Stéréochimie des échanges hydrogène-deuterium des protons benzyliques des arènetricarbonylchrome. Echange des protons en syn du métal

Tetralintricarbonylchromium exchanges anti and syn benzylic protons in a solution of potassium tert-butoxide DMSO-d₆. Under the same conditions the syn benzylic tertiary proton of trans-1-methyltetralintricarbonylchromium remains unchanged. The anti and syn benzylic protons of dihydroanthracenetricarbonylchromium and xanthenetricarbonylchromium undergo exchange and trans-9-methyl xanthenetricarbonylchromium undergoes exchange and epiinerisation.     

Propriétés physico-chimiques de composés à caractère aromatique IX

Résumé Le spectre U.V. de solutions contenant un dérivé N-méthylé aza-aromatique en présence d'un hydrocarbure polycyclique présente une bande supplémentaire, qui est attribuée à un complexe de transfert de charge. Cette hypothèse est étayée par la comparaison des énergies de transition avec celles observées pour les transferts de charge entre les ions I^– et ces mêmes dérivés N-méthylés.Les positions des bandes de transfert de charge de l'iodure de pyridinium sont interprétées sur la base de considérations théoriques.

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The U.V. spectra of solutions of N-methylated monoaza-aromatic compounds show new absorption bands when polycyclic aromatic hydrocarbons are added. This is attributed to the formation of charge transfer complexes. This hypothesis is supported by the comparison of these spectra with those obtained from the interaction of I^– with the same methylated monoazaaromatic compounds.An attempt to interpret the positions of the charge transfer bands in the spectra of pyridinium iodide and N-methylpyridinium iodide, based on theoretical data, is given.

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Zusammenfassung Die UV-Spektren von Lösungen eines N-Methyl-aza-aromaten in Gegenwart eines polycyclischen Kohlenwasserstoffes zeigen eine zusätzliche Bande, die einem Elektronenacceptordonator-Komplex zuzuordnen ist. Diese Hypothese wird durch den Vergleich des Spektrums mit demjenigen des analogen Jod-Komplexes gestützt.Außerdem wird die Lage der Charge-Transfer-Bande des Pyridiniumjodids durch theoretische Überlegungen erklärt.

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Pour I et VIII voir respectivement: a) Coppens, G., et J. Nasielski: Bull. Soc. Chim. Beige 70, 136 (1961); b) Anthoine, G., J. Nasielski et E. Vander Donckt: Bull. Soc. Chim. Beige (sous presse).

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Associé du F.N.R.S.

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Aspirant du F.N.R.S.

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Nous exprimons notre gratitude à Monsieur le professeur R. H. Martin qui a suivi ces recherches avec le plus vif intérêt.Que le Ponds National de la Recherche Scientifique (F.N.R.S.) trouve ici l'expression de notre gratitude pour l'aide morale et financière dont nous avons bénéficié.Nos remerciements vont également au Fonds de la Recherche Scientifique Fondamentale Collective pour le subside octroyé au laboratoire.Nous tenons aussi à remercier très sincèrement Monsieur V. Bellevitch, Directeur du Comité d'Etude et d'exploitation des Calculateurs Electroniques, qui a mis au point le programme de résolution des équations séculaires et qui nous a fourni les vecteurs et valeurs propres utilisées dans ce travail.     

Fonctionnalisations régio et stéréospécifiques successives en méta et en ortho des η6-arènetricarbonylchrome

The η⁶-1-methoxy-2,3-dimethylbenzenetricarbonylchrome and the η⁶-1-dimethylamino-2,3-dimethylbenzenetricarbonylchrome are chemically functional on the methyl group 3 first; the methyl group 2, which is less reactive, is functional later. The η⁶-1-dimethylamino-5,6,7,8-tetrahydronaphthalenetricarbonylchrome is difunctional on positions 5 then 8 using two different electrophiles.     

Développement et validation d'un modèle mécanique de la tête humaine

This paper presents the development and the validation of a 3D finite-element human head model intended to better understand the head injury mechanisms in case of head impact. A very realistic skull geometry has been obtained by digitalisation of a dry adult skull. Based on the established knowledge of bone mechanical properties, an elastic brittle law was attributed to the skull simulated by composite shell elements. The dynamical model response was compared with two experimental impact tests from the bibliography concerning epidural pressure and a third impact involving skull fracture. The results of the model validation appear promising and the model could be a powerful tool to predict the aggressiveness level of a head impact.     

Méthode de dosage du nickel métallique en présence de composés oxydés de nickel dans des matières complexes (minerals)

During investigations on the behaviour of metallic nickel in HgCl₂-, KCN- and HCl-containing media, it was noticed in certain cases that nickel metal dissolution was achieved, while a mixture of nickel oxides remained absolutely unaltered.The working conditions were determined, and on the basis of the results obtained two methods have been developed for the determination of metallic nickel in the presence of nickel oxides in complex materials, including ores.These methods are described, in detail and the results of the experiments are given: they show that an accuracy of about 5 % can be obtained.     

