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81.
82.
Lukas Meier Christian Berchtold Stefan Schmid Renato Zenobi 《Journal of mass spectrometry : JMS》2012,47(5):555-559
In this study, we use an ion funnel (IF) at ambient pressure to enhance the sensitivity of secondary electrospray ionization (SESI). Atenolol, salbutamol and cocaine as test compounds are delivered to the SESI interface in the gas phase and are charged with three nano electrosprays. In our experiments, we show that the compounds can be detected at concentrations in the low pptv range, which is an increase of two orders of magnitude compared with the results without the IF. With a standard SESI interface, the compounds could not be detected at all. With the use of the SESI IF interface for the headspace analysis of bananas and limes, we can detect many more compounds and at higher intensities than with a standard SESI interface. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Hansurudolf Meier Hanspeter Kuenzi Hermann Fuhrer Günher Rist 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):537-538
Abstract The 2.4-bisfunctionalized phenol 1, a commercial antioxidant, is dehydrogenated regioselectively with potassium ferricyanide. affording the corresponding p-quinone methide 2. 1,6-Addition of nucleophiles e.g. thiols to 2 gives rise to the corresponding addition products e.g. the dithioacetals 4 of the corresponding substituted benzaldehyde. On the other hand, treatment of 2 with αα′-azoisobutyronitrile at 90°C leads to compounds 5a-b and 6, addition products of the cyanopropyl radical to the quinone methide 2. The structures of all products are confirmed mainly by 1H-NMR-and 13C-NMR-spectroscopy and the mode of their formation is discussed. 相似文献
87.
Sandra Kolly Hansrudolf Meier Talmo Winkler 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Besides the common cyclisation reactions between divalent electrophiles such as Soc12, SC12, etc. and 2,2′-alkylidene-bisphenols 1 with selective attack by the two oxygens yielding dibenzo[d,g][1,3,2]dioxathiocines [1] we observed previously an unusual cyclisation of 1 with S2CI2 with a nucleophilic attack by the ortho- and para-carbon atoms (C(2) and C(4)) of bisphenol 1 [2]. We now report a new type of cyclocondensation reaction of 4,4′,6,6′-tetrasubstituted 2,2′-alkylidene-bisphenols 1 with ClSCOCl affording spiro[1,3-benzoxathiepin-4(5H),1′-cyclohexa[2,4]dien]-2,2′-diones 2 together with the cyclic carbonates 3. The structures of the products were elucidated mainly by l3C-NMR- and 1H-NMR-spectroscopy. The mode of formation of the novel spiro thiocarbonates 2 resp. the known carbonates 3 [3] is discussed. 相似文献
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1‐Thiacyclooct‐4‐yne (=5,6‐didehydro‐3,4,7,8‐tetrahydro‐2H‐thiocin; 9 ) can be prepared from thiocan‐5‐one ( 6 ) in three steps by applying the so‐called selenadiazole method. The heterocyclic alkyne can be oxidized to the corresponding sulfoxide 16 and sulfone 17 . Due to their geometrical strain, all three cyclic alkynes show high reactivities in Diels? Alder and 1,3‐dipolar cycloadditions. Moreover, tetrathiafulvalenes can be prepared from 9 and 16 by the reaction with CS2. 相似文献
89.
Yuhui Kou Derong Cao Hongqi Tao Lingyun Wang Jianquan Liang Zhizhao Chen Herbert Meier 《Journal of inclusion phenomena and macrocyclic chemistry》2013,77(1-4):279-289
A detailed study of the reaction conditions revealed that a quantitative cyclocondensation of 1,4-dialkoxy-2,5-bis(alkoxymethyl)-benzenes to pillar[n]arenes can be achieved by catalysis of p-toluenesulfonic acid in CH2Cl2. Major product of this new reaction is in each case a cyclopentamer (n = 5), but small amounts of the pillar[n]arenes with n = 6, 7 and 10 can be obtained as well. Different alkoxy groups in 1- and 4-position lead to regioisomers. All cyclooligomers exist in pillar structures as pair of enantiomers, which show a racemisation at room temperature, which is fast in terms of the NMR time scale. The racemisation process occurs by rotation of the 1,4-phenylene segments in the macrocyclic rings. Pillar[n]arenes exhibit novel host–guest behavior. 相似文献
90.
Dr. Sophie R. Beeren Dr. Sebastian Meier Prof. Ole Hindsgaul 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16314-16320
Branched starch polysaccharides are capable of binding multiple hydrophobic guests, but their exploitation as multivalent hosts and in functional materials is limited by their structural complexity and diversity. Linear α(1–4)‐linked glucose oligosaccharides are known to bind hydrophobic guests inside left‐handed single helices in solution and the solid state. Here, we describe the development of an amphiphilic probe that binds to linear α(1–4)‐linked glucose oligosaccharides and undergoes a conformational switch upon complexation, which gives rise to dramatic changes in the 1H NMR spectrum of the probe. We use this probe to explore hydrophobic binding sites in the branched starch polysaccharides amylopectin and β‐limit dextrin. Diffusion‐ordered (DOSY), nuclear Overhauser effect (NOESY) and chemical shift perturbation (HSQC) NMR experiments are utilised to provide evidence that, in aqueous solution, branched polysaccharides bind hydrophobic guests in well‐defined helical binding sites, similar to those reported for complexation by linear oligosaccharides. By examining the binding affinity of the probe to systematically enzymatically degraded polysaccharides, we deduce that the binding sites for hydrophobic guests can be located on internal as well as external branches and that proximal α(1–6)‐linked branch points weaken but do not prevent complexation. 相似文献