Cinetique de degradation thermique de polycondensats reticules

Statistical methods are applied to the theoretical study of the kinetics of the thermal degradation of crosslinked polycondensates. The parameters required by the theory are the crosslinking degree, the molecular weight of monomers, and the number of free chain ends of the polymer sample. There is a good agreement between theoretical results and experimental data obtained by isothermal thermogravimetric analysis of specially synthesized s-triazinic polycondensates.     

Application of a micro carbon rod atomizer as Br-spezific gas-chromatographic detector

Summary A micro carbon rod atomizer has been employed for specific and quantitative bromine determinations. This Br-specific gas-chromatographic detector works by help of InBr-bands and measurement at 372.7 nm. The performance of this flame band emission detector (FBD) is demonstrated by calibration curves and the detection limits of 2 examples (ethyl bromide, ethylene dibromide), the latter being 5 and 36 ng of bromine, respectively. The reproducibility has been found to be 4.3%. An example of this detector in comparison with a thermoconductivity detector (TCD) is presented.

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Verwendung einer Mikro-Graphitküvette als Br-spezifischer Detektor für die Gas-Chromatographie

Zusammenfassung Eine Mikro-Graphit-Küvette wird für spezifische quantitative Brombestimmungen nach der Indium-Methode bei 372,7 nm benützt und in Verbindung mit einem Gas-Chromatographen als Br-spezifischer Detektor eingesetzt. Die Leistungsfähigkeit dieses Detektors wird an 2 Beispielen (Äthylbromid, Dibromäthan) mit Hilfe von Eichkurven, Bestimmung von Nachweisgrenzen u. ä. demonstriert. Die Nachweisgrenzen liegen bei 5 bzw. 36 ng Brom für die 2 genannten Substanzen. Die Reproduzierbarkeit der Messungen liegt bei 4,3%. Ein Beispiel für die Registrierung eines Gemisches verschiedener Substanzen, gemessen mit dem GC + Flammen-Banden-emissions-Detektor (FBD) und zum Vergleich mit einem Wärmeleitfähigkeitsdetektor (TCD), wird dargestellt.

This research work was supported by financial help of the Bundesminister für Forschung und Technologie in Bonn (GFR).     

Synthesis and some properties of gem-dichlorocyclopropane carboxaldehyde acetals and cyclopropane carboxaldehyde acetals

α,β-Unsaturated aldehyde acetals add :CCl₂ (obtained in accordance with Makosza procedure) to form gem-dichlorocyclopropanecarboxaldehyde acetals (1) in high yields when the ratio of reactants is no less than 1:4. The addition of :CCl₂ to polyunsaturated aldehyde acetals in the above conditions proceeds regioselectively at double bonds enriched by electrons. Compounds 1 are reduced by sodium in liquid ammonia to give cyclopropanecarboxaldehyde acetals (2). Both 1 and 2 are hydrolized by dilute H₃P0₄ to the corresponding aldehydes and are added to vinyl ethers in the presence of BF₃·Et₂O to produce only 1:1 adducts which are hydrolyzed by a mixture of AcOH-AcONa-H₂O to give β-formylcyclopropanes which were previously unknown.     

Etude structurale de combinaisons sulfurees et seleniees du molybdene. II. Structure cristalline de Ni0,33Mo3Se4

The crystals of Ni_0,33Mo₃Se₄, are triclinic, space group $\text{P}\text{1}$, with two formula units in a cell: a = 6,727 (9) Å, b = 6,582 (11) Å, c = 6,751 (6) Å, α = 90.61° (10), β = 92.17° (10), γ = 90.98° (12.) The structure was solved by analogy with Mo₃Se₄ and refined by a full-matrix least squares program to R = 0,093 for 822 independent reflexions. The channels present in Mo₃Se₄ are occupied by Ni so that Ni_0,33Mo₃Se₄ is always a metallic compound.     

IR-spektroskopische Untersuchungen wäßriger Lösungen mit Hilfe der ATR-Technik

The ATR-method is qualified for measuring aqueous solutions if the multiplereflection technique is used in such a way that strong water absorptions do not cover a large part of the information on the spectrum. The single-reflection technique is mainly suitable for solutions of 2-molar and higher concentrations. Organic acids, phenols, amides, saccharides and anorganic compounds had been measured. A practical example proved that there is the possibility of also taking quantitative measurements with the ATR-method.     

Mass-spectrometer investigation of 3, 6-dialkyl-2, 5-diketopiperazines

Analysis of mass-spectra of various 2, 5-diketopiperazines gives the basic fragmentation rules for their molecular ions, and the effects of nature and positions of substituents on the process.Mass-spectrometry Laboratory of the Institute of the Chemistry of Natural Compounds.Antibiotics Chemistry Laboratory of the Institute of the Chemistry of Natural Compounds.     

Note sur la préparation et la scission de l'acide (diméthyl-3, 3-butyl)-phosphorique

3,3-Dimethylbutanol treated with polyphosphoric acid or with an equimolecular amount of POCl₃ gives rise to 3,3-dimethylbutyl phosphoric acid, isolated as baryum salt (yield 20 to 30%) or as sodium salt (yield 15%). Stable in NaOH 1N at 100°C, this monoester is split at pH 4.5 and in HCl 1N much slower than choline phosphate.     

Durch elektrochromatographische Untersuchung der komplexen Laurate von Co2+, M2++ und Cu2+

Ohne Zusammenfassung     

Reconocimiento de nicotina en una hebrita de tabaco

Summary Adaption of theLuís method for the detection of nicotine to microscale, usingEmich's capillary technic proved successful, attaining identification limit of 0,03g.Applying a sub-micro steam distillation effect, the nicotine in a speck of tobacco (1 mm² and less) could still be detected by using the above reaction.Extension of the above procedure to mixtures of nicotine with substances not volatile with steam, inorganic (halides) as well as organic compounds (other alkaloids, acids, etc.) proved to be successful, even when the nicotine is present in proportions of only 1 part in 1000.

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Zusammenfassung Die Anwendung der Kapillartechnik vonEmich zum Nachweis von Nikotin nachLuís war erfolgreich und zeigte eine Erfassungsgrenze von 0,03g.Bei Anwendung einer Ultramikrodampfdestillation kann das Nikotin nach obiger Methode noch in Spuren von Tabak (1 mm² und weniger) nachgewiesen werden.Die Reaktion ist auch positiv bei Gemischen von Nikotin mit anderen, mit Wasserdampf nicht flüchtigen sowohl anorganischen (Halogenide) als auch organischen Substanzen (andere Alkaloide, Säuren etc.), selbst dann noch, wenn das Nikotin bloß im Verhältnis von 11000 vorhanden ist.

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Résumé La technique capillaire d'Emich a été utilisée avec succès pour identifier la nicotine suivant le procédé deLuís; la limite de sensibilité est alors de 0,03g. La mise en oeuvre d'un ultramicroentraînement à la vapeur permet en outre, par application de la précédente méthode, d'identifier la nicotine dans des traces de tabac (moins de 1 mm²). La réaction est également positive en présence d'autres substances non entraînables par la vapeur d'eau, qu'elles soient minérales (halogénures) ou organiques (autres alcaloïdes, acides, etc. ...) même si la proportion de nicotine n'est que de l'ordre de grandeur de 1/1000.