Microstructure et détermination des ramifications alkyle dans une série de copolymères éthylène acétate de vinyle

Compounds suitable as models for copolymers of ethylene with vinyl acetate have been prepared and studied by ¹³C-NMR (62.89 MHz). By mixing model compounds, various branched copolymers were simulated. The results have permitted an assignment more complete than previously reported for these copolymers. An investigation was made on the number of branches in nine separate copolymers. The number of ethyl, butyl, pentyl and longer branches per 1000 carbons in the main chain were determined. The number of ethyl branches was around four branches per 1000 carbons; the number of branches longer than butyl decreased from about 20 to 8 per 1000 carbons with increase in vinyl acetate content; the butyl branches predominated over those of other types when the vinyl acetate content was ⩽25% by weight.     

Evaluation des interactions électroniques en série hétérocyclique par la mesure des aires intégrées des bandes infrarouges: Cas de dérivés du benzothiazole substitués en position 2

Infrared νCN vibration bands of some 2-X substituted benzothiazoles (X=H, CH₃, Cl, F, OCH₃, N(C₂H₅)₂, SCH₃ and CN) have been used through their integrated areas, to establish a correlation with substituent characteristic parameters.     

Nouvelle méthodologie de synthèse d'alcaloïdes azétidiniques polyhydroxylés

This paper deals with anew methodology for the synthesis of the polyhydroxylated azetidinic alkaloids encountered in the penaresidin and penazetidin family using the previously described epoxide 6. The main feature of this synthesis lies in the absence of amine and/or hydroxyl protection/deprotection sequences usually encountered in the last steps of thesynthesis devoted to the heterocycle ring closure.     

Tétraazamacrocycles greffés sur polymère,synthèse et propriétés complexantes

A new macrocyclic exchanger has been prepared and characterized by anchoring to chloromethylated polystyrene, 1,4,8,11-tetraazacyclotetradecane (cyclam). The influences of temperature, molar ratio of cyclam to chlorine or sodium hydride and time of reaction on the properties of the resin (mainly the number of NC bonds), the porosity and the ion-binding ability have been investigated. The synthesis has been extended to two other macrocycles viz. 1,5,9,13-tetraazacyclohexadecane and 1,5,10,14-tetraazacyclo-octadecane. The parameters involved in the extraction of Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺ by these resins have been studied.     

Nouvelle méthode de synthèse d’acides et d’esters arylboroniques par électroréduction de dérivés aromatiques halogénés en présence d’agents boratants

Novel synthesis of arylboronic acids and esters by electroreduction of aromatic halides in the presence of borating agents. A novel strategy for the one-step synthesis of arylboronic acids and esters by an electrochemical coupling reaction is described. It is based on the reductive coupling between the aromatic halides and a borating agent (trialkyl borate or pinacolborane). The reactions are carried out in DMF or THF with the use of sacrificial magnesium or aluminium anodes in a single-compartment cell. Arylboronic acids and esters are obtained with moderate-to-good isolated yields. To cite this article: C. Laza, E. Duñach, C. R. Chimie 6 (2003).     

État d'équilibre et cinétique de décollement d'un cylindre rigide en contact avec un élastomère souple

The equilibrium contact of a rigid cylinder applied against the flat and smooth surface of a soft elastomer sample (natural rubber) is examined and a method is proposed for evaluating both the Young's modulus E of the rubber-like material tested and the Dupré energy of adhesion w using a presentation of results similar to that recently described by Chaudhury et al. from the previous work of Barquins. New results on the kinetics of adherence at imposed normal load are presented. They consist of a study of variations of the strain energy release rate G and of the associate dissipation function Φ = ( G - w)/w as a function of the crack propagation speed V at the interface between the rigid cylinder and the elastic solid. As expected, a master curve Φ(V) is found, confirming the variation of Φ as the 0.55 power function of V, as recently established in rolling and rebound experiments by Barquins and Charmer with the same rubber-like material.     

Échelles caractéristiques des domaines tourbillonnaires apparaissant près des irrégularités des frontières

The possibility of the formation of a vortex domain of finite size near complex boundaries is analysed. For the proposed model, when such a scenario is attainable, the curve configuration delimiting the non-zero vorticity domain is found. This curve represents an approximate solution of an integral-differential equation obtained using the proposed model. It is shown that the vorticity level is a function of the characteristic dimension of the vortex domain, which depends on the size of the obstacle and is a homogeneous function of the Reynolds number.     

Sur l'électrophorèse d'un ensemble de particules portant la même densité uniforme de charges

We consider the electrophoresis of solid particles embedded in a possibly non-uniform electric field E_t8. For particles admitting the same uniform zeta potential, the rigidbody motion of each particle is obtained without calculating the total electric field E within the electrolyte.     

