Etude par microcalorimetrie de la reactivite de deux ammoniacates de chlorure de manganese

The reaction [Mn(NH₃)₂]Cl₂+ 4NH₃ [Mn(NH₃)₆]Cl₂, which is of potential use in chemical heat pumps, was studied by means of differential scanning calorimetry. The thermodynamic conditions, the enthalpy of the reaction, and the heat capacity values for MnCl₂, [Mn(NH₃)₂Ch and [Mn(NH₃)₆Cl₂ were measured. The influence of the reaction kinetics of the experimental procedure and some parameters such as sample temperature, ammonia pressure and scanning rate was examined.

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Zusammenfassung Mittels DSC wurde die Reaktion [Mn(NH₃)₂]Cl₂+4 NH₃ [Mn(NH3_{) 6}]Cl₂ untersucht, die von potentieller Verwendung für chemische WÄrmepumpen ist. Thermodynamische Bedingungen, die Reaktionsenthalpie und WÄrmekapazitÄtswerte für MnCl₂, [Mn(NH₃)₂]Cl₂ und [Mn(NH₃)₆]Cl₂ wurden gemessen. Weiterhin wurde der Einflu\ des Versuchsablaufes und einiger Parameter, wie Probentemperatur, Ammoniakdruck und Scanning-Geschwindigkeit auf die Reaktionskinetik untersucht.

     

Synthese regioselective de bases de mannich de cetones dissymetriques

Methods for the regioselective synthesis of Mannich bases starting from unsymmetrical ketones are described. The Mannich base on the more substituted carbon is obtained by reaction with (CH₃)₂N⁺CH₂,CF₃CO₂^- in CF₃CO₂H and its isomer on the less substituted carbon with (iPr)₂N⁺CH₂,ClO₄^- in CH₃CN. In the first case, the orientation corresponds to a non-selective attack of the immonium salt on a mixture of enols in which the more-substituted isomer is predominant. In the second ease, use of a bulky immonium salt induces a selectivity favoring the less-substituted enol.     

Processus de photopolymerisation du methacrylate de methyle en presence de chlorure de zinc

The photopolymerization of methylmethacrylate in solution or in bulk, initiated by DMPA (2,2-dimethoxy-2-phenylacetophenone) and BP (benzophenone), has been investigated in the presence of ZnCI₂ as a complexing agent. We have studied the steady state polymerization (measurement of R, and OT) and the behaviour of the excited states by laser spectroscopy. We have shown the following points: R_p and DP increase with [ZnCI₂]; the rate constant for propagation increases with [ZnC12]; the rate of initiation remains constant in presence of BP-ZnCl₂ but increases with DMPA-ZnCl₂. The results are accounted for by the results of laser spectroscopy.     

Structure de benzoates de fluoroalkyles

The crystal and molecular structure of 2,2,3,3-tetrafluoropropyl-parachlorobenzoate (C₁₀H₇ClF₄O₂) has been determined by X-ray diffraction. The crystals are monoclinic, P2₁, a = 4.826(1), b = 9.036(2), c = 12.442(4)Å, β = 94.64(2)°, V = 540.8 ų, Z = 2, D_x = 1.66 Mg m^?3. Starting from the ¹³C data of this compound, the identification of five other fluoroalkylbenzoates has been achieved by N.M.R. spectroscopy.     

Enthalpies de formation des hydroxynitrates de zinc

The standard enthalpies of reaction of four zinc hydroxide nitrates Zn(OH)(NO₃)-H₂O, Zn₃(OH)₄(NO₃)₂, Zn₅(OH)₈(NO₃)₂·2H₂O et Zn₅(OH)₈(NO₃)₂ and zinc oxide with a solution of nitric acid (2N) were measured in a solution calorimeter. These results, combined with auxiliary thermochemical values from the literature, yielded values of ?429.34, ?442.41, ?897.41 and ?750.70 kcal mol^?1 respectively, for the molar enthalpies of formation of these zinc hydroxide nitrates.     

