bluuebunny/crossref_metadata_2025_split huggingface dataset:
Étude Theorique Ab‐Initio de la Décomposition Thermique des 1‐Pyrazolines
Authors: Jean Y. , Hiberty P. C. 
Published: September 2010

AbstractLa décomposition thermique des 1‐pyrazolines a été étudiée à l'aide de calculs SCF ab‐initio, suivis d'une interaction de configuration 3x3, en bases minimales et étendue. Trois trajets réactionnels limites ont été étudiés. Les deux premiers impliquent la rupture simultanée des deux liaisons C‐N, et la formation d'un diradical triméthylène plan, ou “face à face”. Dans le troisième trajet, les deux liaisons sont rompues successivement et l'on forme un intermédiaire diradicalaire contenant l'azote. Les énergies d'activation calculées sont respectivement 44.1, 47.8 et 44.5 kcal/mole. Les deux mécanismes les moins énergétiques sont précisément ceux qui avaient été proposés par les expérimentateurs pour rationaliser l'inversion de stéréochimie observée lors de la décomposition des pyrazolines mono‐et bicycliques.
Interaction de Configuration Perturbative en Base D'Orbitales Localisées dans le Cadre des Approximations Indo
Authors: Douady J. , Ellinger Y. , Subra R. 
Published: September 2010

AbstractUn nouveau développement de la méthode PCILO est présenté dans le cadre des approximations INDO. Le nombre de configurations prises en compte est considérablement augmenté par rapport à la version CNDO originale. L'énergie de corrélation des doublets libres est incluse dans le traitement. Les barrières d'inversion calculées sont correctes et les géométries obtenues sont en bon accord avec l'expérience. Les qualités de rapidité de la méthode et la facilité d'interprétation des résultats ont été conservées. Cet algorithme ouvre la voie au traitement des phénoménes faisant intervenir les échanges σ‐π.
Note sur L'Influence des Substituants Dans le Mécanisme de la Réaction Diels‐Alder
Authors: Oliva A. , Bertrán J. , Fernández‐Alonso J. I. 
Published: September 2010

AbstractNous avons étudié l'hypersurface de potentiel de la réaction butadiène +éthylène et de quelques réactions avec un groupe donneur sur le butadiène et un groupe accepteur sur l'éthylène. Nous avons constaté que la présence de ces substituants augmente beaucoup l'asymétrie du procès tout en abaissant la barrière de potentiel de la réaction.
Analyse de la Fonction Hartree‐Fock Semi‐Projetée. Problème des Solutions Multiples
Authors: Smeyers Yves Gabriel , Delgado‐Barrio Gerardo 
Published: September 2010

AbstractOn interprète l'ensemble des solutions doubles, qui ont été trouvées dans le modèle Hartree‐Fock semi‐projeté (HPHF), à différentes distances inter nucléaires pour l'état fondamental de la molécule de LiH. Dans ce but, on a re cours à l'analyse des solutions en équivalents configurationnels ainsi qu'à l'étude de la stabilité des solutions HPHF. On trouve que ces solutions peuvent se classer en deux types, qui correspondent à des descriptions physiques différentes et sont, du point de vue variationnel, des minima locaux. Cette classification ne répond pas au critère énergétique. La supériorité d'une solution sur l'autre dépend essentiellement des propriétés que l'on souhaiterait calculer ainsi que la distance internucléaire.
Some Molecular Constants of Group V Hydrides
Authors: Thirugnanasambandam P. , Gnanasekaran S. 
Published: September 2010

AbstractThe Coriolis coupling constants and the centrifugal distortion constants relating to the hydrides and their isotopic analogues of Group V elements have been studied with the help of kinetic constants. The values of these molecular constants are in good agreement with the observed values, showing the significance of the procedure adopted in the present study.
Activated Carbon as a Preconcentration Substrate for X‐ray Analysis of Water
Authors: Vanderborght B. , Verbeeck J. , van Grieken R. 
Published: September 2010

