Structure de l'ion fluoronium FH et chemin de la protonation du fluorure d'hydrogene

The structure of the ion FH is investigated on the basis of semiempirical (INDO ) and nonempirical (extended gaussian basis set) calculations. In agreement with experiment, both methods predict that, when going from FH to FH, there is a lengthening of the F? H bond; also in agreement with infrared analysis, the calculations indicate a bent structure for the fluoronium ion (valence angle at about 120°). The analysis of the FH protonation path reveals the existence of a potential barrier which is exclusively produced by solvation effects; the dependence of the proton affinity of FH on the dielectric constant of the reaction medium is also discussed.     

Le systeme binaire fluorure de rubidium-fluorure d'hydrogene

Résumé Le diagramme des équilibres liquide-solide du système fluorure de rubidium-fluorure d'hydrogène a été tracé dans sa totalité. Six espèces stables se manifestent RbF · nHF (avecn=7, 4, 3, 2, 3/2, 1). Un septième composé dont la composition probable est 2RbF · 5HF se manifeste à l'état métastable.

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Liquid-solid equilibria are studied in the complete binary system RbF-HF. Several compounds are observed: RbF ·nHF withn=7, 4, 3, 2, 3/2 and 1. A seventh compound, 2RbF · 5HF, is detected as an unstable form.

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Zusammenfassung Flüssig-fest Gleichgewichte des Binärsystems RbF-HF wurden umfassend untersucht. Sechs stabile Verbindungen wurden beobachtet: RbF ·n HF (n=7, 4, 3, 2, 3/2 und 1). Eine siebente Verbindung, 2 RbF · 5 HF ist metastabil.

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- RbF-HF. RbF·nHF =7,4,3,2, 3/2 1. — 2RbF·5HF — .

     

Diagramme d'equilibre liquide-liquide de systemes binaires pyridine+n-alcanes

Résumé Liquid-liquid phase diagrams have been determined for binary systems of pyridine+n-hexane, pyridine+n-heptane and pyridine+n-dodecane. A general quasi-chemical theory in terms of group surface interactions has been applied to compute these liquid-liquid phase diagrams.

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Zusammenfassung Es wurden Liquid-Liquid-Phasendiagramme für die bin?ren Systeme Pyridin+Hexan, Pyridin+n-Heptan sowie Pyridin+n-Dodekan bestimmt. Zur Berechnung dieser Liquid-Liquid-Phasendiagramme wurde eine allgemeine quasi-chemische Theorie bezüglich von Gruppen-Oberfl?chenwechselwirkungen angewendet.

     

Diagrammes de phases des systemes binaires KNO3-CsNO3 et KNO3-NaNO3

(K?Na)NO₃ and (K?Cs)NO₃ phase diagrams were drawn using a simultaneous thermal analysis technique in the range 373 to 623 K. The first phase diagram shows a minimum freezing equimolar mixture at 494 K, a continuous solid solution in equilibrum with liquid phase and an eutectic mixture (88 molar % of KNO₃) at 380 K. The second one exhibits an invariant at 400 K corresponding to the KNO₃ solid-solid transition, an eutectoid mixture at 10 molar % of KNO₃ and 418 K involving the CsNO₃ solid-solid transition and an eutectic mixture at 60 molar % of KNO₃ and 495 K.     

RepresentationT-V-x des systemes binaires a tension de vapeur non negligeable

Binary systems with non-negligible vapour pressure may be described by theT-V-x diagram. The use of the volumeV as an independent variable makes it possible to show the part played by the vapour phase in binary systems. This first part deals with the experimental connection betweenT, V andx data measured by DTA with sealed silica ampoules. As an example the eutectic composition is used: the theoretical isothermal, isochoric and isoplethal sections are presented and compared to those of some former works.     

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 ···     

Diagramme d’equilibre liquide-solide de systemes binaires pyridine+n-alcanes

Solid-liquid phase diagrams have been determined for binary systems of pyridine withn-alkanes. These diagrams show the existence of large regions of partial miscibility. A general quasi chemical theory in terms of group surface interactions [1] has been applied to compute these solid-liquid phase diagrams.     

