Photometrische Bestimmung des Aluminiunigehaltes von Kupfer und Kupferlegierungen

Zusammenfassung Es wird über eine photometrische Bestimmung des Aluminiumgehaltes von Kupfer und seinen Legierungen mit Eriochromcyanin-R berichtet, die sich schnell mit großer Genauigkeit durchführen läßt. Die Abtrennung der störenden Kationen wird durch Natronlaugefällung unter definierten Bedingungen ausgeführt.Es können auf diesem Wege Aluminiumgehalte von 0,01–10% bestimmt werden. Die höchste Abweichung von den Sollwerten beträgt ±0,03% Aluminium. Die Durchführung des Verfahrens beansprucht etwa 3 Std.An dieser Stelle möchte ich Herrn Prof. Dr. H. Blumenthal für seine Unterstützung bei dieser Arbeit meinen Dank aussprechen. Ferner danke ich Herrn Salewski für seine Hilfe bei der praktischen Durchführung.     

Fettbestimmungen in Lebens- und Futtermitteln

Ohne Zusammenfassung     

Regioselectivity and Deuterium Isotope Effects in Geraniol Hydroxylation by the Cytochrome P-450 Monooxygenase from Catharanthus roseus (L.) G. DON

The hydroxylation of geraniol ( 8 ) by cytochrome P-450 (P-450_Cath.) from the subtropical plant Catharanthus roseus (L.) G. DON was optimised to give 8-hydroxygeraniol ( 9 ) as the single product in 35% yield. Incubations of different ¹³C- and ²H-labelled geraniols revealed that H-abstraction is completely regioselective in favour of the CH₃ group trans to the chain at C(6) of 8 . An intramolecular isotope effect k_H/k_D = 8.0 was determined, suggesting that H-abstraction is one of the major rate-contributing steps; however, the intermolecular isotope effect was surprisingly inverse at low conversion k_H/k_D = 0.50, indicating the existence of rate-contributing steps preceding the first irreversible, isotope-sensitive reaction in the sequence.     

Nanostructure and thermoelectric properties of ReSi 2+/-x thin films

Anomalies in the nanostructure evolution of ReSi(2+/-x) thin films have proved to be of large interest in connection with their thermoelectric properties. By means of electron microscopic methods the correlation between structural properties and transport behaviour has been studied. The short-range order of the amorphous state was characterised by reduced density functions calculated from diffuse electron diffraction diagram and is found to correlate with the temperature dependence of the electrical resistance. The crystallisation process observed in situ in the transmission electron microscope starts with the formation of relatively large ReSi(1.75) grains (up to 100 nm). In later stages, only smaller grains are growing. This leads to a decrease in the mean grain size and to the increase of the nanocrystalline volume fraction during the heat treatment. This behaviour allows the investigation of the thermopower as function of the nanocrystalline volume fraction. Thus, at a nanocrystalline content of about 35% the thermopower exhibits a maximum in accordance with calculations.     

Homoleptische Zinkamide: Der Übergang zu monomeren Molekülen

Homoleptic Zinc Amides: Transition to Monomeric Molecules Zinc chloride reacts with the lithium salts of the bulky secondary amines HN(i-Bu)₂ and HN(t-Bu)₂ to form the corresponding homoleptic zinc compounds {Zn[N(i-Bu)₂]₂}₂ ( 1 ) and Zn[N(t-Bu)₂]₂ ( 2 ). The NMR spectroscopic and mass spectrometric results as well as the molecular weight determinations and X-ray diffraction data are consistent with a dimeric structure of 1 and a monomeric structure of 2 in the gas phase, in solution and in the solid state.     

Cation-induced charge-transfer absorptions of oligooxa[n.n]Paracyclophane quinhydrones

Intramolecular [n.n]paracyclophane quinhydrones with two oligo= oxaalkylene bridges 2a–e (m = 0,1,2,3 and 4, resp.) have been synthesized. The selective double complexation of these compounds with metal cations of suitable size (e.g. 7) is indicated by remarkable enhancements of the intensity of charge-transfer absorptions.     

Photoelektronenspektroskopische untersuchung von tris(trimethylelement(IV)aminen, -phosphinen, -arsinen und -stibinen

The PE spectra of [(CH₃)₃Sn]₃N, [(CH₃)₃E]₃P (E = C, Si, Sn), [(CH₃)₃Si]₃As and [(CH₃)₃E]₃Sb (E = C, S, Ge, Sn) are analyzed. The constant level of the ionization potentials of the n-hybrid orbitals of N, P, As, and Sb, together with changes in the hybridization and interactions with ligand MO's is discussed by qualitative MO investigations.