Etude vibrationnelle de la sphere de coordination du cuivre dans la malachite

A preliminary method of vibrational assignment was applied to the coordination sphere of the copper atom in malachite: Cu₂(OH)₂CO₃. The number of frequency combinations assigned to species (B_1u), (B_2u), (B_3u) was obtained by means of occasional coïncidences belonging to different symmetry species.It was then shown possible to realise, under certain conditions, the vibrational assignment and direct calculation of the force constants for the coordination sphere of heavy atoms in inorganic and organometallic complex structures.     

Etude de la solvolyse des tosylates d'aryl-2 propyle dans le dimethylformamide

Aryl-2 propyltosylate solvolysis occurs in DMF as in a protic medium, via two competing mechanisms: solvent nucleophilic substitution (rate constant k_s) unimolecular solvolysis with aryl participation (k_Δ). Nucleophilic solvent participation is more important in DMF than in a protic solvent; this is due to the lack of electrophilic assistance of DMF compared to a hydroalcoholic solvent (k_Δ^DMF < k_Δ^{EtOH aq.}), DMF and aqueous carbon nucleophilicities being nearly the same (k_s^DMF ? k_s^{EtOH aq.}). Charge distribution in transition states are of the same type in both solvents.     

Substitution nucleophile aromatique. Etude cinetique de la C-arylation de cyanoacetamides par les halogenonitrobenzenes dans le N,N-dimethylformamide

The C-arylation of the sodium salt of N,N-dimethylcyanoacetamides, in DMF, has been investigated. The kinetics can be explained if two forms of the nucleophile, the isolated carbanion and the less reactive ion pair, are involved by use of Acree's theory, it has been possible to elucidate constants k_i (for isolated carbanion) and k_p (for ion pair) for different aromatic substrates. The variation of k_i/k_p may account for the selectivity observed in some cases.     

Etude de la racemisation induite par la dmap dans les reactions de couplage peptidique

The scope and limitation for the use of 4-dimethylamino pyridine (DMAP) as additive to carbodiimides in peptide synthesis are studied and compared with the results obtained with H-hydroxybenzotriazole (HOBt). The activation of N-acylated aminoacids by the means of DMAP leads to a complete racemization. On the other hand, for the aminoacids protected under their urethans derivatives, DMAP gives better yields than HOBt with racemization extent generally equal to or slightly higer to that observed with HOBt.     

Etude par des methodes semi-empiriques de la chimie theorique dans la serie des pyrazolones—VII : Sur le probleme de la tautomerie des phenylazopyrazolones

The tautomeric equilibrium, configuration, bond order P_CO and structure of the common anion of phenylhydrazopyazolones have been investigated by means of semi-empirical MO methods (Hückel-ω, Extended Hückel). The results have been compared with those in the literature. Experiments have been made in order to verify the theoretical predictions.     

Etude de la stabilisation du polychlorure de vinyle avec des molecules modeles—IV. Composes epoxydes

Chloro-4-hexene-2 (C4H2), a model compound for the study of polyvinylchloride stabilization, reacts with epoxy compounds in dichloroethane but not in tetrahydrofuran. In the latter case, the reaction is catalysed by zinc chloride but this compound is also a catalyst for the polymerization of the epoxy function. The zinc chloride is then modified so that the kinetic laws for etherification and dehydrochlorination of C4H2 are more complex than when the catalyst is CdCl₂, as previously studied by Anderson and McKenzie. With zinc and calcium stearate, one also observes esterification of C4H2, the three reactions being competitive. The synergistic effect of epoxy in the presence of stearate is induced chiefly by modification of ZnCl₂ through the initiation reaction for the polymerization. Therification, as well as esterification, may be reversed by HCl which regenerates C4H2; this fact explains the catastrophic character of degradation after the stabilizer has been consumed. The results of the study on model compounds can be applied to the degradation of PVC upon mastication in a Brabender plastograph.     