AbstractChelation by 8‐hydroxyquinoline and subsequent adsorption on activated carbon allows quantitative enrichment for over 40 trace metals from aqueous solutions, with a 5‐10% precision and no influence of abundant alkali or alkaline earth ions. Collection of the activated carbon by filtration results in suitable samples for X‐ray fluorescence analysis.
Réformulation du modèle à délocalisation, application à la réactivité chimique
Authors: Chalvet O. , Constanciel R. , Décoret C. , Royer J. 
Published: September 2010

AbstractA new formulation is presented for the delocalisation model in which the effects of environment are considered in an explicit manner. The method permits one to find the successive inversions for the selectivity of reactional sites for the 1‐methyl‐quinoleinium ions and for toluene as a function of Mullikens electronegativity, and depending only on the nature of the reactants which are engaged.
Étude de la Synthèse et de la Structure de 2‐Aryl‐4‐Méthyl‐ et ‐4‐Phényloxazoline‐5‐Ones
Authors: Maquestiau A. , van Haverbeke Y. , Vanden Eynde J. J. , Crunelle G. 
Published: September 2010

AbstractThe dimerisation of 2‐aryl‐4‐methyloxazolin‐5‐ones is observed as main reaction when the synthesis occurs in pure acetic anhydride. The cyclisation of a few phenylbenzoylaminoacetic acids leads to the formation of separable tautomers. The equilibrium oxazolin‐5‐one ⇆ oxazolium‐5‐oxide is highly dependent on the substituent at position 2.
Condensation D'Aldéhydes ou de Cétones Aromatiques et de Pyrazoline‐5‐Thiones
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J. C. 
Published: September 2010

AbstractThe reactions of pyrazolin‐5‐thiones and benzaldehyde (or derivatives) lead to unstable 4‐arylidenic compounds, which undergo intermolecular cyclizations. Reactions of the pyrazolin‐5‐thiones with cinnamaldehyde and acetophenone respectively affords unstable cinnamylidenic and arylidenic products, which undergo intramolecular cyclizations.The structures of the new heterocyclic systems so obtained are established by 1H‐ and 13C NMR techniques.
Étude Aux Rayons X de la Stéréoisomèrie de Pyrazoline‐ et Isoxazoline‐5‐Ones
Authors: van Meerssche M. , Verdoncq B. , Germain G. , Declercq J. P. 
Published: September 2010

AbstractX‐ray diffraction has been applied to the structure determination of (A) 3‐phenyl‐4, 1′‐isopropylthiomethyleneisoxazoline‐5‐one and (B) 1,3‐diphenyl‐4,1′‐tertiobutylthiomethylenepyrazoline‐5‐one. Both crystals are racemic. In (A), the asymetric unit contains two different diastereoisomers of the exo Z form. In the crystals of (B) both stereoisomers, exo Z (83 Z), and exo E (17 %), coexists in a disordered structure.
Influence De L'exposant De Slater Sur La Stabilité De Structures Simples De L'oxyde De Magnesium
Authors: André J. M. , Vercauteren D. P. , De Montgolfier Ph. 
Published: September 2010

AbstractWithin the framework of the SCF model using a minimal basis set one examines the influence of varying the Slater exponents on simple systems used to similate a magnesium oxide surface.
The Use of First Order NMR Spectra in Determining the Permutational Character of Intramolecular Rearrangements
Authors: Brocas J. , Buschen J. , Decoster A. M. , Fastenakel D. , Willem R. 
Published: September 2010

AbstractWe present some properties of NMR first order spectra in relation with the permutational character of intramolecular rearrangements. We use the symmetry properties of the effective spin hamiltonian in order to analyse the Kubo‐Sack exchange matrices. In this context, we propose the experimental study of two molecules and we show that this study could give rise to new information about the permutational character of the rearrangements responsible for their non‐rigidity.
Alkylation, Protonation and Bromination of Ynamines
Authors: Fuks R. , Viehe H. G. 
Published: September 2010

