Sur les propriétés électroniques de la phénothiazine et de son radical

Résumé La phénothiazine et son radical sont probablement pliées le long de l'axe passant par les deux hétéroatomes centraux. Des calculs sont effectués par la méthode des orbitales moléculaires sur la modification des caractéristiques électroniques de la phénothiazine en fonction du pliage. On montre, que les densités de spin calculées pour les différentes configurations spatiales possibles du radical phénothiazinique permettent, par comparaison avec les densités expérimentales, de choisir la configuration la plus probable. C'est la configuration pliée dans laquelle le proton attaché à l'azote se trouve placé entre les deux cycles latéraux. L'étude des potentiels d'oxydation polarographique montre qu'au contraire dans les dérivés 10-substitués de la phénothiazine, le substituant aliphatique trop volumineux est placé hors des cycles latéraux.

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Phenothiazine and its free radical are probably folded along the axis passing through the two central heteroatoms. Calculations are carried out by the molecular orbital method on the modification of the electronic characteristics of the phenothiazine ring as a result of folding. It is shown, in particular, that the spin densities calculated for the different possible geometrical configurations of the phenothiazine free radical permit, by comparison with experimental spin densities, to deduce which configuration is the most probable. In the present case, this is the folded configuration in which the proton attached to the nitrogen atom is placed between the two lateral rings. The energy of the highest filled molecular orbital is also a sensitive function of the geometrical configuration of the molecule. The study of the polarographic oxidation potential of substituted phenothiazines shows that, in contrast to the parent molecule, in the N-alkyl substituted derivatives the voluminous alkyl substituent is probably pushed out to an external position with respect to the lateral rings.

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Zusammenfassung Phenothiazin und sein Radikal sind wahrscheinlich längs der N-S-Verbindungslinie geknickt. Wir berechneten nach der MO-Methode die Änderungen der elektronischen Eigenschaften des Moleküls mit dem Knickwinkel. Der Vergleich der für die verschiedenen denkbaren Konfigurationen des Radikals berechneten Spindichten mit Meßwerten erlaubt, eine von ihnen als am wahrscheinlichsten auszuwählen. Es ist die geknickte Form, in der das H-Atom am Stickstoff zwischen den aromatischen Ringen liegt. Die Untersuchung der polarographischen Oxydationspotentiale zeigt dagegen, daß in den N-alkyl-substituierten Phenothiazinderivaten die aliphatische Gruppe von den Seiten-Ringen wegsteht.

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Ce travail a bénéficié de la subvention CY-3073 du Public Health Service des Etats-Unis (National Cancer Institute).     

Polymérisation de monomères organiques dans les plasmas froids—4: Étude des structures de polyéthylènes et polytétrafluoroéthylènes,en particulier par résonance paramagnétique électronique

The ethylene and tetrafluoroethylene polymerization in a “cold plasma” leads to polymers with considerable deficiencies of hydrogen or fluorine atoms. With electronic spin resonance, the various kinds of radicals trapped in the macromolecular structure have been detected and in some cases identified and determined. The mechanisms could be partly explained in thermodynamic terms. Irradiation of the corresponding commercial polymers gives some information about degradation processes in the plasma.     

Caractérisation des propriétés électriques des parois de pores d’une membrane

The characterisation of the surface electrical properties of membrane materials is critical for understanding and predicting the filtration performances of membranes. In this paper, four simple experimental methods – streaming potential, electro-osmosis, pore conductivity and membrane potential –, allowing the characterisation of the charge state of membrane pore walls are presented. The four experimental parameters provide information about the sign of the electrical net charge. Examples illustrating the influence of the pH, electrolyte concentration and nature on the four experimental parameters are given. The zeta potential can be then deduced from these measurements by means of a model.     

Manganèse et imagerie de résonance magnétique du développement cérébral

Divalent manganese ion Mn²⁺ is paramagnetic and has played an important role in the history of Nuclear Magnetic Resonance and in Magnetic Resonance imaging (MRI). In another way it can be taken up by neurons as an analog to Ca²⁺. So, particular interest in the use of Mn²⁺ stems from its potential as an MRI contrast for cerebral studies on normal rodent and on experimental models of diseases. This work presents the three major classes of applications of the Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) for brain experimental studies. The utility of MEMRI method for following development of the brain in physiological and pathological states is particularly pointed out.     

Apport de la coordination des hétérocycles à la connaisance de leurs spectres i.r. Raman—II. spectres de la pyrimidine

A complete assignment is given for the i.r. and Raman spectra of pyrimidine in the liquid state. It depends upon comparison with the spectra of some pyrimidino-chloride complexes of iridium (III) in the 3500-350 cm⁻¹ range. The 17a (A₂) fundamentals have been identified and new frequencies are proposed for the 4, 7b, 10b, 18b modes. Previous interpretations are discussed in the light of the new data.     

