Complexation de l'anion fluorure par des tetramines cycliques protonees.

The $\text{s}$ynthesis of the new tetraazamacrocycle [20]N₄ is briefly described; complexation of F by the fully protonated [16]N₄, [18]N₄ and [20]N₄ macrocycles is investigated.     

Determination de configuration de sulfoxydes cycliques par RMN discussion des differents criteres

The NMR spectra of various sulfoxides derived from thiophane or 4-tert-butyl thiacyclohexane are discussed. The different empirical rules commonly used to establish sulfoxides configuration (J_gem and Δν for an α-methylene group, syn-axial effect, benzene solvent shifts and Eu (dpm)₃ induced shifts) are critically examined, at the light of these experimental data. The conclusions of the NMR study agree with the structures obtained by X-ray analysis and chemical correlation.     

Dosage par activation neutronique d'impuretes dans l'argent tres pur avec separation des elements par extraction

Résumé Nous avons élaboré une méthode d'analyse par activation neutronique de 24 microimpuretés dans l'argent. Pour éliminer la matrice et séparer les impuretés, nous avons utilisé l'extraction. Nous avons évalué théoriquement et vérifié expérimentalement l'effet d'écran des échantillons d'argent sur le flux de neutrons.     

Complexation dans le méthanol anhydre de Cu (II) et Zn (II) par des ligands diaza-polyoxamacrocycliques

Complexation in anhydrous methanol of Cu (II) and Zn (II) with diaza-polyoxamacrocyclic ligands Protonation of five diaza-polyoxamacrocyclic ligands, (L = [2.1], [2.2], [2.1.1.], [2.2.1], [2.2.2]), and their complexing properties towards Cu²⁺ and Zn²⁺ cations have been studied in anhydrous methanolic solutions. Potentiometric measurements have been carried out at 25°, using 5 · 10^?2MEt₄N⁺ClO as support-electrolyte, in order to determine the nature of the species formed upon complexation and their stability constants. The results were confirmed by spectrophotometry, for the cupric complexes of [2.1] and [2.2.2], and the electronic spectra of the different complexes were calculated. Comparison between complexation in aqueous and methanolic solutions have been made: as in water, ML²⁺ species and sometimes protonated MHL³⁺ species, with higher stability constants, are present in methanol; but the main difference is the formation of dinuclear complexes M₂L⁴⁺, between Cu²⁺ and all ligands except [2.1]. In these complexes the Cu²⁺ cations cannot be both ‘encaged’ in the ligand cavity because of its small size. The different possible structures are discussed in terms of the stability constants values. The protonation constants values and the existence of the binuclear complexes may indicate a possible conformational change in the complexing ligand on changing the solvent from water to methanol.     

Substitution de sulfites cycliques osidiques par l'ion azoture

treatment of several sugar cyclic sulfites with NaN₃ in hexamethylphosphoric triamide gives the corresponding α-azido-alcohols with high stereoselectivity.     

Alkylation des carbenoides par des nucleophiles. : II. Substitution nucleophile de l'halogene de carbenoides α phosphonates catalysee par le cuivre(I)

The addition of a catalytic amount (12%) of a copper(I) salt to a mixture of an α-lithio-α-chloroalkylphosphonate and an alkyllithium RLi or a Grignard reagent RMgX leads to the formation of a new organometallic reagent in which the R group has replaced the chlorine atom of the carbenoid. This nucleophilic alkylation of carbenoids can be performed with secondary-alkyl Grignard reagents, and with aryllithium, alkenyllithium and alkynyllithium reagents in good yields (60–80%).     

Mecanisme de formation et de transformation des spirophosphoranes—VI : Nouveaux spirophosphoranes obtenus par addition 1,4 de derives cycliques du phosphore trivalent sur des systemes α-di-insatures

Spirophosphoranes obtained by addition of tricoordinated phosphorus compounds on α diketones and α ethylenic ketones are discussed. Steric and electronegativity factors which determine the number of stable isomers are considered, but no interconversion mechanism is postulated. Phosphorus epimerization has been studied with compounds containing two centres of asymmetry.     

Etude par resonance quadripolaire des noyaux 63-Cu et 75-As de complexes tetrameres de la triethylarsine avec des halogenures de cuivre(I)

63-Cu and 75-As quadrupole resonance results have been obtained for the tetrameric triethylarsine copper(I) halides (Cl, Br and I). Unusual behaviours of the temperature dependence of the 63-Cu and 75-As quadrupole resonance lines have been observed simultaneously. Between 77 and 300 K, the chlorine derivative undergoes two structural phase changes at 93 and 173 K, while phase transformations occur at 152 and 86 K respectively for the bromine and iodine derivatives.     

Complexation metallique des imides. I. Grandeurs thermodynamiques de formation des complexes de Ag(I), Cd(II), NI(II), Cu(II) avec la succinimide

Thermodynamic values for the formation of Ag⁺, Cd²⁺, Ni²⁺ and Cu²⁺ complexes with succinimide were determined at 25°C in aqueous medium 0.5 M KNO₃. The stability constants were calculated from pH metric measurements and the related enthalpies from direct calorimetric determinations. An interpretation of the results is given, based on the character of the established bonds.     

