Polymeres hydrosolubles derives du polyacrylonitrile—I: Etude de la microstructure du polyacrylonitrile modifie par l'amino-2 ethanol et de ses produits d'hydrolyse

Chemical modification of polyacrylonitrile by 2-aminoethanol without a catalyst gives hydrosoluble polymers having no CN- groups. Probably because of the cooperative effect of the adjacent nitrile groups, the modified polyacrylonitriles have two heterocyclic structures-N N'-dihydroxyethylglutarimidine and oxazoline-and a N-hydroxyethyl-amide structure. The cyclized structures probably originate from the reaction between the nitrile groups with 2-aminoethanol giving amidines followed by two types of cyclization with abstraction of ammonia. The first cyclization, probably fast, probably involves two adjacent amidine carbons and gives glutarimidine structures. The second cyclization involving isolated amidine groups probably gives oxazolines. Finally, the presence of N-hydroxyethylamide groups in the modified polyacrylonitriles is likely to be due to the difficulty of achieving chemical modification in anhydrous conditions.     

Effet de la temperature et de la concentration en monomere sur la cinetique de polymerisation du propene par catalyse ziegler-natta

The effects of monomer concentration and temperature on the kinetics of propene polymerization catalysed by δ titanium trichloride (TiCl₃· 1/3 AlCl₃) activated by diethylaluminium chloride have been studied. The study included variation of propene concentration from 0·2 mole/1 to bulk liquid at temperatures between 20 and 80°. Results are in agreement with a mechanism which includes a monomer chemisorption to form a transitory complex (absorption—desorption) and addition of the chemisorbed monomer to the polymer chain. It appears, contrary to the general belief, that addition would be fast compared with the setting up of the chemisorption equilibrium.     

Reactivite des β-cyclopropyl α-enones—I: Etude des transferts electroniques par voltametrie cyclique et de la reduction par l'electron solvate dans l'ammoniac liquide

Species produced by electron transfer to variously substituted bicyclo[3.1.0]hex-3-en-2-ones provide a better insight into the origin of 1,6-addition products sometimes observed by reaction of lithium diorganocuprates with β-cyclopropyl α-enones. Cyclic voltammetry of eight such bicyclohexenones show that the half-lives of the corresponding anion radicals are very short (t_{$\text{1}\text{2}$}?10^?4s) except when the initial molecule is phenyl substituted at C-4. In such cases the anion radicals are very stable (t_{$\text{1}\text{2}$}?6s) owing to the greater charge delocalization and we observe a second wave corresponding to the formation of the Dianion. The reduction of the same substrates by the solvated electron in liquid ammonia exhibits the same difference of behaviour. The molecules giving strongly reactive anion radicals only lead to the straight-forward product expected by conjugate reduction; while the 4-phenyl substituted substrates yield a mixture of products from normal conjugate reduction and rearrangement. This correlation strongly suggest that these last products arise from the rearrangement of the dianion.     

Experimentation du plan de synthese etabli avec l'aide de pascop: Synthese assistee par ordinateur de la phosphacarnegine-II

Synthesis planned for phosphacarnegine 1by the PASCOP procedure was executed. Although some pathways were not appropriate, two successful routes giving 1 in a yield of 15 and 4.5% respectively are described. Limitations of PASCOP are discussed.     

Polymerisation du methacrylate de methyle par le chlorure de tertio-butylemagnesium en solution dans le tetrahydrofuranne—II Comportement de la polymerisation en fonction de la temperature et de la composition du magnesien

The polymerization of methylmethacrylate initiated by tert butyl-magnesium chloride in tetrahydrofuran has been studied in terms of yield and balance-sheet. It has been shown that only the symmetrical form of the Grignard reagent is efficient in initiating the polymerization. Initiation, propagation and termination mechanisms have been proposed.     

Photocycloaddition des hydrocarbures aromatiques polynucleaires en solution—iv: Etude de la fluorescence et de la photoreactivite de l'acenaphtylene et du cyano-1 acenaphtylene

The fluorescence of acenaphthylene follows a Stern-Volmer relationship in air-saturated ether giving a self-quenching constant K_F=0.12M^?1, indicating that the syn photodimer originates from the singlet state of acenaphthylene. By comparison, 1-cyanoacenaphthylene undergoes a more efficient self-quenching (K_F= 2.8 M^?1) in air-saturated ether. No excimer fluorescence was detected for 1-cyanoacenaphthylene nor the parent compound in solution. The triplet state of 1-cyanoacenaphthylene, obtained by sensitization or induced by heavy atom solvent (EtI), was shown to generate exclusively the head-to-head anti photodimer in a high chemical yield. Regiospecificity and stereospecificity observed in this reaction indicates the influence of the acenaphthylenic ring and the cyano group in stabilizing the diradicaloïd transition state.     

Synthese de ligands de type amino-diphosphinites; etude en RMN 13C et 31P. Application a la dimerisation du butadiene par les complexes du nickel

The new chiral aminodiphosphinite ligands are readily prepared from chiral amino acids. These compounds were characterized by ¹³C and ³¹P NMR spectroscopy and their behaviour as homogeneous catalysts was investigated in the linear dimerization of butadiene.     

