Synthese de sequences polychlorure de vinyle α-ω difonctionnelles et extension en copolymeres multisequences

It is possible to synthesize α-ω diacid PVC sequences by direct ozonization of the polymer, but their thermal stability is low because peroxides are introduced simultaneously in the polymer backbone. Also they cannot be used to prepare block copolymers by polycondensation at temperature above 100°. They are reactive enough to be transformed to α-ω acid chlorides which can be condensed with diols, diamines and bisphenol A to give block copolymers. Triethylamine acts as catalyst but also as HCl acceptor and favours high molecular weight formation. The α-ω acid chlorides can be hydroxylated and polycondensed with diphenylmethane diisocyanate. The thermal stability of these block copolymers is satisfactory if the peroxides are previously reduced.     

Etude quantitative de la distinction entre une liaison de covalence et une liaison de coordination: les molecules de borazane et d'aminoborane

Résumé On propose un exemple quantitatif de la distinction entre une liaison de covalence et une liaison de coordination; cette différenciation, fondée sur les propriétés de la molécule une fois formée, semble très nette pour les énergies de liaison, les populations de recouvrement et les charges des groupes; en particulier, un critère récent, proposé par deux des auteurs, est remarquablement vérifié. Enfin, on essaie de préciser la signification des symboles chimiques traditionnels.

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Quantitative studies of the difference between a covalence and a coordination bond: The molecules of amine-borane and aminoborane

An illustration of the distinction between these two types of chemical bonds is proposed, which is based on the properties of the molecule once built. Bond energies, overlap populations and group charges vary considerably from one compound to the other; more, a recent criterion given by two of the authors seems to be particularly suitable for describing the character of the bond. Lastly, one tries to give an explicit signification to the usual chemical symbols.

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Zusammenfassung Es wird ein quantitatives Beispiel der Unterscheidung zwischen einer kovalenten und einer koordinativen Bindung angegeben, die auf den Eigenschaften des vorliegenden Moleküls beruht. Sie erscheint sehr günstig für die Bindungsenergien, die Überlagerungspopulationen und die Gruppenladungen. Insbesondere wird ein Kriterium, das kürzlich von zwei der Autoren angegeben wurde, gut verifiziert. Schließlich wird versucht, die üblichen chemischen Symbole zu präzisieren.

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Les auteurs tiennent à remercier très vivement M. M. Berthier et Millié d'avoir mis à leur disposition le programme de localisation indispensable à ce travail, ainsi que Mademoiselle Le Guen et le C.I.R.C.E. pour la réalisation des calculs sur l'ordinateur IBM 360-75.     

Fonctionnalisation du polypropylene isotactique par le melange oxygene-ozone

Ozonisation of polypropylene in bulk causes chain scission through autooxidation processes at room temperature and produces mainly α-ω diketone polypropylene sequences. With poly(vinylchloride) or polyethylene, formation of α-ω diacid sequences has been observed. Hydroperoxides parallel ketone formation but they are grafted onto the polymer backbone. They may be used to initiate the polymerisation of vinyl monomers during the processing of the polypropylene.     

Sur une voie alternative de synthese de la loganine

An original synthesis of a precursor of loganin is described starting from the bicyclo[3.3.O]octane-3,7-dione using Shapiro's reaction. The structures of the obtained derivatives are established on the basis of ¹H N.M.R., I.R.,and mass spectral data.     

Synthese de dienes gem-diactives : Selon une condensation apparentee a la reaction de stobbe

Condensation of carbonyl compounds with alkylidene cyanacetic esters using an equivalent of base, affords a new route to gem-diactivated dienes or trienes. The synthetic utility of the reaction is discussed with respect to the structure of the reactants. Configurations are determined by NMR after photoisomerisation experiments. Isolation of some δ-lactones, intermediates of the reaction, allows an interpretation of the mechanism and stereospecificity.     

Programme de minimisation de l'energie empirique d'une molecule par une methode simpliciale

A method of assessing the minimum energy of a molecule in a given conformation is discussed. This method can easily be adapted to impose constraints (symmetry, for example) to the molecules studied. The results are compared with recent experimental values and analogous calculations. We show, with butane, cyclopentane and cyclohexane, methods of recognising false minimum values.     