AbstractWhen ynamines 1 react with electrophiles R⊕; X ⊕, the structure of the products depends strongly on the nature of the electrophilic reagent and of the ynamine. The protonation under various conditions leads only to the cyclobutenylcyanine (D) whereas the methylation and the bromination give either (D) and/or the allenamidinium salt (F). Steric factors in the presumed intermediate enaminoketenimium salt (C) appear to decide on the course of the reaction. The keteniminium, existing in equilibrium with its α‐haloenamine tautomeric form (A ⇌ B), is most probably the initial adduct of 1 and RX.
Étude Theorique Des Liaisons Intermoléculaires Par “Transfert De Charge” V. Les Complexes NH3…Cl2, H2O…Cl2 et HF…Cl2
Authors: La Grange Joëlle , Leroy Georges , Louterman‐Leloup Geneviève 
Published: September 2010

AbstractAn ab initio study of the intermolecular complexes NH3…Cl2, H2O…Cl2 and HF…Cl2 has been carried out with a split valence basis set 4–31G using the computer program GAUSSIAN‐70. One finds that the geometry of the complexes may be related to the position of the minimum of the electrostatic potential of the “donor” and that the polarization of the chlorine molecules is important toward the charge transfer.
Correlation of Hammett Parameters (σ σ+) With 1H‐NMRand 13C‐NMR of Some 4‐Aryl‐1, 4‐Dihydropyridines (Hantzsch‐Esters)
Authors: Dommisse R. A. , Lepoivre J. A. , Alderweireldt F. C. 
Published: September 2010

Abstract1H‐NMR and 13C‐NMR spectral data of 4‐aryl‐3, 5‐diethoxycarbonyl‐2, 6‐dimethyl‐1,4‐dihydropyridines (Hantzsch‐esters) are given. The chemical shift variations resulting from the different substituents are related to Hammett σ‐ and σ+‐constants.The 1, 4‐dihydropyridines of the Hantzsch‐ester type have been of increasing interest for studies on their spectroscopic properties and their use as model compounds for the NAD/NADH coenzyme system. Recently a study of the U.V.‐ and I.R.‐spectra of 4‐aryl‐3, 5‐diethoxycarbonyl‐2, 6‐dimethyl‐1, 4‐dihydropyridines has been published (1). Mass spectral data of the same compounds and their N‐alkylated analogs are also available (2). Although 1H‐NMR played a very important role in the determination of the exact structure of several dihydropyridine derivatives, only a small amount of systematic investigation has been done. In this paper the influence of various aryl substituents on the 1H‐NMR and 13C‐NMR chemical shift values in the dihydropyridine moiety of the above mentioned compounds is studied.
Structure Du C‐Chloro‐1,2,4‐Triazole En Phase Gazeuse
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Gheleyns J. P. 
Published: September 2010

AbstractMass analysed ion kinetic energy and collision induced dissociation spectra show that C‐chloro‐1, 2, 4‐triazole can be generated in three different tautomeric forms by ethylene elimination from the N‐ethyl compounds and these ions retain their structure prior to further fragmentation.5‐ and predominantly 3‐chlorotriazole structures are responsible for the mass spectrum of the parent heterocycle.
Studies on Organophosphorus Compounds XVI On O,O‐Dialkyl Dithiophosphoric Acids and N, N, N′, N′‐Tetramethylthiophosphoric Diamide as Thiation Agents: Conversion of Carboxamides into Thiocarboxamides, Alkyl Dithiocarboxylates, or Nitriles
Authors: Perregaard J. , Thomsen I. , Lawesson S. ‐O. 
Published: September 2010

AbstractBy heating carboxamides with O,O‐diethyl dithiophosphoric acid, 1, at 110‐125 °C the corresponding thiocarboxamides and/or ethyl dithiocarboxylates were formed. ortho‐Substituted N, N‐dimethylbenzamides only gave the corresponding thiocarboxamides. By using O,O‐dipropyl dithiophosphoric acid and O,O‐diisopropyl dithiophosphoric acid, thiocarboxamides were also prepared, and the corresponding propyl and isopropyl dithiocarboxylates were isolated after prolonged reaction time. Reactions of sec‐ and tert‐carboxamides with N, N, N,' N′‐tetramethylthiophosphoric diamide, 2, In HMPA at elevated temperatures produced the corresponding thiocarboxamides in high yields. Primary carboxamides were converted into the corresponding nitriles after heating with 2 in HMPA. Small amounts of primary thiocarboxamides were isolated in most of these reactions. Formanilide reacted with 2 in HMPA to give N, N‐dimethyl‐N′‐phenylformamidine in 95% yield.
Complexes of Tertiary Thioamides Part II: Complexes of dimethylthioformamide with Zn(II), Cd(II) and Hg (II)
Authors: Aarts A. J. , Desseyn H. O. , Herman M. A. 
Published: September 2010

