Die indikatoreigenschaften des vicinalen m-Xylenolphthaleins (3′ ,5′ ,3′' ,5′'-Tetramethylphenolphthalein)

Ohne ZusammenfassungMit 1 Abbildung     

Eine Synthese des 3-(N′-Methyl-2′-piperidyl)-chinolizidins

Zusammenfassung Im Anschluß an kürzlich erschienene Arbeiten über Synthesen von 3-(N-Methyl-2-piperidyl)-chinolizidin, einer Verbindung von der gleichen Struktur wie sie dem Alkaloid Pusillin zukommen soll, wird über eine eigene Synthese zweier stereoisomerer Verbindungen dieser Konstitution berichtet.     

Syntheses de la (+)-marmine,des (+)-epoxy-6′,7′- et (-)-epoxy-3′,6′-auraptenes et des racemiques correspondants.

The title compounds were prepared by short enantioselective syntheses from 7-geranytoxycoumarin. The key step to induce optical activity was a SHARPLESS epoxidation. Conditions of electrophilic cyclization were found to obtain good yields. This approach allowed also to obtain the glycol (+)-marmin.     

Eine neue Synthese von Phenylglycin-N,N′-diphenylamidinen und ihre Cyclisierung zu Derivaten des Isatins

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Untersuchungen über Phenthiazinderivate, 13. Mitt.: Derivate des 10-(2′-Hydroxy-3′-amino-propyl)-phenthiazins

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Amélioration des comportements thermique et mécanique des structures vitreuses par addition d'oxyde métallique et traitements thermiques

Improvement of mechanical and thermal properties of glass structures by a metallic oxide addition and suitable heat treatments. The study of glass-ceramic materials based on the system SiO₂-Li₂O-Al₂O₃, using differential thermal analysis (DTA), X-ray diffraction and scanning electron microscopy revealed the nucleation and growth, in the glass structure, of crystalline phases with nature and distribution very sensitively controlled by the heat-treatment program. These phases have a strong effect on the physical and mechanical properties of glass-ceramic materials when their volume fractions reach values higher than 15 %. They also tend to lower the coefficient of thermal expansion and consequently improve the resistance to thermal shock of these materials without reducing considerably the transparence which is characterized by the refractive index and the absorption coefficient. Fracture surfaces produced by thermal and mechanical shocks of glass-ceramic materials put in evidence the role of the morphology and of the crystalline phase distribution on the resistance to abrupt crack propagation.     

Synthesis of 5,5′-Dialkyl-6,6′-dichloro-2, 2′-bipyridines

5,5′-Dialkyl-6,6′-dichloro-2,2′-bipyridines were synthesized starting from 3-substituted 2-chloro-6-iodopyridines using Pd-catalyzed coupling conditions. 6-Alkyl-3,5-dichloro-2H-1,4-oxazin-2-ones were excellent precursors for the synthesis of these functionalized 2-iodo-6-chloropyridines.     

N,N-dialkoxy-N′-alkylureas

The chlorination of N-alkoxy-N-alkylureas (1) by the action oft-BuOCl proceeds regiospecifically to give stable N-chloro-N-alkoxy-N-alkylureas (2). The alcoholysis of2 leads to N,N-dialkoxy-N-alkylureas (3). The alkaline hydrolysis of3 is a new, convenient method for the preparation of dialkoxyamines.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2441–2443, October, 1992.     

La mécanique des fluides numérique outil de recherche,outil industriel ?

With the help of a few examples in the field of nuelear engineering, we show that computational fluid dynamics is both a reasearch and an industrial tool.     

The step dissociation constants of ethylenediamine-N,N′-diacetic-N,N′-dipropionic and ethylenediamine-N,N,N′,N′-tetrapropionic acids

The step dissociation constants of ethylenediamine-N,N′-diacetic-N,N′-dipropionic and ethylenediamine-N,N,N′,N′-tetrapropionic acids at 298.15 K and ionic strengths of 0.1, 0.5, and 1.0 (KNO₃) were determined potentiometrically. The results were extrapolated to zero ionic strength by the equation with one individual parameter. The thermodynamic constants of dissociation were calculated. The results are compared with the corresponding data on related compounds.     

An Efficient Preparation of 4, 4′-Dicarboxy-2, 2′-Bipyridine

A convenient and high yield preparation of 4, 4′-dicarboxy-2, 2′-bipyridine from the oxidation 4, 4′-dimethyl-2, 2′-bipyridine with potassium dichromate in sulfuric acid is reported.     

Synthesis,Crystal Structure and Spectroscopic Properties of N,N′-Diphenyl-N,N′-bis(2-fluorophenyl)-1,1′-biphenyl-4,4′-diamine

A fluorinated tetraphenylbenzidine derivative, N,N′-diphenyl-N,N′-bis(2-fluorophenyl)-1,1′-biphenyl-4,4′-diamine (C36H26F2N2, Mr = 524.59) was synthesized via the palladiumcatalyzed Buchwald-Hartwig reaction of N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine with 2-fluoroiodobenzene (yield: 75%) and structurally characterized. It crystallizes in monoclinic, space group P21/n with a = 9.820(7), b = 14.305(11), c = 10.233(8) , β = 108.973(9)o, V = 1359.3(18) 3, Z = 2, Dc = 1.282 g/cm3, μ(MoKα) = 0.084 mm-1, F(000) = 548, S = 1.018, the final R = 0.0439 and wR = 0.0928. It presents a linear centrosymmetric framework constituted by a linkage of biphenyl as a bridge and two fluorinated diphenylamine moieties. The UV-Vis absorption and fluorescence spectra of the title compound were also investigated. This compound emits intense blue fluorescence with a peak wavelength of 406 nm in film.