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The unsymmetrical N,N,N-trimethyl tris-indolobenzene 3 has been synthesized by several routes, including cyclotrimerization of the O-acetate of indoxyl. This condensation involves a 3→2 rearrangement of the precursor formed in situ. Similar Wagner-Meerwein rearrangements were also prevalent in LAH reductions of some 3,3-diindolyl oxindoles.Treatment of the 3,3-diindolyl indolines with strong acid resulted in a cleavage yielding 3,3'-biindolyls. 相似文献
144.
X-ray photoelectron spectroscopy (ESCA) has been used in a study of CO and O2 chemisorbed on a polycrystalline tungsten sample. Working under ultra-high vacuum conditions, the surface was cleaned and then covered with known monolayer and fractional monolayer quantities of adsorbed CO and O2. The O(ls) and C(ls) spectral features were detected, and the influence of an adsorbed layer on the tungsten spectral features was determined. A chemical shift of 3.4 eV in the O(ls) line from chemisorbed CO is related to the different modes of bonding of CO to tungsten. A model calculation of the photoelectron yields expected from an adsorbed monolayer is in good agreement with the experimental results. 相似文献
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D. G. Peiffer B. L. Hager R. A. Weiss P. K. Agarwal R. D. Lundberg 《Journal of Polymer Science.Polymer Physics》1985,23(9):1869-1881
Far-infrared spectra of a series of un-neutralized and neutralized lightly sulfonated polystyrenes with varying sulfonation levels have been investigated to seek spectroscopic evidence for microphase separation known to control the physical properties of these polymers. Broad, strong absorbance bands, not found in the spectrum of unmodified polystyrene, are observed in the spectra of the sulfonated analogs. The effects on the far-infrared spectra both of sulfonation level and of the mass and charge of the neutralizing cation are discussed in terms of cation motion and the formation of ion-rich domains. 相似文献
147.
The substitution pattern of the two major petroporphyrins of Marl Slate, the ETIO III and the C32 DPEP, is determined by NMR spectroscopy alone, using self-aggregation effects, nuclear Overhauser enhancements and spin-lattice relaxation times. Protoporphyrin IX dimethyl ester was used as a model compound. 相似文献
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Factors of importance for the determination of tin by graphite-furnace atomic absorption spectrometry have been investigated. Losses of tin during the drying and ashing stages were monitored by use of radioactivity measurements. It was found that tin could be lost at 100°C when ordinary graphite or glassy carbon surfaces were used. However, if the sample was dispensed into a droplet of ammonia, no losses occurred until 800°C, independent of the graphite surface, because tin is stabilized as SnO2 (s,l) and chloride is removed as ammonium chloride. High-temperature equilibrium calculations indicate that tin forms volatile oxides, halides and sulphides which are stable up to relatively high temperatures. As is shown experimentally with commercial non-isothermal atomizers, these molecules might be removed from the system before their decomposition temperature is reached. A recently developed constant-temperature furnace was used to vaporize the sample into an environment of high and constant temperature, in which interference effects from chlorine and sulphur were minimized, as predicted by theory. 相似文献
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