Amination of isomeric bromo-1-methylnitropyrazoles

A method was developed for the synthesis of 5-bromo-1-methyl-4-nitropyrazole from 1-methylpyrazole. In the reaction with 25% aqueous ammonia at 180–190 °C, 5-bromo-1-methyl-4-nitropyrazole is readily converted to 5-amino-1-methyl-4-nitropyrazole; the production of 4-amino-1-methyl-5-nitropyrazole from 4-bromo-1-methyl-5-nitropyrazole requires the presence of a copper catalyst; under the same conditions in the amination of 4-bromo-1-methyl-3-nitropyrazole, 4-amino-1-methyl-3-nitro- and 1-methyl-3-nitropyrazoles are formed in a 23 ratio.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1672–1675, December, 1983.     

Flavin-protein interaction in bound glucose oxidase

Glucose oxidase was bound to Sepharose, Sephadex, gelatin, and dextran, yielding immobilized soluble and insoluble derivatives of the enzyme. The soluble preparations possessed higher enzymic activity than the analogous insoluble ones. The reversible dissociation process of the bound enzyme into apoenzyme and flavin adenine dinucleotide (FAD) was studied with the soluble and insoluble glucose oxidase in relation to enzymic activity and conformational changes as measured by circular dichroism and fluorescence methods. Bound apoenzyme was found to be more stable than the apoenzyme obtained from the unmodified glucose oxidase. The binding constant of FAD in bound glucose oxidase (K_diss≈10^-8M) calculated from fluorescent studies was lower than that of FAD in the native enzyme (K_diss10^-10M). The circular dichroism measurements indicated that dextran-bound glucose oxidase has a conformation similar to that of the native enzyme.     

Molecular emission cavity analysis : Part VII. The determination of cadmium

Cadmium salts give an intense cadmium atomic emission in the MECA cavity in a hydrogen-nitrogen-air flame. When a carbon or stainless steel cavity is used, 10–120 ng of cadmium in 5-μl samples can be determined. In the presence of sulphuric acid, anionic interferences are removed. Of the cations, only Fe(III), Cr(III), Mg and Sn(II) interfere seriously.     

A characterization of the Coxeter cap

Designs, Codes and Cryptography - In this paper, we complete the classification of the caps in $$\text{ PG }(n,q)$$ having the property that on every tangent line L, there exists a unique point...     

Generalized mean-square amplitudes of vibration in some XY4 type ions (II)

The generalized mean-square amplitudes of vibration and mean amplitudes of vibration have been computed for CrO^3-₄, Mn¹⁸O^-₄, MoSe^2-₄ and WSe^2-₄ ions at three temperatures, T = 0°K, T = 298°K, T = 500°K, employing Cyvin's method. The results have been discussed in the light of atomic weight and electronegativity of the atom in the ionic system.     

Polarographische Bestimmung des Pyridoxols in pharmazeutischen Präparaten

Zusammenfassung Es wird eine neue polarographische Methode zur direkten Bestimmung des Pyridoxols in Injektionspräparaten und Tabletten beschrieben. Die ausgearbeitete Methode beruht auf der polarographischen Reduktion des Pyridoxolmoleküls im Milieu von Ammoniak-Ammoniumchlorid-Puffern und weiter auf der Bildung einer katalytischen Stufe des Pyridoxols in Veronalpuffern. Die polarographische Methode ist rascher und in manchen Fällen genauer und empfindlicher als die bisher in Gebrauch stehenden Methoden. Die Anwesenheit der in den Präparaten laufend vorkommenden Begleitstoffe des Pyridoxols stört nicht die polarographische Bestimmung. Die Methode kann auch zur Bestimmung des 3-Hydroxy-4-methoxymethyl-5-oxymethyl-2-methylpyridins benutzt werden, das ein Zwischenprodukt bei der Pyridoxolerzeugung ist.

