bluuebunny/crossref_metadata_2025_split huggingface dataset:
Le Comportement Diélectrique des Polymères en Solutions Diluées III. Influence du Solvant sur le Moment Dipolaire et sur la Relaxation Diélectrique
Authors: de Brouckère L. , Lecocq‐Robert A. 
Published: September 2010

AbstractDielectric properties of dilute solutions of polymethyl methacrylate in toluene, chloroform and 1,2‐dichloro ethane, and of polybutyl methacrylate in carbon tetrachloride, in dioxan, in toluene, chloroform and 1,2‐tetrachlor ethane have been measured in a wide frequency range (0,5 Kcycle/sec. to 30 Mcycle/sec.) at temperatures varying from − 30°C to + 25°C. Previous conclusions concerning the influence of temperature and molecular weight have been confirmed.It has been shown that dipole moments in vacuo, extrapolated to infinite dilution, are independent of the solvent.The influence of the solvent on the critical frequency and average relaxation time cannot be explained simply by a viscosity effect. Thus our results are in favour of the theory elaborated by de Brouckère and Mandel. Activation energies are higher for the butyl‐esters than for the methyl esters, and are lower for the more polar solvents.
Recherches Expérimentales sur le Polymorphisme des Corps Organiques
Authors: Naveau J. 
Published: September 2010

AbstractLe présent travail fait partie d'un ensemble de recherches effectuées sous la direction de Mr. le Professeur Timmermans à l'Université libre de Bruxelles.Nous avons considéré les formes polymorphes comme des stéréoisomères dynamiques (1) et essayé de montrer, en répertoriant les cas de polymorphisme en chimie organique (2), jusqu'à quel point les données expérimentales con‐cordent avec cette hypothèse et les corrolaires qui en découlent.En suivant les transformations polymorphiques à l'aide d'un microscope polarisant à platines, chauffante et refroidissante, (de −165 à +200°C) nous sommes parvenus à résoudre un certain nombre de cas litigieux. Nous avons été amenés à mettre au point un dispositif expérimental permettant d'observer le comportement en lumière polarisée de cristaux organiques jusqu'à une température de −165°C.
Potential Constants and Thermodynamic Properties of Some X Y3 Z Type Molecules
Authors: Nagarajan G. 
Published: September 2010

AbstractA general potential function containing thirteen constants seems to be necessary for the molecules of the type XY3Z, but since the latter has only six frequencies all the constants cannot be determined. Making use of an assumption of Voge and Rosenthal that the forces remain constant within certain molecular group in passing from one molecule to another, the frequencies of the molecules SnBrCl3, SnClBr3, TiBrCl3 and TiClBr3 have been calculated, using the most general potential function. The potential constants have been calculated on the basis of Wilson's group theoretical method. Using the observed fundamental frequencies the thermodynamic properties have also been calculated for these molecules.
Études Conformationnelles. VIII. Équilibration des 2‐, 3‐ et 4‐Méthylcyclohexanols et des 3,3,5‐Triméthylcyclohexanols Stéréoisomères
Authors: Chiurdoglu G. , Masschelein W. 
Published: September 2010

AbstractThe equilibration of cis and trans isomers of 2‐3‐ and 4‐methylcyclohexanols is performed by the action of Raney Nickel in the presence of hydrogen. Conformational equilibrium between the two chair conformations possible for each alcohol explains the results. Also cis‐ and trans‐3,3,5‐trimethylcyclohexanols are equilibrated. It may be possible that the trans‐3,3,5‐trimethylcyclohexanol is not present entirely in the chair conformation.
Potential Constants of Iodine Heptafluoride
Authors: Nagarajan G. 
Published: September 2010

AbstractA vibrational analysis has been made for the XY7 type molecules and radicals which have the pentagonal bipyramidal structure belonging to the symmetry point group D5h. An orthonormalized set of symmetry coordinates satisfying the transformation properties has been constructed for XY7 type molecules. The elements of F and G matrices have been worked out and from these matrices the secular equations for the various irreducible representations have been deduced by means of Wilson's group theoretical method. A potential function consisting of the ordinary valence force terms and central force terms has been adopted for the evaluation of potential constants for Iodine heptafluoride.
Potential Constants and Thermodynamic Properties of Some XY4 Type Molecules
Authors: Nagarajan G. 
Published: September 2010

