Etude theorique des ruptures thermique et photochimique de la cyclopropanone

The primary processes involved in cyclopropanone reactivity have been investigated using a SCF-CI abinitio method. The C₂C₃ bond rupture has been found to be thermally favoured and the resulting oxyallyl could have a significant lifetime. By contrast, upon photonic excitation, C₁C₂ cleavage easily occurs, but does lead to stable intermediate. This constitutes the first step of CO extrusion. The results are discussed using simple MO and valence-state considerations, and compared with those of related compounds.     

Photoreduction de la benzophenone par des phtalimidines et des dihydro isoquinolones: Etude chimique par RMN PNIC

Benzophenone is photoreduced by pthalimidines and dihydro isoquinolones. The hydrogen atom α to the nitrogen atom is abstracted and radical coupling leads to adducts. CIDNP studies of these adducts show inversion of polarisation for the adduct on the N-alkyl chain when the nitrogen is bound to a benzylic methylene. This inversion is explained by considering that the radical on the N-alkyl chain derives from the radical on the ring.     

Etude par RMN et uv de la protonation des enamines cationiques

Enamines, substituted on β carbon by a pyrylium cation have a mesomeric structure close to pyrannylidene—immonium. Conjugation between pyrylium nucleus and the double bond influences the relative stability of the C- and N- protonated compounds. This conjugation stabilizes the N-protonated compounds which are in equilibrium with the less conjugated C-protonated. In the same conditions, aliphatic enamines do not comprise such an equilibrium. The positions of the studied equilibria depend partly on the substituents of the β carbon and of the protonating reactant.     

Etude des copolymeres (ethylene-hexene-1) par resonance magnetique nucleaire du proton et du carbone 13

Ethylene 1-hexene copolymers obtained by catalytic polymerization have been examined by ¹H and ¹³C NMR. Copolymer compositions have been determined by ¹H NMR and i.r. and the sequence distributions for 1-hexene by ¹³C NMR. Variations of the copolymer microstructure have been related to the experimental conditions for copolymerization.     

Etude par polarisation nucleaire induite chimiquement de la reaction photochimique de l'anthracene avec des tetrahalogenomethanes

The photoreaction of anthracene with CCl₄, CCl₃Br or CBr₄ was studied by CIDNP. The primary products of the reaction (polyhalogeno 9,10-dihydro anthracenes) are thermally unstable, but evidence was shown for their existence. The initiating radical pair of this reaction is: $\text{9-chloro 10-anthryl/trichloromethyl}$^S. This study was extended to 9-methyl and 9,10-dimethyl anthracenes.     

Etude structurale par spectrometrie infrarouge et raman des composes de coordination: bis(pyridine)- trichloro aluminium(III) et bis(pyridine)tribromo aluminium(III)

The compounds AlX₃-2Py (X = Cl or Br, Py = C₅H₅N or C₅D₅N) have been prepared by using a method based on an exchange of organic ligands. The infrared and Raman spectra, which have been recorded between 50 and 4000 cm^?1, give strong evidence for the existence of the anion AlCl₄^? (or AlBr₄^?) and show that the cation is AlX₂(Py)⁺₄. The comparison of the spectra with those of the compound NiX₂(Py)₄., and of the cations trans-AlX₂(THF)₄⁺ and cis-AlX₂(bipy)₂⁺ indicates that the cation AlX₂(Py)₄⁺ has the helical configuration (helical trans-octahedron) and allows the assignment of the vibrations.     

Etude du comportement thermique de la poly(pivalolactone) par diffraction des rayons-x aux petits angles et par calorimetrie dynamique

Poly(α,α-dimethyl-β-propiolactone) (PPL), known as poly(pivalolactone), has been studied by differential scanning calorimetry (DSC) and small-angle X-ray diffraction (SAXR). DSC measurements indicate the presence of two melting endotherms. Peak 1 and Peak 2, the latter at lower temperatures. Peak 1 is relatively unaffected by the crystallization temperature and its relative intensity decreases with heating rate. Peak 2 is greatly influenced by the crystallization temperature of the sample and its relative intensity increases with heating rate. Peak 2 is associated with the true melting of the PPL samples and Peak 1 with a recrystallization process during the heating cycle. SAXR long periods increase with crystallization and annealing temperatures. Similar increases in density, in melting temperature, in lamella thickness, and in degree of crystallinity have been observed. These results lead to a thermodynamic melting temperature of 268 ± 3 for PPL, and to interfacial free energies of, respectively. 13 × 10^?7 J cm^?2 and (43 ± 4) × 10^?7 J cm^?2 for the lateral surface and the fold surface of the PPL crystal.     

