bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Models of Indole Alkaloids. IV. Solvent effect in IR and NMR spectroscopy of methoxy derivatives of 1, 2, 3, 4‐tetrahydrocarbazole
Authors: van Binst G. , Danheux C. , Martin R. H. 
Published: September 2010

AbstractLa différenciation de la position des substituants méthoxy sur le noyau indolique a été effectuée par l'étude des spectres IR (entre autre par effets de solvant) et par l'étude en spectroscopie de résonance magnétique nucléaire des hydrogènes aromatiques et du proton de la fonction NH de différents dérivés méthoxylés du 1, 2, 3, 4‐tétrahydrocarbazole. En spectroscopie IR, les effets de solvant sur les fréquences des vibrations de déformation CH aromatiques, des vibrations de valence C‐O‐C du groupe méthoxy et sur la fréquence de vibration vnh sont discutés. Les déplacements chimiques des hydrogènes aromatiques, du groupe méthoxy et du proton fixé sur l'azote sont étudiés. Une corrélation avec les alcaloïdes indoliques est envisagée.
On the dimerization of 5,5‐dlmethyl‐2‐cyclohexenone
Authors: Schamp N. , De Bundel E. , Delarue E. 
Published: September 2010

AbstractIn alkaline medium 5,5‐dimethyl‐2‐cyclohexenone forms a dimer, which is shown to be 2‐(3′‐keto‐5′,5′‐dimethyl‐cyclohexyl)‐ 5,5‐dimethyl‐2‐cyclohexenone. The dimerization can be explained as an abnormal Michael addition.
Evaluation of ΔF*, ΔH* And ΔS* for the diazotization of m‐chloroaniline
Authors: Aboul‐Seoud A. 
Published: September 2010

AbstractThe results of a kinetic study of the diazotization of m‐chloroaniline (1), are combined with equilibrium and thermodynamic studies of m‐chloroaniline and its hydrochloride (2), in order to evaluate ΔF*, ΔH* and ΔS* for the nitrosation of m‐chloroaniline, which is the rate‐determining reaction in the diazotization of this amine.
Une Synthèse Simple des Sélénochromones et Sélénoflavones
Authors: Ruwet A. , Renson M. 
Published: September 2010

AbstractNous décrivons une méthode simple et rapide de préparation des sélénochromones et sélénoflavones. Cette méthode est une extension de la réaction de Simonis aux dérivés séléniés.
Clathration of aromatic compounds by coordination complexes of the type dithiocyanato tetrakis (α‐arylalkylamine) nickel(II). IV. Thermodynamics of the clathration of o‐xylene, p‐xylene and p‐dichlorobenzene by the complex of α‐phenylbutylamine
Authors: Hanotier J. , Brändli J. , de Radzitzky P. 
Published: September 2010

AbstractLa clathration des composés aromatiques par les complexes dithio cyanatotetrakis(α‐phénylbutylamine) nickel(II) est un processus réversible qui peut être considéré comme une réaction chimique. Les grandeurs thermodynamiques ΔG, ΔH et ΔS associées à la clathration de l'o‐xylène, du p‐xylène et du p‐dichlorobenzène par ce complexe ont été déterminées et leur comparaison confirme que les sélectivités de clathration sont régies à la fois par des facteurs stériques et énergétiques. Les valeurs obtenues pour les chaleurs de réaction ΔH sont compatibles avec l'intervention de forces par transfert de charge au niveau des noyaux aromatiques des deux constituants des clathrates.
Acylcyclopentanones. V. The reduction of 3‐alkylcyclopentane‐1, 2, 4‐triones and the acylation of the resulting 4‐alkylcyclopentane‐l, 3‐diones
Authors: Vandewalle M. , Compernolle F. 
Published: September 2010

AbstractA specific reduction of the 2‐carbonylfunction of 3‐alkylcyclopentane‐l, 2, 4‐triones is described. The 4‐alkylcyclopentane‐l, 3‐diones, obtained in this way, can be acylated to 2‐acyl‐4‐alkylcyclopentane‐l, 3‐diones.
The preparation of 5‐substituted 1, 2, 4‐triazoline‐3‐thiones and of alkylene and arylene 5, 5'‐bis‐l, 2, 4‐triazoline‐3‐thiones
Authors: Willems J. F. , Vandenberghe A. 
Published: September 2010

