Etude polarographique du méthyl-phényl-dodécyl-triméthylammonium (désogène)

Rèsumè Le méthyl-phényl-dodécyl-triméthylammonium (désogène), donne une vague polarographique caractéristique, en utilisant comme électrolyte de support l'hydroxyde de tétraméthylammonium, le CILi ou le ClK.Les propriétés de cette vague ont été étudiées en fonction de la concentration du saponium. La loi d'Ilkovi est vérifiée.Deux électrons interviennent dans la réduction du saponium.

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Summary The cationic detergent désogène (methyl-phenyl-dodecyl-trimethylammonium) gives a characteristic polarographic wave in LiCl or in tetramethylammonium solution. The wave seems to correspond to a 2 electronprocess, following Ilkovi's law at low concentrations. A typical adsorption maximum, proceeded by a prewave wich does not follow the Ilkovi' law is found at higher concentrations. At high ionic strength this maximum disappears.

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Zusammenfassung Das kationische Detergens Désogène (Methylphenyl-Dodeeyl-Trimethylammonium) gibt in Lithiumchlorid- oder in Tetramethylammoniumhydroxydlösung eine charakteristische polarographische Welle. Diese scheint einem 2-Elektronen-Prozeß zu entsprechen und folgt bei niederen Konzentrationen dem Gesetz von Ilkovi. Ein typisches Adsorptionsmaximum, dem eine dem Ilkovi-Gesetz nicht folgende Welle vorangeht, findet sich bei höheren Konzentrationen. Dieses Maximum verschwindet bei hoher Ionenkonzentration.

     

Structure électronique du fluoroacétylène et du chloroacétylène

Résumé La structure et le spectre électronique du fluoroacétylène et du chloroacétylène ont été étudiés à l'aide d'une méthode matricielle du type LCAO SCF MO où les fonctions monoélectroniques sont des orbitales orthogonalisées de Löwdin. Le transfert de charge de l'halogène au système est d'environ 0,04 électron 2p pour le fluor et 0,08 électron 3p pour le chlore. L'étude des transitions électroniques indique pour la transition du type - située vers 1850 Å un effet bathochrome et une augmentation de la force oscillatrice lorsque l'électronégativité de l'halogène décroît. Ceci permet d'identifier la transition située vers de plus grandes longueurs d'onde avec une transition - dont la force oscillatrice varie en sens inverse de celle de la transition -.

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The electronic structure and spectra of fluoroacetylene and chloroacétylène have been studied by a matricial method of LCAO SCF MO type where the monoelectronic functions are Löwdin'S orthogonalized orbitals. The charge transfer from the halogen to the system is equal to about 0,04 2p electron for fluorine and to 0,08 3p electron for chlorine. A bathochromic effect and an increase of the oscillator strength with the halogen electronegativity decreasing have been found for the - transition at 1850 Å; from the theoretical results it is possible to identify the transition of lower energy as a - transition whose oscillator strength varies the other way than that of the - transition.

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Zusammenfassung Struktur und Elektronenspektren von Fluor- und Chloracetylen wurden mit Hilfe einer Matrizenmethode vom LCAO-SCF-MO-Typ untersucht, wobei die Einelektronenfunktionen nach Löwdin orthogonalisiert wurden. Der Ladungsübergang vom Halogen zum -System entspricht etwa 0,04 2p-Elektronen bei Fluor und 0,08 3p-Elektronen bei Chlor. Für den --Übergang um 1850 Å wird für abnehmende Elektronegativität des Halogens eine bathochrome Verschiebung und eine Zunahme der Oscillatorenstärke gefunden. Das erlaubt, die längerwellige Bande einem - -Übergang zuzuordnen, dessen Oscillatorenstärke sich in entgegengesetzter Richtung ändert.

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Nous tenons à remercier Monsieur Berthier pour de nombreuses discussions sur ce travail, Messieurs Romanet et Wojtkowiak pour avoir attiré notre attention sur les problèmes posés par les spectres ultraviolets des halogéno-acétyléniques et Monsieur H. v. Hirschhausen pour nous avoir signalé une erreur numérique dans la fin de cet article.     