Utilisation de methodes de trempe ultra-rapide pour une nouvelle chimie du fluor

Quick quenching preparation from the melt has been extensively used for new fluoride preparations. Some examples are given for obtaining either non crystalline solids (PbF₂AlF₃; PbF₂ZnF₂; Sb₂O₃SbOF systems) or metastable crystalline fluorides (Li₂ZnF₄; SnF_2+x; Sb(O, F)_2+x). A new quenching method called ‘reactive splat-cooling’ well adapted to fluorides is described.     

Sur une transformation inhabituelle de nitro-2 benzofurannes dans les conditions de la reaction de friedel et crafts

On treatment with acetyl chloride or acetic anhydride in presence of aluminium chloride in methylene chloride. 2-nitro and 5-chloro 2-nitro benzofurans yield 2,3-dichloro benzofurans, 3-chloro 2-coumaranones and 2-acetoximino 3-chloro coumarans. By the action of acetyl chloride, in presence of titanium (IV) chloride in methylene chloride, on 2-nitro benzofuran, 2,3-dichloro benzofuran can be obtained with a fairly good yield beside a relatively restricted quantity of 3-chloro 2-coumaranone. In the same conditions, 5-chloro-2-nitro benzofuran yields not only 2,3,5-trichloro benzofuran but also 2,2,3,3,5-pentachloro coumaran and, occasionally. 3,5-dichloro 2-coumaranone.     

SYNTHESIS OF α,ω-PHOSPHONATE POLYSTYRENE VIA DEAD END POLYMERIZATION

To introduce phosphonate groups into polystyrene, two different routes were investigated, both using a conventional radical polymerization, the Dead End Polymerization (DEP). Route 1 described the synthesis of phosphonated azo-initiator by 4,4′-azobis cyanovaleric acid (ACVA) esterification; the new compound would then initiate the styrene DEP. Unfortunately, the esterification was not quantitative and the separation between ACVA and its phosphonated homologue remained unsuccessful. By route 2, we suggested the phosphonate group incorporation by esterification of α,ω -carboxy polystyrene previously obtained by DEP (initiated by ACVA). The esterification reaction was proved to be quantitative by NMR and FTIR techniques. The α,ω -phosphonate polystyrene synthesis was then realized from several α,ω -carboxy polystyrene with molecular weights ranging from 3000 up to 10000 g/mol.     

Influence de la tension de vapeur sur une transition de phases et un equilibre peritectoide

The compound As₄Se₃ exhibits two polymorphs, α andβ. The latter undergoes a peritectoid decomposition. The two phenomena require a vapour pressure action. They are both explained on the basis of aT- V- x diagram. Two cases are described. In the first hypothesis, no solid solution exists. The second hypothesis implies two solid solutions for the two forms α andβ. A comparative study of these two cases has been made. The existence of two invariant planes has been shown in the second case, which makes it rather different from the first one.     

Calcul des facteurs de diffusion polycentriques sur une base de fonctions Gaussiennes

Résumé L'évaluation des facteurs de diffusion polycentriques se trouve considérablement simplifiée lorsqu'on substitue à la base usuelle des fonctions de Slater, un développement en termes de fonctions Gaussiennes. On donne les expressions analytiques de ces facteurs de diffusion: valeurs ponctuelles et valeurs moyennes. Un exemple numérique permet de confronter les résultats obtenus avec ceux issus d'une autre méthode.

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The evaluation of multi-center scattering factors is considerably simplified when an expansion in terms of Gaussian functions is substituted to the usual basis of Slater functions. Analytic expressions of such scattering factors are given: point values and average values. A numerical example allows comparison of the results with those obtained by another method.

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Zusammenfassung Die Berechnung von Mehrfach-Streufaktoren vereinfacht sich beträchtlich, wenn man eine Entwicklung nach Gaußfunktionen an Stelle der üblichen Slaterfunktionen vornimmt. Analytische Ausdrücke solcher Streufaktoren werden angegeben, und zwar sowohl für punktuelle als auch gemittelte Werte. Ein numerisches Beispiel zum Vergleich der Ergebnisse mit denen eines anderen Verfahrens wird angeführt.