Etude des métallohexammines. II. Etude par thermogravimétrie et spectrographie d'absorption infra-rouge des nickelohexammines

Résumé L'analyse thermogravimétrique et chimique des sels de nickelohexammine fait ressortir le caractère relativement instable de plusieurs d'entre eux. Nous avons tenté de préciser les meilleures conditions de leur préparation et de leur conservation, ce qui nous a permis d'enregistrer leurs spectres d'absorption infra-rouge à l'état de pureté et d'attribuer, en particulier, à la vibration de déformation du squelette octaédrique le nombre d'onde 216 cm^–1.

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Summary The thermogravimetric and chemical analysis of salts of nickelohexammine revealed the relatively unstable character of several of these compounds. An attempt has been made to learn precisely the best conditions for their preparation and conservation so that it has been possible to record their infra red absorption spectra in a pure state and to attribute in particular the wave 216 cm^–1 to the deformation vibration of the octahedral skeleton.

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Zusammenfassung Die thermogravimetrische und chemische Analyse zeigt die relative Unbeständigkeit mehrerer Hexamminnickelate. Wir versuchten, die besten Bedingungen für deren Herstellung und Aufbewahrung festzustellen und ermittelten hierzu deren Absorptionsspektren im Infrarot in reinem Zustand. Insbesondre ergab sich für die Deformationsschwingung des Oktaederskeletts die Wellenlänge 216 cm^–1.

     

Etude structurale de l'hydruro-oxyde LaHO par diffraction des rayons X et par diffraction des neutrons

The hydride-oxide LaHO crystallizes with a fluorite superstructure. The unit cell is tetragonal, space group $\text{P4}\text{nmm}\text{, a = 8,074(1)}$ Å, c = 5,739(1) Å, and Z = 8. The structure has been determined by two complementary techniques: X-ray and neutron diffraction. The La³⁺ ions are situated in the center of cubes at the corners of which four O^2? and four H^? are placed, there exist three different types of environment according to the distribution of the two anion species (the anions of the same type form either a tetrahedron or occupy a face or a diagonal plane of the cube). The LaO(H) distances observed are discussed by taking into account the relationship which exists between bond strength and bond length. The average value of d 〈OH〉 is 2,85 Å, which is rather unusual. It confirms that we are indeed dealing with a hydride-oxide simultaneously associating the O^2? and H^? ions in a ternary combination. Through energy considerations (electrostatic site potential and lattice potential), the structural arrangement of LaHO is compared to that encountered in the case of the homologous lanthanum oxifluorides.     

Etude par spectroscopie vibrationnelle des niobates de sodium et d'argent de structure perovskite

Infrared and Raman spectra of the niobates NaNbO₃ and AgNbO₃ of perovskite structure are analysed. An assignment of the frequencies is proposed. The influence of the antiferroelectric direction upon the NbO bonds is shown, as the influence of the A cation upon the AO and NbO bonds.     

Etude theorique (cndo/s) des etats excites et des transitions electroniques de 2h-chromenes representant la partie responsable de l'ouverture photochimique de spiropyrannes

The excited states and electronic transitions of some 2H-chromenes (considered responsible for photochemical opening of photochromic spiropyrans) have been studied. The relative positions of nπ^* and ππ^* singlet and triplet energy levels of these compounds allow a satisfactory interpretation of their optical properties. Also highly localized electronic charge transfers are demonstrated in the case of 2H-chromenes substituted by a nitro group.     

