bluuebunny/crossref_metadata_2025_split huggingface dataset:
The synthesis of 10‐fluorobenzo[a]pyrene
Authors: Newman Melvin S. , Khanna Vinod K. 
Published: September 2010

AbstractThe synthesis of 10‐fluorobenzo[a]pyrene in four steps from 11‐fluoro‐12‐methylbenz[a]anthracene is described.A current hypothesis concerning the metabolism which is responsible for the carcinogenic activity of benzo[a]pyrene, BP, maintains that BP is converted into isomers of 7,8‐dihydroxy‐9,10‐epoxy‐7,8,9, 10‐tetrahydrobenzo[a]pyrene which are the true carcinogens.1 If any of 7‐,8‐,9‐, and 10‐fluorobenzo[a]pyrenes proved carcinogenic an alternate mechanism for carcinogenesis would be required. If all four fluorinated compounds were non‐carcinogenic strong support of the current hypothesis would be provided.2 Accordingly we planned to synthesize the fluoro BP compounds so that adequate testing could be carried out.
Pyrazines III Condensation Des Dihydropyrazines Avec Les Composés Carbonyles: Synthèse De Pyrazines Substituées Et De Dihydro‐6, 7‐5E‐Cyclopenta [b] pyrazines
Authors: Flament Ivon , Sonnay Philippe , Ohloff Günther 
Published: September 2010

AbstractDihydropyrazines have been found to condense easily and in good yields with carbonyl compounds. 2,3‐Dihydropyrazines were treated with aliphatic, terpenic, aromatic and furan aldehydes and with aliphatic and alicyclic ketones leading to trisubstituted pyrazines. When α, β‐unsaturated carbonyl compounds are used the formation of 6,7‐dihydro‐5E‐cyclopenta [b] pyrazines is observed. When autocondensation of α‐aminoacetone is conducted in the presence of aldehydes these compounds react immediately with the intermediate 3,6‐dihydropyrazine to give trisubstituted pyrazines.
A new hypothesis explaining synergy between two phases in heterogeneous catalysis the case of hydrodesulfurization catalysts
Authors: Delmon Bernard 
Published: September 2010

AbstractWe propose a new mechanistic model, explaining the properties of catalysts composed of sulfides of Group VI and sulfides of Group VIII metals. Spill‐over hydrogen, emitted by the latter, modulates, or controls, the catalytic centers at the surface of the former sulfide. Slightly reduced centers formed by spill‐over hydrogen would be active in hydrogenation, and deeply reduced centers, in hydrodesulfurization. The theory resting on this concept of a remote control agrees qualitatively with all the known catalytic and physico‐chemical properties of the catalysts.
The reaction of β‐ and γ‐lactones with chlorotrimethylsilane + metal halides
Authors: Scheibye S. , Thomsen I. , Lawesson S.‐O. 
Published: September 2010

AbstractGreat efforts have been made to develop non‐saponificative hydrolysis of carboxylates and other esters. Useful methods are so‐called SN2‐type dealkylation of esters1 and the use of halotrimethylsilanes. Thus iodotrimethylsilane2‐4 (ITMS) was originally used and later chlorotrimethylsilane (CTMS) + sodium iodide5 was found to convert alkyl esters into the corresponding trimethylsilyl esters. Also alkyl phosphonates have been cleaved in the same way.6‐10 Bromotrimethylsilane (BTMS) does not react with esters.2 However, in a recent note11 it is stated that BTMS cleaves lactones, which prompt us to publish some of our results at this stage of the investigation.It has been found that CTMS is unreactive towards esters and lactones under different conditions studied. However, when β‐propiolactone was refluxed with CTMS in acetonitrile with anhydrous sodium chloride, sodium bromide, or potassium iodide present the corresponding trimethylsilyl‐3‐halopropanoates, IIa‐c, were isolated in reasonable yields. Both NaI, H2O, and anhydrous magnesium bromide do cleave β‐propiolactone at room temperature to give, after acidification, 3‐iodo‐ and 3‐bromopropanoic acids, respectively. Butyrolactone did only react with CTMS in the presence of potassium iodide to give trimethylsilyl‐4‐iodobutanoate. In the presence of sodium bromide and sodium chloride no reaction took place. In our hands certain lactones such as γ‐valerolactone, 2‐bromobutyrolactone, thiobutyrolactone, and angelica lactone were totally unreactive.All silyl esters were characterized by MS, NMR, IR, and elementary analyses. Hydrolysis also gave known acids.
Structure Cristalline de la L‐(1‐Tosylamino‐2‐Phényl)‐Éthyl Chlorométhyl Cétone (TPCK), Un Inhibiteur Spécifique de l'α‐Chymotripsine
Authors: Michel A. , Durant F. , King G. S. D. 
Published: September 2010

