Polymerisation stereoelective en phase homogene du methyl-2 thiiranne amorcee par des semences optiquement actives

Optically active seeds have been prepared by polymerization of the laevorotatory enantiomer of 2-methylthiirane with cadmium thiolate; they have been used for the polymerization of the racemic monomer, which is stereoelective. These results are explained by the formation of two types of chiral sites in unequal numbers, each type of site choosing only one enantiomer.     

Polymerisation et copolymerisation anioniques du methyl-2 ethyl-2 thiiranne

The anionic polymerization of a novel episulphide (2-methyl-2-ethyl thiirane) has given living polymers. Random and block copolymers could be prepared, and measured and calculated molecular weights are in good agreement. Homopolymers prepared with anionic initiators are semi-crystalline (T_m ≈ 110°C) and soluble. Electron diffraction results suggest however that their crystalline order is imperfect.     

Etude de la fragmentation par impact électronique de dérivés du benzothiazole

Study of Electron-Impact Fragmentation of Benzothiazole Derivatives The mass spectra of eighteen substituted benzothiazoles are reported and discussed. All these compounds are thermodynamically stable and give an intense molecular ion, which undergoes different types of fragmentation depending on the nature of the substituent which is rarely eliminated directly. β-Cleavage with respect to the heterocyclic double bond is often observed. Specific ²H-, ¹³C-, ¹⁵N- and ³⁴S-labelling have been used in order to confirm the fragmentation patterns.     

Polymerisation en phase homogene du methyl-2 thiiranne amorcee par les thiolates de cadmium et de zinc. Influence des interactions monomere-metal sur la stereoregularite des polymeres

The stereoregularity of polymethylthiiranes initiated by zinc and cadmium thiolates depends upon the nature of the metal, temperature, solvent and the monomer/initiator concentrations ratio. Complexation of the metal with monomer has been studied by (¹³C) and (¹H) NMR on a model molecule, dimethylcadmium. Cryoscopic measurements made on a soluble cadmium thiolate have shown the presence of aggregates. The relationship between these observations and polymer stereoregularity is discussed.     

Hexacoordination du phosphore par complexation intramoleculaire

An equilibrium occurs between penta- and hexacoordinated phosphorus when a basic function is located at the end of a branched ligand on pentacoordinate phosphorus. Generally the hexacoordinated form are thermodynamic stable species in solution at room temperature. Eight hexacoordinated compounds (9–11, 13, 14, 18–20, Tables 2 and 3) have been isolated. In few cases, in solution, the pentacoordinated form (15–17, 24) can be observed. The parameters from these equilibria are discussed.     

Analyse systematique du cerium par activation neutronioue

Résumé L'irradiation neutronique produit à partir du cérium une radioactivité importante, aussi des séparations chimiques sont indispensables. Nous avons mis au point une méthode d'échange d'ions en milieu tartrique, et nous dosons ainsi une vingtaine d'éléments. L'emploi d'un détecteur à jonction Ge−Li permet de simplifier notablement ces séparations.     

Etablissement du diagramme binaire hydroxy.2 naphtalene-chloro.2 naphtalene par differentes analyses thermiques

The phase diagram of the 2-chloronaphthalene-2-hydroxynaphthalene binary system has been established in three thermal investigations (calorimetric, crystallographic and optical methods). This diagram is fairly complicated. The main feature is the presence of three invariants: a eutectoid atT _e =309 K, a peritectic atT _p =333 K and a metatectic atT _m =364 K.     

Etude structurale du polypentadiene-1,3 par spectrometrie de RMN du 13C

The structure of stereoregular polymers of 1,3-pentadiene was determined by ¹³C-NMR spectroscopy at 22.6 MHz. Not only was it possible to distinguish between cis-1,4 and trans-1,4 but also between isotactic and syndiotactic cis-1,4 structures. Triad effects were detected in the trans-1,2 syndiotactic polypentadiene; 1,4–1,2 as well as 1,4–4,1 linkages were observed.     

Dosage du molybdene et du tungstene dans les plantes par activation neutronique

A method for the determination of molybdenum and tungsten in plant material using neutron activation analysis was developed. The considered reaction are: $$\begin{gathered} {}^{98}Mo(n,\gamma )^{99} Mo \hfill \\ {}^{186}W(n,\gamma )^{187} W \hfill \\ \end{gathered} $$ The separation for tungsten and molybdenum was carried out using anion exchange separation (Dowex 1×10; 200–400 mesh). Irradiation was carried out in a swimming pool reactor at a thermal flux of about 1–2×10¹³ n·cm^?2·sec^?1 for 15 hours. The samples and standard were allowed to cool for 5–6 hours before chemical processing. the high concentration of calcium in plants (up to 40 mg/g dry material), the use of hydrofluoric acid for a good absorption and quantitative recovery of tungsten led us to dissolve the samples with Ht?H₂O₂ mixtures containing boric acid to prevent the precipitation of fluorides.     

An unusual oxidation/metallation of 2-vinylpyridine

The vinyl group in rans-[PtBr₄{2-(CH₂CH)py}(PEt₃)] undergoes oxidation/metallation metallation ind amp solvents to give [$\text{PtBr}{}_3\text{[2-(C}$H₂·CO)py}(PEt₃)]; the mechanisms of this reaction is discussed. Attempts to prepare this unusual complex from platinum(II) and platinum(IV) complexes containing 2-acetylpyridine were unsuccessful.     

Activation anionique du phosphite de diethyle par le fluorure de potassium depose sur alumine,synthese de phosphonates fonctionalises

Dry reactions of diethylphosphite on KF-Al₂O₃ with different. electrophiles conduct to the synthesis of functionalized phosphonates.     

Etude par spectroscopie raman du chlorhydrate de cocaine

Raman spectra of cocaine hydrochloride in the polycrystalline state and in saturated aqueous solutions have been recorded at room temperature from 0 to 4000 cm(-1) and at 9 K from 0 to 200 cm(-1) (only for the polycrystalline state). They show that cocaine can be characterized by the following proposed assignments. For the tropane nucleus the frequencies 851 and 786 cm(-1) (piperidine) and 896, 870 cm(-1) (pyrrolidine); these frequencies are assigned to ring carbon stretching vibrations V(C-C) Bands for the ester functional groups can be observed at 1713 cm(-1) (v(CO)) and 1203 cm(-1) (v((C-O-O)). The benzene nucleus is also important in characterization of cocaine hydrochloride because of its bands at 616, 990, 1000, 1026 and 1596 cm(-1). Special reference is made first to the work in the low-frequency range at room temperature and 9 K and secondly to the polarization studies of saturated aqueous solutions in the range 700-1726 cm(-1). The results constitute a pool of analytical characteristics which can be used for toxicological investigations, and also show all the possibilities of Raman spectroscopy in this field.