Greffage de polymere en surface des silices par une methode photochimique

Polymer fixed on a silica surface shows interesting properties of hydrocarbon retention. A new method of preparation of such materials is proposed. It consists of the activation of the silica by u.v. irradiation and subsequent reaction with macroradicals generated by photochemistry on the polymers. The influence of the reaction parameters, such as illumination time, polymer content of the system and silica-polymer weight ratio, have been considered.     

Etude par RMN d'une Serie d'Indoanilines et d'Indophenols

We report the results of a study of 25 indoanilines and indophenols by NMR. These measurements yield the stable tautomers and the position of the different substituents on the benzene ring.     

Etude Conformationnelle d'Aldehydes a-Thiopheniques et Furanniques par RMN

We have studied the preferential conformations of α-formyl thiophenes and furans by NMR examining the stereospecific coupling values. We observed changes in the aldehydic conformation with respect to the nature of the ortho substituents. The preferential conformation of these heterocyclic aldehydes is interpreted by the existence of three interaction factors.     

Etude par desorption thermique programmee des proprietes des argiles modifiees

The present work tries to emphasize the effect of acid/basis properties of montmorillonite type clays by ion exchange with cations of different natures. The acidity and basicity measuring was made by thermo programated desorption (TPD)1,2, using ammonia like basis agent and carbon dioxide like acid agent. With TPD method we can determine acid/basis proprietes by measuring of the quantity of the ammonia and carbon dioxide termodesorbed. Clays are crystalline aluminosilicates, similar with the zeolyts, who presents the property of ion exchanging. That propriety can be applicated for pollutants cations from aquatic solutions. Ion exchanging propriety depends of a lot of factors: the cation nature, the valence and the ionic ray of the cation present in the impregnated solution. That's an advantage for depollution process of heavy metals by fixing of these metals by montmorillonite structure. By using TPD metod we can obtaine a caracteristic diagram. This revised version was published online in July 2006 with corrections to the Cover Date.     

Etude de quelques complexes du zirconium(IV) et du hafnium(IV) au moyen de l'extraction des isopropyltropolonates par le chloroforme

The stability constants for zirconium and hafnium, chloride, thiocyanate, sulfate, oxalate and phosphate complexes have been investigated by solvent extraction with β isopropyltropolone. The influence of pH has in general been taken into account.     

Etude des systemes donnes par l'hexafluorure d'uranium avec les fluorures de cesium et de nitrosyle

This study is devoted to two typical systems: solid fluoride (CsF), UF₆ and volatile fluoride (NOF), UF₆. The differences in the dissociation pressures of CsUF₇ and Cs₂UF₈ and of NOUF₇ and (NO)₂UF₈ along with spectral observations make it possible to prepare these compounds in a pure form. Vibrational spectroscopic studies and ¹⁹F chemical shift measurements allow one to propose symmetries corresponding to point group D_5h and O_h for the heptafluoroanions and the octafluoroanions respectively. Crystal forces are likely responsible for the observed slight lowering in symmetry form the above idealized structure. At low temperature, a change of structure is observed for NOUF₇, the symmetry for the heptafluoroanion becoming lower or equal to the symmetry corresponding to the C_2v. group.     

Etude par resonance quadripolaire des noyaux 63-Cu et 75-As de complexes tetrameres de la triethylarsine avec des halogenures de cuivre(I)

63-Cu and 75-As quadrupole resonance results have been obtained for the tetrameric triethylarsine copper(I) halides (Cl, Br and I). Unusual behaviours of the temperature dependence of the 63-Cu and 75-As quadrupole resonance lines have been observed simultaneously. Between 77 and 300 K, the chlorine derivative undergoes two structural phase changes at 93 and 173 K, while phase transformations occur at 152 and 86 K respectively for the bromine and iodine derivatives.     

Etude Electrochimique et Differenciation de Derives des Dibenzodiazepines et des Dibenzothiazepines

Abstract

New psychotropic drugs like Clozapin and Clothiapin were separated and differenciated using D.C., A.C. and D.P.P. polarographic techniques. The mechanism of the electrode reaction is elucidated.