AbstractA method has been developed for the preparation of 5‐substituted 1. 2. 4‐triazoline‐3‐thiones and of alkylene and arylene 5. 5'‐bis‐1. 2. 4‐triazoline‐3‐thiones starting from carboxylic acid esters or dicarboxylic acid esters and thiosemicarbazide in sodium alcoholate medium.
The influence of spatial orientation of free orbitals in pmr spectroscopy influence of vicinal orbitals on3J and2J
Authors: Anteunis M. 
Published: September 2010

AbstractIn accordance with recent literature data, it is proposed that an increment of + 2.3 cps and + 1.8 cps is to be added to the vicinal (3J) and gem (2J) coupling values respectively, each time an α‐oxygen (or α‐nitrogen) atom has one of its free electron pairp‐orbitals parallel with the carbon hydrogen bond of one of the protons involved in the coupling under consideration. An influence on3J coupling values in three membered rings (epoxides) is however not to be considered. Molecular deformations which disturb the parallelity (i.e. in the rigid half chair form of pentacyclic compounds or in the twist form of hexacyclic compounds) nullify this effect. The Karplus rule and the electronegativity rule have regained a great amount of their reliability with this supplementary effect.
A re‐examination of the selectivity in the Friedel‐crafts chalcone synthesis
Authors: Rasschaert A. , Janssens W. , Slootmaekers P. J. 
Published: September 2010

AbstractOn a réexaminé la synthèse de chalcones à partir de chlorures de cinnamoyle (substitués) en présence du chlorure d'aluminium: cette réaction, effectuée d'après les données de la littérature, donne de très mauvais rendements en chalcone désirée. Dans la présente étude on démontre que le rendement en chalcone est quantitatif, à condition que la réaction est effectuée en solution homogène. La pureté du produit ainsi obtenu, déterminée par chromatographie en phase gazeuse, est de l'ordre de 99,9%, la principale impureté étant la 3, 3‐diphényl‐propiophénone.
Chaleurs D'Interaction de Complexes par Liaison Hydrogène. II. — Complexes Phénol — Pyridine Substituée
Authors: Neerinck D. , Lamberts L. 
Published: September 2010

AbstractEnthalpies of hydrogen bond formation between phenol and substituted pyridines are measured by calorimetry. The obtained energies are compared with the base ionization constants in water and the σ values of the pyridine substituents. The relation formation energy to infrared frequency shift is the same as for alcohols or phenols‐pyridine complexes. Distances between O and N atoms linked by the hydrogen bond are related to the infrared frequency shift: it is then concluded that a linear relation exists, for the complexes studied, between the heat of formation and the bond distance. Influence of steric hindrance on the bond distance is discussed.
Studies in organic mass spectrometry. I. — Acyclic 1, 3‐diketones
Authors: Schamp N. , Vandewalle M. 
Published: September 2010

AbstractThe mass spectra of 18 1, 3‐diketones are discussed. Next to the normal α‐cleavage of ketones, the most important fragmentations are the McLafferty rearrangement with the second carbonyl function in the ring, the expulsion of carbon monoxide and a specific σ‐cleavage of the side chain. The fragmentation seems to depend strongly on the enol content of the compound, enol molecules giving mainly α‐cleavage with loss of an alkyl radical, expulsion of carbon monoxide and σ‐cleavage of the side chain, while diketo‐molecules undergo in the first place the McLafferty rearrangement with the carbonyl function in the ring.
Détermination Par Résonance Magnétique Nucléaire de la Position des Atomes D'Hydrogène dans la Kröhnkite
Authors: van Tiggelen P. J. 
Published: September 2010

AbstractThe fine structure of the proton magnetic resonance line in a single crystal of Kröhnkite (Na2Cu(SO42 2H2O) has been investigated in order to fix the position of the hydrogen atoms in the lattice. From the results of the Pake's curves, one of the possibilities for hydrogen bonding can be eliminated. This conclusion is also supported by a thorough study of the paramagnetic influence of the copper atom upon the spectra. The interproton distance (1.57 A) in the water molecule is similar to what has been found in other hydrates. The deviation from the linearity of the hydrogen bonds is respectively 11° and 3°. The water molecule keeps the same angle as in the gaseous state. Furthermore the proposed structure accounts for the perfect cleavage parallel to (010).
Acylcyclopentanones. VI. Halogen derivatives of 2‐acylcyclopentane‐1, 3‐diones
Authors: Vandewalle M. , Schamp N. , De Wilde H. 
Published: September 2010