AbstractThe title compound is a specific inhibitor of a‐chymotrypsin, a proteolytic enzyme which hydrolyses aromatic peptide linkages. Its crystal structure has been investigated by X‐ray diffraction in order to ascertain the molecular conformation and to see how this molecule could fit with specific substrates of this enzyme such as ATEE or BTEE which is closely structurally related.The structure has been solved using direct methods and refined by full matrix least‐squares techniques to R = 0.057.
Conformational Study Of 3‐OXO‐ and 4‐OXO‐thiane‐L‐oxide and their dimethyl acetals. Exemplification of short‐range electrostatic stabilization contributions
Authors: Nachtergaele W. A. , Tavernier D. , Anteunis M. J. O. 
Published: September 2010

AbstractBoth 3‐oxo‐ (3) and 4‐oxo‐thiane‐l‐oxide (1) exist in the chair form with axial sulfoxide bonds. The axial preference is retained in the dimethyl acetal of (1) but not in the dimethyl acetal of (3). Beside steric strain, local electrostatic stabilization identified as a gauche 1,4‐ or a 1,5 (g±, g±)‐interaction between opposite residual charges rationalize the conformational preferences.
Approche Théorique du Problème de la Tautomérie des Triades HX‐YZXY‐ZN. II. Cas des Imines, Hydrazones et Oximes (Y = N, Z = CH2)
Authors: Lhamyani‐Chraibi M. , Gélizé‐Duvigneau M. , Arriau J. , Elguero J. 
Published: September 2010

AbstractThe tautomerism of three classes of related compounds (imines, hydrazones and oximes) has been examined by means of the CNDO/2 and PCILO methods with complete geometry optimization. The calculated geometries agree with the experimental ones but the N‐O distance in the oxime. The total energies favoured the azo and nitroso tautomers at variance with the experiment. The electrostatic potentials of the common anions to both tautomers allow a prediction of the protonation site. This dynamic approach of the prototropic tautomerism gives a better description of the reality than the static approach based on calculated energies.
Enzymatic in vitro reduction of ketones VI. (1) reduction rates and stereochemistry of the HLAD‐catalyzed reduction of 3‐alkyl‐ and 4‐alkylcyclohexanones
Authors: van Osselaer T. A. , Lemière G. L. , Lepoivre J. A. , Alderweireldt F. C. 
Published: September 2010

AbstractReaction rate constants for the catalytic step HLAD‐NADH + ketone → HLAD‐NAD+ + alcohol in the HLAD‐catalyzed reduction of 3‐alkyl‐ and 4‐alkylcyclohexanones are determined from initial rate measurements in the coenzyme recycling system ketone‐ethanol‐NAD+‐HLAD. By rate measurements at several temperatures, activation parameters were determined and isokinetic relationships tracked down. Two different isokinetic relationships show that the 3‐alkylcyclohexanones pass through an other type of transition state than cyclohexanone and the 4‐alkylcyclohexanones, which means that they have a different arrangement on the HLAD‐NADH complex. The results are rationalized in view of the most recent principles on nucleophilic additions to carbonyl functions. The resulting model for the HLAD‐catalyzed reduction adequately explains the observed rate accelerating and decelerating effects and the stereochemistry of the reduction as well.
Light‐Intensity Dependence In The Kinetics Of N‐Gap Photoelectrode Stabilization
Authors: van Overmeire F. , Vanden Kerchove F. , Gomes W. P. , Cardon F. 
Published: September 2010

