Synthese von N-Di(alk-, ar-)oxyphosphoryl-tri(alk-, ar-)-oxyphosphazenen, (RO)2P(O)?NP(OR)3, durch P?N-Bindungsknüpfung

Synthesis of N-Di(alk-, ar-)oxyphosphoryl-tri(alk-, ar-)oxyphosphazenes, (RO)₂P(O)? N?P(OR)₃, by P? N-Bond Formation The title compounds can be prepared from di- and triesters of phosphorous acid, sodium azide, and carbon tetrachloride in a single step procedure and in high yields. Due to the combination of the Atherton-Todd and the Staudinger reaction toxic phosphoric acid ester azides are formed only in situ and their concentration is kept very small. As by-products trichloromethane phosphonic acid esters, (RO)₂P(O)CCl₃, esters of phosphoric acid and condensed phosphoric acids as well as N-alkylimidodiphosphoric acid esters, [(RO)₂P(O)]₂NR, are formed. Their formation can be avoided or reduced by choosing suitable reaction conditions. The mechanism of the reaction is discussed.     

Die Assoziation des Wassers an gespreiteten Filmen IX.: Benetzungseigenschaften siliconisierter Gläser

Zusammenfassung An Polydimethylsiloxan, das auf Wasser gespreitet ist, lagert sich je nach Flächenangebot eine diskrete Anzahl von Wassermolekülen je (CH₃)₂SiO-Einheit an. Bei der Kompression solcher Filme entstehen vier definierte Orientierungszustände.Diese Modellvorstellung wird auf Festkörperoberflächen übertragen. Es wird nachgewiesen, daß bei der Beregnung siliconisierter Gläser vier definierte Benetzungsstufen entstehen, die den Orientierungszuständen zuzuordnen sind.Gläser dieser verschiedenen Siliconbelegung werden hergestellt; an ihnen werden Randwinkel gemessen, die sie mit verschiedenen Flüssigkeiten ausbilden. Aufschlußreiche Zusammenhänge von Adhäsionsarbeit, Festkörperoberflächenspannung, Benetzbarkeit usw. mit der Grenzschichtbelegung werden nachgewiesen, wenn man die Oberflächenspannung der Flüssigkeit gegen die Adhäsionsarbeit aufträgt. Es wird festgestellt, d2ß sich die Moleküle innerhalb der Komplexe bei der Adsorption an der Festkörpergrenz-fläche stark polarisieren, und daß die so gebildete oberste Molekülschicht für die Eigenschaften des Festkörpers verantwortlich ist.Aus der Adhäsionsarbeit wird die Assoziationswärme berechnet, die bei den auf Wasser und auf Glas adsorbierten Polydimethylsiloxanfilmen gleich groß ist. Schließlich lassen sich aus der Assoziationswärme Rückschlüsse auf die Reißfestigkeit von Siliconkautschuk ziehen.

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Summary Depending on the surface area available, a discrete number of water molecules per (CH₃)₂SiO unit attach themselves to polydimethyl siloxane spread upon water. When such films are compressed, four defined states of orientation will result.This concept is transferred to surfaces of solids. It is shown that when silicone-treated glass plates are sprayed with water, four defined states of wetting will form which are to be co-ordinated with the states of orientation.Glass plates with these different states of silicone coating are prepared; they are subjected to measurement of contact angles which they form with various fluids. Informative relationships of adhesion energy, surface tension on solids, wettability, etc., to the interfacial coating are shown when the surface tension of the fluid is plotted versus the adhesion energy. Pronounced polarization of the molecules within the complexes is found while they are adsorbed on .the interface of the solid.The heat of association, which is the same whether the polydimethyl siloxane films are adsorbed on water or glass, is calculated from the adhesion energy. Finally the heat of association allows conclusions to be drawn as to the tensile strength of silicone rubber.

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Mit 3 Abbildungen und 3 Tabellen

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Vorgetragen anläßlich der Arbeitssitzung des Ausschusses Grenzflächen der Gesellschaft für Verfahrenstechnik und Chemieingenieurwesen (GVC) im Verein deutscher Ingenieure am16. 10. 1975 in Boppard.     