Interactions intramoleculaires—XXX. Etude vibrationnelle des conformères de cyclohexénes monosubstitués en 4

Infrared and Raman spectra of 4-cyano cyclohexenes d₀ and d₄-(3,3,6,6) and 4-methyl cyclohexene have been recorded in the liquid state and, for the two first products, in the crystalline state at low temperature. These experimental results and the effect of temperature on the Raman line intensities of 4-methyl cyclohexene, allow us to characterize the spectra of each conformer. The comparison of these spectra with those of 4-chloro and 4-bromo cyclohexenes indicates 24 sequences of common frequencies corresponding to fundamental vibrations of cyclohexene. For each pair of conformers the difference between the sum of squares of these fundamental frequencies is lower than 1%. The identification of conformers is made by analogy with 4-chloro cyclohexene for which the ν(CCl) frequencies are characteristic of the equatorial or axial conformation of chlorine.     

Mesure en laboratoire de la permittivité diélectrique moyenne fréquence de végétaux à 430 kHz à l'aide d'un capacimètre. Relation entre permittivité apparente d'un ensemble d'épis de blé et leur contenu en eau

The laboratory measurements presented here are additional measurements to those performed on a wheat crop by an electrostatic quadrupole at 430 kHz. They give a first calibration for the correlation between water content and apparent dielectric permittivity of ears. These measurements are performed by means of a capacimeter or a plane condenser of which the apparent permittivity is determined. Wheat ears are placed within the condenser and their permittivity is correlated to their water content. A theoretical approach (method of moments) presents the response of the condenser, containing ears similated to a 3D parallelepipedic body in an electromagnetic field.     

Résolution du problème à deux électrons en mécanique quantique par détermination directe des orbitales naturelles

Résumé La fonction d'onde et l'énergie de l'état fondamental de l'atome d'hélium et des ions isoélectroniques sont calculées selon un procédé proposé antérieurement [10]. Les équations intégrodifférentielles relatives aux orbitales naturelles (NO) sont résolues approximativement dans une représentation matricielle utilisant les fonctions complètes de Laguerre comme base, ainsi qu'avec de simples approximations analytiques des NO. On réussit à tenir compte de 95% environ de l'énergie de corrélation. La convergence du développement naturel est telle que les NO dont le nombre quantique principal est plus petit ou égal à 4 sont les seules à apporter une contribution appreciable à l'énergie. Les contributions de l'énergie cinétique et des énergies potentielles, d'attraction nucléaire et de répulsion interélectronique à l'énergie de corrélation sont examinées. Une certaine simplification du potentiel de corrélation aboutit à une justification du principe des intégrales interélectroniques réduites.

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The wave function and the energy of the ground state of the helium atom and the corresponding isoelectronic ions are calculated by a procedure recently proposed by the author [10]. The integro-differential equations of the natural orbitals (NO) are resolved approximatively in a matrix representation using the complete Laguerre functions as its basis as well as in a simple analytical approximation for the NO. The natural expansion converges so rapidly that only those NO whose principal quantum number is 4 or less contribute significantly to the energy. This method succeeds in accounting for some 95% of the correlation energy. The kinetic, potential and interelectronic energy contributions to the correlation energy have been examined separately. By simplifying the correlation potential in a certain manner the principle of reduced electron interaction integrals is justified.

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Zusammenfassung Die Wellenfunktion und die Energie des Grundzustandes des Heliumatoms und der mit ihm isoelektronischen Ionen wird gemäß einer vom Verfasser vorgeschlagenen Methode [10] berechnet. Dazu löst man die Integrodifferentialgleichungen für die natürlichen Einelektronenfunktionen (NO) näherungsweise in einer Matrixdarstellung unter Benutzung der vollständigen Laguerre-Funktionen als Basis. In dieser Näherung erfaßt man etwa 95% der Korrelationsenergie. Die natürliche Entwicklung konvergiert so gut, daß nur die NO mit der Hauptquantenzahl kleiner oder gleich 4 wesentlich zur Energie beitragen. Die Anteile der kinetischen Energie, der potentiellen Einelektronenenergie und der Elektronenwechselwirkungsenergie an der Korrelationsenergie werden untersucht. Ausgehend von einer bestimmten Näherung für das Korrelationspotential läßt sich die Methode der reduzierten Wechselwirkungsintegrale rechtfertigen.

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L'auteur a bénéficié d'une bourse de recherches de l'OTAN qui lui a été accordée par l'intermédiaire de «Deutscher Akademischer Austauschdienst». M. Gaston Berthier, Maitre de recherches au CNRS a pris un grand intérêt à ce travail et y a beaucoup contribué. Qu'il soit remercié cordialement.