Synthesis of 2-substituted pyridines catalyzed by cobalt(I) complexes and promoted by light

A series of pyridines substituted in the 2-position were synthesized by cobalt(I)-catalyzed cotrimerization of alkynes and nitriles. The reactions are usually enhanced by light. The reaction conditions are very mild. Activity and selectivity are satisfactory with respect to formation of pyridines, but depend on the type of nitrile.     

Photoaccelerated synthesis of 2-vinylpyridines from unsaturated nitriles and ethyne

The heterocyclization of unsaturated nitriles and ethyne catalyzed by cyclopentadienyl-1,5-cis,cis-cyclooctadiene-cobalt(I) and promoted by light has been studied in toluene as solvent. Acrylonitrile and substituted acrylonitriles gave results of interest in the preparation of 2-vinylpyridines. No reaction could be observed using fumaronitrile, maleonitrile or allyl cyanide. The (E)/(Z)-ratio of educts and products seems to be not influenced by conditions in the reaction.     

The slip-model for molecular reorientation and the temperature dependence of nuclear relaxation times in neat toluene and chlorobenzene

The temperature dependence of deuterium nuclear relaxation times in selectively deuterated toluene and chlorobenzene is studied. It is shown that the temperature behaviour of molecular reorientation times can be described by the method of Pecora et al. within the limit of rotational diffusion.     

Chloride-enhanced atmospheric pressure chemical ionization mass spectrometry of polychlorinated n-alkanes

The use of high-performance liquid chromatography combined with chloride-enhanced atmospheric pressure chemical ionization for the determination of polychlorinated n-alkanes (PCAs, also called chlorinated paraffins or CPs) is described as an alternative to gas chromatographic methods. Atmospheric pressure chemical ionization in the negative ion mode formed exclusively [M+Cl](-) adduct ions and suppressed fragmentation when a chlorinated solvent was added. Limits of detection were 1-2 ng/microL for technical PCA mixtures. Response factors for single short-chain PCA homologues with different degrees of chlorination varied by not more than a factor of 6.5. The developed method was applied for the determination of the composition of technical PCA mixtures as well as for the analysis of PCAs in household commodities. Medium-chain PCAs were found in paint samples at concentrations of 8.2-11.5% (w/w), compared with 7.4-11.5% obtained by gas chromatography combined with electron ionization tandem mass spectrometry.     

Inexpensive precision ph microcell for volumes of 50–200μl with replaceable glass membrane and diaphragm

Summary The development of an inexpensive microcell for pH measurement is described. The cell can be used for sample volumes of 50–200l. Its main advantages are the easy replacement of both the diaphragm and the pH glass membrane at low cost. The reproducibility with a conventional pH meter is ±0.01 pH unit, but can be improved to ±0.004 pH unit by differential measurement.

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Eine preisgünstige pH-Mikromezelle

Zusammenfassung Die Herstellung einer preisgünstigen pH-Mikromeßzelle wurde beschrieben. Sie kann für Probevolumina von 50–200l eingesetzt werden. Hauptvorteile sind das preisgünstige und einfache Auswechseln von Verschleißteilen, wie pH-Membran und Diaphragma. Thermostatierung der Probe und Mikrotitrationen in der Meßzelle sind möglich. Mit Hilfe einer differentiellen Meßmethode können pH-Messungen mit einer Reproduzierbarkeit besser als ±0,004 pH-Einheiten erzielt werden. Wird ein konventionelles pH-Meter verwendet, so liegt die Reproduzierbarkeit des Meßwertes bei ±0,01 pH.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Studies on the Synthesis of Di‐ and Trisaccharide Analogues of Moenomycin A. Modifications in Unit E and in the Lipid Part

Routes allowing the synthesis of moenomycin analogues with one modified sugar component and with new lipid parts were developed (see 10c, 12c, 16b , and 20b in Schemes 2–4). It is anticipated that such analogues will be useful for studying the mode of action of the moenomycin‐type transglycosylase inhibitors in detail and for preparing analogues with improved pharmacokinetic properties.