Étude de la phényl-2 oxine et de ses chélates: Préparation et propriétés des phényl-2 oxinates

The authors have studied the potentiometric curves obtained during the neutralization, in dilute alcoholic media, of acid solutions containing 2-phenyl-8-quinolinol and metallic cations, with sodium hydroxide. By thermogravimetric analysis the number of water molecules and regions of stability for hydrates and anhydrous compounds were also established.Moreover these results were compared with those previously obtained for oxinates and methyl-2 oxinates.     

Application de la dynamique des solutions concentrées de polymères à la résonance acoustique de réticulation

One can characterize the large-scale displacements of a macromolecule by the time required for the chain to renew completely its conformation. These displacements are displayed by changing the topological orientation of the condensation reactions. This effect is produced by putting the medium through a sound wave or an alternating electric field that is in resonance with the Brownian motion of the macromolecule. The physical contact between the chains is enhanced and the intermolecular reactions are more frequent than the intramolecular reactions. The application of a sound wave or an electric field of a characteristic frequency on the elastomers during chemical crosslinking produces a noticeable change in the crosslinking density.     

Caractérisation part FT-IR des propriétés supercicielles et acido-basiques de la zircone phosphatée

FT-IR Characterization of superficial and acidic properties of phosphated zirconia. The nature of phosphate species formed by impregnation of zirconia by (NH₄)₂HPO₄ followed by decomposition at 400°C was studied by IR spectroscopy. These species present hydroxyl groups characterized by a ν(OH) band at 3666 cm⁻¹ due to the P-OH stretching vibration. The structure of phosphate species was examined using H₂¹⁸O isotopic exchange. Acid-base properties of phosphated zirconia was investigated by CO₂, pyridine and acetonitrile adsorption followed by FT-IR spectroscopy. The introduction of phosphated species, creates Brønsted acid sites on zirconia. A slight increase in Lewis acidity and a strong decrease in basicity is also detected.     

Structure électronique des éthers vinylique et divinylique: Introduction de la déformation des orbitales σ

Résumé La théorie L.C.A.O. améliorée est appliquée à l'étude des éthers vinylique et divinylique. La grande différence d'électronégativité entre les orbitales atomiques entrant dans la liaison entre l'oxygène et le carbone nous a conduits à introduire la déformation réciproque de ces orbitales. Les énergies calculées pour la première transition N V, 6,5 et 6,3 eV, sont en excellent accord avec l'expérience.

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The improved L.C.A.O. theory is applied to the vinyl and divinyl ethers. The large differences of electronegativity between the atomic orbitals which enter the-bond between oxygen and carbon led us to the introduction of the mutual deformation of these orbitals. The calculated energies for the first N V transition, 6,5 and 6,3 eV are in excellent agreement with experiment.

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Zusammenfassung Die verbesserte L.C.A.O.-Theorie wird auf Vinyl- und Divinyläther angewandt. Die große Elektronegativitätsdifferenz zwischen den an der-Bindung zwischen Sauerstoff und Kohlenstoff beteiligten Atomzuständen hat uns veranlaßt, die gegenseitige Deformation dieser Zustände einzuführen. Die für die erste N V-Elektronenbande berechneten Energien, 6,5 und 6,3 eV, stimmen ausgezeichnet mit der Erfahrung überein.

     

Apport de la coordination des hétérocycles à la connaissance de leurs spectres i.r. et Raman—I. Spectres de la pyrazine

The i.r. and laser Raman spectra of pyrazine and some pyrazine-complexes of iridium (III) have been investigated in the frequency range of the internal vibrations of the diazine. Samples were examined in the gaseous, liquid, or solid states or in solution. A complete and coherent vibrational assignment is deduced for pyrazine and previous interpretations are discussed in the light of the new data.     

Structure électronique du phénol,de l'ion phénate et du phénol perturbé par l'établissement d'une liaison hydrogène

The improved LCAO method is used to study the electronic structure of phenol, phenoxide ion, and phenol perturbed by a hydrogen bond. The calculated transition energies are in good agreement with experiment. A new method is proposed to determine the differences of reactivity between the different atoms of the aromatic ring. The results are satisfactory.     

Interprétation des spectres Raman du butyne-2, du pentyne-2 et de quelques composés analogues deutériés ǎ l'état liquide; étude de la résonance de Fermi affectant la vibration ν(CC)

The Raman spectra of three 2-butynes: CH₃CCCH₃, CH₃CCCD₃ and CD₃CCCD₃, and four 2-pentynes: C₂H₅CCCH₃, C₂H₅CCCD₃, C₂D₅CCCH₃ and C₂D₅CCCD₃ in the liquid state have been measured. From a comparative analysis of the spectra, together with previous work on 1-butynes, a vibrational assignment is derived. The analysis of the 2000–2400 cm⁻¹ range allowed us to precise the Fermi resonance interaction between ν(CC) and 2ν_a(CC

CC). An assignment of the several bands shown by the Raman spectrum of 3-hexyne in this range has been proposed.     