AbstractPotential constants of eleven molecules and eleven ions of the XY4 type with the symmetry point group Td have been evaluated on the basis of Wilson's group theoretical method. The thermodynamic properties for the eleven molecules have also been calculated for a rigid rotator, harmonic oscillator approximation.
Étude de la Structure et des Propriétés du Chlorure D'Ortho Mésitoylbenzoyle et de Quelques Homologues
Authors: Golstein‐Golaire J. , Renson M. 
Published: September 2010

AbstractDans ce travail nous montrons que contrairement à la plupart des chlorures d'acides ortho cétoniques aromatiques, le chlorure d'ortho mésitoylbenzoyle possède une structure entièrement normale. De plus, tous ses dérivés présentent également une structure normale non cyclique. Ainsi en présence du diphénylcadmium il donne l'ortho benzoylmésitoylbenzène, dérivé dicétonique, alors que la substance isomère cyclique, la mésityl‐3 phényl‐3 phtalide, peut être obtenue simplement en inversant les radicaux organiques. Nous montrons que la présence des deux groupements méthyles en ortho est nécessaire pour obtenir une structure normale. Enfin nous discutons les interprétations possibles de cette réactivité particulière.
Complexes Métalliques de Polyaminés, Complexes de la NN1‐Di‐(3‐Aminopropyl) Propylènediamine
Authors: Teyssié P. , Anderegg G. , Schwarzenbach G. 
Published: September 2010

AbstractThe formation constants of polyamine complexes with six‐membered chelation rings were measured and compared to those of similar five‐membered chelates; the hexaatomic ring chelates are proved to be much less stable, which reduces the formation of hydrogen complexes.
Stéroides CXC: Préparation de Stéroides Aminés
Authors: Crabbé Pierre , Durazo M. J. , Saloma R. M. , Holton P. G. 
Published: September 2010

AbstractThe synthesis of certain 3‐amino, 6‐amino and 17‐amino steroids as well as of 3,17‐ and 3,20‐bis‐amino‐steroids is described.
Mean Amplitudes of Vibration of Sulphur Trioxide and Aluminium Trichloride Molecules
Authors: Nagarajan G. 
Published: September 2010

AbstractThe theoretical treatment of the planar symmetrical XY3 molecular model for the mean‐square amplitude quantities has been given. Mean‐square amplitude quantities as well as mean amplitudes of vibration for the sulphur trioxide and aluminium trichloride molecules have been computed. The values of the generalized mean‐square amplitudes (mean‐square parallel amplitudes, mean‐square perpendicular amplitudes and mean cross products) in terms of the Σ matrix elements have been reported.
Mean Amplitudes of Vibration and Thermodynamic Functions of the Difluorides of Oxygen and Silicon
Authors: Nagarajan G. 
Published: September 2010

AbstractThe developments in the vibrational assignment and molecular parameters of the difluorides of oxygen and silicon have been reported. The theory of mean‐square amplitude matrices has been applied to the bent symmetrical XY2 molecular model. Four valence force constants have been evaluated on the basis of Wilson's group theoretical method for these two molecules. Numerical values of the ten mean‐square amplitude quantities have been given at the temperatures T=O and T=298°K. The corresponding mean amplitudes of vibration for O – F, Si – F and F – F distances have also been given at these temperatures. The observed fundamental frequencies have been utilized for the calculation of molar thermodynamic functions assuming a rigid rotator, harmonic oscillator approximation for the temperature range from 100° to 1700°K.
Studies on Halogenated Aliphatic Compounds VII. Dipole Moments and Infrared Spectra of Halogenated Acetonitriles
Authors: van Der Kelen G. P. 
Published: September 2010