Abstract2‐Acyl‐2‐halogenocyclopentane‐1, 3‐diones are obtained in high yield, starting from 2‐acylcyclopentane‐1, 3‐diones. Their degradation and isomeration products are described.
The solubilities of current purines, pyrimidines and their nucleosides in urea and sucrose solutions
Authors: Stockx J. , van Aert A. , Clauwaert J. 
Published: September 2010

AbstractThe solubilities of the heterocyclic bases adenine, guanine, cytosine, uracil and the corresponding nucleosides adenosine, guanosine, cytidine and uridine were determined at room temperature in function of urea and sucrose concentration. Although urea exerts a solubilizing effect on adenine, guanine, cytosine, adenosine, guanosine, cytidine and uridine, strong individual differences in behavior emerge.Uracil shows a maximum in solubility around 12% urea.Sucrose solutions promote to a lesser extent the solubilities of adenine, cytosine, adenosine and guanosine; they show no effect on uracil solubility but depress that of the pyrimidine nucleosides.In urea solutions the influence of the ribosyl substituent shows up by enhanced solubility increments of the purine nucleosides and diminished ones for cytidine, uridine taking an intermediate position. In sucrose solutions the attachment of the ribosyl group to the bases results into a negative slope for the relation nucleocide solubility: base solubility ratio vs sucrose concentration for adenosine, cytidine and uridine.
Azoic dyestuffs from α‐bromonaphtylamines colour and constitution
Authors: Bassilios H. F. , Salem A. Y. , Shawky M. 
Published: September 2010

AbstractThe properties of seven new azoic dyestuffs prepared from the possible 1‐bromonaphthylamine isomers, are determined and compared; the best conditions of their development on cotton fabrics are found, their fastness properties are assessed and their absorption spectra in the visible region are determined.
Triterpènes VII. Épimérisation en C‐21 au Cours de L'Hydrolyse Basique de Dérivés Oxydes de la Coriacéolide et de L'Acide Machaerinique
Authors: Daloze D. , Tursch B. , Chiurdoglu G. 
Published: September 2010

AbstractEpimerisation of the C–21 substituent has been observed during methanolic sodium hydroxyde hydrolysis of acetoxy‐12, 19‐dioxo‐Δ9(11), 13(18‐coriaceolide and diacetoxy‐12, 19‐dioxo‐Δ9(11), 13(18‐methyl machaerinate.
Contribution to the Knowledge of the Electrochemistry of Uranium in Molten LiCl‐KCl Eutectic: I. The redox potential of the couple U(IV)/U(III)
Authors: Caligara F. , Martinot L. , Duyckaerts G. 
Published: September 2010

AbstractCareful measurements of the redox potential of the system U(IV)/U(III) in molten LiCl‐KCl eutectic have been carried out in glove‐boxes with dry and inert atmosphere. The cell used was the following:magnified imagewhose e.m.f. have been measured by a high impedance electronic voltmeter.Our efforts have been directed to prevent even the slightest oxidation of the Uranium species involved in the measurements.
Contribution to the Knowledge of the Electrochemistry of Uranium in Molten LiCl‐KCl Eutectic: II. Chronopotentiometric study of the reaction U(IV) + e⇆U(III) and measurement of the diffusion coefficient
Authors: Caligara F. , Martinot L. , Duyckaerts G. 
Published: September 2010

AbstractThe reaction U(IV)+e⇆U(III) in molten LiCl‐KCl eutectic has been investigated by means of chronopotentiometry. The diffusion coefficient of U(IV) passes from 4.46 . 10−6 to 12.15 . 10−6 cm2/sec. when the temperature increases from 400°C to 500°C.The diffusion coefficient of U(III) passes from 4.14 . 10−6 to 13.62 . 10−6 cm2/sec. when the temperature increases from 400°C to 550°C.The mechanism of diffusion is discussed and the hypothesis is put forward that for each ion there is a temperature at which the diffusion takes place according to the viscous flow mechanism.Some aspects of the kinetics of the reaction are also clarified.
Contribution to the Knowledge of the Electrochemistry of Uranium in Molten LiCl‐KCl Eutectic: III. The kinetics of the reactions U(IV)⇆U(III) and U(III)⇆U(O)
Authors: Caligara F. , Martinot L. , Duyckaerts G. 
Published: September 2010

