Utilisation de la haute pression en polymerisation anionique de l'ethylene

The polymerization of ethylene has been initiated anionically and under high pressure (> 1000 bars); the initiators were n butyl lithium, cumyl litnium and benzyl lithium. The melting temperatures and crystallinities of the resulting polymers were obtained.     

Cyclisations homolytiques sur un carbonyle: reexamen des reductions des γ-chlorobutyrophenone et chloro-6 hexanal par l'hydrure de tributyletain

Determination of the reactivity of Bu₃Sn· with the carbonyl group of an alkyl aryl ketone and the chlorine atom of a primary alkyl chloride have shown similar types of reaction. These results led us to reconsider the mechanism of 2-phenyltetrahydrofuran formation in reduction reactions of γ-chlorobutyrophenone by tributyltin hydride. This cyclic ether was obtained by elimination of tributyltin chloride from the product of carbonyl hydrostannation. A similar study on an aldehyde and 1-chloroalkane revealed the mechanism of cyclohexanol formation in reduction reactions of 6-chlorohexanal by tributyltin hydride. Tributyltin hydride treatment of 7-chloroheptan-2-one and 6-chlorohexan-2-one led to heptan-2-one and hexan-2-one in good yields; no cyclization product is observed.     

Réaction de quelques allènes avec l'hydrure de di-isobutyl-aluminium

Reduction of the more substituted of the two double bonds of the allenic linkage can be selectively achieved by the reaction with DIBAH followed by hydrolysis.     

Spectres RMN haute resolution des homopolymeres et copolymeres de l'acrylate de glycidyle avec le chlorure de vinyle

The HR-NMR spectra of the glycidyl acrylate homopolymer and (glycidyl acrylate-vinyl chloride) copolymers are described. The assignment of the different resonance groups allows quantitative determination of the compositions of the copolymers.     

Addition de l'hydrure de diethylaluminium sur des copolymeres porteurs de groupements nitrile

Addition of diethylaluminiumhydride (DEAH) to nitrile functions was studied by nitrogen determination and i.r. spectroscopy in the case of styrene-methacrylonitrile (S-MAN) and styrene-acrylonitrile (S-AN) random copolymers. The various reaction parameters have been studied. The yield of ketimin derivatives is maximum for equimolecular quantities of DEAH and nitrile. Deficiency of hydride leads to secondary reactions of insertion and cyclization in the case of S-MAN copolymers as well as with S-AN copolymers. With the SAN copolymers however, elimination reactions also take place, leading to covalent crosslinking.     

Influence des associations moleculaires sur la copolymerisation de l'acide acrylique avec l'acide methacrylique et avec l'acrylate de methyle

The copolymerization of acrylic acid with methacrylic acid in bulk is investigated at 40 and 60°. It is confirmed that a “matrix effect” occurs only for high contents of acrylic acid. The critical concentration beyond which the matrix effect disappears is shifted towards lower acrylic acid contents for higher temperatures. The copolymer composition is independent of temperature. The copolymerization of acrylic acid with methyl acrylate is investigated in a mixture which determines an “exaltation of the matrix effect” in the homopolymerization of acrylic acid (molar fractions: m_Monomers = 0.34; m_n-Hexane = 0.52; m_Methanol = 0.14). The resulting copolymers are found to contain a much larger fraction of acrylic acid residues than the copolymers formed in bulk or in toluene or DMF solutions.     

Chimie organometallique : IX. Reaction du tungstadiphenylcarbene avec les ethers d'enols cycliques

Treating (CO)₅WC(Ph)Ph with cyclic enol ethers in n-hexane, leads, in the case of the cyclopentanone derivative, to ring-opened product (CO)₅WC(OEt)[(CH₂)₃CHC(Ph)Ph] which has been isolated and characterized. The ring size in the enol ether is the determining factor.     

Reaction de l'oxygene avec les alcoolates de cuivre I.

