Synthese von 2-methylalanin-peptiden,die pH-Abhängiggkeit ihrer 13C-NMR-spektren und eine neue methode zur auswertung über CS-diagramme

The uncommon amino-acid 2-methylalanine (α-aminoisobutyric acid, Aib) was investigated by ¹³C-NMR. The chemical shifts of amino- or carboxy-protected derivatives of Aib and of protected oligopeptides are discussed with respect to neighbouring groups and amino acids. The pH-dependence of the ¹³C-NMR spectra of Aib, Aib-Ala, Ala-Aib, Aib-Ala-Aib and Aib-Ala-Aib-Ala-Aib was studied. Using these examples, a new and advantageous method is demonstrated for the first time for the evalutions of NMR titration curves, which uses so-called chemical shift diagrams (CS diagrams).     

Quantitative separation of gold from cadmium, indium, zinc and other elements by cation-exchange chromatography in hydrochloric acid-acetone medium

Gold(III) can be separated from Cd, In. Zn, Ni, Cu(II), Mn(II), Co(II), Mg, Ca, Al, Fe(III), Ga and U(VI) by adsorbing these elements on a column of AG50W-X8 sulphonated polystyrene cation-exchange resin from 0.1M HCl containing 60% v v acetone, while Au(III) passes through and can be eluted with the same reagent. Separations are sharp and quantitative. The amounts of gold retained by the resin are between 1 and 2 orders of magnitude lower than encountered during adsorption from aqueous 0.1M HCl. Recoveries for mg amounts of gold are 99.9% or better and for ng amounts are still better than 99%, as shown by radioactive tracer methods. Hg(II), Bi, Sn(IV), the platinum metals and some elements which tend to form oxy-anions in dilute acid accompany gold. All other elements, though not investigated in detail, should be retained, according to their known distribution coefficients. Relevant elution curves, results of quantitative separations of binary mixtures and of recovery tests are presented.     

A Molecular modeling study of the changes of some steric properties of the precatalysts during the olefin metathesis reaction

The productive self‐metathesis of 1‐octene with a series of new phosphine ligated Grubbs‐type precatalysts was studied. The resulting structures were used to compare some steric properties of the new precatalysts with those of well‐known precatalysts. The possibility of α‐CC agnostic stabilization as well as the ability of the ligands to shield the metal was studied. A comparison of the obtained data, pointed to the unlikelihood that α‐CC agostic stabilization is a major contribution to the stabilization of the various metallacyclobutane rings. The similarity in the ability of the ligands to shield the metal also raised questions about the comparison of experimentally observed trends with those obtained theoretically. © 2014 Wiley Periodicals, Inc.     

Bestimmung der Ionendichte in strömenden Hochdruckplasmen mittels elektrischer Staupunktsonden

An electrical stagnation point probe used to measure ion densities of flowing high pressure plasmas (p = 10⁵ Pa) was developed. The experimental results of a probe operating in the sheath — convection regime confirm the validity of the used theory according to the shape of the characteristic and the measured ion density compared with spectroscopical values. The deviation between both techniques is less than a half order of magnitude.     

Anstrengungsverhältnis und Festigkeitshypothese

Ohne Zusammenfassung     

7-Chloro-4-methyl-6-nitro-2H-chromen-2-one: a novel type of reagent for fluorescence analysis

Starting from 7-chloro-4-methyl-2H-chromen-2-one 1 we have obtained a new reagent for fluorescence analysis. The synthesised key compound 7-chloro-4-methyl-6-nitro-2H-chromen-2-one 2 forms highly fluorescent derivatives with different amines, which can be introduced by nucleophilic substitution of the chloro atom. Two examples are given which describe the preparation of these derivatives. Additionally, we demonstrate that an increase of fluorescence can be achieved, if a reduction step is performed after the substitution.