AbstractLes moments dipolaires électriques des nitriles CH3CN, CH2ClCN, CHCl2CN, CCl3CN, CH2FCN, CHF2CN et CH2(CN)2 ont été déterminés en solution dans le benzène. Le moment du CF3CN a été observé en phase gazeuse. Les spectres infrarouges de ces substances à l'état pur ont été déterminés. Des calculs vectoriels fournissent les valeurs du moment partiel du groupe CN. Il est démontré, tant par ces valeurs du moment partiel du groupe, que par l'intensité de la bande CN dans l'infrarouge, que le groupe CN subit des influences inductives très prononcés par les atomes d'halogène. D'autre part il est mis en évidence que les moments partiels des liaisons C‐X (X=F,C) ne sont nullement constantes dans ces composés.
Structure des Cyanostilbènes VI. Détermination radiocristallographique de la structure du dibromo‐2,6, α‐cyanostilbène
Authors: Bois D'Enghien H. , van Meerssche M. 
Published: September 2010

AbstractLe dibromo‐2‐6, α‐cyanostilbène est triclinique, Pl, a=9,63, b=9,69, c=7,21 Å; α=90o, β=99,5o, γ=90o Z=2 La structure a été résolue en appliquant la méthode de l'atome lourd aux réflexions hko, hkl, hhl. Elle a été affinée par moindres carrés. La molécule est cis et les deux cycles sont presque perpendiculaires l'un à l'autre.
Synthèse des Sélénosemicarbazides Substituées I. Synthèse des esters isosélénocyaniques
Authors: Collard‐Charon C. , Renson M. 
Published: September 2010

AbstractNous recherchons systématiquement et discutons les méthodes d'obtention des esters isosélénocyaniques en vue de la préparation ultérieure de sélénosemicarbazides substituées.Les méthodes principales de préparation des esters isothiocyaniques ne sont généralement pas applicables à leurs isologues séléniés, et nous devons utiliser des procédés d'obtention moins directs et plus délicats. Les esters isosélénocyaniques sont des substances peu stables, non distillables et done difficilement purifiables.
Furo [3,2‐C] et Thiéno [3,2‐C] Pyridines Ainsi Que Leurs Dérivés DI‐ET Tétra‐Hydrogénés
Authors: Descamps M. , Binon F. 
Published: September 2010

AbstractNew 4‐aryl and 4‐alkyl‐6,7‐dihydrofuro [3,2‐C] or thieno [3,2‐C] pyridines have been synthesized by making use of the Bischler‐Napieralski reaction with the corresponding amides of 2‐(2‐furyl) or 2‐(2‐thienyl)‐ethylamine. This reaction may also be used with the amides of 2‐(2‐benzofuryl)‐éthylamine. The reaction does not appear to be applicable to the amides of furfurylamine.In the case of the 6,7‐dihydrofuro [3,2‐C] and thieno [3,2‐C] pyridines, the corresponding dehydrogenated or tetrahydrogenated derivatives have been obtained. The I.R. and U.V. spectra of some of these derivatives are compared.
Substitution Électrophile Aliphatique II. Influence de l'effet stérique dans la bromo et l'iododemétallation de dérivés alcoylés de l'étain (1)
Authors: Gielen M. , Nasielski J. 
Published: September 2010

AbstractThe rates of the reactions of tetraalkyltins (R4Sn) with bromine in dimethylformamide and acetic acid solutions and with iodine in acetic acid are found to depend on steric effects (kMe> kEt > knPr), caused by the R3Sn leaving group. Trialkyltin bromides (R3SnBr) are cleaved by bromine in acetic acid in a reactivity sequence (kMe < kEt > knPr) which is best explained by an increasing importance of inductive effects.
Quaternisation de Dérivés Monohalogénés de la Pyridine Par L'Iodure de Méthyle
Authors: Coppens G. , Declerck F. , Gillet C. , Nasielski J. 
Published: September 2010

