Studien über Quercetin und seine Derivate

Ohne Zusammenfassung     

Studien über Kernalkylierung

Ohne Zusammenfassung     

Die Winkelderivierte und das Poisson-Stieltjes-Integral

Ohne ZusammenfassungDiese Arbeit wurde von der naturwissenschaftlichen Fakultät der Schlesischen Friedrich-Wilhelms-Universität zu Breslau als Dissertation (D 2) angenommen.     

Synthetic applications of 2-chlorooxiranes: preparation of thiazoles,dihydrothiazoles and selenazoles

The reaction of 2-chlorooxiranes 1 with thioamides and thioureas provides access to thiazoles, 4-hydroxy-4,5-dihydrothiazoles and 2-imino-2,3-dihydrothiazoles under mild conditions and with excellent yields. With 1 and selenourea, near quantitative yields of selenazoles are obtained.     

The preparation of a cabbage reference material for environmental monitoring and food analysis

 Cabbage is frequently used in environmental monitoring and food control, and, hence, cabbage reference materials (RMs) are required for ensuring quality assurance. A cabbage RM was prepared in view of certification of specific elements from the "black list" of high toxicological interest and nutritive importance. All tasks of the RM production (production of the plant material, cutting and freeze-drying, determination of the residual water content, preparation of the RM, homogeneity testing, stability testing, certification measurements) are described in detail. Received: 12 November 1999 / Accepted: 29 January 2000     

A theoretical investigation of titanium aluminium nitrides, (Ti,Al)N: Electronic structure and chemical bonding

Titanium aluminium nitrides, Ti_1-x Al _x N, can be prepared as films by various sputtering methods. They form metastable phases in which the titanium and aluminium atoms are randomlydistributed over the metal sublattice. In the present work two ordered model structures, Ti₃AlN₄ and TiAlN₂, have been chosen, for which LAPW band-structure calculations have been performed. The calculated densities of states (DOS) and the local partial DOS for both model structures are compared with the corresponding values for TiN. Characteristic changes in the DOS of the p band are observed which are caused by the nitrogenp orbitals that point towards the aluminium spheres. The bonding situation is investigated on the basis of electron density and difference electron density plots. The substitution of titanium atoms by aluminium atoms leads to stronger covalent Ti–Ti and N–Ti bonds and to additional ionic bonding contributions by the aluminium atoms whose ionicity increases from Ti_0.50Al_0.50N to Ti_0.75Al_0.25N.     

Flavin–cyclodextrin conjugates: effect of the structure on the catalytic activity in enantioselective sulfoxidations

A series of flavin–cyclodextrin conjugates has been prepared and tested in the enantioselective oxidations of prochiral aromatic and aliphatic sulfides with hydrogen peroxide. The newly prepared conjugates contain isoalloxazinium or alloxazinium moieties attached to the primary rim of α- and β-cyclodextrins at the C-6 positions. In addition, flavinium units were attached to the secondary rim of the β-cyclodextrin macrocycle. The relationship between the structural features and the catalytic performance of the conjugates, including those recently reported by us, was analyzed. The rate and enantioselectivity of the sulfoxidations catalyzed by flavin–cyclodextrin conjugates are influenced mainly by the size of the cyclodextrin cavity, the type of flavin unit (alloxazine or isoalloxazine), and by the relative orientation of the flavin and cyclodextrin moieties.     

Über den Nachweis und die Bestimmung des an Stickstoff gebundenen Alkyls

Ohne Zusammenfassung