AbstractThe complexes of dimethylthioformamide (DMTF) with Zn(II), Cd(II) and Hg(II) are investigated by conductivity measurements and by infrared and Raman spectroscopy. Following complexes are formed: M(DMTF)2Cl2 (M=Zn, Hg), Cd2(DMTF)2Cl4, M(DMTF)2I2(M=Zn, Cd, Hg) and (M(DMTF)4)(ClO4)2 (M=Zn, Cd). DMTF coordinates through its sulphur atom. The metals appear to have tetrahedral geometry.
Investigation on the Kinetics and Mechanism of the Reaction Between Potassium Peroxodisulphate and Tartaric Acid
Authors: Agarwal S. C. , Chandra G. , Jha S. K. 
Published: September 2010

AbstractThe kinetics of tartaric acid oxidation by peroxodisulphate ion has been studied to elucidate the mechanism of oxidation. Uncommon to many peroxodisulphate reactions it shows a variation in order. It is found to progress bimolecularly in the beginning and unimolecularly till completion. H+ ion and O2 gas accelerate the reaction. Some observations with change of surface revealed that area/volume ratio Influences the rate of reaction. In order to explain the observed data the chain mechanism has been proposed and rate expressions have been derived to explain the change of order from two to one.
Bis Heterocycles. Part I: Synthesis of Bis(1,2,4‐Iriazoles, 1,3,4‐Thiadiazoles) and Related Compounds
Authors: Ram Vishnu Ji , Pandey H. N. 
Published: September 2010

AbstractOxalylhydrazide, on reacting with different aryl isothiocyanates yields corresponding thiosemicarbazides which serve as the key intermediate for the synthesis of 3,3′‐bis (5‐mercapto‐4‐aryl‐1,2,4‐triazoles) and 2,2′‐bis (5‐arylamino‐1, 3, 4‐thiadiazoles). The bis‐mercaptotriazoles have been transformed into corresponding sulphides by the action of suitable alkyl halides in alkaline medium. Some of the sulphides are also converted into sulphones by oxidation with acidic potassium permanganate. A coordination compound of silver with bis‐mercaptotriazole has also been prepared and characterised. Some of the compounds are screened for their pesticidal activity and significant viruscidal activity has been found.
Enamine Chemistry ‐ XVII.The Preparation of Quaternary Ammonium Salts and Their Reactions With Potassium t‐Butoxide
Authors: Kolind‐Andersen H. , Lawesson S.‐O. 
Published: September 2010

AbstractReaction of α‐bromoacrylonitrile with enamine derived from aldehydes produces cyclobutanes while enamines from ketones primarily give quaternary ammonium salts. From 1‐morpholino‐1‐cyclohexene also a cyclobutane was isolated. Reactions of the ammonium salts with bromine give the corresponding perbromides. Treatment of the ammonium salts with potassium t‐butoxide results in Stevens rearrangement reactions and Hofmann eliminations to give condensed polycyclic systems of potential synthetic value.
Formation Constants of 3d Metal Ions With N‐m‐Tolyl‐p‐Substituted Benzohydroxamic Acids
Authors: Agrawal Y. K. 
Published: September 2010

AbstractThe thermodynamic metal ligand stability constants of hydroxamic acids with 3 d bivalent metal ions have been determined at 25° and 35°C in different mole fraction of dioxane. The stabilities of the complexes mostly follow the order of besicities of the ligands and also the electron affinities of the metal ions as measured by their ionisation potential. The stability constants of the 3 d transition metal complexes follow the order
L'icacine, Nouvel Alcaloide Diterpenique De Icacina gussfeldtii
Authors: On'okoko Penge , Hans M. , Colau B. , Hootelé C. , Declercq J. P. , Germain G. , van Meerssche M. 
Published: September 2010