Synthese electrochimique de methoxy-2 dioxa-1,4 cyclanes par oxydation anodique de cetals cycliques de β-ceto-carboxylates

Anodic oxidation of β-oxocarboxylate cyclic acetals in anhydrous methanol gives 2-methoxy-1,4-diox-acycloalkanes in 40–60% yields. The mechanism is discussed.     

Extraction liquide-liquide par des esters alkylphosphoriques. I. Extraction de l'yttrium par l'acide di-(2-éthylhexyl)phosphorique

The extraction of macro-amounts of Yttrium from solutions of nitric and perchloric acids by di-(2-ethylhexyl)phosphoric acid has been studied. The extraction of Yttrium is more effective from the perchloric medium and takes place by two mechanisms: an ion-exchange reaction Y³⁺/H⁺ at low concentrations and a solvatation reaction at high concentrations of Yttrium. The stability constant of the mononitratocomplex YNO has been estimated.     

Decomposition des tosylhydrazones cycliques par les organolithiens relations entre la reactivite et la conformation

Tosylhydrazones of a series of cyclanones containing from 7 to 15 carbon atoms are decomposed at room temperature by MeLi or BuLi in ether or hexane, to yield elimination products exclusively. The ratio of cis and trans olefins depends on the size of the ring. These values are analysed in terms of the most likely conformations of the tosylhydrazones.     

Adsorption de CO2 par des zeolithes X echangees par des cations bivalents

Adsorption of carbon dioxide by X zeolites exchanged with bivalent cations. The adsorption of carbon dioxide by X zeolites exchanged by Mg²⁺, Sr²⁺, Zn²⁺ and Cu²⁺ cations was studied by thermogravimetry. The corresponding isosteric heats of adsorption decrease with the filling of pore volume, except for Cu(63)X. This evolution of the heat indicates a specific interaction between cations present within supercages and CO₂ molecules. Several models have been used in order to describe the experimental isotherms. The best fit of sorption isotherm data was obtained with the Sips model.     

Photoreduction de la benzophenone par des thioethers etudiee par pnic

CIDNP (Chemically Induced Dynamic Nuclear Polarization) studies of the photoreduction of benzophenone by R-CH₂-S-R' show evidence for the $\text{formation of vinylic}$ deratives and adducts. The central intermediate in the reaction scheme is the radical pair R-CH-S-R' φ₂-C-OH^t. A study with selenides shows a different behaviour for these compounds.     

Complexation diastereoselective d''alcools benzyliques par le chrome hexacarbonyle. Difference de reactivite des diastereoisomeres en milieu acide.

Reaction of ortho alkyl or alkoxy phenyl carbinol with Cr(CO)₆ affords arene chromium tricarbonyl complexes with 38 to 86% of diastereoisomeric excess. The behavior of the two diastereoisomers shows a striking difference. Equimolar mixture of (RR,SS) and (RS,SR) diastereoisomers treated with concentrated sulfuric acid and methanol gives (RS,SR) ether while (RR,SS) alcool remains unchanged.     

Membranes permselectives obtenues par greffage radiochimique des acides acrylique et methacrylique sur des films de poly(chlorure de vinyle)

Membranes were prepared by subjecting to gamma-rays PVC films swollen in a mixture of acrylic acid and methylene chloride. The kinetics of the reaction were investigated as a function of monomer concentration, temperature and dose-rate. The swelling properties of the resulting membranes were studied as well as those of PVC films grafted with methacrylic acid. It was found that PVC films grafted with methacrylic acid only swell slightly in water even for high grafting ratios and the swelling is very slow. At elevated temperatures the films swell more quickly and reach a higher limiting swelling, but the effect is small. PVC films grafted with acrylic acid swell much more quickly and reach much higher swelling ratios. The extent of swelling markedly increases with temperature but this effect is not reversible: once the membranes have reached a high swelling ratio at elevated temperatures, they keep the same ratio when dipped in water at 20°. The Arrhenius plot of the swelling ratio exhibits a break at 50–60° apparently corresponding to a glass transition temperature. In methanol the swelling is significantly higher for PVC films grafted with methacrylic than with acrylic acid. Swelling of the membranes was also investigated in mixtures of water with methanol and methanol with methylene chloride. The results are interpreted by assuming a strong dipole-dipole interaction between the grafted branches and the trunk polymer resulting in a quasimolecular dispersion of the carboxylic chains in the PVC matrix. The latter acts as a barrier against the penetration of water. Heat treatment favours a segregation of the two polymeric species into microphases and this non-reversible transformation is assumed to be responsible for the unexpected behaviour of PVC films grafted with acrylic acid. The significant differences between the properties of PVC films grafted with either acrylic or methacrylic acid are attributed to the much higher hydrophobic character of the methacrylic chains.