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101.
Marcel Baiwir Gabriel Llabrs Lon Christiaens Jean-Louis Piette 《Magnetic resonance in chemistry : MRC》1981,16(1):14-16
The 77Se chemical shifts of 79 mono- or disubstituted benzo[b]selenophenes are reported. The results in the 2- and 3-substituted derivatives closely parallel those previously obtained in the corresponding selenophenes. The measured parameters also correlate well with those measured in benzo[b]tellurophenes. The 125Te and 77Se chalcogen nuclei appear to be much more sensitive to substituent effects than the more classical nuclei. The effects of Cr(acac)3, Eu(dpm)3 and concentration on the 77Se NMR spectra are briefly discussed. 相似文献
102.
Marie-Claire Lasne Jean-Louis Ripoll Jean-Claude Guillemin Jean-Marc Denis 《Tetrahedron letters》1984,25(35):3847-3848
5,6-dihydropyridine 1 is synthesized either by flash vacuum thermolysis of 1-azabicyclo[2.2.2] oct-2-ene 3 or by dehydrochlorination over solid bases of N-chloro-1,2,5,6-tetrahydropyridine 4 and characterized at low temperature by its 1H and 13C nmr and ir spectra. 相似文献
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In the reaction with benzothiophene, t-butyl hypochlorite acts simultaneously as a smooth oxidizing agent and as a chlorinating agent since it is a source of both hypochlorous acid and chlorine. The mixture of all the products obtained imply that the reaction intermediate is the unstable benzothiophene I-oxide which was shown to be present by the stop flow technique. The chlorine formed traps the highly reactive benzothiophene 1-oxide in situ to give the observed products. 相似文献
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We have measured the position and linewidth of the 13C NMR signal in U2 C3 between 4 and 300 K. This study confirms the existence of an electronic transition around 50 K which brings possibly a non magnetic fundamental state. This transition involves no crystallographic distorsion and no lattice parameter anomaly. 相似文献
110.
Descroix S Le Potier I Niquet C Minc N Viovy JL Taverna M 《Journal of chromatography. A》2005,1087(1-2):203-209
The potential of the commercially available dye sypro orange for in-capillary derivatization was evaluated for the detection of insulin and one gastrointestinal peptide (Arg-Arg-gastrin) by capillary electrophoresis with laser induced fluorescence (CE-LIF). The fluorescent emission intensity (lambda(ex) = 488 nm, lambda(em) = 610 nm) of this probe is very low in aqueous medium, and increases strongly in less polar solvent, e.g. methanol. The hydrophobic character of the two analyzed peptides is too low to induce sufficient interaction with the fluorescent probe for good sensitivity when the latter is alone in the background electrolyte. Thus, the potential of several neutral, zwitterionic, cationic and anionic surfactants to favor probe/peptide interactions has been evaluated. It was demonstrated that a borate buffer (pH 8.5) containing tetradecyltrimethylammonium bromide (TTAB) in sub-micellar conditions can be considered as the most suitable buffer for insulin CE-LIF analysis. In addition, the method showed a good linearity between insulin concentration and the peak area of the labeled insulin, allowing quantitative measurements. The sensitivity achieved so far is comparable with that achieved with UV absorption detection, but even at this level it is interesting for microchip analysis, in which fluorescence detection is much more commonly available than UV absorption detection. 相似文献