Isolation and synthesis of vobparicine,a novel type dimeric indole alkaloid

From the rootbark of Tabernaemontana chippii a novel antimicrobially active dimeric indole alkaloid was isolated which was assigned structure $\text{1}$ on the basis of spectroscopic evidence and its synthesis.     

Photometrische Titration der Carboxylendgruppen in Poly?thylenterephthalat

Zusammenfassung Es wird eine schnelle Methode zur Bestimmung von Carboxylendgruppen in Polyäthylenterephthalat beschrieben; sie beruht auf der Messung der Farbänderung von Bromphenolblauindicator während der Titration einer Lösung des Polymeren in o-Kresol/Chloroform mit alkoholischer Lauge.Resultate von Bestimmungen an einer organischen Säure und an Polymerproben werden gegeben. Die Resultate von Bestimmungen an Polymeren wurden mit denen nach der von Pohl beschriebenen visuellen, nach der von Maurice beschriebenen potentiometrischen Methode und nach der von Ward beschriebenen Infrarotmethode verglichen und gleiche Resultate erhalten. Die photometrische Methode wird aus verschiedenen Gründen bevorzugt.

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Photometric titration of carboxyl end groups in polyethylene terephthalate

The method is based on the continuous measurement of the changes in absorbance of bromophenol blue indicator during titration of a solution of the polymer in o-cresol/chloroform with standard alcoholic potassium hydroxide solution.Results are given of tests with an organic acid and polymers amples. The results obtained with the polymer samples are compared with those obtained by the visual titration method of Pohl, the potentiometric titration method of Maurice and the infrared method of Ward. The four methods yield the same results. For several reasons the photometric method is preferred.

     

The signal vs. concentration relationships in fluorimetry

Formulae for the fluorescence signal are derived which take into account some factors hitherto neglected. From these formulae conditions are deduced, for which a linear relationship exists between the concentration of the fluorescent components and the intensity of the fluorescence. In some cases of practical interest the fulfilment of these conditions cause too low a sensitivity. For such cases a method of optimization is outlined, by means of which the conditions are found which lead to the least deviation from linearity at the required sensitivity.     

Verdampfung von Uranspaltprodukten in Wasserstoff, Stickstoff und Sauerstoff

Zusammenfassung Die Verdampfung der Spaltprodukte Germanium, Arsen, Molybdän, Ruthenium, Cadmium, Zinn, Antimon und Tellur aus bestrahltem U₃O₈ im Wasserstoff-, Stickstoff- und Sauerstoffstrom wurde zwischen 900 und 1500° C untersucht. Bei 1500° C verdampfen die meisten dieser Elemente innerhalb 1 Std mit hoher Ausbeute.

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Summary The volatization of the fission products germanium, arsenic, molybdenum, ruthenium, cadmium, tin, antimony and tellurium from neutron-irradiated uranium oxide in flowing hydrogen, nitrogen or oxygen of atmospheric pressure was investigated between 900 and 1500° C. At 1500° C, most of these elements are volatized with high yield within one hour.

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Herrn Prof. Dr. F. Strassmann danken wir herzlich für die Förderung dieser Arbeit, Herrn I. Bonner für seine Mitarbeit, den Betriebsstäben der Forschungsreaktoren Frankfurt und München, insbesondere Herrn Dr. G. Wolf (Frankfurt), für Bestrahlungen und dem Bundesministerium für wissenschaftliche Forschung für finanzielle Beihilfen.

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Herrn Prof. Dr. W. Geilmann zum 75. Geburtstag gewidmet.

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Aus einer Dissertation, Mainz 1963.     

SCF—CI calculations and the assignment of the absorption spectrum of the excimer of 1-methyl naphthalene; relation to 1,1′-binaphthyl

An SCF MO calculation followed by extensive configuration interaction between all singly-excited singlet states has been performed for the excimer of naphthalene in a perfect and in some distorted sandwich structures. With these results an assignment is given for the bonds in the absorption spectrum of the excimer of 1-methyl naphthalene. It is further shown that the similarity between the optical properties of the 1-methyl naphthalene excimer and those of 1,1′-binaphthyl in fluid solution, is also reflected by the calculations.     

