Les dithiaphospho(III)lanes-1,3,2, noveaux precurseurs de derives du phosphore penta- et dicoordine

The synthesis of new spirodithiaphospholans is described. Lability of these compounds allows to obtain by an orginally way dicoordinated phosphorus derivatives.     

Isomerisation de l'ion moleculaire de derives substitues polycycliques du benzodioxinne-1,4

Three fragmentations (loss of phenyl, hydrogen and a RCO radical) of benzocyclobutene derivatives of differently substituted 1,4-benzodioxin were studied. In some cases these molecules, deuteriated in a specific position, revealed the existence of several isomers of the molecular ion.     

Complexes organometalliques conducteurs derives de metallocenes et du tetracyanoquinodimethane

Organometallic conductors have been obtained from the reaction of substituted ferrocenic,arene-CpFe^II and bis-areneiron(II) salts with TCNQ⁰ and/or TCNQ⁻. The ionic complex of the bis(trimethylbenzene)iron(II) cation and TCNQ⁻ shows a reverse electron transfer from TCNQ⁻ to the cation, after thermal activation, yielding a semi-conductor species.     

Analyse du comportement thermique d'une serie de derives camphoriques

Thermal analysis of a series of camphor derivatives has been studied by differential scanning calorimetry. Different behaviors with the appearance of glassy, amorphous, crystalline, polymorphous compounds and tautomeric mixture were detected.These results have been confirmed by infrared spectroscopy and by X-ray diffraction.

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Zusammenfassung Mittels DSC wurde eine Reihe von Kampferderivaten untersucht. Dabei konnte verschiedenes Verhalten mit dem Auftreten von glasartigen, amorphen, kristallinen und polymorphen Verbindungen und tautomeren Gemischen beobachtet werden.Die erhaltenen Resultate wurden durch IR-Spektroskopie und Röntgendiffraktion bestätigt.

     

Structure electronique de derives sulfures—II : Spectres electroniques du cation dithiolylium-1,2 et de ses derives de monosubstitution

The electronic spectra of the 1,2-dithiolium cation and of four monosubstituted derivatives have been studied by CNDO/S method, extended to the third period with inclusion of 3d orbitals. Calculated effects of a substitution by a methyl or a phenyl group are in good agreement with experimental data.     

Polarisabilite des molecules polyatomiques: Evaluation a partir du modele de Silberstein

The Silberstein models for computing the main polarizabilities of polyatomic molecules are discussed. They apparently constitute the simplest sufficient approach to account for experimental data and assimilate the atoms' electronic surroundings to mutually interacting conducting polarizable spheres. If it is supposed the spheres are centered on the nuclei of the corresponding atoms, interesting but poor results are obtained. More complicated calculations, modifying the center's localisation according to physicochemical evidences, show that a very good estimation of average polarizabilities and anisotropies can be achieved, assuming that in a given molecule the spheres associated to two bounding atoms are tangential and that their polarizabilities are the third power of their proper radius. This “geometrically improved” Silberstein model is compared to the quantum mechanical and “optic valence” models as well as to the other lately used Silberstein models: we put forward its interest and possibilities in relating structure and reactivity, or structure and stability.     

Controle de la qualite des materiaux colles a partir du mode vertical

The paper presents measurements by transmission of an ultrasonic wave on glued sheet immersed in water. The experiments was performed by varying the incidence angle. The study has been undertaken on structures consisting of two identical plates either of aluminium or of steel glued by an epoxy resin. The obtained results reveal the existence of a vertical mode which allows to control the quality of the assembly.     

Cycloaddition de derives organiques insatures du silicium,du germanium et de l'etain

The effect of atom M and of its substituents Σ upon dienophilic activity of Σ₃MCHCH₂ and Σ₃MCCH (MC, Si, Ge, Sn) is interpreted in terms of a perturbation scheme involving the lowest unoccupied orbital of the dienophile and the highest occupied orbital of the diene. This scheme also explains the stereochemistry of Diels-Alder reactions and the regioselectivity of the ene reaction with organometallic compounds.     

Transacetalisation de triols a partir du dimethoxymethane. Selectivite et applications synthetiques

The LiBr assisted/acid catalyzed transacetalation of triols from DMM affords a highly selective method for the synthesis of hydroxy compounds bearing a dioxane ring. These compounds might further conveniently be alkylated by phase transfer catalyzis.     

Sels de cobalticinium : II. Proprietes spectroscopiques et polarographiques de quelques derives du cobalticinium

The spectroscopic and polarographic behaviour of some cobalticinium derivatives have been studied. Due to their positive charge these compounds exhibit particular characteristics in comparison with ferrocene derivatives. They give two successive cathodic waves on a dropping mercury electrode. The first corresponds to the formation of cobaltocene whereas the second represents the reduction of the latter compound to give cobaltocene anion.     

Analyse conformationnelle de derives du thiophane,des sulfoxydes et sulfones correspondants

The conformations of biotin 1, cis 3,4-isopropylidenedioxythiophane 2, its 2,5-methylated homologs, 3, 4 and 5 and those of the corresponding sulfoxides and sulfones have been studied by NMR. Coupling constants, temperature and solvent effects show that all these compounds exist in a highly preferred conformation, the thiophane being in the envelope form with the sulphur atom out of the plane. In series 1, 2, 3 and 5 the arrangement is of the “boat-chair” type, in series 4 of the “crown” type, the sulphur being respectively cis and trans with respect to the other ring.