Analyse vibrationnelle infrarouge et Raman du benzosélénophène et du benzotellurophène

Infrared (4000-200 cm⁻¹; vapour solid and solution dissolved in inert and proton acceptor solvents) Raman (4000-100 cm⁻¹, solid and solution) spectra of benzoselenophene and benzotellurophene have been recorded. A complete attribution of the fundamental vibrations is proposed. The fundamental vibration wavenumbers evolution for a series of monoheteroatomic benzoheterocycles C₈H₆X with X = O, S, Se and Te is analysed.     

Synthèse de polymères du polyéthylène et du polypropylène à greffons fluorés

Synthesis of fluorinated graft polymers was carried out by two methods. In the first, we use a macromolecular initiator to start the polymerization of a fluorinated monomer in solution, emulsion or in bulk; graft copolymers containing up to 30% of fluorinated grafts were prepared. The second method consists in the condensation of a functional oligomer on a functional graft copolymer. This method was very efficient leading to a new series of graft copolymers with 40% of fluorinated chains.     

Etude du phénomène de dépiégeage des ondes de densité de charge dans les systèmes de basse dimensionnalité

Numerical results of the behaviour of a low dimensional system show that the electric resistivity depends on the friction coefficient generated by the defects. We also show that the electric field dependence of the response time at different friction coefficients follows a power law. The divergence of the charge density wave response time near the threshold field indicates that depinning may be viewed as a dynamical critical phenomenon.     

Etude du complexe par liaison hydrogène du carbazole à l'état fondamental par spectroscopie UV

The modifications of UV absorption spectra of carbazole show the hydrogen bonding complex in the ground state. The red shifts of carbazole absorption spectra in solvents able to form a complex are more important than those obtained in aprotic solvents, with high polarity. The solvents with OH groupment can interact with carbazole to form NH ⋯ O and OH ⋯ π type hydrogen bonds.     

Etude expérimentale de l'ammoxydation catalytique du propène dans un réacteur différentiel

The kinetics of ammoxidation of propene has been studied over an industrial Sn/Sb oxides catalyst in a differential reactor at 490 °C.Factorial design of experiments leads to reliable rate equations over the range of partial pressures encountered in a fluidized bed reactor.The rate of disappearance of propene may be represented by the equation r₁ = 1.497 × 10⁻⁷P_C3H6^0.48P_O2^0.48P_NH3^0.19 and the rate of formation of acrylonitrile by r₄ = 1.287 × 10⁻⁷P_C3H6^0.43P_O2^0.52P_NH3^0.47A best fit is obtained by the addition of some empirical pressure interaction terms. Catalytic activity is about the same as for other Sn/Sb oxides catalysts and maximum selectivity at 490 °C is at least 82%.     

Sur une nouvelle méthode de dosage gravimétrique du tungstène

Résumé Cette étude nous a conduit, d'une part à mettre au point un procédé de dosage du tungstène sous forme de tungstate purpuréocobaltique, d'autre part à enregistrer les spectres d'absorption infrarouge des divers tungstates précipités à différentspH, purs ou en mélanges afin de les identifier. A ce point de vue la technique infrarouge se montre plus sensible que l'analyse chimique. Nous avons également entrepris l'étude des spectres dans la région 15 à 25 et nous espérons que les résultats de ces études nous aideront à connaître la structure de ces composés à l'état solide, structure encore bien mal connue.

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Summary This study has taken two directions. It has led to a procedure for determining tungsten as purpureo cobalti tungstate, and to the recording of the infra red absorption spectra of various tungstates precipitated at different p_H values, either pure or in mixtures, in order to identify them. From this point of view, the infra red technique has proved more sensitive than the chemical analysis. We have also undertaken the study of spectra in the region 15–25 and we trust that these results will aid us to discover the structure of these compounds in the solid state, structures which as yet are imperfectly known.

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Zusammenfassung Die vorstehenden Untersuchungen führten einerseits zur Ausarbeitung einer Methode zur Bestimmung des Wolframs ais ChlorpurpureokobaltWolframat, anderseits. zur Bestimmung der Infrarotspektren einiger bei verschiedenem pn gefällter Wolframate zu dem Zweck, sie in reinem Zustand oder in Gemischen zu identifizieren. Hierfür erwies sich die Infrarotteohnik empfindlicher als die chemische Analyse. Welters haben wir auch die Spektren im Bereich von 15 bis 25 untersucht und hoffen, da die Ergebnisse dieser Untersuchungen zur Aufklärung der Struktur dieser Verbindungen im festen Zustand dienen können, die bis jetzt noch ziemlioh wenig bekannt ist.