Structure of association in surface films

Association complexes which from on the polar groups of surface-active compounds during the spreading process on surfaces are described. In the hydration complexes of the interface 1, 2, 4, 9, 16 etc. water molecules surround the hydrophilic group. With the compression of a monolayer spread on water, complexes of higher water contents, out of which the water is pressed, are in thermodynamic equilibrium with the complexes of lower content thus formed.The association equilibrium described apply both to monomear and to polymer compounds, as is shown using the example of polydimethylsiloxane. The principles of the surface structures are discussed with the aid of surface tension, film pressure, space requirement, contact angle and heats of association.     

Temperature jump method in molecular beam relaxation spectrometry applied to catalytic decomposition of CH3OH on polycrystalline Ni foil

A new modification of molecular beam relaxation spectrometry (MBRS) is described: the temperature jump method for studying catalytic surface processes on metal foils. The temperature of the catalyst foil is maintained by direct ohmic heating; a constant particle beam is directed towards the catalyst surface. A jump of the surface temperature caused by a high current pulse generates a response of the fluxes of desorption. The decay of the desorption intensity after the temperature jump contains the relaxation times of the elementary steps involved. The mathematical treatments of unimolecular and bimolecular surface reactions, of sequences of two and three unimolecular steps and of a sequential reaction accompanied by the redesorption of the reactant are given. The application of the new method is shown by a study of the catalytic decomposition of CH₃)OH on polycrystalline Ni: CO and H₂ are the sole reaction products. The limit of the catalytic activity — apart from the low sticking probability of the reactant — must be seen in the abstraction of the first methyl hydrogen from the transient methoxy species. In the temperature range between 320 and 550 K the reaction mechanism can be described as follows:

Rate constants in dependence from surface temperature T are: k₁ = 4.2 × 10⁴ exp$\text{(}\text{?22.4}\text{RT}$$\text{kJ}\text{mol}\text{)}$ s^?1; k₃ = 2.4 × 10⁹ exp$\text{(}\text{?75}\text{RT}$$\text{kJ}\text{mol}\text{)}$ s^?1; k₄ = 1.2 × 10¹³ exp$\text{(}\text{?104}\text{RT}$$\text{kJ}\text{mol}\text{)}$ s^?1; η = 0.2. Typical surface residence times of the intermediates are: 110 ? τ₁ ? 15 ms at 320 ? T ? 450 K; 210 ? τ₃ ? 6 ms at 450 ? T ? 550 K; 98 ? τ₄ ? 6 ms at 450 ? T ? 500 K.     

A Highly Efficient Sandwich‐Like Symmetrical Dual‐Phase Oxygen‐Transporting Membrane Reactor for Hydrogen Production by Water Splitting

Water splitting coupled with partial oxidation of methane (POM) using an oxygen‐transporting membrane (OTM) would be a potentially ideal way to produce high‐purity hydrogen as well as syngas. Over the past decades, substantial efforts have been devoted to the development of supported membranes with appropriate configurations to achieve considerable performance improvements. Herein, we describe the design of a novel symmetrical membrane reactor with a sandwich‐like structure, whereby a largescale production (>10 mL min^?1 cm^?2) of hydrogen and syngas can be obtained simultaneously on opposite sides of the OTM. Furthermore, this special membrane reactor could regenerate the coke‐deactivated catalyst in situ by water steam in a single unit. These results represent an important first step in the development of membrane separation technologies for the integration of multiple chemical processes.     

Zur Umsetzung des Zweikomponentensystems Triethylphosphit/Tetrachlorkohlenstoff mit wasserstoffhaltigen Nucleophilen 1. Die Reaktion mit Säureamiden

Reaction of the Two-component System Triethylphosphite/Carbon Tetrachloride with Nucleophiles Containing Hydrogen. 1. Reaction with Acyl Amides Acyl amides react with the two-component system triethylphosphite/carbon tetrachloride yielding N-acyl phosphazenes, (EtO)₃P?N? Ac. In this way (EtO)₃P?N? P(O)(OEt)₂, (EtO)₃P?N? CN, (EtO)₃P?N? C(O)Ph, and (EtO)₃P?N? SO₂Ph were prepared. Ethyl esters of phosphoric acid and trichloromethane phosphonic acid were obtained as by-products.