AbstractThe influence of the light intensity (L) and the concentration (y) of the Fe(CN)64 ion on the stabilization of n‐GaP photoelectrodes was studied in alkaline medium by means of the rotating ring‐disk technique. The steady‐state stabilization ratio increased with increasing y or decreasing L. A kinetic model, involving surface intermediates, is proposed in order to explain the experimental results.
Étude Par Spectrométrie De Diffusion Ionique De La Structure De La Bi‐Couche D'Oxyde De Molybdene Et De Cobalt A La Surface Du Support Des Catalyseurs D'Hydrodésulfuration
Authors: Delannay F. , Haeussler E. N. , Delmon B. 
Published: September 2010

AbstractIon scattering spectrometry (ISS), a method which allows to measure the atomic composition of the uppermost surface monolayer, has been used to study the atomic arrangement of cobalt and molybdenum deposited on the surface of CoMo/y‐AL2O3, hydrodesulfurization catalysts in their oxidic precursory form. The results prove that the oxidic molybdenum layer is on top of the oxidic cobalt layer. The depth profiling measurements are in excellent agreement with calculations from a straightforward model of the process.
Dielectric studies of hydrogen bonded complexes in n‐butanol‐carbonyls systems
Authors: Shanmugasundaram V. , Mohan R. 
Published: September 2010

AbstractDielectric polarization studies of a few alcohol‐carbonyls systems have been carried out. The formation constants and the dipole moments of the complexes are reported and the observed enhancement of the dipole moment of the complexes is discussed.
Lanthanide perchlorate complexes of o,o' diisopropyl, n(‐4‐antipyryl) phosphoramidate
Authors: Premlatha C. , Soundararajan S. 
Published: September 2010

AbstractFive new complexes of lanthanide perchlorates with a new ligand O,O' diisopropyl N(‐4‐antipyryl) phosphoramidate (DIAP) of the general formula Ln(DIAP)4(ClO4)3 where Ln = La, Pr, Nd, Sm and Gd, have been synthesised and characterized by chemical analysis, IR(200–4000cm−1) and electronic spectra and electrical conductance data.Infrared spectral data indicate the coordination of the ligand to the metal ions in a bidentate fashion, through the C=O oxygen of the antipyrine group and the P=O group. IR and conductance values show that the three perchlorate groups are ionic. Electronic spectrum of the Nd3+ complex in the visible region, indicates reasonable covalency in the metal‐ligand bond. The available data point to an eight coordinate geometry around the metal ions, with each ligand behaving in a bidentate ‘00’ fashion.
The crystal structure of tetragonal nickel(ii)‐hydrogen‐(1)‐malate tetra hydrate
Authors: van Havere W. , Lenstra A. T. H. 
Published: September 2010

AbstractThe title compound Ni2+ (C4H5O5)2−. 4H2O crystallizes in the tetragonal space group P41212 with Z = 4.At ∼ 300°K, the œll constants are: a = 7.49(1)Å, c = 27.40(1)Å. The central skeleton has an “anti” conformation.
The polarographic behaviour of cinnamylidenebenzoichydrazide in solutions of varying ph at the dropping mercury electrode and the effect of surface active substances
Authors: Temerk T. M. , Abu Zhrui A. Z. 
Published: September 2010

AbstractThe polarographic behaviour of cinnamylidenebenzoichydrazide (CHB) in solutions of varying pH has been studied both in the absence and presence of cationic, anionic and nonionic surfactants. The mechanism for the reduction in alkaline and acid media is discussed. The adsorption effects of electrochemically inactive surfactants on the polarographic waves of CBH has been investigated. The values of the kinetic parameters for the electrode reaction at different pH values have been computed.
Influence of the dielectric constant of the medium on the dipole moment of 1/1 complexes between trialkylamines and carboxylic acids
Authors: Huyskens P. L. , Cl. Haulait‐Pirson M. , Kapuku F. 
Published: September 2010