     

Etude par spectrographie d'absorption infrarouge des produits de décomposition du mélange chlorate de potassium-bioxyde de manganèse

Résumé Le chlorate de potassium, chauffé avec du bioxyde de manganèse, donne de l'oxygène et du chlorure de potassium, sans formation transitoire de perchlorate et de permanganate de potassium.

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Summary Potassium chlorate when heated with manganese dioxide yields oxygen and potassium chloride without transitory formation of potassium perchlorate and permanganate.

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Zusammenfassung Kaliumchlorat zerfällt beim Erhitzen mit Mangandioxyd in Sauerstoff und Kaliumchlorid, ohne daß Perchlorat und Permanganat als Zwischenprodukte gebildet werden.

     

Formation et désactivation par l'oxygène moléculaire de l'atome métastable O(5S) dans une décharge oxygène-hélium

O(⁵S) metastable atom production is studied in a microwave induced plasma (2450 MHz, 320 W) as a function of pressure (0.5 to 10 Torr) and oxygen concentration in helium (0 to 15 % O₂). O(⁵S) and He(³S) densities, electron temperature and electron density are determined. Measurements are performed by optical absorption for metastable species and by double probes for electron temperature and density.Results show that: -O(⁵S) density increases and reaches a maximum with increasing pressure and increasing oxygen concentration, then decreases, while He(³S) decreases continuously; -electron temperature decreases with oxygen concentration and with pressure; -electron density variation is a weak function of oxygen concentration and increases with pressure.According to the results obtained a mechanism for O(⁵S) production and destruction is proposed. Assuming a steadystate, the quenching rate constant of O(⁵S) by O₂ was estimated to be: (1.2 ± 0.4) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹.     

Dosage du chrome,du vanadium et du molybdène par la méthode des indicateurs radioactifs

A radiochemical method for the determination of Cr, Mo, and V by means of radioactive silver is described. Using a solution of radioactive silver nitrate, a standard curve is obtained indicating the activity of the precipitate as a function of the quantity of the metal present. Unknown concentrations of Cr, Mo, or V can be easily determined if the same experimental and geometrical conditions are reproduced.     

La séparation et le dosage du tungstène et du molybdène au moyen du chlorure de calcium

A rapid and simple method is described for the separation and the determination of molybdenum and tungsten. Both metals are extracted as their soluble salts, sodium molybdate and sodium tungstate, by means of an alkaline fusion (Na₂CO₃ + Na₂O₂), after which they are separated by precipitation with calcium chloride as reagent. The precipitates of calcium molybdate and calcium tungstate are filtered, washed and then decomposed by concentrated hydrochloric acid. Calcium molybdate passes completely into the filtrate while calcium tungstate leaves a precipitate of tungstic acid. By calcining this precipitate, tungstic trioxide is obtained and weighed. The tungsten content is calculated therefrom.The filtrate from tungstic acid serves for reprecipitation of calcium molybdate on making the solution alkaline and by boiling. Calcium molybdate is filtered by means of a porcelain crucible filter and then calcined. When the weight of the calcined precipitate is constant, the molybdenum content is obtained by multiplying the weight of the precipitate by the conversion factor. Results are satisfactory, separation and determination of both metals not taking more than a day's work.     

Synthèse de complexes du tungstène,du chrome et du rhénium contenant un ligand 1,4-bidenté carbéne-alcéne

A general synthesis of alkene-carbene complexes of tungsten, chromium and rhenium, containing a six-membered ring system, is outlined and the crystal structure of two new complexes of this type, (CO)₄WC(OEt)(CH)(η²-CH₂CHCH₂) (CH₂CHCH₂) and (CO)₉Re₂(OCH₂CH₃(CH₂(CH₂(CH₂CHCH₂), is described.     

