Transfert d'un Atome de Chlore lors d'un Réarrangement de Type McLafferty

The mass spectra of three ω-chloro allenes provide avidence for two McLafferty type rearrangements, one involving migration of a hydrogen Atom and the other involving migration of the chtorine atom.     

Formulation d'un element fini adapte a la resolution des problemes de poutres stratifiees ou sandwiches

Among the numerical methods, there is the “finite element method” which is particularly adapted for the solution of the problems of the mechanics of continuous media. The presence of an interface in the case of anisotropic materials (stratified, sandwiches, etc .) is due to a disorder like delamination. Therefore, the modelling of this type of materials needs the formulation of an element susceptible to take into account this singularity. For solving this problem the formulation of a triangular element, having four degrees of freedom per node is needed, which permits at the interface the continuity of displacement, normal stress and shear stress. This element belongs to the Reissner element (assuring the continuity of stresses and displacements), but it is modified by an elimination method to keep only the degrees of freedom translating the continuity at the interface. The work of Aivaz-Zadeh and Verchery is based on the developed element. A comparison of the results is presented.     

Inequivalence magnetique en serie imidazolidine : Application a la determination de la configuration relative de diastereoisomeres

The magnetic inequivalence of benzylic protons in N,N′-dibenzyl 2- or 4-monosubstituted and 2,4-disubstituted imidazolidines has been used to assign cis configuration to substituents at position 2 and 4.     

Effet de la temperature sur la structure cristalline d'un biocorail

Coral is a natural biomaterial used nowadays frequently in medical applications. Our recent studies show that a coral implanted in bone tissue is gradually transformed to become a neoformed bone. In some special cases, high temperature has to be used as sterilization mean instead of gamma or electron irradiations. Here, we perform this method and we analyse cristalline behaviourvs. temperature with X-rays diffractions. We show that coral aragonite and mineral pure aragonite have two different temperatures for aragonite-calcite phase transition: 300° and 470°C.However until 200°C and under atmospheric pressure, any transformation are observed at macroscopic scale.

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Zusammenfassung Korallen sind ein natürliches Biomaterial, welches heute oft medizinisch angewendet wird. Unsere jüngsten Untersuchungen zeigen, daß im Knochengewebe implantiertes Korallenmaterial nach und nach in neugeformtes Knochengewebe umgewandelt wird. In einigen speziellen Fällen müssen anstelle von Gamma- oder Elektronenbestrahlung hohe Temperaturen zur Sterilisierung eingesetzt werden. Diese Methode wurde hier angewendet und mittels Röntgendiffraktion das kristalline Verhalten in Abhängigkeit von der Temperatur analysiert. Es wurde gezeigt, daß Korallen-Aragonit und mineralisches reines Aragonit für die Aragonit-Kalzit Phasenumwandlung zwei verschiedene Temperaturen aufweisen: 300° und 470°C.In allen Fällen werden bis 200°C und unter Normaldruck Umwandlungen makroskopischen Ausmaßes beobachtet.

     

Modelisation de la reaction chimique de durcissement d'un systeme epoxy

Chemical, as well as spectroscopical methods, were used to try to describe, as quantitatively as possible, the different kinds of chemical bonds constituting the network of a cured epoxy matrix, the tgmda/ DDS system. The chemical approach consisted, on the one hand, in synthesizing model compounds; on the other hand, model reactions from diepoxy and amino compounds were followed by chemical, chromatographical and spectroscopical analysis, in order to correlate structure of the products with reactivity of the starting molecules. Spectroscopical method, which was found most useful for this resin system, is solid state ¹³C CP/MAS NMR spectroscopy. As the spectra were not directly interpretable, because consisting largely of broad, bad-resolved peaks, the aliphatic carbon region was decomposed into elementary lines. Structural assignments of the latter were made by using the solution state ¹³C NMR data of model compounds. On account of the anticipated mechanisms, 85 % of the aliphatic carbons could be identified and quantified.     

