylcholine are bound in water at pH 5‐8. Some possible applications of these results are discussed.
Non Steady‐State Transient Kinetic Approach with Deuterium Labelling. I. Improved Method to Relate Catalytic Activity to Surface Coverage
Authors: Lienard G. , Degols L.
Published: September 2010

A method is described to acquire, in addition to catalytic reaction rates, the reactant adsorption rate, the surface coverage and its rate of formation. It is based on a non steady‐state transient technique, initiated by a pressure step of one reactant corresponding to adsorption (build up of the catalytic active surface) or to desorption (titration of adsorbed species). Deuterium is used instead of light hydrogen to differentiate by labelling, in the adsorption step, the reactant molecules (deuterated isomers) being desorbed without further reaction. The relaxation of the catalytic system is followed and time constants are defined (exponential variations with time), characterizing the different rates.

A novel UHV apparatus, working in the pressure range 10−5 to 1 Torr, is described. Data are acquired by a computer that controls the electromagnet of a magnetic deflection mass spectrometer. A complete spectrum is scanned in less than 12s by a peak jumping method. The technique is applied to a typical experiment of hydrogenolysis of ethane, on a Rhodium evaporated film. Ethane rate of adsorption remains constant during the build up transient effect while the rate of hydrogenolysis and of perdeuterated isomer increase with time and are characterized by the same time constant as the rate of formation of the carbonaceous layer (Rcs). This indicates that the observed activity variations are not directly related to the adsorption rate. A quantitative relationship between Rcs, the rate of hydrogenolysis and the rate of formation of perdeutered isomer is established. The role of deuterium for the determination of the adsorption rate is analysed.
Non Steady‐State Transient Kinetic Approach with Deuterium Labelling. II. Ensemble Effect and Mechanism Proposal in Ethane Hydrogenolysis Over Model Rh Catalyst
Authors: Lienard G. , Degols L.
Published: September 2010

Reaction of ethane over rhodium model catalyst is studied using a method combining non steady‐state transient effect and labelling with a large excess of deuterium. Relaxation of the catalytic system after an ethane pressure jump as well as rates at steady‐state activity are measured, at 50°C, in a deuterium pressure range from 10−3 to 10−1 Torr. The method differentiates the part of ethane adsorption rate (Rac) that produce carbonaceous species, intermediates for hydrogenolysis.

The important variations of the rates of ethane adsorption Rac and of hydrogenolysis with hydrogen pressure and temperature are analyzed in the frame of the ensemble model developped preciously. Both rates are regulated by the demanding character of finding an ensemble of free sites but a larger ensemble is required for hydrogenolysis than for ethane adsorption. In using the formalism of the ensemble model, activation energies are calculated as low as 17 kJ/mole for adsorption and 8kJ/mole for hydrogenolysis. The temperature factors experimentaly measured are strongly depending on the hydrogen coverage θH.

It is concluded that all the steps in the reaction scheme, except the desorption one, are reversible but in a more or less degree, depending on the hydrogen coverage. Thus the ethane adsorption step may vary, according to the experimental conditions (p,T) from complete irreversibility (hydrogenolysis formation), at low θH, to nearly complete reversibility, for high θH coverage values. In this case ethane adsorption still proceeds without hydrogenolysis.
Growth of Large Crystals of Aluminophosphate Molecular Sieve AlPO4‐5
Authors: Kornatowski Jan , Finger Gerd
Published: September 2010

Large crystals of the molecular sieve AIPO4‐5 up to 920 μm in length have been grown during hydrothermal synthesis by using triethylamine as a templating agent. The yield of the AlPO4‐5 phase is within a range of 50 ‐ 60%.
Gradients in the Composition of Enamel and Dentin Mineral in Rat Incisors
Authors: Driessens F. C. M. , Goldberg M. , Heijligers H. J. M. , Carreau J. P. , Verbeeck R. M. H.
Published: September 2010