AbstractThe kinetics of the reactions U(IV)+e⇆U(III) and U(III)+3e⇆U(O) in molten LiCl‐KCl eutectic are investigated by means of Tafel lines.For the first reaction, the slope of the line is RT/F, both for reduction and oxidation, which indicates that the electron‐transfer is not the rate determining step. The rate determining step is the rearrangement of the solvation shell, which follows the electron‐transfer. The slope of the Tafel line, for the second reaction, is nearly zero; it is suggested that the great exchange current does not allow the attainment of the Tafel zone.
Solubility and Complex Formation of Some Silver Halides in Dimethylsulfoxide
Authors: Rumbaut N. A. , Peeters H. L. 
Published: September 2010

AbstractThe solubility of AgCl, AgBr and AgI in a dimethylsulfoxide solution of ammonium nitrate has been determined by a potentiometric method.At 25°C the solubility products in terms of molarities are 2 × 10−10, 9 × 10−11 and 3 × 10−12 resp. in a 0.1 M NH4NO3 solution.The stability constants of the complexes AgCl2− AgBr2− and Ag2I3−, which are formed with excess halide ions are 4 × 1010, 4 × 1010 and 9 × 1023 resp., under the same conditions of temperature and inert salt concentration.Extension of the measurements to other temperatures supports the view of a “structural change” of the solvent at higher temperatures, affecting the solution equilibria.
Addition Des Sulfènes Sur Les Nitrones Et Les Nitriles Oxydes. Synthèse Et Propriétés Des Benzoxathiazépines
Authors: Eloy F. , van Overstraeten A. 
Published: September 2010

AbstractA new class of heterocyclic compounds, benzoxathiazepines, has been synthesized by condensing aromatic nitrones with sulfenes. Their chemical and spectral properties have been studied. Attempts to form oxathiazoles by adding sulfonyl chlorides to nitrile oxides led to the formation of sulfonyl derivatives of chloroximes.
Studies in Organic Mass Spectrometry III 1, 3‐Cyclohexanediones
Authors: Vandewalle M. , Schamp N. , De Wilde H. 
Published: September 2010

AbstractThe mass spectra of 1, 3‐cyclohexanedione and its 2, 4 and 5 substituted derivatives are discussed.Most fragmentation patterns can be rationalised starting from the diketo form, through initial 1.2 and 1.6 bond cleavages. Evidence is advanced that ionised enol‐molecules mainly yield retro Diels‐Alder type degradations. Ring bond cleavage processes are strongly dependent on the position and size of the substituents.
Studies in Organic Mass Spectrometry IV. Fragmentation of 2‐Alkyl‐ 1, 3‐cyclohexanediones
Authors: Vandewalle M. , Schamp N. , De Wilde H. 
Published: September 2010

AbstractIn 2‐propyl‐ and 2‐butyl‐1, 3‐cyclohexanediones, fragmentations in the side chain carry most of the total ionisation. Exact mass measurements and deuterium labeling led to mechanistic interpretations for the formation of the principal fragment ions.
Spectres De Masse De Quelques Dérivés De La Dimédone
Authors: Maquestiau A. , Lejeune P. 
Published: September 2010

AbstractThe mass spectra of dimedone, 2‐methyldimedone, 2‐ethyldimedone (mixture of tautomers, type A), of 2,2‐dimethyldimedone (pure ketonic form, type B) and of (3‐keto‐5,5‐dimethyl‐cyclohexenyl) ethyl ether (pure “enolic” form, type C), as well as these of deuterated analogues, have been recorded. Examination of the spectra showed, besides some common features, sufficient specificity of the fragmentation patterns to distinguish between the dimedone derivatives of either type A, B or C, and to yield information about the size and position of substituents on the ring.
Association of the Carboxylic Acids and Viscosity
Authors: Meeussen E. , Debeuf C. , Huyskens P. 
Published: September 2010