AbstractIcacine, a new heptacyclic diterpene alkaloid from Icacina gussfeldtii ASCHERS has been shown to possess structure 1 by X‐ray analysis.Some chemical and spectroscopic properties of icacine are described.
Studies on Organophosphorus Compounds XIX. About PSClx (NMe2)3‐x Compounds as Thiation Reagents
Authors: Pedersen B. S. , Lawesson S.‐O. 
Published: September 2010

AbstractThe thiation properties of phosphorus compounds of type PSClx‐(NMe2)3‐x (x = 0‐3) (1‐4) have been investigated by reactions with secondary and tertiary carboxamides in the temperature range 80‐150°C. Reagents 2–4 yielded in most cases the corresponding thiocarboxamides while 1 gave no products, even at elevated temperature. The reaction of 2 with carboxamides has been thoroughly investigated: Primary carboxamides gave nitriles in quantitative yields and most secondary and tertiary carboxamides yielded quite high yields of thiocarboxamides. In some cases (acetanilide, formanilide, saccharin) the reaction products were amidines or amidine salts.
Optically Active Transition Metal Complexes, LIII . Optically Active Ni‐Complexes Obtained from the Reaction of Nickelocene With Unsymmetrically Substituted Acetylenes
Authors: Brunner H. , Pieronczyk W. 
Published: September 2010

AbstractTwo types of products are formed in the reaction of nickelocene I with acetylenes II: green compounds III containing a bridging acetylene between two CH5H5Ni groups and red compounds IV with the acetylene added to one of the C5H5‐rings in nickelocene. The reaction was carried out for a series of unsymmetrically substituted acetylenes R‐C≡C‐R' for which the mononuclear complexes IV are chiral. The two diastereoisomers, arising from the two different ways of adding HOOC‐C≡C‐COOmenthyl to Ni (C5H5) could be separated on the basis of their different solubilities in methanol. The configurationally stable (+)‐ and (−)‐isomers differ in their 1H nmr spectra.
A Radical Post‐Scavenging Study of Irradiated Cyclic Hydrocarbons in the Solid State
Authors: Tilquin B. , Allaert J. , Claes P. 
Published: September 2010

AbstractCycloalkanes were irradiated in the solid phase at 77 K. Post‐irradiation scavenging of radicals by dissolving the irradiated cycloalkane at low temperature (100 ‐ 165 K) in a propane‐oxygen mixture lowers the dicycloalkyl and cycloalkene G values to an extent of 35‐55%. From the Δ G decrease values, we propose that the trapped radical G values be 3.1, 2.7 and 2.7 at 77 K for cyclopentyl, cyclohexyl and cycloheptyl radicals, respectively.
A Reconsideration of the Rotameric Preference of the 4‐Oniummethyl Side Chains in Fourneau's 1,3‐Dioxolane and Related Compounds in Solution
Authors: Valckx Ludo A. , Borremans Frans A. M. , Anteunis Marc J. O. 
Published: September 2010

AbstractIn contrast with previous proposals it is shown from the use of new 13C‐criteria that the rotor C(4)‐CH2N⊕R3 and C(4)‐CH2P⊕R3 in 2,4‐disubstituted 1,3‐dioxolanes is characterized by a clinal orientation with respect to the O(3)‐C(4) bond.The preparation, conformation and muscarinic activity of cis−, and trans‐2‐methyl‐4‐dimethyl‐phosphinomethyl‐1, 3‐dioxolane methiodide and of cis‐, and trans‐2‐methyl‐4‐(N‐methylpyrrolid‐2‐yl)‐l, 3‐dioxolane methiodide are reported.
Tentative De Corrélation Entre Les Fréquences De Vibration Des Modes ν(So) et ν(SS) et Les Distances Interatomiques d(SO) et d(SS) Des Groupements S2O3 Coordonnés Dans Quelques Thio‐Sulfates Inorganiques
Authors: Gabelica Zélimir 
Published: September 2010

