Diffusion de la lumiere par des suspensions de particules anisotropes—III. Particules orientees par un champ electrique et diagrammes de diffusion aux petits angles

The theoretical modifications of the small-angle light scattering patterns are studied, when the scattering particles are anisotropic and subjected to an electric field. Particular attention is paid to discs fully orientated round their diameter.     

Le developement de l'etude de la diffusion de la lumiere et des neutrons par les polymeres a strasbourg

In this paper one recalls the history of the development of scattering studies after the first world war in Strasbourg. Tremendous progress has been made and some examples of this progress are discussed     

Etude du comportement thermique de la poly(pivalolactone) par diffraction des rayons-x aux petits angles et par calorimetrie dynamique

Poly(α,α-dimethyl-β-propiolactone) (PPL), known as poly(pivalolactone), has been studied by differential scanning calorimetry (DSC) and small-angle X-ray diffraction (SAXR). DSC measurements indicate the presence of two melting endotherms. Peak 1 and Peak 2, the latter at lower temperatures. Peak 1 is relatively unaffected by the crystallization temperature and its relative intensity decreases with heating rate. Peak 2 is greatly influenced by the crystallization temperature of the sample and its relative intensity increases with heating rate. Peak 2 is associated with the true melting of the PPL samples and Peak 1 with a recrystallization process during the heating cycle. SAXR long periods increase with crystallization and annealing temperatures. Similar increases in density, in melting temperature, in lamella thickness, and in degree of crystallinity have been observed. These results lead to a thermodynamic melting temperature of 268 ± 3 for PPL, and to interfacial free energies of, respectively. 13 × 10^?7 J cm^?2 and (43 ± 4) × 10^?7 J cm^?2 for the lateral surface and the fold surface of the PPL crystal.     

Caracterisation Thermodinamique de Quelques Derives Acyles de la 3-Indazolone

The following acetylated derivatives of indazole: 3-indazolone, l-acetyl-3-indazolone, 2-acetyl-3-indazolone, l,2-diacetyl-3-indazolone and 3-acetoxy-l-acetyl-indazole were studied by combustion calorimetry. The enthalpies of formation were calculated from enthalpies of combustion. The isomeri-sation enthalpies were also calculated. The phase transition temperatures as well as caloric capacities of the studied compound in the crystalline phase were determined by DSC.     

Analyse conformationnelle a l'aide de la notation des angles de torsion-VIII: Interpretation conformationnelle de la reaction de substitution nucleophile(SN2) dans la serie des cycles petits et moyens

Taking geometric constraints into account, involved at the carbon atom undergoing configurational inversion in S_N2 displacement reactions of cyclic compounds, the conformational course of the reaction can be analysed. This method allows a rationalization of the relative rates of S_N2 reactions of isomeric compounds in the cyclohexane, cyclohexene, cyclopentane, and cyclopentene series. Conformational factors involved in the displacement reaction, which may orient it towards either S_N2 or S_N2' type of reaction are discussed.     

Solvatation preferentielle dans les systemes ternaires polyvinylpyrrolidone/solvant halogene/solvant donneur de proton—I: Etude par diffusion de la lumiere

Light scattering measurements of apparent molecular weights show that polyvinylpyrrolidone dissolved in 1,2-dichloroethane (or chloroform)/ethanol (or acetic acid) mixtures adsorbs preferentially either of the two solvents according to the range of composition. The preferential solvation of polyvinylpyrrolidone by proton-donor solvents was confirmed by experiments involving fluoroethanols and phenols. Comparison of our experimental data with preferential adsorption theory leads to rather good agreement for the polyvinylpyrrolidone/chloroform/ethanol system.     

Analyse conformationnelle a l'aide de la notation des angles de torsion—V : Cours sterique de la cis-addition de reactifs sur les olefines de cycles petits et moyens; le cas des derives cyclopenteniques

The steric course of suprafacial cis-addition to cyclopentenes can be interpreted or predicted using the following assumptions: (a) cis-addition to an olefin is not a synchronous process; (b) the reaction involves the least amount of conformational distortion from the reactant to the primary product; (c) the addition takes place so as to give preferentially the axial product. Using the torsion angle notation,^2,3 the sign sequence of torsion angles, taken clockwise before and after the double bond, is related to the direction of cis-addition; the (+0?) sequence corresponds to β-cis-addion, above the mean plane of the ring, and the (?0+) sequence corresponds to α-cis-addition, below the mean plane of the ring.     

Structure de la gouregine,alcaloïde orginal apparente aux cularines

The structure of guoregine, a new isoquinoline alkaloid from $\text{G}$$\text{u}$$\text{a}$$\text{t}$$\text{t}$$\text{e}$$\text{r}$$\text{i}$$\text{a}$$\text{o}$$\text{u}$$\text{r}$$\text{e}$$\text{g}$$\text{o}$$\text{u}$, Annonaceae, has been deduced by spectral analysis and confirmed by an X-ray structure determination. It is the first member of a new class of cularine-related alkaloids (α-$\text{g}$$\text{e}$$\text{m}$-dimetyltetradehydrocularines).     

Reaction de metathese des olefines induite photochimiquement en presence d'un complexe de metal de transition: III. Caracterisation generale de la transformation

Activated sodium hydride (NaHRONa) was treated with Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Zr, Mo, Pd, W salts to give the new complex reducing agents NaHRONaMX_n (CRA). Their reactivities were examined for reduction of 1-bromonaphthalene. In most cases, the CRA exhibited very good reducing abilities, which can be varied by changing the solvent, the alkoxide, or the temperature. Moreover, some CRA act as coupling agents for aromatic halides. Easy to prepare and handle on a preparative scale, CRA must be regarded as very promising tools for organic synthesis.     