AbstractWhen carboxylic acids are dissolved in trialkylamines, the dipole moments μab of the 1/1 complexes increase when the molefraction of the acid becomes greater. This is due to the enhancement of the dielectric constant of the medium which affects the transfer constant Kt of the proton in the hydrogen bonds, causing an increase of the proportion of the ion‐pairs with respect to the number of complexes where no proton transfer occurs. An equation is proposed which takes quantitatively this effect into account. The transfer constant Kt in a given medium at roomtemperature is nearly the same in the complexes of propanoic, butanoic and pentanoic acid by is significantly higher in the complexes of tributylamine than in those of triethylamine. This can be explained by the higher pKa of the former base. In these ab complexes the transfer constant remains always smaller than one.
Déplacement spectral de la bande π‐π*(1Lb) du benzaldéhyde par effet de solvant
Authors: Morales Raúl G. E. 
Published: September 2010

AbstractThis work determines the spectral solvent shift of the first π‐π* band of benzaldehyde corresponding to the 1A−1 Lb electronic transition. The spectral shift in solution relative to the vapor phase is obtained by determining the maximum of absorption in the vapor phase (36705 cm−l) corresponding to the maximum of absorption in solution.The maximum vibronic transition in the vapor phase is located to 1230 cm−l from the 0'–0” transition. This determination has been done through an analysis of the band intensities as a function of temperature (77°K to 398°K), and the curve fitting procedure of the pseudovibronic bands, which simulate the solution spectra. The spectral shifts vary from 500 to 1000 cm−l.
The sulfoxide bond as stereochemical probe in methyl‐1,4‐thiazane‐1‐oxide. Conformational preference in 1,4‐thiazane‐l‐oxide
Authors: Nachtergaele Willy A. , Anteunis Marc J. O. 
Published: September 2010

AbstractOxidation of 3‐methyl‐l,4‐thiazane provides two sulfoxide isomers. The isomer with the axial sulfoxide bond is formed in threefold excess. Comparison of 1H NMR spectral characteristics of cis‐ and trans‐3‐methyl‐l,4‐thiazane‐l‐oxide with these of 1,4‐thiazane‐1‐oxide points out that in the conformational equilibrium of the latter the sulfoxide bond in axial, position is somewhat favoured. From the “slow exchange” 13C NMR spectrum we estimate the axial sulfoxide isomer to be present for 57% (ΔG° = 0.46 kJ/mol ± 0.35 kJ/mol) at 203 K. Estimation from proton shifts and interproton couplings result in an axial population ranging from 53 to 69%. The presence of the N‐lone pair orbital influences substantially the conformational behaviour, as follows from the increased axial sulfoxide character in the protonated and N‐acetyl‐derivatives.
Conductometric titrations in the presence of indifferent electrolyte
Authors: Tan S. H. , Kies H. L. 
Published: September 2010

AbstractFavourable conductograms are obtained in various titrations of solutions in the presence of a large excess of indifferent electrolyte. Titration cells with high cell constants, up to 2000 cm−1, are used in conjunction with a differential measuring bridge. Conductivity cells with lower cell constants (ca. 25 cm−1), equipped with three electrodes also provide effective elimination of polarization effects, and are used for the titration of solutions with moderate electrolyte concentration, such as complexometric titrations in buffered media, using a conventional measuring bridge. To avoid adsorption effects, platinization of the electrodes has been avoided.
Enamine chemistry XX. synthesis of furan derivatives by reductive cyclisation of enamines
Authors: Carlsson S. , El‐Rarbary A. A. , Lawesson S. ‐O. 
Published: September 2010

AbstractEnamines, I, prepared from cyclohexanones or cyclopentanones and pyrrolidine are alkylated with 2‐bromoesters (ethyl 2‐bromoethanoate, ethyl 2‐bromopropanoate, methyl 2‐bromopropanoate) to give the new enamines, II, which after treatment with LiAlH4 undergo reductive cyclisation reactions giving the furan derivatives, III (7a‐pyrrolidino‐octahydrobenzofurans, 6a‐pyrrolidino‐hexahydrocyclopentafurans) in almost quantitative yields. The compounds III are hydrolyzed with hydrochloric acid to octahydrobenzofuran‐7a‐ols or hexahydrocyclopentafuran‐6a‐ols, IV. Elimination of pyrrolidine from III with oxalic acid in anhydrous dioxane yields condensed dihydrofurans, V.
Formation de dioxolannes a partir de l'épichlorhydrine du glycerol. Hydrolyse aisée de dioxolannes par le tosylate de pyridinium
Authors: Thuy Vu Moc , Petit Huguette , Maitte Pierre 
Published: September 2010