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Summary A new polarographic method is described for the direct determination of pyridoxol in injection preparations and tablets. This method is based on the polarographic reduction of the pyridoxol in ammonia-ammonium chloride buffer medium and also on the formation of a catalytic stage of the pyridoxol in veronal buffers. The polarographic method is faster and in many cases more accurate and more sensitive than the methods now in use. The presence of the materials which always accompany the pyridoxol in the preparations does not interfere with the polarographic determination. The method can likewise be used for determining 3-hydroxy-4-methoxymethyl-5-oxymethyl-2-methylpyridine, which is an intermediate product in the manufacture of pyridoxol.

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Résumé On décrit une nouvelle méthode polarographique pour le dosage direct du pyridoxol dans les préparations pour injections et dans les comprimés. La méthode élaborée repose sur la réduction polarographique de la molécule de pyridoxol dans le milieu tampon ammoniaque-chlorure d'ammonium, et, en outre, sur la formation d'une phase catalytique du pyridoxol dans les tampons au véronal. La méthode polarographique est plus rapide et dans de nombreux cas plus exacte et plus sensible que les méthodes utilisées jusqu'ici. La présence d'impuretés existant couramment dans les préparations à côté du pyridoxol ne gêne pas le dosage polarographique. On peut aussi utiliser la méthode pour le dosage de l'hydroxy-3 méthoxyméthyl-4 oxyméthyl-5 méthyl-2 pyridine, substance intermédiaire dans la préparation du pyridoxol.

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Herrn Dr.P. Zuman danken wit für Ratsehläge bei der Abfassung dieser Arbeit.     

Unsteady propagation of longitudinal shear cracks

In all problems of unsteady crack propagation which have been solved to date [1 to 3], it has been assumed that the crack propagates at a constant speed. This assumption was not prompted by physical considerations of the problem, but by the methods of solution, therefore, the applicability of the results is limited. It would be more realistic to consider the speed of crack propagation as a function of time based on explicit physical hypotheses. Unfortunately, the general case of the resultant problem cannot be solved by existing methods. However, the problem of longitudinal shear cracks i.e. the plane problem in which the displacement is parallel to the crack boundary, may be solved for an arbitrary given variation in crack propagation speed, utilizing the method developed in connection with the theory of supersonic flows [4 and 5].

Note that equilibrium problems of longitudinal shear cracks have been studied in [6 and 7].     

Die Phosphatbestimmung mit elektrischer Endpunktanzeige und ihre Anwendung zur Analyse organischer Substanzen. II

Zusammenfassung Nach Untersuchungen über die Einflüsse der Temperatur, organischer Lösungsmittel, und des Carbonatgehalts der Lösung wurde eine neue Vorschrift ausgearbeitet zur Phosphattitration mit Lanthanmaßlösung mit einer Endpunktanzeige mittels eines p_H-Meters. Mit einer Standardabweichung von weniger als 1% lassen sich 0,3 bis 1,5 mg P bestimmen. Die Standardabweichung bei der Phosphorbestimmung in organischen Substanzen beträgt 0,11% absolut.

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Summary Investigations of the influences of temperature, organic solvents, and the carbonate content of the solution led to the development of a new procedure for titrating phosphate with a lanthanum salt solution; the endpoint is indicated by a p_H meter. It is possible to determine 0.3 to 1.5 mg P with a standard deviation of less than 1%. The standard deviation in the determination of phosphorus in organic substances is 0.11% absolute.

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Résumé On a mis au point un nouveau mode opératoire d'après des études sur l'influence de la température, du solvant organique et de la teneur en carbonate de la solution pour titrer les phosphates par une solution étalon de lanthane avec indication du point d'équivalence sur un ph-mètre. On peut doser 0,3 à 1,5 mg de P avec un écart-type de moins de 1%. L'écart-type dans le cas du dosage du phosphore dans les substances organiques s'élève à 0,11% en valeur absolue.

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Wir danken herzlichst HerrnH. de Wit und HerrnW. Hulshof für wertvolle Mithilfe und Ausführung zahlreicher Analysen.