AbstractThe reactivity of six monohalogenated pyridines with methyl iodide has been determined conductimetrically in nitrobenzene. The results are: (k25∘ EA; log PZ):2‐chloropyridine (0,204.10‐5; 16,5; 6,41) 3‐chloropyridine (3,0.10‐5; 15,1; 6,56); 4‐chloropyridine 7,3.10‐5; 14,7; 6,66), 2‐bromopyridine (0,11.10‐5; 16,9; 6,44) 3‐bromopyridine (3,5.10–5; 15,2; 6,7), 4‐bromopyridine (16,9.10‐5; 14,2; 6,63).Combining these figures with data from the literature, one obtains a good Hammett plot yielding ρ=‐2,5.The relation between the activation energies and the pKas gives a value of 4.6 for the pKa of 4‐bromopyridine and suggests the following values for the compression energies of ortho substituents Cl:0,17, Br:0,65 and CH3:0,50 Kcal/mole.Side reactions, such as polymerization of the reactants or the products, did not interfere with kinetic measurements, suggesting that the instability of 4‐halogenopyridines has been somewhat exaggerated.
Stéroides CCXXXIII(1) Préparation et Stéréochimie de la 16β‐Hydroxyméthyl Isoprogestérone
Authors: Crabbé Pierre , Romo J. 
Published: September 2010

AbstractThe synthesis of 16β‐hydroxymethyl‐17α‐Δ5‐pregnene‐3β‐ol‐20‐one (IV) and 16β‐hydroxymethyl‐isoprogesterone (IXa) is described. The configuration assigned to these substances and their derivatives is based on rotatory dispersion, nuclear magnetic resonance and circular dichroism considerations.
Oxidation of Cholesterol II. Influence of The Nature of The 3β‐Ester Group on The Yield of 17‐Ketosteroid
Authors: Maas S. P. J. , van Dam M. J. D. , De Heus J. G. , Mulder D. 
Published: September 2010

AbstractAn improved method of oxidation with chromic (VI) oxide of dibromocholestanyl esters has been developed. Application of this technique to both pure 5β, 6α‐dibromocholestanyl acetate and benzoate, as well as to mixtures resulting from mutarotation of several laevorotating dibromocholestanyl esters gave yields of 17‐ketosteroid which were considerably higher than those mentioned before.
Mean Amplitudes of Vibration and Thermodynamic Functions of the Hydro and Deutero Sulphides and Selenides
Authors: Nagarajan G. 
Published: September 2010

AbstractRegarding the molecular structure and vibrational spectral studies of the hydro and deutero sulphides and selenides, a brief survey of the work done so far has been narrated. The computed numerical values of (1) mean‐square amplitude quantities, (2) generalized mean‐square amplitudes (mean‐square parallel amplitudes, mean‐square perpendicular amplitudes and mean cross products) and (3) mean amplitudes of vibration for the temperatures at T=0 and T=298°K have been given for hydrogen sulphide, deuterium sulphide hydrogen selenide and deuterium selenide. Using the vibrational fundamental frequencies the molar thermodynamic functions have been calculated on the basis of a rigid rotator, harmonic oscillator approximation for the temperature range from 200° to 2000°K.
Étude du Comportement D'isomères Géométriques Sous L'impact Électronique. II. Les Cis et Trans Hexahydroindanes
Authors: Natalis P. 
Published: September 2010

AbstractThe influence of geometrical isomerism on the behaviour of cis and trans hexahydroindanes under electron impact appears in two different ways.Firstly, mass spectra, although qualitatively identical, show important differences between abundances of several main fragment ions, especially C5H7+ and C6H9+. Relative abundances of molecular ions also differ, by about 15%, and indicate a greater stability of ionized trans isomer.Secondly, from the standpoint of energetics, two results are to be noticed. (a) Ionization potentials of cis and trans hexahydroindanes are the same within experimental uncertainties, which means that an effect due to isomerism appears in both ionized molecules. (b) Appearance potentials of the main fragment ions show that a lower energy is required to dissociate ionized cis hexahydroindane into fragments, which has to be related to the energy provided by steric conformation in this molecule.These results are in perfect agreement with those previously obtained in a study of cis and trans decalines.
Chromatographie Sur Couche Mince De Quelques Alcaloides Des Légumineuses
Authors: Ramaut J. L. 
Published: September 2010