AbstractWe described a versatile synthesis of dioxolanne from 1‐chlor 2, 3‐epoxypropane epichlorhydrine and different carbonyl compounds in presence of activated montmorillonite which is easily eliminated after the reaction. The hydrolysis was performed in mild conditions with pyridinium p‐toluene sulfonate.
Thienoisothiazoles, thienoisoselenazoles et selenoloisoselenazoles
Authors: Onyaraboko N. V. , Weber R. , Dereu N. , Renson M. , Paulmier C. 
Published: September 2010

AbstractSynthesis of five new fundamental biheterocyclic systems was realized through condensation of the isothiazole or isoselenazole ring on the thiophene or selenophene ring.These new heterocycles were characterized by elemental analysis, U. V., N. M. R. 1H, 13C, 77Se spectroscopy and by mass spectrometry.
Reactions of trimethyltinsodium with alkyl halides. effects of structure and solvent on course of reaction and reactivity
Authors: Kuivila Henry G. , Reeves William G. 
Published: September 2010

AbstractThe reactions of eleven alkyl chlorides and bromides with trimethyltinsodium have been examined. It has been found that primary and secondary halides react smoothly and rapidly to provide good yields of substitution products in THF and TG at 0°. The reaction is less satisfactory for allyl bromide and unsatisfactory for cinnamyl chloride and tertiary halides. Trimethyltinsodium and 2‐chlorobutane react with second order kinetics. Relative reactivities of the halides have been determined in the two solvents and are discussed. Lithium, sodium and potassium as counterions yielded the same results in the reaction of the trimethyltin‐alkalis with primary, secondary and tertiary butyl bromides in THF.
Synthesis and x‐ray crystal structure of two triorganostannylcobalt complexes
Authors: Gielen M. , Vanden Eynde I. , Polet F. , Meunier‐Piret J. , van Meerssche M. 
Published: September 2010

AbstractThe synthesis and X‐ray crystal structure analysis of two triorganostannylcobalt complexes (I) and (II) containing an asymmetric tin and an asymmetric carbon atom,magnified imagewith R;CH2‐C*H(CH3)(C6H5) and R;C6H5 for (I) and R;C(C6H5)3 and R′N(CH3)[(S)‐C*H(CH3)(C6H5)] for (II) are described.
Endothermic or exothermic character of the dissociation of ion pairs
Authors: Huyskens P. L. 
Published: September 2010

AbstractIn the gaseous phase the dissociation enthalpy ΔHd, of ion pairs is always positive. In the liquid phase the polarization of the molecules of the medium around the separate ions decreases the dissociation enthalpy and in some cases renders it negative. Other factors which influence the enthalpy of dissociation are the formation of hydrogen bonds or charge transfer bonds between the ions or between the ions and the solvent molecules. An equation based on the theories of Denison and Ramsey and of Gilkerson which takes these effects into account is: ΔHd, = (e2N/aD) (1 + d In D/d ln T) ‐ ΔH*h ‐ ΔH*s. This equation is confronted with the data of the literature.
Metalloimmunoassay. IV. Manganese‐labelled metallohaptens via cymantrene derivatives
Authors: Cais Michael , Tirosh Nilly 
Published: September 2010

AbstractThe principle of metalloimmunossay (MIA) is briefly described. Results are presented for the synthesis of phenobarbitone metallohaptens incorporating manganese atom labels via functionalized cymantrene derivatives. An atomic absorption calibration curve for the measurement of Mn concentrations with these metallohaptens indicates the feasibility of quantitative detection in the 10−9g. ml−1 range.
Instrumental Neutron Activation Analysis of Geological Materials With Low Energy Photon Detectors: Monte Carlo Evaluation of Photon Absorption in the Samples
Authors: Hertogen J. 
Published: September 2010

