Synthese et reactivite de silanes propargyliques ω-Fonctionnels : preparation de vinylidene-3 oxolannes,oxannes, oxepannes et oxocannes

The ω-silyloxypropargyltrimethylsilanes regiospecifically react with aliphatic and aromatic aldehydes to lead to vinylidene oxygen-containing heterocycles,such as 3-vinylidene oxolanes, oxanes, oxepanes and oxocanes.     

Étude Théorique de la Conductivité, Photoconductivité et de l'absorption Photoinduite de BaTiO3:Fe et KNbO3:Fe

Calculation of dark conductivity, and study of photoconductivity and light-induced absorption in BaTiO₃ :Fe and KNbO₃:Fe are performed at many light intensities. The results are interpreted in a two impurity level band model. This model allows to calculate the dark conductivity, to explain the behavior of the photoconductivity with the respect to the light intensities, and to study the light-induced absorption coefficient.     

Étude de la photolyse de sels de sulfonium,photoamorceurs cationiques

Arylonium salts allowed the development of cationic photopolymerization. A number of reports about the photolysis of triarylsulfonium salts can now be found in the literature. These works deal with salt photofragmentation kinetics, the visualization of the photolysis process by real time pH mesurements and with the acid photoliberation kinetics by potentiometric titrations.     

Synthese diastereoselective d'une composante de la pheromone sexuelle de “l'ecaille rouge de californie” : l'acetate d'isopropenyl-6 methyl-3 decene-9 yle (3S, 6R)

6-Isopropenyl 3-methyl 9-decen yl acetate (3S, 6R) has been synthesized from readily available trans (-)-dihydrocarvone. Regioselective ozonolysis of this ketone silyl enol ether is the key step of the sequence and allows to preserve both chiral centers.     

Synthese de vinylidene-3 pyrrolidines,piperidines, perhydroazepines a partir D'ω-monoalkyl-aminopropargyltrimethylsilanes par processus D'aminomethylation-desilylation intramoleculaire

In acidic medium, the ω-monoalkylaminopropargyltrimethylsilanes regiospecifically reacted with formaldehyde, affording 3-vinylidene nitrogen-containing heterocycles, such as 3-vinylidene pyrrolidines, piperidines and perhydroazepines.     

The Lewis basicity of nitrido complexes. Theoretical investigation of the structure and bonding of Cl2 (PH3)3ReN–X (X = BH3, BCl3, BBr3, AlH3, AlCl3, AlBr3, GaH3, GaCl3, GaBr3, O, S, Se, Te)

Quantum chemical calculations using gradient-corrected density functional theory (B3LYP) and ab initio methods at the MP2 level are reported for the geometries and bond energies of the nitrido complexes Cl₂ (PH₃)₃ReN–X (X = BH₃, BCl₃, BBr₃, AlH₃, AlCl₃, AlBr₃, GaH₃, GaCl₃, GaBr₃, O, S, Se, Te). The theoretical geometries are in excellent agreement with experimental values of related complexes which have larger phosphine ligands. The parent nitrido complex Cl₂(PH₃)₃ReN is a very strong Lewis base. The calculated bond dissociation energy of Cl₂(PH₃)₃ReN–AlCl₃ is D _e = 43.7 kcal/mol, which is nearly as high as the bond energy of Me₃N–AlCl₃. The donor-acceptor bonds of the other Cl₂(PH₃)₃ReN–AY₃ complexes are also very strong. Even stronger N–X bonds are predicted for most of the nitrido-chalcogen complexes, which exhibit the trend X = O ≫ S > Se > Te. Analysis of the electronic structure shows that the parent compound Cl₂(PH₃)₃ReN has a Re–N triple bond. The Re–N σ bond is clearly polarized towards nitrogen, while the two π bonds are nearly nonpolar. The Re–N σ and π bonds become more polarized toward nitrogen when a Lewis acid or a chalcogen atom is attached. Bonding in AY₃ complexes should be described as Cl₂(PH₃)₃ReE≡N→AY₃, while the chalcogen complexes should be written with double bonds Cl₂(PH₃)₃Re=N=X. The charge-decomposition analysis indicates that the nitrogen-chalcogen bonds of the heavier chalcogen complexes with X = S, Se, Te can also be interpreted as donor-acceptor bonds between the nitrido complex acting as a Lewis base and the chalcogen atom with an empty p(σ) orbital acting as a Lewis acid. The nitrido oxo complex Cl₂(PH₃)₃ Re=N=O has a covalent N–O double bond. Received: 27 July 1998 / Accepted: 26 October 1998 / Published online: 16 March 1999     

Etude theorique de la dynamique du réseau de batio3 en phase quadratique

The lattice dynamics of barium titanate BaTiO₃ is discussed quantitatively in the framework of a shell model taking into account the electronic polarizabilities of the constituent ions and including Coulomb and short-range interactions. The results of calculations point out the important role of the anisotropic oxygen polarizability. There is a good agreement between calculated and experimental dispersion curves.     

