Polymérisation anionique des diènes. III. Etude thermodynamique de la propagation du butadiène et de i'isoprène par les organo-alcalins

The present work is concerned with the influence of the polymerization temperature on the propagation mechanisms of polyisoprenyl- and polybutadienyl-alkali metals. The thermodynamic parameters of the contact ion pairs and free ions propagations have been calculated. With Li⁺ in dioxane solvent, the vinyl propagation is stereospecific (for isoprene, the propagation is mainly 4–3). In comparison with benzene, the vinyl propagation of the polydienyl-Li contact ions pairs should be due to complexation of Li⁺ by dioxane, an electron donor having a weak dielectric constant. In general, the stereospecificity of the propagation of contact ion pairs decreases with increasing counterion size; little difference has been observed with K⁺ and Cs⁺ ion pairs in dioxane and benzene media. For isoprene, the methyl substituant should have chiefly a steric effect in the propagation of free ions, whereas it should confer a polar character to the isoprene molecule in the presence of ions pairs.     

Etude du mécanisme de perte d'ethylène (propène) des N-ethyl (propyl) bromo-1,2,4-triazoles

C-bromo-1,2,4-trizole is generated in three different tautomeric forms by ethylene elimination from the N-ethyl compounds and these toutomes are shown to retain their structure prior to further fragmentation. The analysis of mass analysed ion kinetic energy and collision incuded dissociation spectra confrrms that ethylene loss proceeds by a tw-step mechanism with a five- (or four-) centred hydrogen transfer. The results show also that the 3- and 5-bromotriazole structures only are responsible for the mass spectrum of the parent heterocycle. Similar data are dicussed for the loss of propene from N-propylbromotriazoles.     

Réaction de l''oxygène singulet avec quelques vinylallènes

The dye sensitized photooxidation of three diversely substituted vinylallenes leads to Δ-4 tetrahydropyrane-3-ones.     

Action du chlorure de nitrosyle sur le trichloréthylène et sur le tétrachloréthylène

Nitrosyl chloride is only chlorinating in darkness and above 100°. In the sun light and at room temperature it reacts as a chlorinating, nitrosating, nitrating and oxidizing agent. With trichlorethylene in fact pentachlorethane 1,1,1,2-tetrachloro-2-nitrosoethane, 1,1,1,2-tetrachloro-2-nitroethane, dichloracetic acid and a compound of empirical formula C₄H₂Cl₅NO₂ are obtained. Tetrachloroethylene carried to hexachlorethane, pentachloronitrosoethane and tetrachloro-2-(pentachlorethyl)-1,2-oxazetidine. Introduced nitrosyl chloride provided nitrogen monoxide prouved by gaz chromatography. This monoxide reacted afterwards to give nitrogen which is the single nitrogenous gazeous compound. Carbondioxide is a minor component of the gaz.     

Etude de copolymères ABS (acrylonitrile–butadiène–styrène): Solvatation préférentielle du polybutadiène par les promoteurs

ABS resins formed by copolymerization of styrene and acrylonitrile (AN) in presence of polybutadiene, consist of a mixture of SAN graft copolymer on polybutadiene (PBut) and of ungrafted SAN copolymer (styrene-co-acrylonitrile). The kinetic study was completed by showing a preferential solvation of polybutadiene by the initiator. This solvation effect was studied as a function of the concentration ratio SAN/PBut and in relation with the type of initiator. The adsorption of initiator appeared to be maximum when its solubility parameter (σ) is close to that of polybutadiene. As a function of the polybutadiene characteristics, this selective adsorption can be given by where I₁ is the quantity of initiator in the polybutadiene medium, I is the total amount of peroxide, [PBut] is the concentration of polybutadiene, and M?_n its molecular weight. It has been shown furthermore that the preferential solvation of polybutadiene by the benzoyl peroxide can be increased by addition of SAN or acrylonitrile. The consequences of this solvation effect on the characteristics of the grafting reaction, more precisely on the molecular weight of grafted and ungrafted SAN and on the rate of polymerization, were examined.     

Oligomérisation anionique de l'ethylène. II. Etude des paramètres thermodynamiques

A kinetic study, as a function of temperature, of ethylene oligomerization by the n-BuLi–TMEDA complex allowed us to evaluate the thermodynamic parameters (ΔS^? < ?23.7 u.e.) and thus to support a transition state where the ethylene is coordinated to the lithium atom.     

Sur quelques aspects de la polysubstitution de l'amino-2-fluorène et de l'acide amino-2-fluorène-sulfonique-7

Electrophilic sulfonation and cyclisation orientation studies were carried out with 2-aminofluorene and 2-aminofluorene-7-sulfonic acid. Positions 1 and 3 are competing. A new synthesis of 2-aminofluorene-7-sulfonic acid and the syntheses of derived sulfonamides are described.     

Sur 1'o-chlorobenzylidène-9-fluorène

9-o-Chlorobenzylidenefluorene is obtained in good yield from fluorene and o-chlorobenzaldehyde by condensation in methanol in the presence of sodium methoxide, while in ethanol containing sodium ethoxide 9-o-chlorocinnamylidenefluorene is formed as a by-product. The latter is absent in the methanol condensation system.     

Polymérisation “basse pression” de l'ethylène en préasence de noir de carbone

The polymerization of ethylene with Ziegler-Natta catalysts in the presence of carbon black has shown three characteristic features both with a heterogeneous catalyst, AlBu₃? TiCl₄, and with a soluble catalyst, Cl₂Ti(C₅H₅)₂? AlEt₂Cl. They are, in order of increasing importance: reactivity of the organoaluminum derivatives with surface chemical groups of the carbon black, adsorption of a certain amount of organoaluminum compounds on the carbon black surface, and influence of the specific surface of carbon black, which controls the dispersion degree of the catalytic system. Furthermore, it was possible to obtain polyethylene by this procedure, containing different amounts and different types of carbon black.     