Methode de mesure de la periode d'un corps radioactif et applications

The authors propose a function describing a curve taken on a multiple-stage instrument. This function depends on three parameters; the time, the half-life, and the initial dead-time. The latter has been measured accurately on an electronic unit developed for this purpose. The half-lives of certain elements (Hf, Ag, Se, Na, V, Sc, Al) have been determined and the differences in the half-lives of an element and its salt have been pointed out.      

Aminophosphines: Influence des Substituants lies au Phosphore sur la Barriere a la Rotation Autour de la liaison P?N et sur la Nucleophilie de L'atome D'azote

The ΔG* values for the barrier to rotation around the P? N bond have been determined in some aminophosphines and are dependent on the substituents bound to the phosphorus atom. The comparison between ³J(P? N? C? H) and ΔG* values indicates that p_π—d_π overlapping between nitrogen and phosphorus is the main effect. The nucleophilic behaviour of the nitrogen atom has been measured by the rate of the chemical exchange between methyl-trifluoroacetate and various aminophosphines: the results of this kinetic study are in good agreement with the NMR conclusions.     

Dérivés Alléniques du Phosphore. Influence de l'État de Coordination du Phosphore et de la Nature des Radicaux Liés au Phosphore sur les Signes de J(P?H)

The signs of the phosphorus-proton coupling constants in various allenic organophosphorus compounds have been determined by either analysis of the AB₂X spectra or double resonance. Probable absolute signs have been obtained by taking ³J(P? H) as positive. In allenic phosphine oxides, the following signs are obtained: ²J(P? H) +ve, ³J(P? H) +ve, ⁴J(P? H) ?ve, ⁵J(P? H) +ve and the ⁴J(P? H) coupling constant varies mostly with the inductive effect of the substituents bound to the phosphorus atom. In allenic phosphines, these sings are: ²J(P? H) +ve, ³J(P? H) +ve, ⁴J(P? H) ?ve and +ve and the ⁴J(P? H) coupling constant varies with both the inductive and resonance effects to the substituents. This coupling constant is negative except when the phosphorus atom is bound to groups which are electron-donating by resonance effects. These results are discussed in relation to the pπ? dπ bonding in phosphine.     

Reduction electrochimique de la fonction amide d'un compose antitumoral,l'echinosporine

The electrochemical reduction of the amide group of echinosporine on mercury leads to the corresponding alcohol or aldehyde according to the operative conditions, with no hydrolysis of the lactone function.     

Determination de la structure d'un produit de pyrolyse caracteristique des enchainements 3,4 dans les polyisoprenes de synthese

The flash pyrolysis of polyisoprene, obtained by Ziegler-Natta catalysis and having a high proportion of 3,4 units, gives an isomer of dipentene which is characteristic of the particular type of growth reaction. Mass spectrometry, i.r. and PMR studies have shown that this isomer of pentene is either 1,4-dimethyl-4-vinyl cyclohexene or 2,4-dimethyl-4-vinyl cyclohexene. It may result from DielsAlder condensation between isoprene, liberated during pyrolysis, and the isopropenyl pendant group of a 3,4 unit followed by a depolymerization process of the chain.     

Realisation d'un derivateur permettant la mesure precise et continue de tres faibles variations de temperature

Résumé Cet article présente un dérivateur de température à très bas niveau. Il permet la mesure exacte et continue des vitesses de chauffage ou de refroidissement, de l'ambiante à 900°C avec un seuil de détection de 30°C. s^–1. Cet appareil peut être utilisé pour faire de l'analyse thermique dérivée ou comme générateur de rampes linéaires.

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A very low level temperature derivative apparatus is described. It is able to give a true and continuous measurement of heating or cooling rate from room temperature up to 900° with a detection threshold as low as 30°Cs^–1. This apparatus can be used for derivative thermal analysis and as slope temperature generator.