Étude par spectrographie infrarouge de la structure de l'acide iodique,de l'acide anhydroiodique et des polyiodates alcalins

Résumé L'étude par spectrographie infrarouge entre 2 et 33 des divers produits de déshydratation de l'acide iodique et des nombreux iodates «acides» et «pyroiodates» qu'il donne avec les iodates alcalins montre l'existence de ponts I-O-I analogues à ceux qui existent dans l'anhydride iodique I₂O₅. Ces liaisons se caractérisent dans la région explorée par deux groupes de bandes fortes à 400–460 cm^–1 et à 515–646 cm^–1, c'est-à-dire en dehors des régions d'absorption caractéristiques des groupements IO₂ ou IO₃.

---

Summary The infrared spectrographic study between 2 and 33, of various products of dehydration of iodic acid and numerous acid iodates and pyroiodates which it yields with alkaline iodates reveals the existence of I-O-I bridges analogous to those in I₂O₅. In the regions explored, these links are characterized by two groups of strong bands at 400–460 cm^–1 and at 515–646 cm^–1, i. e. beyond the absorption regions characteristic of the IO₂ or IO₃ groups.

---

Zusammenfassung Die IR-spektrographische Untersuchung verschiedener durch Wasserabspaltung aus Jodsäure hergestellter Produkte, zahlreicher saurer Salze und mit Alkalijodaten gebildeter Pyrojodate zwischen 2 und 33 zeigt das Vorhandensein von J-O-J-Brücken, wie sie analog im Jodsäureanhydrid J₂O₅ vorliegen. Charakteristisch für diese Bindung sind im untersuchten Bereich zwei starke Bandengruppen bei 400 bis 460 cm^–1 und bei 515 bis 646 cm^–1, das heißt jenseits des Bereiches der charakteristischen Absorption der Atomgruppen JO2 oder JO3.

---

---

En l'honneur du ProfesseurF. Feigl, pour son 70^e anniversaire.     

Les α et β-Cetophosphonates,des Precurseurs de Pyrrolidines et de Quinoleines Phosphonatees

The condensation of primary amines on α- or β-ketophosphonates affords the corresponding iminophosphonates. The reaction was found to be highly stereoselective, affording the E isomer exclusively. These phosphonylimines were then treated in basic media to give pyrrolidines and quinolines through intramolecular cyclization. The structures of all obtained products were confirmed by NMR spectroscopy (¹H, ³¹P, ¹³C), and in some cases by mass spectrometry.     

A new gluco indole alkaloid, 3, 4-dehydro-5-carboxystrictosidine, from Peruvian Uña de Gato (Uncaria tomentosa)

A new gluco indole alkaloid, 3,4-dehydro-5-carboxystrictosidine, was obtained from Peruvian U?a de Gato (Cat's Claw, original plant: Uncaria tomentosa) together with two known gluco indole alkaloids. This compound was the first example of isolation of a gluco monoterpenoid indole alkaloid having a 3,4-dihydro-beta-carboline ring system from nature. A characteristic feature of the compound was the quick replacement of the methylene hydrogens on C-14 with deuterium that was observed when it was dissolved in CD3OD. We demonstrated a similar proton-deuterium exchange on a model compound, 1-methyl-3,4-dihydro-gamma-carboline, in CD3OD solution.     

Champ de force de valence du 3-Méthyl 4-nitro pyridine N-oxyde (POM)

The Simplified Generalized Valence Force Field of the 3-methyl 4-nitro pyridine N-oxide molecule (POM) has been determined. In order to verify the transferability of the force field from the parent molecule 4-nitro pyridine N-oxide (NPO) to POM, the calculations have been made first using the CH distances determined by X-ray diffraction for NPO, and the final results correspond to the real geometry determined by neutron diffraction. Moreover, it has been necessary to re-assign 5 of the observed vibrational frequencies of POM.     

