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- Building-blocks (1)
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- Crystalline aluminium fluorides (1)
- Etal-complexes (1)
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Most of the methane (CH4) emission from rice fields is derived from plant photosynthates,
which are converted to CH4. Rice cluster I (RC-1) archaea colonizing the
rhizosphere were found to be the methanogens responsible for this process. Hence, RC-1
methanogens seem to play a crucial role in emission of the greenhouse gas CH4. We
determined the community composition and activity of methanogens colonizing the
roots of eight different rice cultivars after growth on both Italian rice soil and river bank
soil, which contained different communities of methanogenic archaea. The community
composition was analyzed by terminal restriction fragment length polymorphism and
cloning/sequencing of the archaeal 16S rRNA gene and the mcrA gene coding for a
subunit of the methyl coenzyme M reductase. When grown on rice field soil, the
methanogenic community of the different rice cultivars was always dominated by RC-1
methanogens. In contrast, roots were colonized by Methanomicrobiales when grown on
river bank soil, in which RC-1 methanogens were initially not detectable. Roots
colonized with Methanomicrobiales compared with RC-1 exhibited lower CH4 production
and CH4 emission rates. The results show that the type of methanogens colonizing
rice roots has a potentially important impact on the global CH4 cycle.
A comprehensive spectroscopic characterization of all known crystalline AlF3 phases (α-, β-, η-, κ-, θ-AlF3) is presented for the first time in this study. Beside their X-ray diffraction powder patterns, which were already published in the literature, 27Al and 19F MAS NMR, FT IR and XPS spectroscopic techniques were applied for all phases in a consistent manner. For all phases prepared the utilization of 27Al satellite transition (SATRAS) NMR allowed to determine the quadrupolar parameters of the aluminium sites including their distributions.
In addition, η-AlF3 was isolated with high phase purity and characterized following a new preparation path different from those known so far in the literature.
Catalytic C–F bond activation reactions of mono- and polyfluoroalkanes at Lewis acidic amorphous aluminum chlorofluoride (ACF) are presented. The hydrogen sources Et3GeH or Et3SiH control the selectivity of the conversions. The immobilization of Et3GeH at ACF resulted in catalytic dehydrohalogenation reactions to yield olefins under very mild conditions. In contrast, if Et3SiH is immobilized at ACF, C–C coupling occured and the formation of Friedel–Crafts products was observed. MAS NMR spectroscopic studies revealed information about the surface binding of the substrates.