Etudes electrique et Raman de borotungstates et de boromolybdates de lithium vitreux

Conductivity studies of glasses obtained from the B₂O₃Li₂OLi₂MoO₄ and B₂O₃Li₂OLi₂WO₄ systems have been carried out. The presence of the transition element in tetrahedral coordination and with two different oxidation states is discussed. A Raman spectroscopy study shows that the MoO₄ or WO₄ tetrahedra are slightly compressed by the network forming lattice.     

Etude de la metallation de l'oxyde de diferrocenyl phenyl phosphine

The reaction of n-BuLi with phenyldiferrocenylphosphine oxide yields a mixture of two isomeric dianions. This mixture reacts with Me₃SiCl, Br₂, CO₂, PhCHO and PhCHNPh to give bifunctional products. With CoCl₂, Me₂SiCl₂, Ph₂SiCl₂, Bu₂SnCl₂ and PhCOOEt, the same mixture gives cyclic products. In almost every case each of these compounds is a mixture of two isomers corresponding to the original compound. The characteristic patterns of the PMR spectra are in full agreement with the structures proposed for the isomeric dianions.     

Cinetique de polymerisation de monomeres complexes par des acides de Lewis. Etude du systeme methacrylate de methyl-chlorure de zinc-azobisisobutyronitrile

The polymerisation of methyl methacrylate (MMA) initiated by azo-bis-isobutyronitrile (AIBN) in the presence of ZnCl₂ as complexing agent has been investigated. Increase of the polymerisation rate and a minimum in the average polymerisation degree were observed by increasing the ZnCl₂ concentration. By assuming the existence of complexes {AIBN · ZnCl₂} and {MMA · ZnCl₂}, a kinetic scheme is proposed; it is in good agreement with the experimental results and allows calculation of the characteristics of the system.     

Fabrication de128Xe comme traceur pour l'analyse de traces de xenon

¹²⁸Xe is produced by one-day irradiation of potassium iodide at a neutron flux of 10¹³ n·cm⁻²·s⁻¹ at a rate of 0.9 mm³ TPN for one gram of iodine. Xe is separated from the matrix by melting or hydrolysis. The main part of water is removed from the gas by cooling. Xenon (∼99%) thus obtained is freed from H₂, O₂, N₂, CH₄ and the last traces of water by gas chromatography and used for isotopic analysis.      

La fluoration de l'hexachlorobenzene et de la pentachloropyridine en milieu de fluorure de potassium solide

The fluorinations of hexachlorobenzene and pentachloropyridine were carried out in sealed tubes with KF in presence of inert gas; the fluorinated derivatives C₆F_xCl_y x + y = 6 0?x?6 and C₅F_xCl_yN x + y = 5 0?x?5 are obtained. The influence of contact time, temperature and the concentration of the ion F^? are investigated and compared; the molar yield varied from 45% to 90%. It is possible to get directly and selectively some fluorinated derivatives as C₅Cl₂F₃N. The fluorinations in liquid KFKCl and solid KF are compared.     

Determination par calorimetrie de dissolution des enthalpies de formation de quelques silicates,aluminates et alumino-silicates de calcium

The enthalpies of formation of 13 calcium silicates, aluminates, alumino-silicates and ferro-alumino-silicates were measured by dissolution calorimetry with the help of a high-temperature Calvet calorimeter. Dissolution experiments were performed in a lead metaborate (2PbO?B₂O₃) baths at 1173 K. The synthesis of the samples was realized by melting together pure silica, alumina, ferric oxide and calcium carbonate in appropriate ratios. The samples obtained in this way were examined by X-ray diffraction and scanning electronic microscopy. The free lime content was also determined by chemical analysis. The enthalpy of formation of silicates and aluminates obeys two different linear relations with respect to the ratio Ca/X (X=Al or/and Si) except for Ca₁₂Al₁₄O₃₃ which does not exist in its pure form but has to be stabilized by anions as OH^? or Cl^?. The data corresponding to the two aluminosilicates are located between these lines. The enthalpy of formation of tricalcium silicate (Ca₃SiO₅ i.e. C₃S according to the Bogue terminology) from dicalcium silicate and lime could be calculated as ?6kJ·mol^?1. This reaction is the most important one in the industrial process of clinkerization.     

