Udo Groß

Non-aqueous synthesis of high surface area aluminium fluoride-a mechanistic investigation

Fluoride can do it too! Sol–gels of metal fluorides play an important role in the formation of high surface area metal fluorides. The synthesis of amorphous high surface area metal fluorides via a recently discovered two-step synthetic route was investigated in detail, exemplified for aluminium fluoride. The first step is fluorination of aluminium alkoxide with anhydrous HF in organic solvents, which proceeds as a sol–gel process known until now only for metal oxide formation. The reaction pathway is illustrated including crystal structure determination of the intermediate aluminium alkoxide fluoride. The resulting amorphous aluminium alkoxide fluoride has to be freed in a second step of solvating alcohol and of residual alkoxidic groups. This is done by heating in a stream of a mild fluorinating agent like a HCFC or CFC or in HF to obtain high surface area and very high Lewis acidity; an inert gas such as N2 is not sufficient. Using a variety of analytical techniques, including liquid and solid state NMR, X-ray structure analysis and XPS, the reaction pathways have been elucidated.

Persistent fluorocarbon radicals generated by elemental and electrochemical fluorination

Abstract Stable fluorocarbon radicals ware obtained by fluorination of branched fluoro-olefins and unsaturated partially fluorinated tertiary amines. As a fluorine source, elemental fluorine as well as the electrochemical fluorination process (ECF) in anhydrous hydrogen fluoride (AHF) were used. The persistent radicals were investigated by ESR spectroscopy concerning their structure and stability. ECF-generated fluorocarbon radicals give some evidence of intermediately formed atomic fluorine as a key factor of the AHF-based electrochemical process. These findings favour and electrofluorination mechanism similar to that of elemental fluorine. Because of their unusual stability, the radicals can be used as spin markers and to obtain 2D images by using an ESR tomographic technique. Stabilized with emulsifiers, they form stable aqueous emulsions.

Phospholipid Vesiculated Fluorocarbons-Promising Trend in Blood Substitutes

Dispersions of fluorocarbons (PFCs) made with phospholipids have unusual properties, e.g. very high stability, due to the formation of thermodynamically stable vesicles. They can be used for high PFC concentrations as well as e.g. for ESR imaging.

Über synthesen von difluoraminopyrimidinen

Zusammenfassung Es wird uber Synthesen von Difluoraminopyrimidinen berichtet. Bei der Direktfluorierung der Aminoderivate worden die entsprechenden Difluoraminoverbindungen neben weiteren Fluorierungsprodukten erhalten. Im Falle der Alkylierung von Difluoramin durch protonierte Pyrimidine wird die Bildung der Difluoraminoverbindungen diskutiert.

Asymmetric lamellar phospholipid aggregates bearing fluorocarbons

Abstract Phospholipid-encapsulated fluorocarbons form vesicle-like aggregates. Because of the lipophilic nature of fluo-rocarbons in the core, the number of surrounding lipid layers is consequently uneven. The lamellar structures of droplet coating have been confirmed by physical methods such as NMR spectroscopy, optical and cryo-electron microscopy, zeta potential, etc. The observed line broadening of signals in the 1H NMR spectra has been shown to be a result of hindered segmental motions in PFC-saturated lamellar structures. The existence of a negative surface charge as supported by the zeta potential contributes to an increase in the dispersion stability. Whereas light microscopy confirmed the isotropic nature of the dispersion, cryo-electron micrographs allowed the film thickness of the lamellae to be measured. The conditions under which such particles are prepared, especially the nature of the phospholipids used, are described. In addition, some new applications based on these aggregates are discussed.

Synthesis of perfluoroethers for use as blood substitutes

Abstract Perfluorinated alicyclic ethers are promising candidates for blood substitutes. Fluorination of 1. ethers with 1 oxygen atom over cobalt trifluoride were carried out. The effect of structure on the formation of perfluoroethers is outlined. Ethers of the first and the third group provided good yields of the corresponding perfluorinated ethers. But only perfluoroethers of group 3 have proved to be promising candidates for use as blood substitute. [1] These precursors were synthesized by Dr. V.E. Platonov at Institute of Organic Chemistry, Sibirian Division of the Academy of Science of the U.S.S.R., 630090 Novosibirsk.