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Zusammenfassung Ein Derivativgerät mit sehr niedrigem Temperaturniveau wird beschrieben. Es ermöglicht eine wahre und kontinuirliche Messung der Aufheiz- und Abkühlgeschwindigkeit von Raumtemperatur bis zu 900°C mit einer Nachweisschwelle von weniger als 30°C s^–1. Dieses Gerät kann zur derivativen Thermoanalyse und als Neigungstemperaturgenerator eingesetzt werden.

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. , 900° 30 °C. ^–1. , .

     

Etude de l'influence de la bentonite et de l'eau sur les proprietes thermophysiques et le pouvoir gazeifiant d'un moule a vert

Investigation of the effects of bentonite and water on the thermophysical properties and gasifying power of a moist mould. The quality of moulded products is related to that of the mould because the latter is the source of many defects such as porosity, blowholes, etc.… The formation of gaseous defects in the moulded products is generated by gas penetration into the parts and this happens during the formation of the first crust of solidified metal. Thus, the problem of defects due to gas penetration must be addressed in order to suppress the responsible factors. Our investigation aimed at determining the influence of bentonite and water on the thermophysical properties (such as thermal conductivity, effusivity, specific heat and diffusivity) and the gasifying power of a green moulding sand in order to obtain a good moulded product. The consequence of our results is to propose a new mixture.     

Sur la structure d'un nouveau type: D'Acides mycoliques de mycobacterium smegmatis

The structure Ia is proposed for a novel type of mycolic acids isolated from Mycobacterium smegmatis. The major constituent has the formula C₆₂H₁₂₂O₃ and the structure VI.     

Détermination de la Conformation et de la Configuration de Sulfoxydes à Sept Chainons,Intermédiaires de Synthèse d'un Analogue de la Biotine

The conformation of the two isomeric 8,10-diaza-8,10-dibenzyl-4-thiabicyclo[5.3.0]decan-9-one 4-oxides has been studied by NMR. The vicinal coupling constants show that these two sulfoxides exist in a highly preferred chair conformation where the S→O bond is axial.     

Etude de la Protonation du Groupe Amide par Resonance Magnetique Nucleaire. Comportement des Anilides Substitues en Milieu Acide Concentre

Five substituted anilides of general formula were studied in acidic media (H₂SO₄? MeOH and HSO₃Cl? Me₂CO). The unsolved problem of the protonation site (O-protonation and N-protonation) is discussed in terms of the observed NMR shifts [(δNH) and δ(CO? H)] taking into account several factors including hydrogen bonding and solvent effects. New dramatic evidence is presented of N-protonation of the amide group; in the case of 2,4-dinitro formanilide, the NO₂ groups in the molecule enhance the relative basicity of the nitrogen atom in such a way that the amount of N-protonated amide can be detected. N-protonation is a function of the acidity, showing a maximum in the region of 40 to 50%.     

Application de l'analyse par activation neutronique a la determination des vins provenant de differents crus. Possibilite d'identification d'un vignoble par la determination des oligo-elements

Neutron activation analysis has been used for the determination of trace elements in different wines coming from various french vineyards. The technics used are non destructive for short and middle half-life radionuclides (²⁸Al−⁷⁶As−⁴⁹Ca−³⁸Cl−⁴²K−²⁷Mg−⁵⁶Mn−²⁴Na−⁵²V). A radiochemical separation is necessary for longer half-life radionuclides (⁶⁰Co−⁵²Cr−¹³⁴Cs−⁵⁹Fe−⁸⁶Rb−⁶⁵Zn). The results of our study show that the identification of vineyards based on the determination of specific oligo-elements can be proposed. However more data are needed to demonstrate that the knowledge of the amounts of specific oligo-elements in a wine corresponding to a given vineyard can be used for disclose frauds more particularly in the cases of wine watering or mixtures of wines coming from different vineyards.