Etude de stabilisation de verres a base de YF3

New fluoride glasses were obtained in the InF₃-BaF₂-YF₃ system. Evidence for phase separation was found in this basic ternary system, suggesting that glasses based on yttrium fluoride could be formed. Indeed such glasses could be prepared by fast cooling. The mean sample thickness was 2–3 mm. Glass transition, crystallization and melting temperatures were measured.     

Obtention de phosphore élémentaire et de phosphures de nickel par électrolyse de solutions de pentoxyde de phosphore dans des bains à base de cryolithe

By electrolysis of cryolitic solutions of P₂O₅, elementary pure phosphorus is obtained on carbon cathode and Ni phosphides on Ni cathode. The most probable mechanism of phosphorus formation in these conditions seems to be the final dissociation of P₂O₅ in P⁵⁺ and O^2? and the primary electrodic discharge of these ions.     

Preparation de nouveaux difluorodioxophosphates a partir de l’oxyde de difluorure de phosphoryle Partie V. Reactions aur le trioxyde d’uranium

UO₂(PO₂F₂)₂ has been synthesized from the action of P₂O₃F₄ on UO₃ or uranyl nitrate. The monofluorophosphate UO₂(PO₃F) was obtained by thermal decomposition. Infrared and Raman spectroscopic investigation of UO₂(PO₂F₂)₂ suggest a chain structure with oxygen phosphorus-oxygen bridges.     

Les fluorations comparees des chloropyrimidines et de la chloro-s-triazine en milieu de fluorure de potassiun solide

The fluorinations of tetrachloropyrimidine, 2,4,6-trichloropyrimidine and trichloro-s-triazine were carried out in sealed tubes with KF in presence of inert gas and then compared. The fluorinated derivatives C₄F_xCl_yN₂ with x + y = 4, 0?x<4 , C₄HF_xCl_yN₂ with x + y = 3, 0?x?3 and C₃F_xCl_yN₃ with x + y = 3, 0?x?3 were obtained. The influence of contact time, temperature and concentration of the ion F^? were investigated and compared; the molar yields were found to be always higher than 50% in our experimental conditions. We compare with the fluorinations of 2, 4 and 4, 6-dichloropyrimidine. It is possible to obtain directly, in good proportions, such fluorinated derivatives as 5-chlorotrifluoropyrimidine, trifluoropyrimidine and others. At high temperature (400°C for 16^h), tetrachloropyrimidine, in presence of KF, gave products of pyrolysis and condensation such as the fluorinated derivatives of C₆Cl₆ and C₅Cl₅N : C₆FCl₅, C₆F₂Cl₄ ··· or C₅FCl₄N, C₅F₂Cl₃N ···     

Determination de l'enthalpie de formation du pentafluorotellurate IV et hexafluorotellurate IV d'ammonium par calorimetrie de reaction

The standard enthalpies of formation of ammonium penta or hexafluorotellurate IV have been determined by reaction calorimetry in aqueous hydrogen fluoride as Δ_fH°₂₉₈ NH₄TeF₅ = -1547 ± 15 kJ.mol^-1 Δ_fH°₂₉₈ (NH)₄₂TeF₆ = -2026 ± 20 kJ.mol^-1     

Etude par Spectrométrie de Masse de Silanes et de Stannanes Aromatiques

The mass spectra of six compounds of the type Et₃Si? C₆H₄? ZR_xR_3?x (R=Et, R′ = CI, Z = Si, Sn) have been measured. The fragmentation patterns can be interpreted on the basis of an ionized hexa-1,3-diene-5-yne intermediate.     