Analyse conformationnelle théorique des molécules de benzylidène-aniline, stilbène et azobenzène : Partie II. Résultats de la méthode PCILO et ajustement d''un potentiel empirique

A conformational study of the benzylidene-aniline stilbene and azobenzene isoelectronic molecules has been carried out by the PCILO method in terms of torsional angles, bond lengths and valence angles. Initially, the conditions of application of this method to highly conjugated molecules were defined. The optimized geometries are in good agreement with those determined in the gas phase. Furthermore the rotation around a Ф—N or Ф—C bond can be specifically related to the variation of the second-order correction to the energy. This term was used to adjust the torsional potential in an empirical method adapted to this kind of molecule and able to account for both theoretical and experimental results.     

Synthèse de flavones et de xanthones dans la série du benzo[4,5]thiophène

We describe the first synthesis of 2-arylbenzo[4,5]thieno-[2,3-b]pyran-4-one and of 2-arylbenzo [4,5] thieno [3,2-b] pyran-4-one, from benzo [4,5] thiophene and we have extended these cyclizations to obtain the heterocyclic analogs of the xanthones.     

Calcul de l'Énergie de Corrélation pour l'État Fondamental de la Molécule d'Acétylène

Correlation effects in the acetylene molecule are studied by a method using the technique of Feynman-like diagrams. The introduction of the reduced atomic electronic integrals decreases considerably the value of correlation energy.     

Oligomérisation anionique de l'ethylène. I. Etude cinétique

A kinetic study of ethylene oligomerization in hexane, in the presence of n-BuLi–TMEDA complexes, allowed us to suggest a new mechanism for anionic ethylene oligomerization. n-BuLi and n-Bu(CH₂CH₂)Li species have the same reactivity. The RLi–TMEDA complex in a 1-to-1 stoichiometry is the active species. The following kinetic equation has been established: It reflects the intervention of associated species (n-BuLi–TMEDA)₂ as well as the influence of the concentration of the complexing agent on the kinetics of oligomerization.     

Isomérie Conformationnelle autour de la Liaison Carbone–Carbone dans les Sels de Propénylylidène Ammonium

¹H n.m.r. measurements of a series of propenylylideneammonium salts at temperatures varying from ?90 °C to 70 °C reveal the existence of two conformers. Values of chemical shifts and coupling constants are explained by rotation about a carbon–carbon bond; this hypothesis is supported by the ¹³C n.m.r. results. Free energies of activation are given for various substituents.     

Etude de l'action de l'oxyde d'azote (III) sur l'indène et ses homologues

Addition of nitrogen trioxide to indene and alkylindenes N₂O₃ adds to indene and homologous yelding pseudonitrosites which are converted to aminoindanes. Treatment of the pseudonitrosites with alcoholic potassium hydroxide gives the correspondent nitroindenes.     

Copolymerisation radicalaire du méthacrylate de méthyle et du chlorure de vinylidène avec ou sans dérive de composition

Two sets of methylmethacrylate-vinylidene chloride copolymers were prepared via radical copolymerization in dimethylformamide. The first set is carried out in batches. Gas-chromatographic analysis of samples allows a kinetic study from which the reactivity ratios r_M - 2.73 and r_C - 0.24 are derived. For the second set a new apparatus, briefly described, has been used. It permits to keep constant the composition of the monomer mixture, through addition of methyl methacrylate, monitored by a chromatographic analysis. The two sets of copolymers are analyzed using nuclear magnetic resonance (60 MHz) leading to the triad distribution, from which the reactivity ratios are derived. Owing to the composition drift, the method cannot be applied to the first set of copolymers; but in that case, it is possible to calculate the triad distribution, the knowledge of the reactivity ratios, and the calculation fits quite well the experimental results.     

Etude des systèmes binaires formées par le chlorure de cyanogène et par les tétrachlorures de carbone,de silicium,de germanium et d'étain

Study of binary systems formed by cyanogen chloride and the tetrachlorides of carbon, silicon, germanium and tin. The diagrams of binary mixtures of cyanogene chloride with the tetrachlorides of carbon, silicon, germanium and tin were studied. Only SnCl₄ gives an addition compound: SnCl₄ · 2ClCN. The existence of the complex was confirmed by X-ray diffraction and vapour pressure measurements. This complex gives SnCl₄ · 2NOCl on treatment with nitrosyl chloride.     

Oligomérisation anionique de l'ethylène. III. Application à la synthèse d'alcools à longue chaine

Living oligomers of ethylene obtained by n-BuLi complexed with TMEDA have been deactivated by ethylene oxide. The nuclear magnetic resonance study of the product obtained allowed us to follow the influence of TMEDA toward the functionalization. Three products have been characterized: By increasing the ratio [TMEDA]/[n-BuLi] one obtains a decrease of the functionalization reaction.     

Chloration et S-oxydation du benzo[b]thiophène par l'hypochlorite de tertiobutyle. Mécanisme de la réaction

In the reaction with benzothiophene, t-butyl hypochlorite acts simultaneously as a smooth oxidizing agent and as a chlorinating agent since it is a source of both hypochlorous acid and chlorine. The mixture of all the products obtained imply that the reaction intermediate is the unstable benzothiophene I-oxide which was shown to be present by the stop flow technique. The chlorine formed traps the highly reactive benzothiophene 1-oxide in situ to give the observed products.