Etude de la fragmentation de derives de L'uracile et de la thymine par Spectrometrie de masse

Original mass spectra of uracil and thymine derivatives are presented with the corresponding fragmentation schemes. In the first series of spectra, the fragmentations of thymine derivatives, including ¹⁴C-2-thymine, dimers, and bromo thymines, confirm the basic retro Diels-Alder mechanism. The second series includes dihydro 5,6-derivatives of uracil (hydroxy and bromo substituents). The behaviour of these molecules is quite different; they are more sensitive to the substituents and a part of the fragmentation is often explained by protonated molecular ions.     

Influence de la Structure de Diverses Fonctions sur l'Evaluation de l'Energie de Correlation

The influence of various correlation functions, multiplying the monoelectronic space function, is studied and applied to the Helium atom and its isoelectronic series. We used Slater-type basis orbitals and the ground and first excited states have been studied, taking into account the virial and cusp conditions. In the ground state, a very good value for the correlation energy is obtained, using a function of the type For the excited states, this type of function overestimates the assumed value of the correlation energy.     

Processus de photopolymerisation du methacrylate de methyle en presence de chlorure de zinc

The photopolymerization of methylmethacrylate in solution or in bulk, initiated by DMPA (2,2-dimethoxy-2-phenylacetophenone) and BP (benzophenone), has been investigated in the presence of ZnCI₂ as a complexing agent. We have studied the steady state polymerization (measurement of R, and OT) and the behaviour of the excited states by laser spectroscopy. We have shown the following points: R_p and DP increase with [ZnCI₂]; the rate constant for propagation increases with [ZnC12]; the rate of initiation remains constant in presence of BP-ZnCl₂ but increases with DMPA-ZnCl₂. The results are accounted for by the results of laser spectroscopy.     

Etude de l'incorporation de l'oxyde de cuivre dans le reseau de l'oxyde de nickel par traitement thermique

NiO prepared at 950° has been impregnated with a solution of copper nitrate and heated at 300°. The incorporation of CuO issued from this treatment in the lattice of NiO during sintering at 450–1100° has been studied by DTA and TG, and chemical analysis. A few experiments by radiocrystallographic analysis and electron diffraction have also been done. The process of incorporation begins at about 600° and is nearly complete at 900°. A sample elaborated at 1100° is homogeneous in the mass but presents in the surface an excess of copper ions which seems to be located at certain points.

---

Zusammenfassung Bei 950° erzeugtes NiO wurde mit Kupfer(II)nitratlösung impregniert und auf 300° erhitzt. Der Einbau von CuO (5 %) in das NiO-Netz bei thermischer Behandlung von zwischen 450–1100° wurde durch DTA, TG und chemische Analyse untersucht. Einige Proben wurden auch einer Prüfung durch Radiokristallographie und Elektronendiffraktion unterworfen. Der Einbau beginnt bei 600° und ist bis 900° praktisch vollendet. Eine bei 1100° erzeugte feste Probe, obzwar homogen in der Masse, zeigt an der Oberfläche einen Überschuß von an gewissen Stellen lokalisierten Kupferionen.

---

Résumé NiO préparé à 950° a été imprégné par une solution de nitrate cuivrique et chauffé à 300°. L'incorporation de CuO (5 %), ainsi engendré, dans le réseau de NiO, lors de traitements thermiques à 450–1100° a été étudiée par ATD, ATG et analyses chimiques. Quelques essais d'analyses radiocristallographiques et de diffraction électronique ont également été effectués. Le processus d'incorporation se manifeste à partir de 600°. Il est pratiquement complet vers 900°. Un solide élaboré à 1100°, bien qu'homogène dans la masse, présente, en surace, un excédent d'ions Cu^{+ +} qui semble localisé en certains points. , 950°, 300°. , , , 450° 1100°. . 600° 900°. , 1100°, , .

---

---

Nous tenons à exprimer nos remerciements à Messieurs H. Urbain et R. Bacaud, à Mesdames G. Dalmai-Imelik, C. Leclerq et M. A. Gresteau, et à Monsieur A. Renouprez pour leur contribution à cette étude.     

Etude par microcalorimetrie de la reactivite de deux ammoniacates de chlorure de manganese

The reaction [Mn(NH₃)₂]Cl₂+ 4NH₃ [Mn(NH₃)₆]Cl₂, which is of potential use in chemical heat pumps, was studied by means of differential scanning calorimetry. The thermodynamic conditions, the enthalpy of the reaction, and the heat capacity values for MnCl₂, [Mn(NH₃)₂Ch and [Mn(NH₃)₆Cl₂ were measured. The influence of the reaction kinetics of the experimental procedure and some parameters such as sample temperature, ammonia pressure and scanning rate was examined.