Representation T-V-x des systemes binaires a tension de vapeur non negligeable

The effect of the variableV/m on the appearance of DTA endotherms has been used to obtain quantitative data on theT-V-x representation of the NdAs-As system. The peritectic reaction is NdAs₂ (solid)+vapour ? NdAs (solid)+liquid at 1185 K. At this temperature, the four phases set up a quadrangle in theV/m-x plane. The sides of this quadrangle have been defined by experiment: the vapour phase is composed of 87 mol% As and itsV/m value is 12.2 mm³ mg^?1. The peritectic liquid is composed of 87 mol% As. The eutectic equilibrium at 1080 K appears to be NdAs (solid)+As (solid)+vapour ← liquid It sets up a triangle, inside which the liquid phase is placed. The vapour phase is composed of 100 mol% As, and itsV/m value is 10 mm³ mg^?1. The eutectic liquid is composed of 90 mol% As. Three polythermal sections of the NdAs-As binary system are described for a constant volume.     

Representation des courbes de vaporus dans les systemes binaires a tension de vapeur non negligeable

The binary system As₂Se₃-As is first described for a constant value of the specific volumeV/m. The results corroborate the data given by other authors. The system is then described by aT-V-x diagram, by using DTA and electron microprobe analysis. From our experimental results and from the literature crystallographic and vapour pressure data, aT-V-x phase diagram was set up, showing the vaporus curves and the eutectic, peritectic and peritectoid invariant planes.

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Zusammenfassung Das binäre System As₂Se₃-As wird zunächst für einen konstanten Wert des specizifischen VolumensV/m beschrieben. Die Ergebnisse bestätigen die Daten anderer Autoren. Danach wird das System imT-V-x-Diagramm beschrieben, wobei DTA und Elektronenmikroproben-Analyse angewandt werden. Von eigenen Versuchsergebnissen und der Literatur entnommenen kristallographischen und Dampfdruckdaten wurden dasT-V-x-Phasendiagramm aufgestellt, das die Dampfdruckkurven und die eutektischen, peritektischen und peritektoiden invarianten Flächen zeigt.

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As₂Se₃-As V/m. , , , T-V-x. , , T-V-x., , , .

     

Representation T-V-X d'une monotexie dans les systemes binaires a tension de vapeur non negligeable

Binary systems with non-negligible vapour pressure in which a monotectic equilibrium takes place are described in aT-V-x diagram. Two kinds of equilibrium may occur, which correspond to the following reactions:S+L ₁ ? L ₂+V, andS+L ₁ +V?L ₂, when the temperature rises. The first generates a quadrilateral monotectic invariant. The second generates a triangular monotectic invariant. These two invariants are described in theT-V-x diagram and discussed.     

Enthalpies molaires de melange a T=303,15 K des systemes binaires liquides de cyclohexanone avec chloroethanes

Experimental heats of mixing Δ_mix H at 303.15 K and normal atmospheric pressure were obtained for the binary mixtures cyclohexanone+(1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane,1,1,2,2-tetrachloroethane or pentachloroethane), using a Calvet microcalorimeter. The Δ_mix H values for all the mixtures were negative, indicated that important interaction occur between the ketoxy group and chloroalcane. This revised version was published online in August 2006 with corrections to the Cover Date.     

Les systemes binaires AlPO4−M3PO4 (M=Li,Na, K)

The liquid-solid phase diagram of the binary systems AlPO₄?M₃PO₄(M=Li, Na, K) have been established. The additional compounds Na₃Al(PO₄)₂, Na₃Al₂(PO₄)₃ and K₃Al₂(PO₄)₃ have been found again. A new compound K₃Al(PO₄)₂ is observed. The melting point of Na₃PO₄ is 1545°C and K₃PO₄ does not melt up to 1700°C.     

Croissance et caracterisation de monocristaux de fluorure de neodyme obtenus par la methode des flux

Single crystals of neodynium fluoride NdF₃ have been grown by a flux technique using a melted mixture of neodynium chloride and potassium chloride. They have been characterized by chemical analysis X-ray diffraction and optical studies. The electrical transport properties are reported and discussed.     

Les orthoarseniates de sodium et de terre rare

Sodium rare-earth arsenates Na₃Ln(AsO₄)₂ may occur in five allotropic varieties. Their structural evolution has been studied as a function of rare-earth size, temperature, and pressure. The structures are isotypic with those of homologous phosphates and vanadates previously described.     