AbstractAccording to several experiments, it is stated that thin layer chromatography of Leguminosae alkaloids yields very good results with the following technique:Adsorbent: Kieselgel G‐Plates dried at 110°C for 30 minutes. Colour reagent: Dragendorff modified by Munier. Solvent: Cyclohexanol‐Cyclohexane‐Hexane (1:1:1+5% in vol. diethylamine).After chromatographying, the plates were dried at 100°C for 1 h and sprayed afterwards.The majority of alkaloids appeared red orange (coloured); Orensin, Adenocarpin and Santiaguin were yellow or yellow‐orange (coloured); Lupinin was beige.
Potential Field and Force Constants of Antimony Pentafluoride and Niobium Pentachloride
Authors: N'agarajan' G. 
Published: September 2010

AbstractFor the 'XY'5 type molecules possessing the trigonal bipyramidal Structure with the symmetry point group 'D'3'h' an orthonormalized set of symmetry coordinates satisfying the transformation properties has been constructed. The potential and kinetic energy matrices have been derived. For the antimony pentafluoride and niobium pentachloride molecules the potential energy constants have been evaluated.
La Dégradation Enzymatique de L'Acide Désoxyribonucléique. IV.‐Mise au Point et Application D'Une Méthode D'Adsorption
Authors: Hacha R. , Fredericq E. 
Published: September 2010

AbstractCalf thymus deoxyribonucleic acid (DNA) was hydrolyzed by pancreas and by spleen deoxyribonucleases (DNases I and II). The hydrolysates were adsorbed on Ecteola cellulose and eluted by successive amounts of 0.1, 0.2 and 0.3 M NaCl. Oligonucleotides of increasing sizes were present in the eluates and were determined spectroscopically. This provided a simple method for following the whole course of the enzymic hydrolysis. Moreover it was possible to estimate the percentage and the average degree of polymerization of the oligonucleotides produced.The enzymic action of DNase I was studied in varied conditions of temperature and in the presence of several activating cations. It was confirmed that there were two phases: a rapid one mostly activated by Mg ions and by Mn2+ and Co2+, a slow one activated by Ca2+. The highest rate was obtained with mixtures of Mg2+ and Ca2+. These results were interpreted by supposing the existence of a second enzyme in the DNase preparation, an oligonucleotidase.With DNase II, higher oligonucleotides were produced.Native DNA, DNA denatured by heat or by desionization and DNA degraded by ultrasonic waves were submitted to the action of both DNases. Their behaviour was very similar. It seems that the intact structure of native DNA is not an important requirement for the enzymic action.
Substitution Nucléophile Sur L'Atome D'Étain. Mise en Évidence de Complexes Pentacovalents du Type R3SnBr I−.
Authors: Gielen M. , Nasielski J. , Yernaux R. 
Published: September 2010

AbstractTrialkyltin bromides are found to act as Lewis acids towards iodide ions. Equilibrium constants for the complexation in acetone solution are reported.
The Calculation of the Stability Constants of Some Lanthanide‐α‐Hydroxy‐Carboxylate Complexes Using a High Speed Digital Computer
Authors: Deelstra H. , Vanderleen W. , Verbeek F. 
Published: September 2010

AbstractThe four successive stability constants and their standard deviations have been determined for the α‐hydroxy‐isobutyrate and lactate complexes of the lanthanide elements and yttrium. A least squares treatment of the experimental data obtained by the Calvin‐Bjerrum potentiometric titration method using an I.B.M. 1620 high speed digital computer is described.
Sur Une Nouvelle Méthode de Synthése Des Oxadiazoles‐1,2, 4 Disubstitués
Authors: Eloy F. , Lenaers R. 
Published: September 2010

AbstractA new one‐step synthesis of disubstituted 1, 2, 4, oxadiazoles is described. The process consists in condensing a hydroxamyl chloride with an iminoether at relatively low temperature.
Halogen Substituted 1,3‐Cyclohexanediones I. Reaction of 2,2‐dichlorodimedone with bases
Authors: Schamp N. , Verzele M. 
Published: September 2010