In order to investigate possible differences in the mineral composition of rat incisors, Wistar rats received either a zinc‐deficient or a normal diet (the latter were pair fed or ad libitum). Three incisors from each group were subjected to microanalysis by the electron microprobe. No differences were found in mineral composition between the three groups. The average molar Ca/P ratio in the enamel and the dentin were (1.62 ± 0.05) and (1.50 ± 0.05), respectively. The distribution of sodium and magnesium over the dentin was homogeneous and inhomogeneous, respectively. Dentin did not contain detectable amounts of chlorine. The gradients for sodium, magnesium and chlorine as a function of depth in enamel were similar to those reported for these elements in human and rhesus monkey enamel: sodium and magnesium had a low concentration at the enamel surface, whereas chlorine had a high concentration there.
Sorption of organic compounds from water with new polymer sorbents
Authors: Martel Bernard , Delporte Michèle , Lekchiri Yahya , Morcellet Joëlle , Morcellet Michel
Published: September 2010

New organic polymer sorbents based on macroporous polymers containing amino groups and β‐cyclodextrin residues have been synthesized by suspension polymerization. The sorption capacity of these sorbents with respect to organic pollutants such as phenol has been determined and discussed in terms of polarity and specific interactions.
Polymerization of methyl and phenyl oxazoline initiated with alkyl chloroformates
Authors: Dworak Andrzej , Schulz Rolf C.
Published: September 2010

It has been shown that alkyl chloroformates are capable of initiating the polymerization of oxazolines. Esters itself initiate rather slowly and the polymerization proceeds via covalent growing species. Exchange of counter ions with triflate or iodide anions leads to faster initiation and higher reaction rates. The polymerization is of living character.
Facilitated passive copper(II) ion transport through binary liquid membrane
Authors: Szpakowska Mariola , Nagy Ottó B.
Published: September 2010

Facilitated passive transport of Cu(II) through binary liquid membranes of variable composition has been studied in steady state conditions. It is shown that transport kinetics obeys the competitive preferential solvation(COPS) theory in the whole concentration range. The geometric‐electronic structure of the metal ion‐carrier complex seems to play a decisive role in the preferential solvation.
Synthesis of trideoxyhexopyranosylated and hexenopyranosylated nucleoside analogues as potential anti‐HIV agents
Authors: Herdewijn P. , van Aerschot A.
Published: September 2010

The 2‐deoxy‐D‐arabino‐hexopyranosyl nucleoside analogues of thymidine, deoxyuridine and deoxycytidine have been prepared by sugar‐base condensation and a 3,4‐unsaturated bond was introduced via the bisdithiocarbonates. Hydrogenolysis in the presence of Pd on carbon afforded the 2,3,4‐trideoxy‐D‐glycero‐hexopyranosyl analogues.
Photolytic α‐scission in Acyl Phosphonic Acid Esters
Authors: Majima T. , Schnabel W.
Published: September 2010

A re‐investigation of the photolysis of acyl phosphonic acid dimethyl‐ and diethyl esters revealed that commonly α‐scission occurs although the quantum yield ϕ(α) depends on the chemical nature of the acyl group:

magnified image

ϕ(α) = 0.2‐0.3 in the cases of pivaloyl and substituted benzoyl phosphonates and ϕ(α)=0.03 in the case of benzoyl phosphonic acid diethyl ester (BPDE). The major route of deactivation of electronically excited phosphonates involves intersystem crossing (ISC) to the triplet manifold. ISC was studied by triplet quenching using naphthalene. Quantum yields of triplet formation ϕ(T) = 0.5‐0.6 were found in all cases except BPDE (ϕ(T) = 0.9). The reaction mechanism of a typical phosphonate (2,6‐dichlorobenzoyl phosphonic acid dimethyl ester, DCPME) is discussed on the basis of recent results.
Cationic Photoinitiators: A Laser Flash Photolysis Study of the Interaction of Onium Salts with Ketocoumarins
Authors: Manivannan G. , Wu S. K. , Fouassier J. P.
Published: September 2010

Time‐resolved laser‐spectroscopy investigation has been performed for the first time on the excited state interaction of different ketocoumarins with onium salts in methanol. Ketocoumarins'triplet state quenching by monomers lead to evaluate the quantum yield values of charge transfer.
On the Tautomeric Structure of 5‐hydroxy‐ and 5‐mercapto‐1H‐1,2,3‐triazoles: −13C NMR analysis
Authors: L'abbé Gerrit , Delbeke Pieter , van Essche Gonda , Luyten Ingrid , Vercauteren Karin , Toppet Suzanne
Published: September 2010