Effets de sels dans la reaction de trialkylaluminium avec le benzaldehyde

Tetra-n-butylammonium halides and, to a lesser extent alkali fluorides, enhance the addition/reduction ratio in the reaction of trialkylaluminium with benzaldehyde in ether, and lower the reactivity of the organoaluminium compounds. These results are consistent with the existence of complexes between salts and organoaluminium compounds [MX•R₃ Al (1/1) and MX•2R₃ Al (1/2)]. The more stable the complex, the more important are the effects I⁻ Br⁻ Cl⁻ F⁻ and NaF KF Bu₄ NF. The 1/1 complexes are more stable and less reactive than their corresponding 1/2 complexes.     

Etude de l'incorporation de l'oxyde de cuivre dans le reseau de l'oxyde de nickel par traitement thermique

NiO prepared at 950° has been impregnated with a solution of copper nitrate and heated at 300°. The incorporation of CuO issued from this treatment in the lattice of NiO during sintering at 450–1100° has been studied by DTA and TG, and chemical analysis. A few experiments by radiocrystallographic analysis and electron diffraction have also been done. The process of incorporation begins at about 600° and is nearly complete at 900°. A sample elaborated at 1100° is homogeneous in the mass but presents in the surface an excess of copper ions which seems to be located at certain points.

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Zusammenfassung Bei 950° erzeugtes NiO wurde mit Kupfer(II)nitratlösung impregniert und auf 300° erhitzt. Der Einbau von CuO (5 %) in das NiO-Netz bei thermischer Behandlung von zwischen 450–1100° wurde durch DTA, TG und chemische Analyse untersucht. Einige Proben wurden auch einer Prüfung durch Radiokristallographie und Elektronendiffraktion unterworfen. Der Einbau beginnt bei 600° und ist bis 900° praktisch vollendet. Eine bei 1100° erzeugte feste Probe, obzwar homogen in der Masse, zeigt an der Oberfläche einen Überschuß von an gewissen Stellen lokalisierten Kupferionen.

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Résumé NiO préparé à 950° a été imprégné par une solution de nitrate cuivrique et chauffé à 300°. L'incorporation de CuO (5 %), ainsi engendré, dans le réseau de NiO, lors de traitements thermiques à 450–1100° a été étudiée par ATD, ATG et analyses chimiques. Quelques essais d'analyses radiocristallographiques et de diffraction électronique ont également été effectués. Le processus d'incorporation se manifeste à partir de 600°. Il est pratiquement complet vers 900°. Un solide élaboré à 1100°, bien qu'homogène dans la masse, présente, en surace, un excédent d'ions Cu^{+ +} qui semble localisé en certains points. , 950°, 300°. , , , 450° 1100°. . 600° 900°. , 1100°, , .

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Nous tenons à exprimer nos remerciements à Messieurs H. Urbain et R. Bacaud, à Mesdames G. Dalmai-Imelik, C. Leclerq et M. A. Gresteau, et à Monsieur A. Renouprez pour leur contribution à cette étude.     

Etude theorique de la reactivite des ions libres intervenant dans la polymerisation anionique de quelques monomeres vinyliques

The reactivities have been calculated for free ions involved in anionic polymerization of vinyl monomers. The copolymerization constants k_AB available in the literature are compared to the stabilization energies involved in the reaction of carbanions with the same monomer. The reactivities of carbanions of living poly (2-vinyl pyridine), poly styrene and poly (substituted styrenes) with respect to 1-1,diphenylethylene have been computed. The rate constants of homopolymerisation have been compared with the variation of π energy between the “monomer” and “carbanion” states of these monomers. The occurrence of side-reactions during the polymerization of vinyl-pyridine has been investigated using quantum chemistry methods.     

Etude théorique de l'isomérisation syn-anti dans la Formaldoxime

Semi empirical CNDO and ab initio methods are applied to the analysis of syn-anti isomerization mechanism of formaldoxime. Semi empirical calculations are carried out with complete geometry optimization and lead to predicted inversion barrier equal to 37.5 kcal/mole. A bicentric partitioning of the total energy and the expression of the density matrix in hybride basis set reveal the chemical origin of the shape of the potential line.

