Etude theorique des proprietes thermodynamiques du radical CN et de ses dimeres

Using the ab initio LCAO—SCF—MO method and the 6–31G extended basis set, the CN radical and its possible dimers (NCCN, CNNC or CNCN) have been studied in terms of nuclear equilibrium geometries, normal modes of vibration, IR spectrum and thermodynamic properties. The results show that quantum chemical calculations enable these parameters to be obtained with adequate accuracy. Working properly, one can build a local potential energy surface on which to perform a harmonic vibrational analysis. Hence all the required information to apply the principles of statistical thermodynamical analysis is available.     

Etude de la corrosion du nickel et du cuivre par le dioxyde de soufre pur ou en presence d'oxygene au moyen des proprietes electriques

Electrical measurements of corrosion scales growing on copper and nickel in SO₂O₂ atmospheres show a different behaviour for both metals. For copper, the electrical conductivity indicates that Cu₂S is formed in pure SO₂ and Cu₂O in SO₂O₂ mixtures (ratio P_SO2/P_O2 = 10⁵). In the case of nickel, the high conductivity of product scales in atmospheres containing pure SO₂ or SO₂O₂ is consistent with an interconnected Ni₃S₂ phase in NiO. In all cases the corrosion scales have a positive Seebeck coefficient.     

Etude de la permittivite complexe d'ellipsoïdes disperses dans un milieu continu. Analyses theorique et numerique

Resumé Les lois de mélange classiques valables en général pour de très faibles fractions volumiques en matière dispersée sont étendues aux fortes concentrations par la méthode de Bruggeman. On indique les relations obtenues pour la distribution aléatoire d'ellipsoïdes au sein d'un milieu continu. Le cas des ellipsoïdes anisotropes est considéré ainsi que celui des systèmes multidispersés á plusieurs constituants.En illustration on a étudié par analyse numérique le cas des ellipsoïdes isotropes de révolution dispersés dans un milieu isolant en mettant l'accent sur l'influence du rapporta/b des demi-axes.

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Blending laws derived for very small volume fractions of dispersed medium are extended to high concentrations, using Bruggeman method. Derivation is made in the case of a random distribution of ellipsoids dispersed in a continuous medium. The case of non isotropic ellipsoids and the case of multicomponent systems are also considered.As an example, a numerical analysis is made in the case of isotropic ellipsoids of revolution dispersed in an insulating medium; particularly, the effect of the semi-axis ratioa/b is pointed out.

     

Etude conformationnelle des formes ouvertes d'un spiropyranne benzothiazolinique

The results of the conformational study of a benzothiazolinic dimethinmérocyanine (open form) are described. Variations of electron π energy (Pariser-Parr-Pople method) and of non bonding energy are considered.All possible conformations have been investigated and the results of computations give evidence for a twisted structure, confirming a previous study taking account of σ and π electrons (Extended Huckel method).     

Correlation entre structure,conductivite ionique et proprietes thermodynamiques dans la serie des halogenofluorures de l'etain II

Fluorides and some mixed halogen fluorides of tin(II) have been studied by X-ray diffraction, differential scanning calorimetry, and conductimetry. From a consideration of structural properties a relationship has been established between the co-ordination sphere, ionic mobility and entropy of fusion.     

Influence du pH sur les proprietes chimiques et structurales des films d'oxyde formes sur l'acier 316L et les alliages 600 et 690 dans les milieux aqueux a haute temperature

Influence of pH on the chemical and structural properties of the oxide films formed on 316L stainless steel, alloy 600 and alloy 690 in high temperature aqueous environments. The oxide films formed on 316L stainless steel, alloy 600 and alloy 690 at 320°C in high temperature aqueous environments of different pH have been examined by glow discharge optical spectroscopy, scanning electron microscopy, atomic force microscopy and capacitance measurements. The analytical study reveals that the films formed at pH 5 are mainly composed of chromium oxides. When the pH increases the chromium concentration decreases and those of the other two elements (Ni and Fe) tend to increase. The films formed at pH 5 on 316L stainless steel and alloy 600 are thick and powder-like. The film formed at the same pH on alloy 690 is thin and is composed of a compact protective inner layer and a less-compact outer layer formed by crystals of mixed iron-nickel-chromium oxides. The morphological appearance of the thick films and that of the thin films is very different. However, equivalent morphologies can be observed for the relatively thin duplex films formed at pH8 and pH9.5 on the 316L stainless steel and nickel-base alloys. The evolution of the chemical composition of the films is accompanied by important changes from the point of view of their semiconductivity.     

Etude du changement de phase solide-liquide en relation avec la stabilite thermique des formes polymorphes et pseudopolymorphes du lorazepam et identification spectrale

Thermal decomposition of lorazepam begins by lose of a water mole between two groups NH-OH and occurs at different temperatures depending on the formes of polymorphs. Melting temperature of a form can be determined only if it is below that of decomposition.The thermoanalytical and spectral study of lorazepam commercial drugs (a) and (b) recrystallisation product at 20°C in benzine (c), in carbon tetrachlorid (d), in acetonitrile (e) were carried out.Thermal behaviour, RX diffraction, IR spectroscopy allow us to identify polymorph (a, b, c) and two solvates (d and e). The solvates stoechiometry (d and e) has been determined by thermogravimetry (3-2) d, (2-1) e, and confirmed by magnetic nuclear resonance for (e).