The title compounds have been analyzed by 13C NMR spectroscopy and compound with the N‐3 methyl and O/S alkyl derivatives. The mesoionic structures 2a,b are rejected in favour of 1a,b on the basis of the C5=CH coupling constants and the chemical shifts. Incremental substituent effects for triazoles are discussed.
Photopolymerization of N,N‐Didodecyl‐N‐Methyl‐N‐(2‐(Methacryloyloxy)ethyl)Ammonium Chloride, a Reverse Micelle and Monolayer Forming Surfactant
Authors: De Schryver Frans , Voortmans Gilbert , Jackers Carine , Wittouck Nadine , Persoons André
Published: September 2010

In previous reports it was shown that the photopolymerization of N,N‐didodecyl‐methylethylmethacrylate ammonium chloride, a reverse micelle forming surfactant, leads to a transparent polymerized inverse micellar solution1,2. The polymerization leads to high molecular weight polymer as determined by GPC. However recent results indicate that GPC, due to the association of the polymer overestimates the molecular weight.

In addition a more extensive characterization of the polymeric aggregates is presented. The polymerization of the inverse micellar solution leads to a more stable and less dynamic inverse micellar system. However, the obtained aggregates are much larger then the monomeric inverse micelles. On the basis of the aggregation behaviour of the polymer and the characteristics of the polymer aggregates a model describing the structure of the polymer aggregates is proposed.

Finally the monolayer formation and properties of the monomer and polymer are compared.
Conductance Study of Tetraphenylboride Salts of Alkaline Earth Metals in Tetrahydrofuran
Authors: De Groof B. , De Smedt C. , Vankerckhoven H. , van Beylen M.
Published: September 2010

The conductance behavior of the tetraphenylboride salts of the alkaline earth metals (MB2) has been studied in the temperature range from + 20°C to ‐70°C in tetrahydrofuran (THF). A detailed knowledge of their dissociation into free MB−+ and B− ions is desirable in order to better understand their influence in anionic polymerizations of e.g. styrene with alkaline earth metals as counterions. The thermodynamic parameters as well as the λ+0‐values for the respective salts are taken to indicate a double solvent separated ion pair structure for the calcium and strontium salt represented as B−//M2+//B− and a mixed ion pair structure for BaB2 represented as B−, Ba2+//B−. For MgB2 an ion pair structure B−, Mg2+//B− is proposed at higher temperature changing to B−//Mg2+//B− at lower temperatures.
The Mechanism of Action of Hindered Amine Stabilizers. Production of Nitroxy Radicals and Inhibition of the Photo‐Oxidation in Different Polymers
Authors: Geuskens G. , Kanda M. N. , Nedelkos G.
Published: September 2010

Oxidation of bis[2,2,6,6‐tetramethyl‐4‐piperidinyl] sebacate (HALS) to itroxy radicals has been monitored by ESR spectroscopy in three polymers: an ethylene‐propylene random copolymer (EPM), a styrene‐butadiene‐styrene block copolymer (SBS) and the same block copolymer previously hydroperoxidized by reaction with singlet oxygen. Nitroxy radicals are produced in all three polymers on irradiation in the presence of oxygen and, in the last one also in the dark, at room temperature. The mechanism of the reaction is discussed: it involves direct interaction of a peroxy radical with the piperidine nitrogen. The role of clustered hydroperoxides as a source of peroxy radicals is emphasized.

Inhibition of the photo‐oxidation of all three polymers by HALS has been studied by oxygen absorption measurements and by infra‐red spectroscopy in the carbonyl region. The results indicate that HALS not only inhibits the propagation of the photo‐oxidation but also catalyses a new type of termination that, in some polymers, delays the production of ketones. It is suggested that the practical efficiency of HALS in keeping the mechanical properties of polyolefins exposed to sunlight is mainly due to that last effect.