Zur Bestimmung der Jodzahl von El?ostearins?ure und Holz?l

Ohne Zusammenfassung     

Mononuclear anionic formyl complexes; synthesis and properties

A series of kinetically unstable mononuclear anionic formyl complexes have been prepared by the action of Li(C₂H₅)₃BH on neutral metal carbonyl precursors. One of these, Li⁺[(CO)₄Mn(COC₆H₅)(CHO)]^?, is shown to decompose by a hydride transfer disproportionation mechanism involving the by-product (C₂H₅)₃B.     

Eine Elektrophoresebestimmung von Kreatinin in Fleischextrakt, Fleisch und kohlenhydrathaltigen Fleischprodukten

Ohne Zusammenfassung     

Beryllium

Ohne Zusammenfassung     

Versatility of the dipolar filter selection: from 1H nuclear spin diffusion experiment to the measurement of nuclear Overhauser effect in homopolymer melts

Dipolar filters select ¹H magnetization according to local dipolar dephasing, which corresponds to site mobility in systems with heterogeneous molecular mobility. Combined with a conventional exchange experiment, it is usually applied to polymeric samples exhibiting structures on the nanometer length scale associated with a strong dynamic contrast. There, the resulting ¹H nuclear spin diffusion experiment yields the size of the structure. When the same experiment is applied to homopolymer melts exhibiting a weak dynamic contrast and dynamic heterogeneities on significant shorter length scales, the recorded magnetization decay is in agreement with decays expected from a heterogeneous nanostructure. However, dipolar filters actually can also select mobile parts of the repeat unit, e.g. the end of the alkyl side chains and the subsequent magnetization transfer then can occur via cross relaxation due to non coherent zero-quantum transitions (nuclear Overhauser effect, NOE). The difficulties of distinguishing these two cases are examined and it is demonstrated that NOE experiments exploiting magnetization selection via the dipolar filter allow quantifying the local dynamics of the side chains. This opens new possibilities for measurements of local dynamics in non isotopically labeled homopolymer melts.     

Ultrafast molecular dissociation of water in ice

Using x-ray emission and photoemission spectroscopies to measure the occupied valence levels in a thin crystalline ice film, we resolve the ionization-induced dissociation of water in ice on a femtosecond time scale. Isotope substitution confirms proton transfer during the core-hole lifetime in spite of the nonresonant excitation. Through ab initio molecular dynamics on the core-ionized state, the dissociation and spectrum evolution are followed at femtosecond intervals. The theoretical simulations confirm the experimental analysis and allow for a detailed study of the dissociative reaction path.