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11.
The first enantioselective synthesis of (8S,13S,14R)-7-oxa-estra-4,9-diene-3,17-dione with the trans-C/D ring junction is described. Key features of the synthesis include Ag2O-mediated C-O bond formation, thermodynamically controlled axial-equatorial inversion, one-pot of halogen exchange and Co/Cr-mediated C-C bond formation, and intramolecular aldol condensations. 相似文献
12.
本文制备了一系列富勒烯及其衍生物,并利用多种质谱技术进行了鉴定、表征、揭示了它们在离子源条件下的稳定性及解规律。这些富勒烯及其省生物在FDMS、ISMS中均得到了较强的准分子离子峰且碎片峰很少。结果表昨FDMS,LSIMS技术均适于富勒烯及其衍生物的定性分析,是目前富勒烯分析鉴定中较好的方法。 相似文献
13.
Yi Ming Liu Sui Ping Deng Hui Zheng Jian Ming Ouyang 《中国化学快报》2007,18(3):345-348
The ring patterns of calcium oxalate crystals were induced by domains in Langmuir-Blodgett (LB) films of dipalmitoylpho- sphatidylcboline (DPPC). The result was explained by the defects at the ring boundaries of liquid condensed (LC) and liquid expanded (LE) phases of LB film. These boundaries could provide less free energy and much more nucleating sites for COM crystals. 相似文献
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Aggregation of sodium 1-(n-alkyl)naphthalene-4-sulfonates in aqueous solution: micellization and microenvironment characteristics 总被引:2,自引:0,他引:2
Tan XL Zhang L Zhao S Li W Ye JP Yu JY An JY 《Langmuir : the ACS journal of surfaces and colloids》2004,20(17):7010-7014
In aqueous solution, the micellization and microenvironment characteristics of the micelle assemblies of three anionic surfactants, sodium 1-(n-alkyl)naphthalene-4-sulfonates (SANS), have been investigated by steady-state fluorescence and time-resolved fluorescence decay techniques using pyrene, Ru(bpy)3(2+), and 1,6-diphenyl-1,3,5-hexatriene as fluorescence probes. The critical micelle concentrations (cmc's), effective carbon atom numbers (neff's), hydrophilic-lipophilic balances (HLBs), mean micelle aggregation numbers, micropolarities, and microviscosities of these surfactant micelles have been determined. The logarithmic cmc of the alkylnaphthalene sulfonates decreases linearly with an increase in the neff. The logarithmic aggregation number of the alkylnaphthalene sulfonates increases linearly with an increase in the neff. However, in contrast to the alkylsufonates and the alkylbenzene sulfonates, the aggregation for these alkylnaphthalene sulfonate molecules is less sensitive to the increase in the neff. The micropolarity of these alkylnaphthalene sulfonate micelles is less sensitive to the increase in the alkyl chain length and is lower than that of sodium dodecyl sulfate (SDS). The microviscosity of these alkylnaphthalene sulfonate micelles increases with an increase in the alkyl chain length and is lower than those of nonionic surfactants and zwitterionic surfactants. These results suggest that naphthyl rings have a notable effect on the micellization of SANS. 相似文献
17.
Wei Sheng Feng Hong Wei Li Xiao Ke Zheng Sui Qing Chen 《中国化学快报》2007,18(12):1518-1520
Two new megastigmane O-glucopyranosides,named (2R,3R,5R,6S,9R)-3-hydroxy-5,6-epoxy-β-ionol-2-O-β-D-glucopyrano- side(1) and (2R,3R,5R,6S,9R)-3-hydroxyl-5,6-epoxy-acety-β-ionol-2-O-β-D-glucopyranoside(2) together with six known mega- stigmanes,were isolated from the leaves of Broussonetia papyrifera (Linn.) Vent.Their structures were established by chemical methods and spectroscopic techniques including 2D NMR. 相似文献
18.
Chu YP Gong Y Tan XL Zhang L Zhao S An JY Yu JY 《Journal of colloid and interface science》2004,276(1):182-187
Alkylnaphthalene sulfonates with high purity were selected as model components to research synergism for lowering interfacial tension (IFT) in surfactant/alkali/acidic oil systems. The dynamic IFTs between alkylnaphthalene sulfonates with different alkyl chain length and n-decane, oleic acid model oil, or Shengli crude oil were measured. The results showed that the alkylnaphthalene sulfonates with different alkyl chain lengths had different synergism with different acidic components and their ionized acids under the same conditions. The synergism for lowering dynamic IFT in alkylnaphthalene sulfonate/alkali/acidic oil systems was controlled by alkylnaphthalene sulfonate concentration, alkyl chain length, alkali concentration, alkali type, and oleic acid concentration: optimal physicochemical conditions were necessary to the best synergism. This indicates that the synergism among added surfactant acidic components in crude oil and their ionized acids is controlled by the ratio of their interfacial concentrations. 相似文献
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20.
The readily available alkyl dicyanoacetates 1 reacted with the 1,3-dipolar reagents arenecarbonitrile oxides 2 ′ and arenecarbonitrile imines 5 ′ to afford 1,2,4-oxadiazol and 1,2,4-triazol derivatives. The arenecarbonitrile oxides 2 ′ with electron-donating groups on the arene ring gave products 3a – d resulting from addition on both CN groups of 1 , and those with electron-withdrawing groups provided mono-adducts 4a – e (Scheme 1). Arylnitrile imines 5 ′ reacted with 1 to offer both bis- and mono-addition products (Scheme 2); the bis-adducts 8a , b possess an ester structure, whereas the mono-adducts 6a – d present a ketene-hemiacetal structure. 相似文献