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121.
Hans Günther Wahl Silke-Yvonne Habel Norbert Schmieder Hartmut M. Liebich 《Journal of separation science》1994,17(7):543-548
Identification of cis/trans isomers of unsaturated fatty acids cannot usually be achieved by GC-MS (gas chromatography-mass spectrometry) without reference substances. In this study a GC-FTIR-MS system (gas chromatography-Fourier transform-mass spectrometry) was used to identify fatty acid methyl esters (FAMEs) and differentiate between the cis/trans isomers. Besides methyl esters, 2-alkenyl-4,4-dimethyloxazoline derivatives (DMOX), which have been used to locate double bond positions of unsaturated fatty acids, were examined with respect to their suitability for cis/trans differentiation. A combined GC-FTIR-MS system with a wide band (4000–550 cm?1) mercury cadmium telluride (MCT) detector was used in series and parallel to identify 31 reference unsaturated fatty acids, including 7 pairs of cis/trans isomers. Serum samples of healthy persons and commercially available fish oil were analyzed as examples of complex mixtures. Using splitless injection the detection limit for the less sensitive IR detector was 25 ng/μl in case of the weak cis and trans bands. In the FTIR spectra cis/trans isomers were identified by analysis of bands arising from C? H out-of-plane (oop) bending: for both the FAME and DMOX derivatives cis-1,2-disubstituted double bonds give a strong band near 720 cm?1 and the corresponding trans isomers near 967 cm?1. cis Isomers could be identified further by a band at 3012 cm?1. With the combined data of the GC-FTIR-MS system it is now possible to identify polyunsaturated fatty acids with regard to the discrimination of cis/trans isomers. 相似文献
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Brigitte Voit Sven Fleischmann Hartmut Komber Arnulf Scheel Katrin Stumpe 《Macromolecular Symposia》2007,254(1):16-24
Summery: The potential of cycloaddition (CA) reactions for the synthesis of dendritic polymers is pointed out. The [4 + 2] Diels Alder cycloaddition as well as 1,3-dipolar CA reactions including “click chemistry” are addressed, and the advantages of these reactions like high selectivity, thus high tolerance towards additional functionalities, high yields and synthesis under mild reaction conditions are highlighted. New perfectly branched dendrimers as well as hyperbranched polymers have been prepared and modified using the 1,3-dipolar cycloaddition reaction of azines with alkynes. The 1,3-dipolar CA reaction of bisazine with maleimides results in hyperbranched and thus, irregular and broadly distributed polymers though with a degree of branching of 100% due to special intermediate formation. The [4 + 2] Diels Alder cycloaddition was successfully applied for the synthesis of highly branched polyphenylene structures using the AB2 + AB and the A2 + B3 approach. CA reactions are also very suitable for highly efficient polymer analogous reactions and thus, they can also be used to prepare complex polymer architectures like dendronized polymers. 相似文献
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Dipl.‐Chem. Felix Koch Dr. Andreas Berkefeld Dr. Hartmut Schubert Claudius Grauer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14640-14647
This work reports on the redox and acid–base properties of binuclear complexes of nickel from 1,4‐terphenyldithiophenol ligands. The results provide insight into the cooperative electronic interaction between a dinickel core and its ligand. Donor/acceptor contributions flexibly adjust to stabilize different redox states at the metals, which is relevant for redox reactions like proton reduction. Proton transfer to the [S2Ni2] core and Ni?H bond formation are kinetically favored over the thermodynamically favored yet unproductive proton transfer to ligand. 相似文献
128.
Cover Picture: On The Potential of Dynamic Nuclear Polarization Enhanced Diamonds in Solid‐State and Dissolution 13C NMR Spectroscopy (ChemPhysChem 17/2016) 下载免费PDF全文
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Dynamic Nuclear Polarization Provides New Insights into Chromophore Structure in Phytochrome Photoreceptors 下载免费PDF全文
Daniel Stöppler Dr. Chen Song Dr. Barth‐Jan van Rossum Michel‐Andreas Geiger Christina Lang Prof. Dr. Maria‐Andrea Mroginski Dr. Anil Pandurang Jagtap Prof. Dr. Snorri Th. Sigurdsson Prof. Dr. Jörg Matysik Prof. Dr. Jon Hughes Prof. Dr. Hartmut Oschkinat 《Angewandte Chemie (International ed. in English)》2016,55(52):16017-16020