Nous exprimons nos vifs remerciements à Madame Eliane Toreilles, Directeur de recherche au CNRS (Laboratoire de Chimie Organiques UA 458 CNRS, Ecole Nationale Supérieure de Chimie de Montpellier) pour sa collaboration personnelle en spectroscopie.     

Sur quelques méthodes de microdosage du soufre dans les composés organiques — Etude comparative et critique

Résumé Les auteurs rappellent et comparent quatre méthodes de minéralisation des composés organiques en vue d'y doser le soufre: ce sont la méthode de combustion oxhydrique, la combustion dans l'oxygène, soit en tube droit vide, soit en fiole du type «Schöniger» et la minéralisation réductrice en tube scellé par le potassium. Ils les associent aux méthodes de titrage des ions SO₄ ^2– ou S^2–.Leur étude leur permet de sélectionner parmi les méthodes décrites la minéralisation réductrice par le potassium associée au titrage iodométrique des ions S^2– comme la plus universelle et la plus sûre d'entre elles.Résumé Four methods of mineralization of organic compounds are recalled and compared with respect to determining sulfur in them; they are the oxyhydrogen combustion method, combustion in oxygen, in an empty tube, or in a flask of the Schöniger type, and the reductive mineralization in a sealed tube by potassium. They are combined with the titration methods for the SO₄ ^2– or S^2– ions. This study has enabled the authors to select the reductive method of mineralization by means of potassium followed by the iodometric titration of S^2– ions as the most general and most reliable among the various procedures.

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Zusammenfassung Die Verfasser berichten vergleichend über vier Methoden zur Mineralisierung organischer Verbindungen, deren Schwefelgehalt bestimmt werden soll, und zwar die Verbrennung in der Knallgasflamme, im Sauerstoffstrom im leeren Rohr, im Schönigerkolben und die reduktive Zerstörung mit Kalium im verschlossenen Röhrchen. Diese Methoden wurden mit der maßanalytischen Bestimmung des Sulfats bzw. Sulfids kombiniert. Daraus ergab sich, daß die Reduktion mit Kalium und die nachfolgende jodometrische Bestimmung des Sulfids am allgemeinsten anwendbar und am sichersten ist.

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A M. le ProfesseurJureek, D. Sc. à l'occasion de son 60ème anniversaire.     

Etude par effusiometrie de torsion des proprietes thermodynamiques en phase solide des laitons binaries (Cu,Zn)

The Gibbs thermodynamic variables which we have determined for thirteen brass alloys (Cu, Zn) are in good accord with the literature. The experimental conditions were as close as possible to those of sublimation in static vacuum. The application of the test of the third law in β-brass shows that our free enthalphy measurements are in agreement with the measurements of specific heat by Moser. The primary solid solution α copper of the binary brasses shows quasi-regular behaviour over the whole composition range. Our measurements seem to indicate the existence of a β′/(α + γ) eutectoïd at a temperature less than 100°C. The high degree of order of the γ phase is seen in the large negative values of excess entropy.     

Réduction du soufre par un sulfure et oxydation électrochimique d'un sulfure dans le diméthylsulfoxyde

Progressive addition of sodium sulphide to a sulphur solution in dimethylsulphoxide results in the formation of polysulphide ions, identical to those obtained by electrochemical reduction of sulphur in the same solvent. Conversely, electrochemical oxidation of sulphide leads to the formation of sulphur-sulphur bonds, and cyclooctasulphur S₈ is finally obtained.     

Etude Quantique du Pouvoir Rotatoire Naturel et de la Biréfringence Gyrotropique dans un Cristal

A quantum calculation of the optical activity and gyrotropic birefringence is used in a molecular crystal to deduce symmetry properties. A study of the variation of the components of these tensors, when a change of origin occurs, is used to account for the formula for the electric excitation proposed by Landau and Lifchitz. It is shown that the results obtained are valid in the case of crystals with nonlocalized electrons.     

Etude des petits cycles—XXXVII: Syntheses et proprietes spectrales du tetracyclopropylidene ([4]rotane) et des composes polycyclopropylspiraniques de la serie

The syntheses of [4]rotane and polycyclopropylspiranic derivatives are reported. One route involves the formation of cyclopropane rings from C₄-acyloins; a second route uses the dimerisation of bicyclopropylidene. Spectroscopic data do not point to any particular electronic interactions between cyclopropane rings in these compounds.     