---

Zusammenfassung Mittels DSC wurde die Reaktion [Mn(NH₃)₂]Cl₂+4 NH₃ [Mn(NH3_{) 6}]Cl₂ untersucht, die von potentieller Verwendung für chemische WÄrmepumpen ist. Thermodynamische Bedingungen, die Reaktionsenthalpie und WÄrmekapazitÄtswerte für MnCl₂, [Mn(NH₃)₂]Cl₂ und [Mn(NH₃)₆]Cl₂ wurden gemessen. Weiterhin wurde der Einflu\ des Versuchsablaufes und einiger Parameter, wie Probentemperatur, Ammoniakdruck und Scanning-Geschwindigkeit auf die Reaktionskinetik untersucht.

     

Fragmentation de derives phenyles de l'isobenzofuranne et de l'isoindole

The fragmentation patterns of two paris of heterocycil compounds are investigated in order to discuss the effect of the nature of the heteroatom.     

Regioselectivite de la reduction de tropones de la quinoxaline

The reduction of quinoxalinotropones by some borohydrides is studied. We calculate the electronic structures, ab initio STO 3G method, of the various possible complexes and compare to the α-enones. It is demonstrated that the borohydride reduction of these tropones is under orbital frontier control and that the important element is carbonyl complexation by the cation.     

Mesure de l'enthalpie de decomposition du carbonate de cadmium

Résumé Après avoir établi le diagramme d'équilibre (p, T) du système CdCO₃-CdO-CO₂ jusqu'à des pressions de gaz carbonique de 300 bar, nous déterminons l'enthalpie de la réaction en appliquant l'équation de Van't Hoff; la valeur ainsi obtenue est 96±4 kJ.mol^–1.La mesure par ATD quantitative, en prenant comme étalon l'enthalpie de transformation du sulfate de potassium, conduit à la valeur de 103±5 kJ.mol^–1.

---

The equilibrium diagram (p, T) of the CdCO₃-CdO-CO₂ system was established up to 300 bar CO₂ and the reaction enthalpy was calculated using the Van't Hoff equation; the value obtained is 96±4 kJ.mol^–1.By quantitative DTA measurement, using the transformation enthalpy of potassium sulphate for calibration, a value of 103±5 kJ.mol^–1 resulted.

---

Zusammenfassung Nach Ermittlung des Gleichgewichtsdiagramms (p, T) des Systems CdCO₃-CdO-CO₂ bis zu Druckwerten von 300 bar des Kohlendioxidgases wird die Enthalpie der Reaktion an Hand der Van't Hoff-schen Gleichung bestimmt; der auf diese Weise erhaltene Wert beträgt 96±4 kJ.mol^–1.Die Messung mit Hilfe der quantitativen DTA unter Anwendung der Umsetzung von Kaliumsulfat als Eichgröße der Enthalpie, ergibt den Wert von 103±5 kJ.mol^–1.

---

CdCO₃-CdO-CO₂ 300 - 96 ± 4 · ^–1. , 103±5 · ^–1.

     

Synthese regioselective de bases de mannich de cetones dissymetriques

Methods for the regioselective synthesis of Mannich bases starting from unsymmetrical ketones are described. The Mannich base on the more substituted carbon is obtained by reaction with (CH₃)₂N⁺CH₂,CF₃CO₂^- in CF₃CO₂H and its isomer on the less substituted carbon with (iPr)₂N⁺CH₂,ClO₄^- in CH₃CN. In the first case, the orientation corresponds to a non-selective attack of the immonium salt on a mixture of enols in which the more-substituted isomer is predominant. In the second ease, use of a bulky immonium salt induces a selectivity favoring the less-substituted enol.     

Modification chimique de polyisoprenes et de polybutadienes de faible masse par addition de trichlorosilane

The addition of trichlorosilane to carbon-carbon double bonds of low molecular weight polyisoprenes and polybutadienes has been studied with hexachloroplatinic acid as catalyst. The reaction was carried out in benzene as solvent, at 110, under nitrogen pressure. The reaction rate decreases as the carbon-carbon double bond substitution increases. In most cases, addition of trichlorosilane is accompanied by cyclization reactions more or less important depending on the polymer structure, except for 1,2-polybutadiene. Trichlororosilyl groups have been modified to trimethyl and trimethoxy derivatives.     

Mecanismes de Fragmentation de l'Oxazole

The fragmentation mechanisms of oxazole have been studied in detail on using various experimental techniques (refocusing of metastable ions, deuteration, AP measurements) and by theoretical calculations.     

Spectres de Masse de Derives de l'Atractyloside. Determination du Nombre de Substituants par Combinaison d'Acetylation et de Silylation

Different transformations of the functions fixed on a heterocyclic molecule were made. It is thus possible to quickly determine the number of functions of each type present in the molecule: e.g. (i) all the functions are silylated and (ii) the alcohols are acetylated whilst the sulfates and acids are silylated. Mass spectra of atractylate, apoatractylate and gummiferine have been studied and the substituents are counted and enumerated.     

