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951.
ULTRASONICALLY DISPERSED POTASSIUM AS DEPROTONATING AND COUPLING AGENT──SYNTHESIS OF 1,6-DINITRILES IN SITUULTRASONICALLYDISP...  相似文献   
952.
pH滴定-主成分回归法同时测定酚类同系物   总被引:8,自引:0,他引:8  
本文利用pH滴定-主成分回归法同时测定了苯酚、邻苯二酚、邻苯三酚的混合物,结果良好。通过交差验证法,本文还对采样区间和采样间隔作了详细讨论。  相似文献   
953.
李红双  罗庆尧 《分析化学》1993,21(8):908-910
本文研究了钪-铋-三溴偶氮胂络合物的共显色反应。实验表明,共显色反应是由于形成混合多核络合物所致。钪络合物最大吸收峰在635nm,表观摩尔吸光系数为7.1×10~4L·mol~(-1)·cm~(-1)。钪在0~5μg/25ml遵守比尔定律。  相似文献   
954.
本文研究了2-(-5-Br-2吡啶偶氮-5-二乙氨基)-酚与铑(Ⅲ)的显色反应。在pH为4.0的邻苯二甲酸氢钾缓冲液介质中,Rh(Ⅲ)与试剂形成稳定的橙红色络合物,其组成比为1:4,最大吸收波长为490nm,表现摩尔吸光系数为1.3×10 ̄5L·mol ̄(-1)·cm ̄(-1)。铑含量在0~4μg/10mL范围内服从比尔定律。  相似文献   
955.
A novel heterohexanuclear complex [Ni2Ag4(μ-dppm)4(pymt)6](SbF 6)2 · 2DMF · H2O (1), was synthesized by self-assembly with [Ag2(μ-dppm)2(MeCN)2](SbF6) 2 and [Et4N][Ni(pymt)3] (dppm = bis(diphenylphosphino)methane, pymt = pyrimidine-2-thiolate) as components and characterized by IR spectra, elemental analysis, 1H-NMR spectrum, 31P-NMR spectrum and Visible-Ultraviolet spectrum. Structure of the complex was determined by X-ray analysis.  相似文献   
956.
We have previously used inelastic incoherent neutron scattering spectroscopy to investigate the properties of aqueous suspensions of biomolecules as a function of hydration. These experiments led to the identification of signals corresponding to interfacial (hydration) water at low water content. A prediction from these studies was that in the crowded environment inside living cells, a significant proportion of the water would be interfacial, with profound implications for biological function. Here we describe the first inelastic incoherent neutron scattering spectroscopy studies of living cells and tissues. We find that the interfacial water signal is similar to that observed for water interacting with purified biomolecules and other solutes, i.e., it is strongly perturbed in the librational and translational intermolecular optical regions of the spectrum at 20-150 meV. The ratio of interfacial water compared to total water in cells (approximately 30%) is in line with previous experimental data for hydration water and calculations based on simple assumptions.  相似文献   
957.
The combination of Lewis and Bronsted acids catalyzed the addition of beta-ketoesters to cyclic diene. Lactonization occurs in situ to afford fused bicyclic lactones directly. The catalysis provides an expedient route to bicylic lactones via a zip-process.  相似文献   
958.
A series of N-aryl β-bromodifluoromethyl β-enaminoketones were regioselectively synthesized in good yield by the reaction of N-aryl bromodifluoroacetimidoyl chlorides with methyl ketones. β-Bromodifluoromethyl β-enaminoketones smoothly cyclized to give a novel class of cyclic (2,2-difluoro-5-phenyl-furan-3-ylidene)-aryl-amines under basic condition. An intramolecular halophilic substitution mechanism was proposed.  相似文献   
959.
Zhang D  Wu LZ  Yang QZ  Li XH  Zhang LP  Tung CH 《Organic letters》2003,5(18):3221-3224
[structure: see text] Platinum(II) terpyridyl acetylide complex (1) was incorporated into Nafion membranes as a photosensitizer, and the Nafion was immersed in an aqueous or organic solution of 7-dehydrocholesterol, alpha-pinene, or cyclopentadiene. This photosensitizer system can generate singlet oxygen ((1)O(2)) in high quantum yield to oxidize the alkenes in the solution outside the Nafion and can be easily removed from the reaction vessel at the end of the photooxidation.  相似文献   
960.
A system is described for the on-line extraction of a digested protein in a gel spot. The extract obtained was on-line transferred to a precolumn, used to desalinate and preconcentrate the sample. The precolumn was switched in-line with an LC-ESI-MS system to separate the digest products prior to detection. By using this approach sample losses were minimized and the sample was quantitatively transferred. The benefits of the system were shown for the in-gel tryptic digest of several model proteins. Using this system, the sensitivity was 13-fold increased compared to the off-line extraction of in-gel digest products leading to a higher sequence coverage and thus a better identification potential. Also, the within day repeatability was a factor 2.5 improvement using the on-line procedure compared to the off-line extraction procedure.  相似文献   
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