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61.
E. Miyoshi T. Iura Y. Sakai H. Tochihara S. Tanaka H. Mori 《Journal of Molecular Structure》2003,630(1-3):225-232
We investigated the interactions between the Si(111) surface and the Na, Mg, and Al atoms using cluster model calculations. Calculations were performed at levels of complete-active-space self-consistent-field (CASSCF) and multi-reference singly and doubly excited configuration interaction (MRSDCI) calculations using the model core potential method. Our calculations revealed that the most favorable sites of Na, Mg, and Al adsorption on Si(111) are on top (T1), bridge (B2), and 3-fold filled (T4) sites, respectively. The nature of chemical bonds between these metal atoms and the dangling bonds of the surface Si atoms are found to be essentially covalent. 相似文献
62.
自行研制了电子碰撞离子化的飞行时间型质量分析器(TOFMS),用于物质的化学分析。用研制的TOFMS测量了Ar离子化的飞行时间谱和离子的部分电离截面积比与碰撞电子能量的依赖关系,将它与Stepshan等人的实验结果进行了比较。 相似文献
63.
A selective method of determination of amines and quaternary ammonium salts by solvent extraction and thermochromism of ion-association complexes has been established. The method is based on the formation of ion-association species with tetrabromophenolphthalein ethyl ester and the thermochromism effect in the organic phase at low temperature. The absorbance of the red amine charge-transfer complexes decreases quantitatively (DeltaA) with increase in temperature (DeltaT), and Delta A Delta T is characteristic of a particular species. This characteristic has been applied for the sensitive and selective determination of amines. The absorbance of the blue quaternary ammonium ion-association complexes does not vary with temperature, however, and the quaternary ammonium compounds can be determined without interference by amines because of the disappearance of the red species at 60 degrees . Methylephedrine, diphenhydramine, ephedrine (amines), benzethonium and/or berberine (quaternary ammonium compounds) in two- and three-component mixtures can be determined by using the thermochromism effect. The method is highly selective, sensitive and reproducible. 相似文献
64.
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66.
A redox reaction of cysteine with iron(III) proceeds slowly in the presence of 1,10-phenanthroline (phen). However, this reaction is accelerated in the presence of copper(II) as a catalyst, producing an iron(II)-phen complex (lambda(max)=510 nm). A sensitive spectrophotometric flow-injection method is proposed for the determination of copper(II) based on its catalytic action on this redox reaction. The dynamic range was 0.1-10 ng ml(-1) of copper(II) with a relative standard deviation of 1.0% (n=10) for 1.0 ng ml(-1) of copper(II) at a sampling rate of 30 h(-1). The detection limit (S/N=3) is 0.04 ng ml(-1). The proposed method was successfully applied to the determination of copper in river water as a certified reference material. 相似文献
67.
1-Chlorovinyl p-tolyl sulfoxides were synthesized from several kinds of cyclic ketones and chloromethyl p-tolyl sulfoxide in good yields. Treatment of the 1-chlorovinyl p-tolyl sulfoxides with cyanomethyllithium at −78°C to room temperature gave spirocyclic enaminonitriles in high yields. Acidic treatment of the enaminonitriles afforded spiro[4.n]alkenones in good yields. By using an unsymmetrical cyclic ketone, α-tetralone, and optically active chloromethyl p-tolyl sulfoxide, this procedure afforded enantiomerically pure spiro[4.5]decenone in good yield with excellent asymmetric induction from the sulfoxide chiral center. By using this method a formal total synthesis of a racemic spirocyclic sesquiterpene, acorone, was realized. 相似文献
68.
Regio- and stereoselective arylation of 2-alkenylpyridines with aryl bromides is catalyzed by specific Ru(II)-phosphine complexes affording beta-arylated (Z)-2-alkenylpyridines, in which the aryl moiety is introduced cis to the pyridyl group. This geometrical selectivity is in sharp contrast to the Mizoroki-Heck reaction. [reaction: see text] 相似文献
69.
T. Nagai K. Sakai T. Asaka A. Yamazaki Y. Matsui 《Journal of solid state chemistry》2006,179(6):1898-1903
The crystal structure of our newly discovered Sr-Co-O phase is investigated in detail through high-resolution electron microscopy (HREM) techniques. Electron diffraction (ED) measurement together with energy dispersive X-ray spectroscopy (EDS) analysis show that an ampoule-synthesized sample contains an unknown Sr-Co-O ternary phase with monoclinic symmetry and the cation ratio of Sr/Co=1. From HREM images a layered structure with a regular stacking of a CdI2-type CoO2 sheet and a rock-salt-type Sr2O2 double-layered block is observed, which confirms that the phase is the parent of the more complex “misfit-layered (ML)” cobalt oxides of [MmA2Om+2]qCoO2 with the formula of [Sr2O2]qCoO2, i.e. m=0. It is revealed that the misfit parameter q is 0.5, i.e. the two sublattices of the CoO2 sheet and the Sr2O2 block coexist to form a commensurate composite structure. We propose a structural model with monoclinic P21/m symmetry, which is supported by simulations of ED patterns and HREM images based on dynamical diffraction theory. 相似文献
70.
Addition reaction of two geometrical isomers of 1-chlorovinyl p-tolyl sulfoxides, derived from unsymmetrical ketones and chloromethyl p-tolyl sulfoxide, with lithium enolate of tert-butyl acetate gave single isomers of the adduct, respectively. Treatment of each diastereomer with i-PrMgCl resulted in the formation of magnesium carbenoids. Highly regiospecific 1,3-CH insertion reaction was found to take place from the magnesium carbenoids to afford cyclopropanes in high yields. Stereochemistry of the adducts, reaction mechanism, and origin of the regiospecificity are discussed. 相似文献