AbstractThe empirical relationship between sulfur‐oxygen stretching frequency and the corresponding bond length proposed by Gillepsie and Robinson(1) has been tested in the case of S2O3 ions coordinated in various inorganic thiosulfates. It is inadvisible to use the ν(SO)‐d(SO) plot for predicting d(SO) values for different thiosulfate‐to‐metal associations as the bond length change upon coordination does not lead to a sufficiently accurate deviation from the experimental error in many of the bond length determinations. Only the precise values of the symmetric and asymmetric S‐O stretching frequencies can be fairly correlated to a given thiosulfate‐to‐metal coordination. Similar conclusions have been obtained from a tentative correlation between thiosulfate sulfur‐sulfur bond lengths and stretching frequencies.
Anomalies Observées Dans Les Spectres Infrarouges De Quelques Thiosulfates Inorganiques
Authors: Gabelica Zélimir 
Published: September 2010

AbstractDifficulties may be encountered in the interpretation of infrared absorption spectra of most of the inorganic thiosulfates through the use of the alkali halide pellet technique. Four typical examples including various physical and chemical interactions between the halide matrix and the salt are discussed.For comparison the spectra were also recorded using the mull technique. Even then exchanges between the salt and the alkali halide window can occur through the simple contact with the mineral oil medium as shown in the case of the freely soluble cadmium thiosulfate dihydrate. Anomalies can be avoided by the use of inert insoluble windows in the mull technique such as Tl2BrI or polyethylene.
Solution Conformation of the Ionophore X‐206 and its Sodium Salt
Authors: Anteunis Marc J. O. 
Published: September 2010

AbstractThe data (TABLES I and 2) extracted from the 1H‐nmr spectra of X‐206 (1) and its sodium salt confirm the unique conformation reported for the solid state 1a and which is found to be identical in bulk Solution (Figure 7). The backbone of the antibiotic follows the seam of a tennis ball of about 14 Å in diameter thus forming a loop closed by end‐to‐tail hydrogen bond bridging. The behaviour of the hydroxylic groups is quite unique, most being orientated towards the inner cavity. At least six oxygen atoms serve as coordination sites for the trapped cation in an irregular hexagonal fashion. A central water molecule is possibly present in the free acid form that mimics the position of the cation in the salt.
Tautomérie De Pyrazoline‐5‐Thiones N1‐Substituées
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J.‐C. 
Published: September 2010

AbstractThe tautomerism of alkyl and/or arylpyrazolin‐5‐thiones, which can exist under three prototropic forms (CH, NH, SH) is examined by N. M. R., I. R. and U. V. spectroscopy.The equilibrium takes place between the SH and NH tautomers: in neutral solvents, the SH isomer is predominant while in aprotic basic media, the ratio [NH]/[SH] depends upon, several polarity parameters.In protic media (alcohols),the percentage of the NH form increases with the hydrogen bond donating power of the solvent.Some substituents (acyl‐, phenylazo‐) are able to stabilize one of the tautomers via an intramolecular bond. The differences in the tautomeric behaviour between pyrazolin‐5‐ones and 5‐thiones are discussed in terms of relative polarity and stability of the carbonyl and thiocarbonyl groups.
Synthesis and Hydrolysis of 2‐(2,6‐Dichlorophenyl)‐4,6‐Dimethyl‐1,3‐Dioxane
Authors: Schacht Etienne H. , St. Pierre Tom , Desmarets Guido E. , Goethals Eric J. 
Published: September 2010

AbstractThe cis and trans isomers of 2‐(2,6‐dichlorophenyl)‐4,6‐dimethyl‐1,3‐dioxane were synthesized and characterized. Acid catalysed hydrolysis in dioxane/water (29/1) at 60°C demonstrated that the trans isomer hydrolizes much faster (15x) than the cis compound. The individual rate constants for the hydrolysis of both isomers were determined and discussed.
Aggregation of Methyl Orange in Aqueous Acidic Solution
Authors: De Vylder M. , De Keukeleire D. 
Published: September 2010

AbstractDeviations from the Lambert‐Beer's law of concentrated aqueous acidic solutions of methyl orange are shown to be due to the formation of aggregated species. Electrostatic attraction forces are most important in the aggregation process. As it is observed that daylight may abbreviate the induction period of the reaction, it is presumed that the aggregates are formed through the intermediary of the syn isomers of the dye.