     

Synthesis and Properties of Long-Chain Aromatic Telechelic Monodispersed Diols Radical-Initiated,Addition of 2-Mercaptoethanol onto α, ω Nonconjugated Dienes

Abstract

The synthesis of aromatic telechelic mono dispersed diols produced from the radical-initiated addition reaction of a twofold excess of 2-mercaptoethanol onto original α,ω nonconjugated dienes reaction is presented. These novel α,ω nonconjugated dienes were prepared by addition reaction of m-isopropyl α,α′dimethyl benzylisocyanate with mono dispersed telechelic diols obtained by fractionation of oligo(ethylene terephthalate)s. In these cases, the long chain α,ω diols were produced selectively and quantitatively. The products are soluble in most organic solvents in contrast to classical oligo (ethylene terephthlate)s and posses a lower glass transition and melting temperatures.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Figures S1-S3.     

Experimental evidence for the breakdown of conventional elasticity in smectics A

Abstract

Grinstein and Pelcovits have shown that anharmonic terms in the ‘microscopic’ elastic free energy lead to a qualitative change in the macroscopic elastic expressions describing the equilibrium behaviour of smectic A liquid crystals. In particular, they showed that the elastic moduli B(ω = 0,q) and K ₁ (ω = 0,q) vanish and diverge, respectively as In(q) for small wavevector q. In the dynamical case (ω ≠ 0), as predicted by Mazenko, Ramaswamy and Toner, the influence of anharmonicity is more dramatic: some viscosities diverge as 1/ω We present in this paper a finite ω version of the non-linear hydrodynamics of smectic A and what we believe to be the first experimental evidence of the decrease of the layer compressional modulus B(ω, q), at low frequency ω and wavevector q.     

Etude de la reaction de polonovski sur une molecule modele,la dregamine

The effect of acylating reagent on the Polonovski reaction with dregamine, the N-oxide was studied using acetic anhydride, trifluoroacetyl acetate (a mixed anhydride) and acetyl chloride under Schotten-Baumann conditions.     

Formamidines as α-amino carbanion precursors. The synthesis of 2-arylpiperidines, -pyrrolidines,and nicotine analogs

Metallation of the $\text{t}$-butyl formamidines of benzyl or picolinyl amines followed by alkylation with α,ω -dihaloalkanes gives the title compounds after hydrazinolysis.     

Sur un effet de solvant inhabituel sur une reaction de menschutkin intramoleculaire

The influence of solvation on the reaction rate of an intramolecular quaternisation, may be different from the rate observed for an intermolecular reaction of the same type. In the intermolecular reaction, if the polarity of an aprotic solvent increases, the partially charged transition state is more stable than the initial state. In the contrary, for an intramolecular reaction the conformation of the different states (initial and transition) plays an important role. So that, if the polarity of an aprotic solvent increases, one conformation of the uncharged initial state may be, by its geometry more stable than the partially charged transition state. An interpretation based on the conformation, explains why in one case and in comparison with CH₃CN, methanol accelerates the intramolecular reaction whereas the contrary is always observed for an intermolecular one.     

Addition de n-butyle mercaptan sur des oligomeres polybutadienes fonctionnels: Proprietes des oligomeres modifies et des polyurethannes lineaires correspondants

Radical addition of n-butyl mercaptan to α-ω dihydroxylated oligobutadiene gives amorphous and entirely saturated products having relatively low viscosity at room temperature, in spite of the increase in molecular weight. For (1.4) microstructural oligomers, there is increasing glass transition temperature and decreasing functionality. Owing to the difficulty of RSH radical addition to (1.4) butadiene, the addition is slow. For (1.2) microstructural oligomers, the glass transition temperature decreases with increase of the addition ratio and the functionality is not changed. Linear polyurethanes are synthesized from the modified oligomers, diphenylmethane diisocyanate and 1,4 butanediol. The high weight percent of soft segments to hard segments and the steric hindrance of side chains carried by the soft block result in poor mechanical properties.     

Sur une methode simplifiee de dosage microbiologique du ms-inositol

A simplified microbiological assy for inositol involving the use of Schizuscicchurnmyces pombe Lindner is decscribted. The results are very reproducible and the method is simple to operate.