AbstractSmall, extra‐high resolution semiconductor detectors are extremely useful for the measurement of low energy gamma‐and X‐rays (< 100 keV) emitted during the decay of neutron activated geological materials. However, photon absorption in the samples is a potential source of substantial systematic errors.Photon absorption effects in cylindrical samples have been evaluated with the aid of Monte Carlo computer simulations. For accurate absorption corrections, it is essential to calculate the apparent absorption for a given sample‐detector geometry. For cylindrical samples this correction strongly depends upon the diameter/height ratios. However, the choice of an appropriate standard rock can eliminate the need for cumbersome absorption corrections in routine analyses.
Réactivité de L'Acide Fulminique=Transfert Intramoléculaire Du Proton Et Protonation Des Produits D'Addition
Authors: Nguyen Minh‐Tho , Sana Michel , Leroy Georges 
Published: September 2010

AbstractIn this work we study the further transformations of the addition products of the fulminic acid HCNO. The proton 1,3‐and 1,4‐intramolecular transfer and the anions protonation are investigated. All the calculations have been carried out by using the LCAO‐SCF‐MO method of Roothaan and the STO‐3G and 4‐31G basis sets of Pople.We show the transformation can follow different ways. The electrostatic potential is unable to predict the site of the anion protonation.Finally the proton 1,3‐and 1,4‐intramolecular transfer have activation barriers respectively of about 60 kcal mol−1 and 10 kcal mol−1 in gaseous phase (4‐31G basis set).
Empirical Force Field Calculations XIII. The Ring Interconversion Modes of cis‐1, 2, 3, 4, 4a, 5, 8, 8a‐Octahydronaphthalene and its 1α, 4α‐Dimethyl Derivative
Authors: Vanhee P. , Tavernier D. , Baas J. M. A. , van De Graaf B. 
Published: September 2010

AbstractThe inversion of the (half‐chair) chair conformers of cis‐1, 2, 3, 4, 4a, 5, 8, 8a‐octahydronaphthalene (1) and of its 1α, 4α‐dimethyl derivative (2) are studied with molecular mechanics using the white and Bovill empirical force field. It is a multi‐stage process: first the chair form of the saturated ring transforms into a twist conformation, then the (half‐chair) twist form can follow several pseudorotational paths on which the one half‐chair form of the unsaturated ring passes into the other via a boat form, and finally the twisted saturated ring converts into the inverted chair conformation. In 1 the first part of this process is of higher energy (ΔH≠ = 34.4 kJ mol−1) than the lowest pseudorotational path (30.8 kJ mol−1), in 2 it is the pseudorotational part of the inversion that is of somewhat higher energy (34.0 kJ mol−1) than the chair‐to‐twist stage (32.9 kJ mol−1). The methyl substituents cut off low energy pseudorotational paths available to 1 and direct the pseudorotation in 2 to regions of higher energy. The experimental determination of the inversion barrier of 1 yields ΔG≠ = 41.4 kJ mol−1.
The Synthesis of 1,8‐Diazaspiro|4,5|‐Decanes
Authors: van Parys Marc , Vandewalle Maurits 
Published: September 2010

AbstractThe synthesis of some substituted 1,8‐diazaspiro|4,5|decanes starting from l‐benzyl‐4‐oxo‐piperidine is described. This skeleton is isosteric to the 1,3,8‐triazaspiro|4,5|‐decane structure present in important neuroleptic agents.
Étude Conformationnelle D'Analgésiques Narcotiques: Structure Cristalline de r 1000: Chlorhydrate de Phényl‐4(Phényl‐3 Propényl‐2)‐1 Piperidine‐4 Carboxylate D'Éthyle
Authors: Lamotte C. , Eloy B. , Evrard G. , Durant F. 
Published: September 2010

AbstractThe title compound is a narcotic analgesic belonging to the 4 phenyl piperidine family. Its crystal structure has been investigated by X‐ray diffraction in order to ascertain the molecular conformation and compare it to those of other derivatives of this family such as phenoperidine, meperidine and β‐prodine.