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.     

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.     

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.     

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.     

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.     

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.

     

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.     

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.     

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

     

Synthese de chlorofluorovinylsilanes et de quelques derives

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

Spectres de vibration et conformations du propionate et de l'isobutyrate de méthyle

Infrared and Raman spectra (3600–3620cm^?1) of methyl propionate CH₃CH₂-COOCH₃, CH₃CH₂COOCD₃ and methyl isobutyrate (CH₃)₂CHCOOCH₃, (CH₃)₂CHCOOCD₃, in liquid and crystalline states, have been recorded. Rotational isomerism, by rotation around the C-C bond α to the carbonyl group, is detected and the energy difference between the conformers is 1.1 ±0.3 kcal mol^?1 for methyl propionate and 0.5 ±0.1 kcal mol^?1 for methyl isobutyrate. Vibrational assignments in terms of group frequencies are proposed for each conformer, only the more stable being present in the crystal.     

Reactivite des carbenes et carbenoides issus de diazomalonates mixtes de methyle et de benzyles substitues. Synthese de composes cycloheptatrieniques

The title diazomalonates, when treated with copper powder in octane, yield lactones of 1-hydroxymethyl 7-carboxy cycloheptatrienes. The yields of cyclisation product from such diazoesters may be increased either by a gem-dimethyl grouping or by an electron rich mesomeric group attached to the benzene ring. The methoxy-cycloheptatriene compound 3d is hydrolysed to the spirodienone 8. The carbenes formed from the diazomalonates 2a and b by photolysis or thermolysis undergo Wolff rearrangement and yield insertion products into CH bonds of solvent.     

Les orthoarseniates de sodium et de terre rare

Sodium rare-earth arsenates Na₃Ln(AsO₄)₂ may occur in five allotropic varieties. Their structural evolution has been studied as a function of rare-earth size, temperature, and pressure. The structures are isotypic with those of homologous phosphates and vanadates previously described.     

Conformation et Spectrometrie de RMN

Examination of PMR spectra of the four 3-dimethylamino-trans-2-decalols and the corresponding quaternary ammonium iodides allows the suggestion to be made that the ordinary double chair conformation usually admitted for trans-decalin is disurbed in the above compounds, especially when the amino and hydroxy groups are (a, e); truer conformations would, in fact, be better represented as ‘flattened chair’ in the case of the dimethylamino compound and ‘twist chair’ in the case of the quaternary ammonium salt.     

Spectres de masse des anomeres pyranniques et furanniques de la thymidine,de leurs acetates et des bromohydrines correspondantes

The mass spectra of furanic and pyranic anomers of thymidine as well as those of acetates and bromohydrines of these four molecules are studied and compared. The stability of molecular ions is correlated with the chemical stability of these copmpounds. Molecular ions of β forms are more stable than those of α forms. The instability of the bromohydrines molecular ions is such that they are only observed for β furanic anomers. The eliminmation of the ·CH₂OH or ·CH₂OAc radical is noterd only for the furanic compound. The cleavage of CH₂O in the β furanic substances is correleated with the steric vicinity of the base and the sugar 5′ hydroxide. The ions[BH ? Ch?CH₂]⁺ and those resulting from this rearrangement and cleavage of sugar moiety, are enhanced in the case of furanic forms. After rupture of the N-glycosidic bon, the [B + H]⁺˙ and [B + 2H]⁺ ions resulting from the base and [S]⁺ are related to the molecular stereochemistry. The eliminationof one water molecular(or acetic acid) is easier in a sixs membered ring(pyranic). The concerted elimination of two water molecules (or acetic acid), more important in the furanic form, enables us to establish a ring cleavage mechanism which gives an ion with a conjugated aliphaticf structure; the pyranic form gives an aromatic cyclic ion in two steps.