Electrode Hybride Pour la Determination de Phosphates et de Polyphosphates. Application aux Problemes Lies a l'Environnement

Abstract

The determination of phosphates and polyphosphates has been effected using an hybrid electrode, which consists of a glucose oxydase enzymic membrane and a Solanum tuberosum tissue slice. This membrane, rich in acid phosphatase, catalyses the glucose-6-phosphate hydrolysis. This reaction is quantitatively inhibited by phosphate. Several factors involved in the electrode response, like substrate concentration, pH, ionic strength and type of buffer are discussed in detail. At a 4.10^?4 M glucose-6-phosphate concentration, the linear ranges of phosphates and polyphosphates are, respectively, 6.10^?5 M to 1.6.10^?3 M and 3.10^?5 M to 1.10^?3 M. The urinary phosphate contents determinated by this biosensor are in good agrement with those obtained by usual spectrophotometric techniques.     

≪ Monocristaux ≫ de copolymères triséquencés styrène/isoprène/styrène présentant la structure cylindrique: I. Étude de l'orientation par diffraction des rayons X aux petits angles

Résumé Des copolymères triséquencés polystyrène-polyisoprène-polystyrène, présentant la structure en cylindres ont été soumis à un cisaillement plan.L'orientation, ainsi obtenue, a été étudiée par diffraction des rayonsX aux petits angles de Bragg. On a pu montrer que les échantillons présentent une texture monocristalline bien développée: les cylindres sont paralléles à la direction du cisaillement et le réseau cristallin lui-méme est oriente de façon unique à travers tout le volume du matériau.

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Summary SIS three-block copolymers presenting the cylindrical structure, have been submitted to a plane shear flow. Their orientation has then been studied by low-angle X-ray diffraction.Samples have been found to be oriented in a well developed single-crystalline texture. The cylinders are all parallel to the flow direction, and the crystal lattice itself is oriented in a unique way throughout the whole volume of the polymer.

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Zusammenfassung Mit Hilfe der Röntgenkleinwinkelstreuung wird die eine Orientierung als eine zylindrische Struktur zeigende Styrol-Isopren-Styrol-Copolymer-Probe erforscht. Die Probe wird so hergestellt, daß man sie als ein Monokristall betrachten kann. Nicht nur alle Zylinderachsen laufen parallel zur Scherrichtung, sondern auch die sechseckigen Gitterblöcke der Kristalline zeigen eine einheitliche Orientierung mit der Scherungsfläche.

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Mit 2 Abbildungen und 11 Tabellen

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Avec 9 figures et 1 tableau     

Analyse conformationnelle a l'aide de la notation des angles de torsion X: Interprétation de la régiosélectivité d'ouverture des époxydes de composés bicycliques incorporant des cycles petits et moyens

Using the dynamic method of conformational analysis through the implementation of the torsion angle notation and applying the rules of distortion compatibility at the junction of fused rings, permits the interpretation or prediction of the regioselective opening of epoxides and analogous three-membered heterocycles of the halonium type fused to small and medium rings.     

Solvatation preferentielle dans les systemes ternaires polyvinylpyrrolidone/solvant halogene/solvant donneur de proton—III: Confrontation des resultats obtenus par diffusion de la lumiere et par spectroscopie infra-rouge

We have compared the experimental results of study of the preferential solvation of polyvinylpyrrolidone in halogenated solvent/proton-donor solvent mixtures, obtained by light scattering and i.r. spectroscopy and described in the two preceding papers. The preferential adsorption of the proton-donor solvent is explained by the formation of a hydrogen-bond complex of polymer with proton-donor solvent, on which other proton-donor molecules are bound by induced autoassociation. This complexing occurs even in mixtures where the “inert” solvent (1,2-dichloroethane) is preferentially adsorbed; this is experimental proof of a differing solvation of the chains in their close neighbourhood and within short range of them.     

Etude de la cycloaddition du dimethylcetene aux allenes—I : Aspects synthetiques

Thermal cycloaddition of dialkylketenes to 1,2 dienes is a versatile synthetic route to conjugated alkylidenecyclobutanones. The central carbons of the allene and of the ketene react together resulting in a regiospecific addition.     

Extraction Rapide de la Cafeine Urinaire Sur Cartouche C18 Et Dosage Par Chromatographie Gazeuse

Abstract

A rapid method for urinary caffeine extraction on C₁₈ cartridge before GC determination is proposed in view of doping controls in sport. The choice of the standard and of the analytical procedure has been directed by the necessity of rapid determination.

Caffeine extraction on C₁₈ reverse-phase is achieved with a good efficiency (recovery : 98 %, CV = 3 %), so that use of an internal standard was not found necessary. Amobarbital was chosen as internal standard in GC because of several advantages : retention time, thermal stability, interesting properties in mass fragmentometry.     

Heteroyohimbane a noyau furannique. Nouvelle voie d'acces aux derives de la furo[3,2-c]pyrone et de la furo[3,2-c]pyridine

3,4-Dicarbomethoxyfuran bearing an acetonyl or a phenacy group in the 2 position w3as prepared by pyrolysis of the dihydrocyclo adduct from methyl acetylendicarboxylate and 2-acetonyl- or 2-phenacylfuran. Condensation of 2-acetonyl-3,4-dicarbomethoxyfuran with tryptamine gave a new heteroyohimbane with a furan ring, indolo[2,3-a]furo[3,2-c]quinolizine, a potential precursor of yohimbane. Ketodiacids from saponification allow one to obtain derivatives of the following heterocyclic ring systems, namely 4H-furo[3,2-c]pyran-4-one and furo[3,2-c]pyridine.