Zum Einfluß der Gasphase auf die thermische Zersetzung von K2[SiF6]

Effect of the Gas Phase on the Thermal Decomposition of K₂[SiF₆] K₂SiF₆ produced in usual ways is contaminated by traces of oxygen and protons. These and traces of water fed by gas atmosphere influence the thermal decomposition reaction. To study the influence of the gas phase definite amounts of H₂O and HF were added. The formation of SiF₄ was determined. The development of a SiO₂ phase in presence of H₂O and other experimental results suggest the construction of a layer on the K₂SiF₆ surface, which hinders further SiF₄ being developped. Temperature and linear velocity of the gas influence the length of a zone of decomposition migrating through the solid. This is explained by sorption and reaction behavior of intermediately formed fluorosiloxanes.     

Die thermische Zersetzung von Bariumazid-Einkristallen, 5. Mitt.: Der Einfluß der Korngröße auf die thermische Zersetzung von Bariumazid

Decomposition studies on ground samples of anhydrous Ba(N₃)₂ with defined particle size are described. The kinetic equations derived for single crystals hold for the decomposition of powders too. The far faster decomposition of powders is caused both by the increased numberN ₀ of potential nuclei forming sites and the larger specific surfaceF ₀/V ₀, whereas the rate constantsk ₁ andk ₂ for nucleation and linear nucleus growth, resp., and their respective activation energies coincide with the data for single crystals. The proportionality between the rate of decomposition and the specific surface is confirmed experimentally and thereby a further proof of the geometric decomposition model is established. Independent of particle size and temperture always 75% of the azide are transformed into nitride during thermal decomposition, this value corresponding exactly to the theoretical one. It is shown experimentally that with decomposition conditions no reaction takes place between metallic Ba and N₂ in its electronic ground state and therefore the mechanism proposed for nitride formation is confirmed.     

Die thermische Zersetzung von Kupferacetatmonohydrat

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Die thermische Zersetzung von Natriumnitrat

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Der Einfluß der Koordinationssphäre von Samarocenen auf die Synthese von flüssigkristallinen Polymethacrylaten

The Influence of the Coordination Sphere of Samarocenes on the Synthesis of Liquid Crystalline Polymethacrylates (C₅Me₅)₂Sm(THF)₂ ( 1 ) reacts with 1,3‐Diisopropyl‐4,5‐dimethylimidazoline‐2‐ylidene C₃N₂Me₂iPr₂ (iPr‐carben) with formation of (C₅Me₅)₂Sm(iPr‐carben) ( 3 ). The reaction of (C₅Me₄Et)₂Sm(THF)₂ ( 2 ) with Al₂Me₆ in toluene yields [(C₅Me₄Et)₂Sm(CH₃)Al(CH₃)₃]₂ ( 6 ). 3 and 6 were characterized by single crystal X‐ray structure analysis. Via living polymerization of mesogenic methacrylates with the organosamarium complexes 1 , 2 , 3 , (C₅Me₅)₂Sm(C₃H₅) ( 4 ), (C₅Me₅)₂Sm(CH₃)(THF) ( 5 ), 6 , and (C₅Me₄Et)₂SmCH(SiMe₃)₂ ( 7 ), liquid crystalline homo‐ and blockcopolymers were obtained with narrow molecular mass distribution indexes in high yield. Partial competitive mechanisms are observed dependend of the structure of the catalyst and the polarity of the solvents.     

Der Gaskomplex MnAlF5 und sein Einfluß auf die sublimative Reinigung von AlF3

The Gas Complex MnAlF₅ and its Influence on the Purification of AlF₃ by Sublimation The gas complex MnAlF₅ has been determined mass spectroscopically by the ions MnAlF₅⁺ and MnAlF₄⁺. The gas complex MnAlF₅ is formed above 973 K by heating up mixtures of AlF₃/MnF₂ or AlF₃ · 3 H₂O endowed with Mn²⁺ or by heating up solid MnAlF₅ too. At 1 008 K the enthalpie of dissociation is 197 kJ/mole. The equilibrium structures of the high spin molecule MnAlF₅ (S = 5/2) were examined with ab initio calculations at the HF-level by comlete gradient optimizing. Two minimum structures were found on the potential energy surface. A bidentate fluorine bridged structure was found to be the most stable at the HF-level. Vibrational frequencies and thermodynamic functions of complex formation were estimated for both minimum structures. The importance of the formation of the gas complex for the separation of MnF₂ and AlF₃ by sublimation is discussed.     

Die Fehlordnung des Natriumazides und deren Einfluß auf die thermische Zersetzung, 3. Mitt.: Modell einer diffusionskontrollierten thermischen Zersetzung des Natriumazides

Zusammenfassung Abweichungen von der normalen Leitfähigkeit des NaN₃ lassen vermuten, daß bei der Keimbildung und beim Keimwachstum atomare Diffusionsprozesse stattfinden. Unter der Annahme, daß die Zersetzungsreaktion durch das Keimwachstum an denhk0-Begrenzungen des Kristalls gegeben ist und für jedes an den Kontakt Na/NaN₃ diffundierende Natriumion die äquivalente Menge Stickstoff frei wird, wird mit Hilfe eines Zylindermodells eine Geschwindigkeitsgleichung abgeleitet. Zur experimentellen Überprüfung werden isotherme Zersetzungen von NaN₃-Pulvern mit definierter Korngröße herangezogen. Die analytische Auswertung der Umsatz/Zeit-Funktion ergibt eine quadratisch-hyperbolische Teilchenradienabhängigkeit sowie eine der Diffusion entsprechende Temperaturabhängigkeit der Geschwindigkeitskonstante, wie sie durch das Modell gefordert wird.

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From deviations of the normal ionic conductivity of NaN₃ it may be concluded that atomic diffusion processes are taking place with nucleiation and nucleus growth. A rate equation can be derived by means of a cylindric model, supposing that a decomposition reaction is given by nucleus growth athk0-planes of the crystal and supposing that for each sodium ion diffusing to the sodium/sodiumazide-contact an equivalent quantity of nitrogen becomes free.Isothermic decompositions of NaN₃ powders with defined particle size are carried out for experimental examination. The analytical evaluation of the pressure—time-function shows a squarehyperbolic dependence of the particle radius as well as a temperature dependance of the rate constant correponding to the diffusion as it is requested by the model.

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Die thermische Zersetzung von Metall-?thylendiaminoxalatkomplexen

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