Caractéristiques et rôle du RNA3, RNA satellite du virus des anneaux noirs de la tomate

Viruses of the Nepovirus group have a bipartite genome. In the case of the tomato black ring (TBRV) subgroup, the two RNA of MW 1.5 × 10⁶ and 2.5 × 10⁶ daltons are respectively diistributed in two nucleoproteins B and M. Some severe TBRV strains have an additional small RNA of 0.5 × 10⁶ daltons called RNA3 encapsidated in two special nucleoproteins M′ and T′.TBRV-S strain containing such an RNA3 was specially investigated here. Elimination of RNA3 from this strain is difficult, and requires polyacrylamide gel electrophoresis under denaturing conditions (urea 8 M, 65°C). Elimination of RNA3 from the strain does not result in any modification of symptoms. RNA3 has all the characteristics of a satellite RNA which does not multiply by itself. Its multiplication needs the presence of the two RNA of the S strain: it cannot be introduced in another strain naturally free of a small satellite RNA or in 2 pseudorecombinant strains containing respectively one of the major RNA of the S strain. Its only role in the infection process, is to modify the relative proportions of the virus RNA.     

Étude de la phényl-2 oxine et de ses chélates: Préparation et propr1étés de la phényl-2 oxine

The authors prepared phenyloxin by three different methods. They obtained a product whose melting point was 59° C and then another form melting at 72° C. Ultraviolet absorption spectra were determined in cyclohexan and in alcohol-watermixtures; from these determiaations, the solubilities of phenyloxin in water and in alcohol-water mixtures of different concentrations were obtained. If ultraviolet absorption spectra are plotted for different pH values (from 1.1 to 13.7) several isobestic points are noted.     

Identification des régimes d'un écoulement eau—air à partir d'une représentation spatio-fréquentielle

This note presents a method for two-phase flow regime identification. The diagnostic, based on signal characterization with three parameters (frequency, space and shape), has been qualified with horizontal air-water flow. After a review of the main results obtained with different methods based on signal analysis, like time-frequency analysis, we show that a space—frequency representation is well suited to discriminate and classify the flow regimes.     

Influence de l'oxygène sur les propriétés cristallographiques et électriques des materiaux de type tysonite

Influence of the substitution of oxygen for fluorine on the structural and electrical properties of Ce_1−xBi_xO_xF_3−2x solid solutions isostructural with ThOF₂ has been investigated. A structure of ThOF₂ has been proposed after use of a theoretical simulation method and comparison with that of LaF₃. Correlations between transport properties and structural data have been established.     

Premières applications des spectres d'absorption infrarouges réalisés sur une goutte de solution aqueuse

Résumé L'auteur obtient, dans une région choisie, des spectres d'absorption sur une goutte de solution aqueuse emprisonnée entre deux lamelles de bromo-iodure de thallium. Il indique ensuite comment on peut identifier divers anions seuls ou en mélanges avec une sensibilité d'ailleurs médiocre; puis il explique sur un exemple la marche pour suivre sur une seule goutte, une expérience de cinétique chimique.

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Summary In a selected region, there are obtained absorption spectra on a drop of aqueous solution confined between two small disks of thallium bromoiodide. It is then shown how it is possible to identify various anions alone or in mixture with a sensitivity that is moderately good. By means of an example, an explanation is given of the course to be followed in order to carry out an experiment in chemical kinetics on a single drop.

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Zusammenfassung Innerhalb eines ausgewählten Bereiches sind mit einem zwischen zwei Lamellen aus Thalliumbromidjodid eingeschlossenen Tropfen einer wässerigen Lösung Absorptionsspektren zu bestimmen. Der Verfasser beschreibt die Identifizierung verschiedener Anionen, allein oder in Gemischen, mit guter Empfindlichkeit. Weiters wird an Hand eines Beispieles die Durchführung einer reaktionskinetischen Untersuchung mit einem einzigen Tropfen beschrieben.

     

Étude générale sur la nature des tungstates formés à haute température au cours de diverses réactions à l'état solide

Résumé L'étude de la décomposition du paratungstate de sodium par la chaleur met en évidence la formation de tétratungstate Na₂W₄O₁₃ et de bitungstate Na₂W₂O₇. Ce dernier tungstate, existant seulement à l'état solide, présente un spectre d'absorption caractéristique. On peut l'obtenir pur en faisant agir l'anhydride tungstique sur le tungstate de sodium Na₂WO₄.

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Summary The study of the thermal decomposition of sodium paratungstate reveals the formation of sodium tetratungstate Na₂W₄O₁₃ and the bitungstate Na₂W₂O₇. The latter tungstate exists only in the solid state and gives a characteristic absorption spectrum. It may be obtained pure by causing tungstic anhydride to react with sodium tungstate Na₂WO₄.

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Zusammenfassung Das Studium der thermischen Zersetzung von Natriumparawolframat erwies die Bildung von Tetrawolframat Na₂W₄O₁₃ und von Biwolframat Na₂W₂O₇. Letzteres besteht nur in festem Zustand und bietet ein charakteristisches Spektrum. Man erhält es in reinem Zustand durch Einwirkung von Wolframtrioxyd auf Natriumwolframat Na₂WO₄.