Remarkable O(2)-effect in 1,4-additions of diethylzinc to 6-acyloxy-2H-pyran-3(6H)-ones and 6-alkoxy-2H-pyran-3(6H)-ones

Under the influence of air, a facile 1,4-addition of diethylzinc to acyloxypyranones and alkoxypyranones 1 takes place. Reaction of diethylzinc with molecular oxygen provides EtOOZnEt, which catalyzes the addition of diethylzinc.     

The luminescence of uranime-activated yttrium tungstate (Y2WO6)

The luminescence of uranium in Y₂WO₆ can be excited with long wavelength ultraviolet radiation at temperatures below room temperature. The emission consists of a fairly narrow band in the orange part of the spectrum. Its characteristics are comparable with the luminescence of uranium in MgWO₄ and the scheelites MWO₄ (M = Ca, Sr, Ba). It is possible to relate the thermal quenching temperature of the luminescence to spectral data. Energy transfer from the tungstate group to the uranate group is observed, but its efficiency is not very high compared with other systems.     

Expert system for precision testing in validation of liquid chromatographic methods

After a liquid chromatographic method has been developed, it must be validated to establish its limitations in daily use. Method validation is becoming increasingly important as stricter rules are applied by regulatory authorities. Precision testing is a vital step in this validation; both intralaboratory testing and interlaboratory testing are needed. In an intralaboratory test, repeatability and ruggedness tests are usually done. Expert systems are available for both tests. Here they are integrated to form an intralaboratory precision-testing expert system; special integration architecture is described. Important features of the integrated system are a supervisor containing planning knowledge about the tests and a common data structure containing all the objects necessary for an expert system in this area.     

Solvatochromism and piezochromism of dicyano-, tricyano-, and tetracyano-diimine-iron(II) complexes

The solvatochromism of several dicyano-bis-diimine-iron(II) complexes in various binary aqueous solvent mixtures has been established, at 25 °C. A solvent sensitivity scale has been developed for these complexes. The solvatochromic properties of two tricyano-terdentate ligand iron(II) complexes in several solvents have also been determined, as have those of a series of tetracyano-diimine complexes in DMSO–water media. These results have been analysed and systematic but varied trends of solvation were demonstrated. Piezochromic parameters for two complexes have been obtained and are discussed in the context of a solvatochromism/piezochromism correlation.     

Synthesis and Catalytic Properties of Di- and Trinuclear Palladium Complexes with PCP-Pincer Ligands

Linear and branched conjugated pincer ligands having Ph₂P groups were synthesized: 3,3',5,5'- tetrakis(diphenylphosphinomethyl)diphenylacetylene, 3,3',5,5'-tetrakis(diphenylphosphinomethyl)diphenyldi- acetylene, 1,3,5-tris[3,5-bis(diphenylphosphinomethyl)phenylethynyl]benzene, and hexakis[3,5-bis(diphenylphosphinomethyl)phenylethynyl]benzene. Palladation of these ligands by heating with Pd(BF₄)₂(MeCN)₄ in boiling acetonitrile gave the corresponding di- and trinuclear ionic pincer palladium complexes. No individual complex was obtained from hexakis[3,5-bis(diphenylphosphinomethyl)phenylethynyl]benzene. The ionic com- plexes were converted into the corresponding chloride complexes by treatment with sodium chloride in a mixture of water with methylene chloride. The structure of the ionic palladium complex with 3,3',5,5'-tetrakis(diphenylphosphinomethyl)diphenylacetylene was established by X-ray analysis. The obtained palladium complexes exhibited a considerable catalytic activity in the Heck reaction of iodobenzene with ethyl acrylate and in the Michael addition of ethyl cyanoacetate with methyl vinyl ketone. The catalytic activity per palladium atom decreases as the number of palladium atoms in the complex increases.