Détermination colorimétrique de l'Iode sous forme de triiodure de Nitrone

Résumé Etudiant l'action mutuelle du nitron (Nt) et certains complexes halogènes on a obtenu le composé NtI₃. On a établi les propriétés, la composition et le mécanisme de la formation du composé. Ses propriétés ont servi de base à l'élaboration d'une méthode d'extraction et de détermination colorimétrique de microquantités d'iode. La méthode est basée sur l'oxydation de I^– en IO₃ ^–, réduction de ces derniers à l'aide de I^– en milieu acide et obtention de I₃ ^–, qu'on extrait sous forme de NtI₃ à l'aide de C₂H₄Cl₂ en presence de NtHSO₄. La méthode peut être mise à profit en présence de SO₄ ^2–, Cl^–, Br^– et NO₃ ^–.Cette méthode permet la détermination de 2 à 20g d'iode, dans 25 ml de solution, le coefficient des variations étant de ±3%. On s'est servi de cette méthode pour déterminer l'iode dans des eaux de sondage.

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Fluorimetric determination of iodine in the form of nitron triiodide

Summary The compound NtI₃ has been obtained by studying the mutual action of nitron (Nt) and certain halogenated complexes. Its properties have been established, also its composition and the mechanism of the formation of the compound. Its properties have served as the base for the elaboration of an extractive method for the colorimetric determination of microquantities of iodine. The method is based on the oxidation of I^– into IO₃ ^–, reduction of the latter through I^– in acidic surroundings and obtaining I₃ ^–, which is then extracted in the form of NtI₃ with the aid of C₂H₄Cl₂ in the presence of NtHSO₄. The method may be employed to advantage in the presence of SO₄ ^2–, Cl^–, Br^–, and NO₃ ^–. This method permits the determination of from 2 to 20g of iodine in 25 ml of solution, the coefficient of variation being ±3%. The procedure has been used to determine the iodine in boring waters.

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Zusammenfassung Bei der Einwirkung von Nitron (Nt) auf gewisse Halogenkomplexe wurde die Verbindung NtJ3 erhalten, deren Eigenschaften, Zusammensetzung und Bildungsweise untersucht wurde. Sie eignet sich für die Extraktion und kolorimetrische Bestimmung von Mikromengen Jod. Jodid wird zu Jodat oxydiert, dieses in saurer Lösung mit Jodid reduziert und das dabei entstehende J3^– als NtJ3 mit Dichloräthan in Gegenwart von NtHSO₄ extrahiert. Das Verfahren ist bei Anwesenheit von Sulfat, Chlorid, Bromid und Nitrat anwendbar und eignet sich zur Bestimmung von 2–20g Jod in 25 ml Lösung mit einem Variationskoeffizienten von ±3%. Es wurde für die Jodbestimmung in Brunnenwasser verwendet.

     

Elaboration de poudres de yig par coprecipitation

This paper deals with an original method for the preparation of ferrites with the garnet structure by coprecipitation.The different transformations of the coprecipitated hydroxide during heat treatment are studied and reported.YIG crystallization from amorphous oxide is significantly dependent of some parameters.However, pure homogeneous materials can be obtained at low temperature (800–850C) for Al substituted YIG Y₃Al_xFe_5–xO₁₂ with 0.5x1.

     

Spectres de vibration et conformations du propionate et de l'isobutyrate de méthyle

Infrared and Raman spectra (3600–3620cm^?1) of methyl propionate CH₃CH₂-COOCH₃, CH₃CH₂COOCD₃ and methyl isobutyrate (CH₃)₂CHCOOCH₃, (CH₃)₂CHCOOCD₃, in liquid and crystalline states, have been recorded. Rotational isomerism, by rotation around the C-C bond α to the carbonyl group, is detected and the energy difference between the conformers is 1.1 ±0.3 kcal mol^?1 for methyl propionate and 0.5 ±0.1 kcal mol^?1 for methyl isobutyrate. Vibrational assignments in terms of group frequencies are proposed for each conformer, only the more stable being present in the crystal.