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991.
Reinvestigation on the Reaction of Salicylic Chloride with Salicylic Amide and X-ray Crystal Structure of a New Macrocyclic Polyester 总被引:1,自引:0,他引:1
DU Da-Ming② CHEN Xiao HUA Wen-Ting JIN Xiang-Lin 《结构化学》2003,22(5):512-516
1 INTRODUCTION In the systematic studies on the synthesis, structure and recognition of macrocyclic phospho- ramidate containing biaryl oxadiazole[1, 2], we need to synthesize benzoxazines. Lattmann reported that the salicylic chloride reacts with salicylic amide at 170℃ to give 2-(2-hydroxyphenyl)benzo[1,3]- oxazine-4-one[3]. However, Palazzo got bisamide 1 in 90% yield under similar conditions[4]. Titherley reported that amides of type 1 underwent cycli- zation to benzoxazines if hea… 相似文献
992.
本文提出了极谱法测定痕量亚硝酸根的一个新体系。在含有Ni~(2+)和SCN~-的稀硫酸底液中,在单扫示波极谱仪上,有一灵敏的亚硝酸根配合物吸附波,峰电位为-0.57V(vs SCE)。一阶导数峰高与亚硝酸根浓度在2×10~(-8)~2×10~(-6)mol/L之间成线性关系。检测限达8×10~(-9)mol/L。回归方程为:Y=0.47x+0.096,相关系数为0.998,相对标准偏差为1.6%。该法具有良好的选择性,尤其是大量硝酸根不干扰测定。成功地应用于实际样品中痕量亚硝酸根的分析。 相似文献
993.
Surface-enhanced Raman scattering (SERS) spectra of single-walled carbon nanotubes (SWCNTs) on metal-coated filter paper are reported for the first time. Experimental results show that the metal-coated filter paper is very effective and active. The SERS spectrum not only shows that all Raman bands of SWCNTs in normal Raman scattering have been generally enhanced, but also shows many new bands, which characterize the structure of SWCNTs and the interaction between SWCNTs and silver/gold nanoparticles, arising from symmetry lowering and selection rule relaxing of SWCNTs induced by the silver/gold surface. In our case, it is difficult to separate the contributions of the electromagnetic and chemical mechanisms to the great enhancement of the Raman signal. The analysis shows that the SERS spectra of SWCNTs on the metal-coated filter paper provide convenience for probing the sample molecules with fine structures related to defects of SWCNTs, the diameter of SWCNTs, and the SERS mechanism of SWCNTs deposited on metal-coated filter paper. Moreover, this can be used as a probe technique for monitoring the synthesis quality of SWCNTs with significant higher sensitivity than other methods, which has promise of being a new technique for monitoring synthesis quality of SWCNTs. 相似文献
994.
995.
ReCI(CO)5 catalyzed the dehydration reaction of aromatic compounds with 1,3,5-trioxane or aqueous formaldehyde (37 wt%) under air. The reactions of a variety of aromatic compounds beating electron-donating group(s) with 1,3,5-trioxane afforded the corresponding diarylmethanes in moderate to good yields. 相似文献
996.
通过圆二色谱(CD)和吸收光谱研究了Cu(2+)对三螺旋poly(A:2I)的解旋行为,并从结构的角度分析了其解旋机理。结果表明:Cu(2+)通过与poly(A:2I)中的碱基的结合,破坏了Hoogsteen碱基对和Watson-Crick碱基对中的氢键,从而导致了三螺旋poly(A:2I)不可复性的解旋。 相似文献
997.
Electrospray ionization tandem mass spectrometry (ESI-MS(n)) and the phase solubility method were used to characterize the gas-phase and solution-phase non-covalent complexes between rutin (R) and alpha-, beta- and gamma-cyclodextrins (CDs). The direct correlation between mass spectrometric results and solution-phase behavior is thus revealed. The order of the 1 : 1 association constants (K(c)) of the complexes between R and the three CDs in solution calculated from solubility diagrams is in good agreement with the order of their relative peak intensities and relative collision-induced dissociation (CID) energies of the complexes under the same ESI-MS(n) condition in both the positive and negative ion modes. Not only the binding stoichiometry but also the relative stabilities and even binding sites of the CD-R complexes can be elucidated by ESI-MS(n). The diagnostic fragmentation of CD-R complexes, with a significant contribution of covalent fragmentation of rutin leaving the quercetin (Q) moiety attached to the CDs, provides convincing evidence for the formation of inclusion complexes between R and CDs. The diagnostic fragment ions can be partly confirmed by the complexes between Q and CDs. The gas-phase stability order of the deprotonated CD-R complexes is beta-CD-R > alpha-CD-R > gamma-CD/R; beta-CD seems to bind R more strongly than the other CDs. 相似文献
998.
Characterization and Dehydrogenation Activity of SBA-15 and HMS Supported Chromia Catalysts 总被引:2,自引:0,他引:2
IntroductionEnormousstudyhasbeendevotedtoM4 1S ,thefirstfamilyofmesoporousmolecularsievesreportedin1992 ,1,2 includingtheirmodificationsandapplicationsincatalysis .Theattractivepropertiesofthesematerialsaretheirhighspecificsurfacearea (>10 0 0m2 /g) ,well de finedstr… 相似文献
999.
Yu X Wang Z Jiang Y Zhang X 《Langmuir : the ACS journal of surfaces and colloids》2006,22(10):4483-4486
We have developed a simple method to fabricate a gradient from superhydrophobicity to superhydrophilicity. It is based on the controlled self-assembled monolayer consisting of a thiol molecule on a gold surface and the amplifying effect of the wetting property on a rough surface. Using a relatively dilute HS(CH2)11CH3 solution (0.05 mmol/L), we found that the density of molecules on the surface can be controlled by varying the immersion time. Slowly adding the dilute solution to the container holding the rough gold substrate will lead to a density gradient along the surface. After the complementary adsorption of HS(CH2)10CH2OH, the surface exhibits a gradient from superhydrophobicity to superhydrophilicity. The slope of the gradient can be conveniently tuned by varying the speed of addition. Cassie-Baxter and Wenzel equations are employed to explain this special property based on the rough structure and the molecular composition gradient that have been determined by XPS. This kind of material would provide a larger oriented driving force for many important biological and physical processes and might have potential applications in water droplet movement, oriented axonal specification of neurons, protein adhesion, and so on. 相似文献
1000.
电阻型湿敏材料的核磁共振研究 总被引:1,自引:0,他引:1
利用核磁共振氢谱研究了不同湿度和温度条件下聚乙烯亚胺,聚乙烯铵盐及环氧乙烷3种电阻型湿敏材料,通过化学位移变化分析了感湿机理,指出3种材料中的活泼氢和水作用后能形成新的活泼氢,新旧活泼氢可发生快速交换现象,并产生带电离子,因而材料的电阻值随湿度的增加而大幅度地降低。 相似文献