Retention of configuration in the opening of 2-arylcyclopropyl bromides by potassium acetate/18-crown-6 in dimethyl sulfoxide

E and Z 2-phenylcyclopropyl bromides react with the title reagents to yield E and Z cinnamyl acetates respectively. No reaction is observed when halide nucleophiles or other aprotic solvents are used suggesting a novel mechanistic role for the acetate ion.     

Die Oxidelektrode als Indikator bei der Amperometrischen Titration von Metallionen MitÄDTA

Zusammenfassung Der Endpunkt von chelatometrischen Titrationen kann amperometrisch indiziert werden, wenn man einen Platindraht, der mit einem Oxid überzogen ist, als Anode und blankes Platin als Kathode benützt und eine Spannung von 0,8 bis 1,0 Volt anlegt. Bei einem Überschuß anÄDTA steigt der zwischen den Elektroden fließende Strom sehr stark an. Als Oxide eignen sich: Thallium(III)-oxid, Nickel(III)-oxid bzw. Cobalt(III)-oxid. Je nach Kation erhält man eine V-förmige oder eine gewinkelte Titrationskurve. Die Eigenschaften dieser Oxidelektroden wurden ermittelt. Die Höhe der Indikation hängt vom pH-Wert der Lösung ab: bei pH 3,5 bis 5 sowie bei pH 10 treten Maxima in der Indikationshöhe auf. Die Bestimmung verschiedener Metallionen mit diesem Indikationssystem wird beschrieben.

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The oxide electrode, an indicator for EDTA in the amperometical titration of metal ions. The thallium (III)-oxide-electrode the nickel-(III)-oxide-electrode and the cobalt(III)-oxide-electrode

The equivalence point in chelatometric titrations can be indicated amperometrically, if a pin of platinum, coated with an oxide, is used as anode and bright platinum as cathode. A voltage of 0,8 to 1,0 volt is put on the electrodes. The current, flowing between the electrodes, increases very much, if there is an excess ofEDTA in the solution. Following oxides are suitable for coating the anode: thallium(III)-oxide, nickel(III)-oxide and cobalt(III)-oxide. The titration curve is either V- or angle-shaped, according to the cation.The behaviour of these oxide electrodes was investigated. The indication depends on the acidity of the solution. The highest indication is found at pH 3,5 to 5 and also at pH 10. The offered method is applicated for determining various metal ions.

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Mit 7 Abbildungen

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Herrn Univ.-Prof. Dr.-Ing.H. Nowotny in Verehrung gewidmet.     

The effects of water vapor on the separation of methane and carbon dioxide by gas permeation through polymeric membranes

The effects of water vapor on the separation of CO₂ and CH₄ using cellulose acetate, polyethersulfone, polysulfone and sulfolene modified poly(vinylidene fluoride) membranes were determined. Response surfaces of flux on a dry basis and separation factor clearly show the effects of feed gas water vapor content and temperature on the permeation characteristics of the film. Strong trends of a plasticizing effect due to the concentration of water in the membranes were apparent. In general, in the commercial films, the flux went through a maximum with increasing feed water content while the separation factor decreased. These variables changed little in the sulfolene modified film. At 90°C, water permeation accounted for up to 35 percent of the total permeate.     

Decomposition of graph functions

The V-functions of Tutte [1] are generalized to U-functions on graphs with a distinguished subset of vertices. The class of U-functions of two variables generalize dichromatic polynomials as well as the W-functions defined by Tutte [2]. The values of U-functions on a graph G are characterized in terms of spanning subgraphs of G and also in terms of collections of simple graphs constructed from G. Decompositions of dichromatic polynomials as well as dichromatic U-functions are obtained in terms of decompositions of G.