Echange de ligands mono- et penta-haptocyclopentadienyles en serie du titanocene

The action of cyclopentadienyl anions on the compounds CP₂TiA₂ is described (Cp  substituted or non-substituted cyclopentadienyl ring, A  Cl, n¹Cp or aryloxy group). In all cases the redistribution of cyclopentadienyl ligands, either by direct substitution at the n¹ or n⁵ ligands, or by intermolecular exchange of n¹ ligands, was observed.     

Hydrogenation asymetrique de precurseurs d'aminoacides a l'aide de mono- et diphosphines derivees de sucres

Mono- and di-phosphines derived from sugars are synthesized and used as ligands in asymmetric catalysis. In the presence of a base (triethylamine, KOH…) the cationic complex [Rh(COD)dioxop]⁺ClO₄^?, catalyzes reduction of α-amino acid precursors with high optical yields (78–86%). The influence of the base is discussed.     

Etudes electrique et Raman de borotungstates et de boromolybdates de lithium vitreux

Conductivity studies of glasses obtained from the B₂O₃Li₂OLi₂MoO₄ and B₂O₃Li₂OLi₂WO₄ systems have been carried out. The presence of the transition element in tetrahedral coordination and with two different oxidation states is discussed. A Raman spectroscopy study shows that the MoO₄ or WO₄ tetrahedra are slightly compressed by the network forming lattice.     

Spectres de vibration et champ de force de l'antimoniate et de l'arseniate de calcium CaSb2O6 et CaAs2O6

The i.r. and Raman spectra of the antimonate CaSb₂O₆ and arsenate CaAs₂O₆ belonging to the “PbSb₂O₆ type” structure are studied. A normal coordinate calculation permitted us to calculate and to compare their relative force fields. A comparison with results obtained for other antimony and arsenic oxides is presented.     

Nombre de transport et conductivite cationique dans les oxydes de calcium et de strontium

The cationic transference numbers have been determined for alkaline earth oxides using sample linear expansion measurements coupled with coulometric titration.Single crystal CaO has been studied in the temperature range 1200–1450°C, under oxygen partial pressures varying from 1 to 10^?5 atm. Under air, t_Ca at 1300°C is close to 0.02.Polycrystalline samples of SrO, under air, were tested from 1100°C to 1350°C, and showed a t_Sr value of 0.012 at 1300°C.The total conductivity of CaO was measured to obtain a value for the cationic conductivity. This value is compared with the data obtained from the self diffusion coefficient of Ca in CaO.     

Preparation et oxydation de dialkylgermyl- et stannyltetraphenylporphyrines

Some new organo-germanium and -tin tetraphenylporphyrins were obtained. Their behaviour in solution shows that they are readily oxidized into peroxides by light and oxygen. Some of these derivatives must be prepared under especially mild experimental conditions, indicating a surprising unstability for metal IVB — carbon bonds.     

Polymerisation et copolymerisation de monophenyl et de diphenylethylenes amorcees par des graphitures de metaux alcalins

The bulk polymerization at -24° of α-methylstyrene initiated by the alkali metals and the graphitides LiC₁₂, KC₂₄ and KC₃₆ has been studied. The tacticities of polymers have been measured by [¹H] NMR. The alkali metals give polymers having the same tacticity and the propagation of the stereoconfiguration is bernouillian; LiC₁₂ yields more racemic diads while KC₂₄ and KC₃₆ yield more meso diads and show a penultimate effect. By measuring the growing of the thickness of KC₂₄ flakes, it appears that the more sterically hindered a monomer the more slowly it penetrates into the graphitide. The copolymerizations at 25° of styrene with 1-1 diphenylethylene or 1–2 diphenylethylene (trans stilbene) (comonomer ratio 1/1) initiated by KC₂₄ in tetrahydrofuran (THF), xylene (XL), decahydronaphthalene (decalin DL) and cyclohexane (CH) have been studied. The amount of styrene units in the copolymers depends on the nature of the solvent: it increases as the interaction solvent-graphitide decreases. All the results support the view that the polymerization proceeds between the graphite layers.     

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.     

