Steroids and steroidases—XIX : Comparison of diazomethane and tiffeneau-demjanov homologations of 5α-3-oxosteroids. Evidence for predominant equatorial approach of the C-3 carbonyl group by diazomethane

Quantitative comparisons of the product ratios of the mechanistically similar diazomethane and Tiffeneau-Demjanov homologations of 17β-hydroxy-5α-androstan-3-one and 5α-cholestan-3-one have shown that equatorial approach of diazomethane to the C-3 CO group predominates to the extent of 70–79%. The data for both the C-17β-OH and -C₈H₁₇ substituted steroids are in close agreement thereby confirming that the C-17 substituents do not exert any significant long range effect on the reactions studied.     

A method of general applicability for the micro determination of chlorine,bromine and iodine

Summary A method is described for the combustion of halogen containing organic compounds in milligram quantities in a closed system. It has been found to have greater applicability than existing techniques. After combustion the halogen is determined by an amperometric titration, which permits the determination of Cl^–, Br^– and I^– either singly or in admixture. The accuracy is probably better than existing micro methods for single halides and comparable with these methods for mixed halides.

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Zusammenfassung Eine Methode zur Verbrennung von Milligrammengen halogenhaltiger organischer Verbindungen im geschlossenen System wurde beschrieben. Sie hat einen größeren Anwendungsbereich als bisher bekannte Verfahren. Nach der Verbrennung wird das Halogen durch eine amperometrische Titration bestimmt, womit Chlorid, Bromid und Jodid sowohl einzeln wie in Gemischen bestimmt werden können. Die Genauigkeit seheint besser zu sein als bei bekannten Mikromethoden für die Bestimmung einzelner Halogene und etwa gleich gut wie bei Methoden zur Analyse von Halogengemischen.

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Résumé On décrit une méthode de combustion en vase clos, des composés organiques contenant des halogènes en quantités de l'ordre du milligramme. Cette méthode a été trouvée comme ayant un domaine d'applications plus grand que celui des techniques existant déjà. Après combustion, l'halogène est dosé par titrage ampérométrique, ce qui permet le dosage de Cl^–, Br^– et I^– isolés ou en mélange. La précision est probablement meilleure que celle des microméthodes existant pour les halogénures isolés et comparable à celle de ces méthodes pour les mélanges d'halogénures.

     

Darboux transformations for higher-rank Kadomtsev-Petviashvili and Krichever-Novikov equations

It is shown that the action of a special rank 2 or rank 3 Darboux transformation, calledtransference, upon a pair of commuting ordinary differential operators of orders 4 and 6 implements the Abelian sum on their elliptic joint spectrum. A consequence of this is that, under the deformation of these commuting operators by the KP flow, every rank 2 KP solution corresponds to a solution of the Krichever-Novikov (KN) equation, and vice versa, with the transference process providing the correspondence between (2+1) and (1+1) dimensions. For a singular joint spectrum, it is further shown that transference at the singular point produces a correspondence between solutions of the singular KN equation and those of the KdV equation. These correspondences are illustrated by considering examples of a nondecaying rational KdV or Boussinesq solutions and the corresponding rational, singular-KN and rational KP solutions which the transference process generates.