     

Etude de la conductivite anionique dans quelques fluorures amorphes obtenus par hypertrempe

Fluoride ion conductivity has been investigated in amorphous materials obtained in the BaF₂-ZnF₂, PbF₂-ZnF₂ and BaF₂-MnF₂ systems using both NMR and complex impedance techniques. The activation energies appear to be about 0.53 eV with a good agreement between both methods. Ionic conductivities have been found to be larger than 10^-5ω^-1cm^-1 at 180°C, values which are among the best ones so far obtained for fluorine conducting glasses.     

Etude par ESCA de la repartition des charges dans les ylures de pyridinium

The charge density distribution in pyridinium type A and B ylides has been studied by ESCA. From the binding energies of the 1s electrons of their nitrogen atoms it can be concluded that the negative charge remains on the nitrogen atom of type A compounds, but that the negative charge usually assigned to the carbon atom on type B ylides is delocalised in electronegative substituents. From this fact, we propose a new mechanism to explain the reactivity of type B ylides, which react either by a 1,2-cycloaddition mechanism or as 1,5-dipoles. The reactions of the type B ylides can be interpreted better on this basis.     

Etude theorique de la premiere protonation de la proflavine

A comparison between theory and experiment (the last performed by J. H. Lhoste) gives consitent results pertaining to the difference in acid-base behaviour of proflavin in the ground state and in the excited singlet and triplet states. In particular, several facts emerge. An extraordinary inequality between the different pK′s of acid-base equilibria are indicated: p_triplet^K < p_fondamental^K < p_singulet^K A change occured by protonation in the electronic configuration of the lowest triplet state of that molecule and the variation of solvation energy during the absorption ground state-first excited singlet state plays an important part.     

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.     

Preparation de membranes hydrophiles obtenues par le greffage de la n-vinylpyrrolidone dans le poly(chlorure de vinyle)

PVC films were radiation-grafted in NVP-methanol solutions. Unusual kinetics relations were observed: an increase in monomer concentration or in temperature decreased the reaction rate. These effects are attributed to a higher mobility of the growing chains leading to faster chain termination and resulting in a drop of the overall rate and shortening of grafted chains. The graft copolymers swell homogeneously in water and in methanol. The swelling rate and limiting swelling ratio increase linearly with the grafting ratio. The swelling ratio was found to depend on chain length, being higher for short chains. An irreversible increase of the swelling ratio was found by raising the temperature. These unusual swelling properties of the grafted films are attributed to strong interactions between pyrrolidone groups and the Cl atoms of the PVC.     

Etude de la fragmentation de semi-carbazones terpeniques

Terpene semicarbazones have been investigated using high resolution mass spectrometry. We have studied correlations between rings and functional semicarbazone degradations. The mass spectra are more complicated than the mass spectra of oximes, methyloximes and hydrazones. Cleavages are explained by known mechanisms. An interpretation of almost all the peaks is offered. The fragmentation of the semicarbazone skeleton is less marked than in the oximes. Fragmentation processes induced by the functional group are numerous. Ions obtained are concerned in secondary cleavages. Thus it is not surprising that the predominant feature is localisation of charge upon the imino nitrogen atom. Other centres may, however, be responsible for the appearance of several peaks.     

Etude physico-chimique de la solubilite de la polyvinylpyrrolidone et d'autres polybases de lewis,dans des melanges binaires de solvants polaires

We have measured the solubility of polyvinylpyrrolidone and some other polar polymers in organic mixtures composed of halogenated solvents and proton donors such as alcohols or carboxylic acids. As a general rule, a coacervation zone appears which is limited by a closed curve. This property is explained by a selective adsorption of the donor compound by the polymer, leading to a macromolecular complex via hydrogen bonds. This phenomenon is particularly marked when both solvents are near demixing conditions.