AbstractNous avons étudié l'influence de l'autoassociation des acides carboxyliques sur leur viscosité dans des solutions où le solvant avait approximativement la même masse moléculaire que l'acide. A partir de l'acide propionique l'élévation relative de la viscosité avec la fraction molaire de l'acide, dη/η.dX2, est assez semblable pour les différents homologues étudiés. La variation de la viscosité avec la fraction volumique est, dans ces cas, analogue, aux basses concentrations, à celle des solutions dans les mêmes solvants d'un hydrocarbure saturé de masse moléculaire double. A forte concentration elle devient plus élevée. Cette comparaison est en accord avec les mesures de moments dipolaires qui indiquent une forte prédominance des dimères cycliques dans un large domaine de concentration. Dans le cas de l'acide acétique les écarts aux fortes concentrations et à l'état pur sont beaucoup plus importants, ce qui suggère un degré moyen d'association plus élevé dans ces conditions.
NMR Experiments on Ketals IX 1, 3‐Dioxanes with axial Alkyl Substituents
Authors: Tavernier D. , Anteunis M. 
Published: September 2010

AbstractPMR Spectroscopic evidence has been advanced (3) to prove that the fundamental conformation of 4‐t. Bu‐4‐Me‐1, 3‐dioxane (Ia) is the stretched boat form (Ib). This paper discusses the PMR spectra of trans‐4, 6‐dialkyl‐1, 3‐dioxanes, including trans‐4, 6‐di‐t. Bu‐1, 3‐dioxane a genuine boat conformation model. It is concluded that the features, which have led to the boat form Ib, are not characteristic of stretched forms, but may be found in some chair form 1, 3‐dioxanes.It is shown that stretched forms do not contribute significantly to the properties of trans‐4, 6‐dialkyl‐1, 3‐dioxanes.
The Diazotisation of Aniline and of the Chloroanilines in Dilute Sulphuric Acid Solutions: A Kinetic Study
Authors: Aboul‐Seoud A. 
Published: September 2010

AbstractThe rate of diazotisation of aniline, o‐, m‐, and p‐, chloroaniline, in 0.1 mol/l sulphuric acid, was determined at different temperatures. The values of the specific reaction rate, free energy, enthalpy, entropy, and energy, of activation, for the rate‐determining reaction, viz, the nitrosation of the free amine by nitrosyl sulphuric acid, were calculated and compared. Relations were drawn between each of the specific reaction rate, and the free energy of activation, for the rate‐determining reaction, and base strength. The effect of the chlorine atom, in the different positions of the benzene nucleus, of the chloroanilines, on the reaction rate, is discussed.
Propriétés Physico‐Chimiques De Composés À Caractère Aromatique X (). Réduction polarographique de composés monoaza‐aromatiques N‐oxydés
Authors: Anthoine G. , Nasielski J. , Vander Donckt E. , Vanlautem N. 
Published: September 2010

AbstractSeven aza‐aromatic‐N‐oxides have been reduced polarographically. It is suggested that the mechanism involves an intermediate (V) having the structure of an unsaturated cyclic hydroxylamine which partially dehydrates to the corresponding deoxygenated base. The half‐wave potentials of the first reduction wave correlate reasonably well with the energy of the lowest vacant orbital as calculated by various refinements of the HMO method.
The Proton Magnetic Resonance Spectra of Ethyltin Compounds
Authors: Verdonck L. , van Der Kelen G. P. 
Published: September 2010

AbstractLes spectres de R.M.N. des protons dans les composés organostanniques (C2H5)nSnX4‐n (X = Cl, Br, I, OCH3, C6H5) ont été étudiés. L'analyse de ces spectres du type A3B2X a été faite. Le déplacement chimique, tant pour les protons CH3 que pour les protons CH2, est déterminé conjointement par l'effet inductif et par l'anisotropie diamagnétique de la liaison Sn–X. Il est démontre que les couplages spin‐spin indirects Jsn117/119‐‐A et Jsn117/119‐‐B entre les atomes d'étain (Sn117 et Sn119) et les protons du groupe éthyle sont principalement déterminés par le terme de contact de Fermi. En second lieu ces couplages dépendent de la polarité des liaisons et de l'anisotropie magnétique des liaisons Sn–X et C–H.
Spread Mixed Monolayer of Senegin and Seneginin with Cholesterol at the Air‐Water Interface
Authors: Joos P. , Ruyssen R. 
Published: September 2010