Structure de benzoates de fluoroalkyles

The crystal and molecular structure of 2,2,3,3-tetrafluoropropyl-parachlorobenzoate (C₁₀H₇ClF₄O₂) has been determined by X-ray diffraction. The crystals are monoclinic, P2₁, a = 4.826(1), b = 9.036(2), c = 12.442(4)Å, β = 94.64(2)°, V = 540.8 ų, Z = 2, D_x = 1.66 Mg m^?3. Starting from the ¹³C data of this compound, the identification of five other fluoroalkylbenzoates has been achieved by N.M.R. spectroscopy.     

Synthese de polyacrylamides porteurs de groupements iminodiacetate et etude de leur pouvoir de complexation vis-a-vis de quelques cations metalliques

Water soluble polymers were prepared by topochemical reaction of sodium iminodiacetate with polymethylolacrylamide. Their complexing properties towards some metallic cations were investigated by potentiometric and spectroscopic techniques and compared with the complexing properties of iminodiacetic acid and of a model molecule of the polymer ionic unit. The results showed that polymer and model 1-1 chelates are stronger than iminodiacetic complexes. We explain this difference by participation of the amide group in the coordination of cation by the two first ligands.     

Elaboration de capteurs de gaz a partir de ceramiques conductrices ioniques de type NaSICON

The elaboration of Na⁺ super-ionic conductor (NaSICON) ceramics is studied in this work. These solid electrolytes can be used as sensor for detection of polluted gases in air. Two sorts of ceramics with different chemical compositions are synthesised by soft chemistry route: a zirconium-based NaSICON and a hafnium-based NaSICON. DTA-TG and temperature depending X-ray diffractometry were used to follow the thermal decomposition of the precursor phases. The electrical properties of these ceramic sodium ionic conductors are investigated by complex impedance spectroscopy (CIS). The substitution of the zirconium by the hafnium increases the ceramic conductivity and decreases the activation energy E ^a (from 0.29 to 0.12 eV). This revised version was published online in August 2006 with corrections to the Cover Date.     

Quelques caracteristiques morphologiques de melanges de polymeres a base de propene et de butene

This paper reports a study of the morphology of blends of polypropene with polybutene as a function of composition. Techniques such as differential thermal analysis, thermomechanical analysis and dilatometry were used. The “compatibility” of these polyolefines is considered. Glass transition temperatures of the homopolymers are detectable when using the various techniques.     

Chromatographie sur couche mince de microparticules de gel de silice

Résumé On décrit la préparation de plaques efficaces pour la chromatographie en couche mince (sans liant), utilisant les pertites particules de gel de silice à présent disponibles (5–40 m). On discute le performances obtenues et les illustre par différentes séparations de mélanges faites tant en chromatographie d'adsorption qu'en chromatographie du type partage avec phases inversées. On discute les paramètres qui contrôlent la migration du solvant et l'élargissement des bandes et montre qu'il n'y a pas une nouvelle méthode révolutionnaire de chromatographie mais le progrès normal d'une technique analytique classique, progrès prévu de longue date [1].

---

Thin-layer chromatography with microparticles of silica gel

Summary The preparation of efficient thin-layer plates (binder free) made with the newly available samples of small silica gel particles (5 to 40 m) is described. The performances are discussed and illustrated by various applications to the separation of mixtures by adsorption and reversed phase partition chromatography. The parameters which control solvent migration and band broadening are discussed. It is shown that there is no such revolutionary concept as high performance thin-layer chromatography, but merely the normal advance of a conventional analytical technique following predictions made long ago (1).

     

Etude de stabilisation de verres a base de YF3

New fluoride glasses were obtained in the InF₃-BaF₂-YF₃ system. Evidence for phase separation was found in this basic ternary system, suggesting that glasses based on yttrium fluoride could be formed. Indeed such glasses could be prepared by fast cooling. The mean sample thickness was 2–3 mm. Glass transition, crystallization and melting temperatures were measured.     

Application de quelques methodes de microanalyse a l'etude des couches de passivation de l'acier inoxydable

Résumé Dans le but de préciser les phénomènes responsables de la corrosion fissurante de l'acier inoxydable, nous avons analysé les films de passivation formés à la surface d'échantillons exposés au MgCl₂ bouillant. Suivant la durée du traitement l'épaisseur de ces films varie entre quelques centaines et quelques milliers d'angstr?ms. Les méthodes d'analyse utilisées sont l'activation aux neutrons et aux particules chargées, l'émission ionique secondaire et la io noluminescence atomique. Les résultats obtenus sont décrits et comparés entre eux. Ces expériences mettent en évidence l'intérêt qu'il y a à associer les méthodes qui apportent des renseignements complémentaires.