Etude,par thermogravimétrie et spectrographie d'absorption infrarouge,de quelques sulfates doubles de la série magnésienne. I. Courbes de thermolyse

Résumé L'auteur étudie le comportement thermique des sulfates doubles du type M₂M(SO₄)₂ · 6 H₂O, avec M=K et NH₄ et M=Ni, Co, Mg, Zn et Fe.

---

Summary A study was made of the thermal behavior of double sulfates of the type M₂M(SO₄)₂ · 6 H₂O where M=K or NH₄ and M=Ni, Co, Mg, Zn, Fe.

---

Zusammenfassung Das thermische Verhalten der Doppelsulfate vom Typus M₂M(SO₄)₂ · 6 H₂O wurde untersucht. In dieser Formel steht M für K oder NH₄, M für Ni, Co, Mg, Zn oder Fe.

---

---

En l'honneur du Prof.A. A. Benedetti-Pichler, respectueusement.     

Dénombrement de cascades de colonnes de rectification complexes

A recursive procedure for enumerating separation sequences involving columns with one or two feed streams and several sidestreams is presented in t     

Préparation Chimique,Caracterisation Cristallographique,Etudes Thermique et Vibrationnelle du Cyclotriphosphate Hexahydraté de Manganèse et de Tetra-Argent,MnAg 4 (P 3 O 9 ) 2 .6H 2 O

The cyclotriphosphate hexahydrate of manganese and silver, MnAg 4 (P 3 O 9 ) 2 .6H 2 O, was prepared by Boullé's process. MnAg 4 (P 3 O 9 ) 2 .6H 2 O crystallizes in the triclinic system, P-1, Z = 1 and its structure was determined by Rietveld's method. The refinement of 54 parameters by this method, using 1752 independent reflections leads to Rw p = 0.098, R p = 0.065 and R B = 0.033 on the basis of its isotype NiAg 4 (P 3 O 9 ) 2 .6H 2 O. The unit cell parameters of this salt are the following a = 8.824(1)Å, b = 8.485(1)Å, c = 6.609(1)Å, f = 90.30(1)°;, g = 92.89(1)°; and n = 107.28(1)°;. The thermal behavior of this new compound was studied, between 25 and 600°;C, under atmospheric pressure by infrared spectrometry, X-ray diffraction, thermal analyses TGA and DTA coupled. This study allows us the identification and the crystallographic characterization of a new phase, MnAg 2 (PO 3 ) 4 isotype of ZnRb 2 (PO 3 ) 4 , obtained between 350 and 450°;C, mixed with the long-chain polyphosphate of silver AgPO 3 . The kinetic characteristics of the dehydration of MnAg 4 (P 3 O 9 ) 2 .6H 2 O and the thermal phenomena accompanying this dehydration were determined and discussed on the basis of the proposed crystalline structure. The vibrational spectrum of the, MnAg 4 (P 3 O 9 ) 2 .6H 2 O, was examined and interpreted in the domain of the stretching vibrations of the P 3 O 9 rings, on the basis of the proposed crystalline structure and in the light of the calculation of the thirty fundamental IR frequencies for the idealized D 3h symmetry.     

Extraction et dosage de traces de rhénium,en particulier dans les molybdénites

A simple solution to the difficult problem of the separation and determination of traces of rhenium contained in molybdenites is suggested. After the preliminary attack of the cres, rhenium is extracted quantitatively between, pH 8 and pH 9 by chloroform in the form of tetraphenylarsonium perrhenate. In this pH region the molybdenum remains in the aqueous phase.Calculation has allowed the determination of favourable conditions for the extraction of perrhenates by tetraphenylarsonium chloride and chloroform. Practical results are in satisfactory agreement with theory.The extracted rhenium, after conversion to the ions ReO₄^- in acid solution, is determined colorimetrically by reaction with thiocyanate and stannous chloride.By applying the method described it is possible to isolate and determine rhenium in molybdenites when the weight ratio rhenium/ore ecxeeds 10^-7.     

Effet de la température,de la pression et de la composition sur l'intensité diffusée par un mélange de deux polymères

Phase diagrams of polymer blends and solutions are usually studied by measuring the scattered intensity (by light or neutrons) as a function of composition, temperature and pressure. If one expands Flory's χ parameter as a function of the composition, one sees that in order to have deviations from Flory's laws, thermodynamic quantities such as volume, heat capacity or compressibility should vary with respect to composition by a power law of degree larger than two. In some cases, the direct measurement of these quantities could lead to a more precise and rapid determination of the miscibility conditions.