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie I. Etude du pentafluorotellurate IV de lithium LiTeF5

Lithium pentafluorotellurate (IV) LiTeF₅ has been prepared by different methods:

• •slow evaporation of a 1/1 mixture of lithium fluoride and tellurium dioxide or tellurium tetrachloride in anhydrous hydrogen fluoride,
• •heating a 1/1 mixture of lithium fluoride and tellurium tetrafluoride. LiTeF₅ is orthorhombic

(a = 9,52 Å b = 9,12 Å c = 11, 60 Å)     

Preparation et etude des proprietes complexantes de polycondensats contenant des diazapolyoxamacrocycles dans la chaine principale

Some diazapolyoxamacrocycles have been polycondensed with different difunctional compounds to give polymers and gels. Their synthesis and their complexing properties towards alkali metals and calcium cations are reported.     

Etude du polymorphisme des orthophosphates de lithium et de zinc

A partial study of the Li₂O-P₂O₅ and ZnO-P₂O₅ binary diagrams led to establishment of the polymorphism of Li₃PO₄ and of Zn₃(PO₄)₂. Three crystalline forms were found for Li₃PO₄, differring from one another only on the cation distribution at the tetrahedral sites of the almost hexagonal compact arrangement of the anions. Li₃PO₄ differs from the isostructural compounds Li₃VO₄ and Li₃AsO₄ in its irreversible transformation at low temperature. Zn₃(PO₄)₂ is dimorphic, with a reversible transformation. It displays a slight non-stoichiometry through a ZnO deficiency.

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Zusammenfassung Aufgrund einer teilweisen Untersuchung der binären Diagramme von Li₂O-P₂O₅ und ZnO-P₂O₅ konnte der Polymorphismus der Verbindungen Li₃PO₄ und Zn₃(PO₄)₂ näher beschrieben werden. Für Lithiumorthophosphat wurden drei kristalline Formen gefunden. Sie unterscheiden sich voneinander nur in der Kationenverteilung in den tetraedrischen Gebilden der fast hexagonal kompakten Anordnung der Anionen. Li₃PO₄ unterscheidet sich von den isostrukturellen Verbindungen Li₃VO₄ und Li₃AsO₄ durch seinen irreversiblen Übergang bei niedriger Temperatur. Zinkorthophosphat ist dimorph und zeigt eine reversiblen Umwandlung. Es weist wegen ZnO-Mangels eine geringe Abweichung von der stöchiometrischen Zusammensetzung auf.

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Reaction du cyclopentadienylthallium avec les liaisons P-Cl : Preparation et proprietes des cyclopentadienylphosphines

The reaction of cyclopentadienylthallium with chlorophosphines yields cyclopentadienyl phosphines 1, 4, 6 and 8. Some of their derivatives (oxides, sulfides and methyl iodides) have been prepared. Their NMR shows that phosphorus is mainly bonded to the first position of the cyclopentadiene nucleus. Starting with diphenyl (1,3-cyclopentadienyl) phosphine sulfide 2 we have also studied the Diels-Alder reactivity, the bromination and the metalation of the cyclopentadienyl group. This last reaction allows the synthesis of some new phosphorus substituted fulvenes 16, 17 and 18. We have also prepared the new cyclopentadienylid 19 from the dimeric methyliodide 11.     

Etude dans la serie des organogallylazoles I. Synthese et structure

A series of N-dimethylgallylazoles have been prepared by treatment of azoles (imidazoles, benzimidazoles, pyrazoles, s-triazole and benzotriazole) with trimethylgallium.The structure (monomeric, dimeric, polymeric) of the resulting compounds depends on the position of the nitrogen atoms in the azole moiety. In the case of pyrazolyl derivatives, the NMR study in acetone or acetonitrile shows the existence of an equilibrium between the monomeric and dimeric forms.     

Polythioamides aliphatiques—IV. Etude des proprietes thermiques en correlation avec la structure du motif

We have already studied some physicochemical properties of aliphatic polythioamides and the contribution of the thioamide group to some of them. We now report the thermal behaviour of these condensation polymers and determine the functional group participation to molar melt and glass transition functions. These results allow us to compare polyamides, polyesters and polythioamides. We have also studied some polythioamides containing ether-linkages. Thermal degradation has been studied by thermogravimetric analysis.     

Equilibre lactime-lactame des hydroxy-pyridines et des hydroxy-pyrimidines (uraciles) en milieu apolaire : Etude infra-rouge

In contrast to what observed with mono hydroxy-pyridines and -pyrimidines the lactim-lactam equilibrium of uracils is not found to be markedly influenced by solvent polarity.     

Application des echangeurs d'ions et des filtres inorganiques au dosage du selenium et du tellure dans le cuivre

Selenium and tellurium isotopes formed by thermal neutron irradiation have longer half-life than the copper isotope. The non-destructive analysis fails even after the complete decay of copper because of the other radioisotope present. The radioisotopes were separated by ion exchange chromatography on Dowex 1X8 (200–400 mesh) and “Pertitanic” resins in order to obtain a highly sensitive analysis. The limits of detection of 5 ppb for tellurium and 0.5 ppb for selenium were obtained.