Applications de la reaction de ritter en serie steroide-—III: Ouverture d'epoxy-4,5β cholestanes par l'acetonitrile. Conformation du groupe amide

4,5β-Epoxy 3β-cholestanol 1 and its acetate 2, 4,5α-epoxy 3β-cholestanol 3, and 4,5β epoxy 3α-cholestanol 4, are cleaved by acetonitrile in the presence of perchloric acid with scission of the OC⁵ bond following a “modified S_N2” mechanism. While 1 gives a vicinal trans diaxial hydroxy amide, 2, 3 and 4 give dihydrooxazines through participation of the 3-oxy group. The influence of the 5α-acetamido group upon the chemical shifts of the 4α proton, as well as a solvent effect, confirm the hypothesis of a preferred conformation for the amide group.     

Methode d'analyse debitmetrique appliquee a l'etude de reactions de la forme solide 1⇌solide 2+gaz,en fonction de la temperature et de la pression

Résumé Une méthode d'analyse débitmétrique à laquelle peut Être associée ATD est présentée. Elle s'applique à l'étude de réactions de la forme solide 1 solide 2+gaz dans des domaines de températures et de pressions jusqu'à 900 et 150 bar.On décrit le principe de la mesure et les conditions de fonctionnement d'un dispositif expérimental plus particulièrement mis au point pour l'étude de la décomposition thermique de CdCO₃ en atmosphère de CO₂.Cette méthode sensible et précise permet d'obtenir des résultats quantitatifs.

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An experimental device based on the measurement of gas flow rate is described, to which a DTA apparatus can be attached. The method is suited to the investigation of reactions of the type Solid₁Solid₂+gas, in the temperature interval up to 900C and at pressures up to 150 bar. The principle of the measurements is given, as well as the working conditions of an experimental device constructed specially to study the thermal decomposition of CdCO₃ in a CO₂ atmosphere.This sensitive and accurate method enables quantitative results to be obtained.

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Zusammenfassung Es wird eine Methode der Strömungsmessungs-Analyse beschrieben, an die DTA angeschlossen werden kann. Sie eignet sich zum Studium von Reaktionen des Typs: Festkörper 1 Festkörper 2 + Gas im Temperatur- und Druckbereich bis zu 900, bzw. 150 bar.Das Meßprinzip wird beschrieben, sowie die Betriebsbedingungen einer besonders zum Studium der thermischen Zersetzung von CdCO₃ in CO₂-Atmosphäre entwickelten Versuchsvorrichtung.Diese empfindliche und genaue Methode ermöglicht quantitative Ergebnisse.

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, , . = + 900 150 . , CdCO_{3 2}. , , .

     

Reactions en milieux hyperacides—XVI: Action de l'hydrogene sur divers estranes insatures. Synthese de nouveaux anthrasteroides

Estrone and unsaturated estranes, are reduced in HF-SbF₅ by hydrogen. The major product is an anthrasteroid whose structure and configuration of asymetric carbon atoms are determined. A second compound, 14-iso-estra-3,17-dione is obtained with 25% yield.     

Determinations cinetiques par microcalorimetrie differentielle en programmation de temperature. II. Influence de la variation de la sensibilite du calorimetre avec la temperature sur les valeurs trouvees pour les constantes de vitesse et les enthalpies de reaction

The variation with temperature of the sensitivity of a “Thermanalyse” microcalorimeter has been determined using the electrical calibration system of the apparatus. From the results, a method for the correction of the differential scanning microcalorimetric diagrams has been developed. The influence on the determination of the rate constants during kinetic studies of the decompositions of free radical initiators and on enthalpy measurements has been studied.     

Synthese et etude de celluloses echangeuses d'ions. Leur emploi dans l'epuration des eaux residuaires de l'industrie textile-III: Traitement des eaux residuaires de l'industrie textile par une cellulose greffee par des chaines d'acide polyacrylique et par une cellulose renfermant des fonctions ammonium quaternaire

Modified celluloses previously described have been studied for ability to remove colour from the effluents of textile industry. The lowest dye concentration for which the celluloses are efficient are far below the lowest concentrations in effluents. It appears that the modified celluloses are more efficient than carbon black and are well adapted for the purification of pretreated or rinsing waters. Their abilities to extract surfactants from effluents and so to break emulsions of water with solvents have been examined and appear to be large. The treated waters can be recycled.     

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.     

Etude de l'effet stérique en chimie organique au moyen du volume d'activation. : Etude de l'influence de la pression dans les copolymérisations de l'anhydride maléique avec des éthylèniques substitués

The concept of activation volume derived from high pressure kinetics is shown to be an interesting parameter for the investigation of crowded transition states. In the free radical copolymerisation of maleic anhydride with mono- and poly-substituted olefins, increasing substitution of the comonomer involves greater pressure acceleration and hence more negative activation volumes and later transition states. This result may be of substantial synthetic importance. The concept of steric activation volume is introduced and a linear relationship between ΔV^≠_σ and the size of the substituent is developed.