Préparation du complexe endoédrique hydrogène moléculaire fullerène C60, associé à du C60 hydrogéné

Preparation of endohedral complexes of molecular hydrogen-fullerene C_60, together with hydrogenated C₆₀. Using our new method described elsewhere, we have obtained the preparation of endohedral complexes H₂@C₆₀, together with hydrogenated C₆₀. Analyses by ¹H NMR, and by infrared and vacuum ultraviolet spectroscopies have been carried out, which proved the existence of these two kinds of compounds in our samples. A quantitative measurement has been done, giving values for the endohedral complexes of about 18%, and for the hydrogenated C₆₀ of about 35%. To cite this article: B. Oksengorn, C. R. Chimie 6 (2003).     

Comportement électrochimique du ferrocène,du pérylène et du tétracène dans une électrode à pâte de carbone à liant électrolytique dans les mélanges eau–acide phosphorique

The carbon dough electrode with incorporated electrolyte has been used to analyse the electrochemical behaviour of ferrocene, tetracene and perylene in phosphoric acid media 0.1 to 14.8 M. The cyclic voltammetry results obtained for ferrocene with the carbon dough electrode corroborate with polarographic data. Voltamperometric study of the aromatic hydrocarbon oxidation Ar such that of perylene and tetracene on the carbon dough electrode has allowed to establish the normal potential of the corresponding oxido-reducing systems. The existence of the four oxidation states: Ar, Ar⁺, ArH⁺ and Ar²⁺ at different concentrations of phosphoric acid is specified. The results of this study can be used to establish correlations between some of concentrated solution properties of different acids.     

Etude polarographique du mercure (Hg+2) en présence d'acide éthylènediaminotétracétique : Influence du pH sur le potentiel de demi-vague - constante de stabilité du complexe

The ethylenediaminotera-acetic acid (complexon) generates an anodic polarographic wave of depolarization to be ascribed to the formation of a stable complex with mercury, and the potential of which becomes more negative when there is an increase in pH.The complex formed between complexon and the mercuric ion is reducible by polarography, but its half-wave potential is slightly more negative than that of the anodic wave under the same conditions of pH and buffers.By studying the variation with the pH of the Redox equilibrium potential of the wave constituted by a solution containing equimolecular quantities of complex and complexon in excess, it was possible to show that in the range of pH from 4.50 to 9.25, the only complex existing in considerable proportion corresponds to the formula HgY^-2; its stability constant is equal to 10^-22.15±0.05 (t = 25° C,μ =0.065).The constant of diffusion current of the reduction wave of the complex, as well as that of the anodic wave of depolarization by the complexen, is equal to 2.86 ± 0.03 (t = 25° C, pH: 4.60 to 7.50).     

Utilisation de matériaux à base d’argiles modifiées dans la conversion du toluène

Clay materials, montmorillonite from Maghniya deposits (Algeria), were used as an acidic catalyst in toluene conversion. Toluene disproportionation reaction in gaseous phase was used. These clays were modified by ion exchange with uranyl ions UO₂²⁺. The surface acidity of catalysts was determined by the stepwise desorption technique (STD) of probe molecules using butylamine and ammonia. Thus, total acidity and distribution of the acidity strength were determined. The results show that materials presented an appreciable total acidity and catalytic activity in studied reaction. The acidity strength of catalysts due to UO₂²⁺ ions was kept at a temperature of 550 °C. A relationship was found between the catalytic activity and acidity strength generated by the introduction of uranyl ions in the clay structure.     

L'analyse polarographique appliquée aux produits de la métallurgie du zinc

The application of polarographic analysis to products of zinc metallurgy is of particular interest for the estimation of traces of Pb, Cd, and Zn and in concentrations up to 10%. The use of a manually registering polarograph is considered to be very convenient in these cases.     

Réactivité des macromonomères styréniques du polyoxyéthylène en transfert radicalaire

During the homo- and copolymerization with butyl acrylate of styrenic macromers of polyoxyethylene, the molecular weight of the polymer is found to increase continuously because of transfer to the polymer. The polymerization of butyl acrylate in the presence of non-polymerizable model compounds of the macromers has been studied. It is shown that the transfer involves chiefly the benzylic protons; the transfer constant is 2.1 × 10^–3, i.e. larger than that corresponding to the ethylene oxide moiety, which is about 3 × 10⁻⁴. A kinetic study shows that the efficiency of the transfer radicals for reinitiation is about 0.75.