AbstractThe reaction of 2,2‐dichlorodimedone with bases gives complex mixtures, but with silver oxide a straightforward reaction leads with high yield to 6,6‐dichloro‐4,4‐dimethyl‐5‐oxohexanoic acid and/or to 4,4‐dimethyl‐5‐chloroacetyl‐2‐tetrahydrofuranone. Identical reactions occur with 2,2‐dichloro‐1,3‐cyclohexanedione.
Substitution Électrophile sur Carbone Saturé IV. Oxydation chromique de tétra‐alkylétains
Authors: Deblandre C. , Gielen M. , Nasielski J. 
Published: September 2010

AbstractSymmetrical tetraalkyltins react with chromic anhydryde to yield aldehydes and acids. The rates have been measured, and the kinetic results suggest a five‐membered transition state for this bimolecular electrophilic substitution on a saturated carbon atom.
The Theoretical Treatment of Ionized Molecules
Authors: Hall G. G. 
Published: September 2010

AbstractThe calculation of molecular ionization potentials and of the structure of ions is reviewed and some extensions of the theory to enable it to include inductive effects are discussed. The status of some theories of the unimolecular dissociation is considered critically in relation to experimental facts and to theoretical requirements. A new theory of this dissociation is presented which uses some of the ideas of quantum mechanical scattering theory and provides a proper foundation for further investigations.
The Ionization and Dissociation Energies of the Hydrides and Fluorides of the Elements
Authors: Price W. C. 
Published: September 2010

AbstractPlots of the bond dissociation energies of the hydrides and fluorides are presented together with those for the corresponding isoelectronic ions derived from ionization potential data. These show the dependence of the energies on the closed shell configurations appropriate to the shape of the radical or ion. The curves are also used to derive certain proton affinities and to explain the feasibility of ion‐molecule reactions.All the processes to be considered in the present article refer to the monomeric species and the bond dissociation energies are with reference to the lowest states of the atoms, radicals or ions. Exceptions to the latter statement occur for NH, HF and Ne+F where the removal of a pπ electron does not lead to the lowest state of the ion.
Recherches Dans la Série Des Benzofurannes XI‐Synthèse de pyrazoles et d'isoxazoles a partir de composés céto‐3 benzofuranniques
Authors: Descamps M. , Binon F. , Van Elst J. Der 
Published: September 2010

AbstractIt is shown that hydrazine and methyl hydrazine react with 3‐keto benzofurans to yield trisubstituted pyrazoles having a phenolic character. Several pyrazole compounds have been prepared. R. Royer and E. Bisagni have shown that phenolic trisubstituted isoxazoles are formed by the action of hydroxylamine on the 3‐keto benzofurans; we have prepared other phenolic isoxazoles, thus showing how very general the reaction is.Finally we have synthesised β‐N‐diethylaminoethylether derivatives of all phenolic pyrazoles and isoxazoles.
Préparation et Propriétés de la Sélénochromannone‐4 et de la Sélénochromone
Authors: Renson M. 
Published: September 2010

AbstractNous décrivons une méthode nouvelle et pratique de préparation de la sélénochromannone. Cette substance constitue le point de départ d'un travail dont nous décrivons quelques réactions dans ce premier article.
Réactions du Sulfoxyde de Diméthyle I — Synthèse des halogénures de diméthyl‐hydroxyaryl‐sulfonium et pyrolyse de ces corps en méthyl‐hydroxyaryl thioethers
Authors: Goethals E. , De Radzitzky P. 
Published: September 2010

Abstract15 dimethyl‐hydroxyaryl‐sulfonium chlorides have been prepared by condensing dimethylsulfoxide on hydroxyaromatic compounds with hydrochloric acid. The structure of the sulfonium salts and the mechanism of their formation are discussed. The pyrolysis of those sulfonium chlorides gives a quantitative yield of the corresponding methyl‐hydroxyaryl‐thioethers. The combination of those two reactions provides a very convenient way to introduce a methylthio‐group on an aromatic nucleus already carrying an hydroxyl group.