AbstractDoor spreidingsproeven van gemengde monolagen werd aangetoond dat tussen Seneginine (het aglucon van Senegine) en cholesterol geen interactie optreedt aan het grensvlak. Bij het systeem Senegine‐cholesterol daarentegen werd een duidelijke interactie vastgesteld. Terwijl bij de meeste vroeger onderzochte systemen, die interactie vertonen, een contractie‐effect optreedt, werd hier een expansie‐effect gevonden. Dit expansie‐effect duidt op een chemische interactie. Ook werd een tijdseffect waargenomen. Deze feiten zijn een bevestiging van vroegere resultaten (geadsorbeerde gemengde filmen en penetratieproeven).
Application of the Average Potential Model to Simple Liquid Mixtures
Authors: Bellemans A. , Vilcu R. 
Published: September 2010

AbstractThe excess free energies and volumes of the five following liquid mixtures: CH4‐Kr, N2‐CH4, A‐Kr, N2‐CO and CO‐A, are compared with the theoretical predictions of the Average Potential Model of Solutions, developed by Prigogine and his coworkers.
Oxydation Du Cyclohexane: Activation Par Les Aldéhydes
Authors: Rouchaud J. 
Published: September 2010

AbstractThe oxidation of cyclohexane in liquid phase at 150°C by a mixture of oxygen and nitrogen in the ratio of 1:1 under an initial partial pressure of 11 kg. cm−2 by oxygen, and catalyzed by cobalt naphtenate ([Co] = 50 ppm by weight), gives principally cyclohexanol, cyclohexanone and adipic acid. The transformation of cyclohexane carried out in a stainless steel autoclave, is powerfully accelerated when concentrations of about 0 to 0.5 mol.l−1 of aldehydes are added to the cyclohexane at the start. Thus the rate of oxidation of cyclohexane in the presence of 0.150 mol.l−1 of benzaldehyde, is ten times greater in the mixture than the rate at which pure cyclohexane is oxidized under the same conditions. The activities of aldehydes, in the oxidation of cyclohexane, are in the order of: m‐methoxybenzaldehyde, 2, 3‐dimethoxybenzaldehyde > benzaldehyde, acrolein > p‐methoxybenzaldehyde > acetaldehyde > 3, 4‐dimethoxybenzaldehyde > phtalaldehyde. The dragging effect varies following the power one of the concentration of additive. Nevertheless, whenever this concentration exceeds a certain value, the acceleration diminishes. Therefore the optimum conditions for the use of these additives are situated in feeble concentrations of aldehyde. In addition, the induction time of reaction is reduced in their presence (t> 4 min, when [benzaldehyde] = 0.150 mol.l−1). The dragging effect is attributed to the increase in the concentration of radicals, produced by the oxydation of the additives. A comparison of the rate of oxidation of pure cyclohexane and of the same in the mixture form, permits an approximate evaluation of the rate constants specific to the oxidation of cyclohexane and relative to the different stages of the reaction mechanism:k3 = 1.8.102 (mol.l−1−1 (RO2.+RH → ROOH+R);k5 = 2.2. 10−3 sec−1 (ROOH → RO.+.OH); k8 = 3.6. 10−2 (mol.l−1)−1. sec−1 (ROOH+RH → 2 ROH); k9 = 2.2. 10−1 sec−1 (ROOH → R1 CO R2+H2O).
Acylcyclopentanones VII (1): Synthesis of 2, 5‐diacetyl‐1‐cyclopentanone and 2, 5‐dibenzoyl‐1‐cyclopentanone
Authors: Vandewalle M. , Dewaele S. 
Published: September 2010

Abstract2, 5‐Diacetyl‐1‐cyclopentanone and 2, 5‐dibenzoyl‐1‐cyclopentanone are obtained by base induced cyclisations of ethyl 2‐acetyl‐6‐oxo‐heptanoate and ethyl 2, 5‐dibenzoyl‐pentanoate. Competing with this condensation aldol type cyclisations occur.