Conversion des furfurylalkyl et arylcetones en derives de l'isocoumarine et de l'isoquinoleine

Cycoladducts of furfurylakyl and arylketones with methyl acetylendicarboxylate undergo acid-catalysed rearrangement in high yield to 6-hydroxyphthalates bearing an acetonly or a phenacyl group in the 3-positionl. These phthalic compounds are useful intermediates for the synthesis of polyfunctional derivatives in the isocoumarin and the isoquinoline series.     

Etude de la Fragmentation du Benzisothiazole et de Quelques Benzoselenazoles et Benzisoselenazoles

The mass spectra of benzisothiazole, three benzoselenazoles and three benzisoselenazoles have been determined and compared with those of the corresponding benzothiazoles. The elimination of CS known to occur from these latter substances is confirmed in the case of benzisothiazole, but a different mechanism is proposed. The fragmentation of the selenium analogues led to ions of the same type as the benzothiazoles and benzisothiazole, through extrusion of molecules of the type CN—R, but loss of the heteroatom was not accompanied by loss of carbon. Furthermore, the isoselenazole structure seems to be more sensitive to electronolysis than its isomer. All six selenium heterocyclics investigated gave rise to two ions (130 and 132) resulting from a recombination of various fragments, suggesting that this is a characteristic feature of the electron-impact fragmentation of compounds of this type.     

Preparation et caracterisation de reticulats-modele de polydimethylsiloxanes

Three-dimensional crosslinked gels of polydimethylsiloxanes with well-defined pore-size have been obtained by reaction of the Si-H endgroups with a polyfunctional allyloxy compound. The swelling behaviour of such gels has been investigated. The variation of the swelling degree at equilibrium with the structure of the gel was found in good agreement with the theoretical expectation.     

Effets de substituants et conformation de stilbenes

Simultaneous study of para nitrostilbenes by X-ray diffraction and ¹³C nuclear magnetic resonance shows a quantitative relationship between the effect of a para nitro substituent on the chemical shift of ethylenic carbon not adjacent to the substituted phenyl ring and the dihedral angle between this phenyl ring and the central double bond. The alternative introduction of substituents in each phenyl ring discloses at the position of carbon β a certain π-polarization which extends to the double bond and to an unsaturated group carried by carbon α.     

Analyse Thermique de la Cellulose et de Quelques Derives Etherifies et Esterifies

The cellulose and its derivatives are used more and more, especially like excipients in pharmaceutical industry.The identification of cellulose and some of its derivatives: cellulose acetophthalate, hydroxy-propylmethylcellulose acetosuccinate, sodium carboxymethylcellulose, hydroxysthylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, methylcellulose, hydroxypropylmethyl-cellulose phthalate, is possible by thermal analysis (simultaneous DTA-TG). For that reason, one consider the temperature of the DTA maximum peaks and the DTG minimum peaks. This identification is easy when these products are a majority in pharmaceutical specialities.

     

Synthese de chlorofluorovinylsilanes et de quelques derives

Several chlorofluoroolefins were prepared from 1,1-dichloro-2,2-difluoroethylene via chlorofluorovinylsilanes.     

Etude analytique et dosage de micro- et submicro-traces de manganese par polarographie inverse

A method is proposed for the determination of manganese(II) by anodic stripping polarography. A systematic study was made of the various factors affecting the course of pre-electrolysis as well as the anodic stripping. A procedure is given for the determination of i ng of manganese with a precision of ± 12.7%. The selectivity of the method was studied in the presence of 14 cations ; hydrogen ions interfere at pH <5, Co²⁺ interferes at concentrations equal to that of Mn²⁺, and Mo⁷⁺ and V⁵⁺ at concentrations ?50 times that of Mn²⁺. The other ions studied do not interfere at concentrations 100–1000 times higher. An application to pharmaceutical analysis is described.     

Elaboration,caracterisation et stabilite thermique des arseniures de germanium et de silicium

SiAs has been prepared by chemical transport using silicon, arsenic and iodine, and GeAs by reaction of gaseous arsenic on germanium in a temperature gradient.Chemical analysis and X-ray diffraction have been performed to characterize these compounds and especially to distinguish GeAs from GeAs₂ which also appears during the GeAs preparation. GeAs and SiAs have been shown to be quite stable up to 500°C and 700°C, respectively. The evaporation of GeAs becomes important above 650°C according to the three equilibria

In the same way the evaporation of SiAs becomes important above 900°C and can be written