Étude de la microdiffusion de l'ion fluorure sous forme de fluorure d'hydrogène

Résumé Au cours de ce travail, nous avons tenté d'étudier certains facteurs qui influencent la séparation des ions fluorures par microdiffusion. La vitesse du phénomène est relativement lente et les expériences que nous avons entreprises ont permis d'établir une équation qui traduit le fait que la proportion de fluorure d'hydrogène absorbé après le tempst, est proportionelle, d'une part à la quantité de fluorure de sodium présentée initialement et, d'autre part, à la moyenne géométrique des surfaces d'absorption et d'émission. Le volume de la solution dans la cellule a un effet sur la vitesse qui, toutes choses égales d'ailleurs, est inversément proportionelle à ce dernier.Il est donc facile de prévoir qu'en augmentant le volume de la phase liquidev, en sorte que l'on recouvre tout juste toute la surface, la vitesse augmente quand on diminue les dimensions linéaires de l'appareil.La relation que nous avons établie et qui relie le temps aux différents facteurs gouvernant la vitesse de diffusion, nous semble des plus importantes: elle permet en effet, à l'analyste, de prévoir, à tout moment, théoriquement, une fois la cellule étalonnée, la durée minimale pour que la diffusion, à température donnée, soit complète.

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Study of the microdiffusion of the fluoride ion in the form of hydrogen fluoride

Summary In the course of this investigation we have endeavored to study certain factors that influence the separation of fluoride ions by microdiffusion. The speed of the phenomenon is relatively slow and the experiments we have undertaken have enabled us to set up an equation that expresses the fact that the proportion of hydrogen fluoride adsorbed after the timet is proportional on one hand to the quantity of sodium fluoride present initially and on the other hand to the geometric mean of the adsorption and emission surfaces. The volume of the solution in the cell has an effect on the speed which, all other things being equal, is inversely proportional to the latter. Therefore it is easy to foresee that by increasing the liquid phasev, in such manner that all of the surface is exactly as it was, the speed increases when the linear dimensions of the apparatus are decreased. The relation that we have established and which connects the time to the various factors governing the speed of diffusion appear to us to be the most important: they permit in fact the analyst to foresee, at every moment, theoretically, the minimal period required for the diffusion to be complete at a given temperature, once the cell has been standardized.

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Zusammenfassung Der Einfluß bestimmter Faktoren auf die Abtrennung von Fluorid durch Mikrodiffusion wurde untersucht. Die Geschwindigkeit dieses Vorganges ist relativ gering. Aus unseren Beobachtungen ergab sich eine Gleichung, wonach die Menge des in der Zeitt absorbierten Fluorwasserstoffes einerseits abhängig ist von der eingesetzten Menge Natriumfluorid, andrerseits von dem geometrischen Mittel der Oberflächen des Absorptionsmittels und der gasenden Flüssigkeit.Das Volumen der Lösung in der Diffusionszelle beeinflußt unter sonst gleichbleibenden Parametern die Geschwindigkeit im umgekehrten Sinn. Mit steigendem Volumen der flüssigen Phase, aber gleichbleibender Oberfläche, kann man die Geschwindigkeit erhöhen, indem man die linearen Dimensionen des Geräts verkleinert.Die von uns hergestellte Beziehung zwischen der Zeit und verschiedenen, die Diffusionsgeschwindigkeit regelnden Faktoren scheint uns sehr wichtig: sie bietet nämlich die Möglichkeit, für jeden Fall das geeignete Diffusionsgerät auszuwählen und bei gegebener Temperatur die erforderliche Mindestzeit für die vollständige Diffusion vorzusehen.

     

Cryptates—X: Syntheses et proprietes physiques de systemes diaza-polyoxa-macrobicycliques

The synthesis and the physical and conformational properties of diaza-polyoxa-macrobicyclic compounds are described.     

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.     

Equilibres liquide-vapeur isothermes de melanges binaires de la piperidine et de la N-methyl piperidine avec certains ethers

The authors have measured the vapour pressure of the four binary systems, piperidine +tert-butyl methyl ether, piperidine +1,4 dioxane, piperidine + tetrahydropyrane and N-methyl piperidine +tert-butyl methyl ether. The measurements were carried out using an isoteniscope built by J. Jose [1], The vapour pressure, excess Gibbs free energies at 298.15, 303.15, 313.15, 323.15, 333.15 and 343.15 K, are reported for these mixtures. The excess Gibbs free energies have been fitted to the Redlich-Kister equation.

     

Equilibres liquide-vapeur isothermes de melanges binaires de la piperidine et de la N-methyl piperidine avec certains ethers

The authors have measured the vapour pressure of the binary four systems, piperidin +1,4-dioxan, piperidin+tetrahydropyran, piperidin+tert-butyl methyl ether and N-methyl piperidin+tert-butyl methyl ether. The measurements were carried out using an isoteniscope built by J. Jose [1]. The vapour pressure, excess Gibbs free energies at 298.15 K, 303.15 K, 313.15 K, 323.15 K, 333.15 K and 343.15 K, are reported for these mixtures. The excess Gibbs free energies have been fitted to the Redlich-Kister equation.