Copper (I) alkoxides are oxidized by molecular oxygen in acetonitrile to carbonyl compounds ; a mechanism involving Cu(III) intermediates is proposed.     

Etude des solutions solides d'oxyde de lithium dans l'oxyde de nickel. I. proprietes des solutions solides preparees sous pression reduite d'oxygene

Heating mixtures of lithium and nickel oxides at 1073°K under reduced oxygen pressure (<10^?6 Torr) produces the incorporation of lithium ions in the nickel-oxide lattice. The solubility appears to be limited at 1.9 at Li %. From a study of several properties of solid solutions, it is concluded that the incorporation of lithium ions creates and stabilizes anionic vacancies.     

Influence des solvants sur la copolymérisation de l'acrylamide avec l'acrylonitrile

The copolymerization of acrylamide with acrylonitrile was investigated in various solvents, which can be put into three groups according to their influence on molecular associations; (1) solvents autoassociated by hydrogen- bonds (acetic acid, methanol, water, dimethylformamide); (2) polar solvents which can associate with the NH group of acrylamide (acetonitrile, dioxane, acetone); (3) inert solvents (toluene, benzene, hexane). The reaction kinetics and the compositions of the copolymers are different for each group of solvents. The composition of copolymers formed in solvents of group 1 vary widely, depend- ing on the solvent. Copolymers formed in all solvents of group 2 have the same composition which is that of copolymers formed in bulk. The amount of acrylamide is highest in copolymers formed in inert solvents of group 3. Such parameters as the degree of conversion, the reaction temperature, the mode of initiation and the extent of dilution only slightly affect the composition of copolymers. Homopolymerizations of acrylamide and acrylonitrile were investigated in all solvent used.The results suggest that the effects of solvents on the copolymerization of acrylamide with acrylonitrile are consequences of the various modes of molecular association of acrylamide. The solvents affect the equilibrium between auto- association of acrylamide and its association with solvent and thereby affect the reactivity of the monomer.     

Reaction de l'acetylene dicarboxylate d'ethyle avec l'oxo-6 (2H) cyclohepta (c) pyrrole ; mecanismes de formation des adduits

The cycloaddition reactions of 6-oxo (2H) cyclohepta (c) pyrroles $\text{4a, b and c}$ with diethyl acetylene dicarboxylate an electron-deficient dienophile of relatively low LUMO energy level, afford the 1:2 adducts $\text{5a, b}{}_1\text{-b}{}_2\text{and c}$ respectively The kinetics of the reactions, investigated By ¹H NMR spectroscopy, have allowed to precise the mechanism of the addition In particular, new-intermediates, 1:2' adducts $\text{6b and c}$ have been observed and isolated for the compound $\text{6c}$.     

Copolymérisations radicalaires sous haute pression. Influence de la pression sur les rapports de réactivité

The pressure effect upon the reactivity of the radicals in copolymerizations can be important. The present work reports the pressure dependence of the reactivity ratios for some radical copolymerizations involving monomers of various polarities and proposes an interpretation concerning their variations with pressure based upon the Q—e scheme (or Alfrey–Price scheme). The direction as well as the magnitude of the pressure effect can thus be predicted.     

Etude des phases β et haute pression du phosphate tricalcique par la RPE de l'ion Cu2+

Copper (II)-doped powdered samples of β-Ca₃(PO₄)₂ and of its high-pressure phase, which is an isotype of Ba₃(VO₄)₂, were studied by ESR. In each case the RT spectrum is due to a unique type of defect exhibiting orthorhombic and respectively axial symmetry. The spin-Hamiltonian parameters were determined using the method proposed by Rollmann and Chan for polycrystalline specimens. The contribution of each of both copper isotopes was resolved with stressed samples. Our results show that isolated copper ions substitute preferentially for calcium in Ca(III) sites of β-calcium orthophosphate, these sites corresponding to those of Ca(I′) in the high-pressure phase.