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91.
采用密度泛函理论(Density Functional Theory DFT)研究Au(100)和Au(111)表面含有不同Pd构型时表面的形成能.结果表明,非连续Pd构型的形成能较连续Pd构型的低,在表面易形成,其中第二临位Pd对构型被证实是乙烯与醋酸结合生成醋酸乙烯反应中催化活性最高的构型.随后计算CO在不同表面Pd原子的顶位吸附能和Pd原子的d带中心,结果显示表面Pd原子与相邻金原子之间几乎没有电子传递,并且PdAu(111)表面的Pd原子d带中心随周围Au原子个数的增加而远离费米能级,伴随着CO在其上吸附能的减小,但是同样的趋势在PdAu(100)表面不存在.最后,通过计算,CO在金属表面的吸附机理为CO成键轨道5σ的电子传递给Pd原子的d带,而Pd原子的d带电子又反馈回CO的反键轨道2π*. 相似文献
92.
An Efficient and Environmentally Friendly Method for Directly Converting Trityl and Benzyl Ethers to the Corresponding Acetates
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Acid sensitive benzyl and trityl ethers are frequently used as protecting groups to mask alcohols. They are also needed to be transformed into more stable ester groups toward acids in multistep synthesis. A mild and efficient one‐pot protocol for the selective transformation of benzyl and trityl ethers into their corresponding acetates was successfully developed. Several distinct advantages to this procedure include direct transformation, minimal generation of waste, a non‐aqueous workup and the recovery and recycling of the benzyl acetate and trityl alcohol by‐products, which were readily recovered in greater than 90% yields. 相似文献
93.
Treatment of benzoquinone/naphthoquinone with aryl mercury chloride in the presence of palladium chloride and lithium chloride gives the corresponding aryl substituted benzoquinone/naphthoquinone at the quinonoid position. 相似文献
94.
An imidazolidin-2-one chiral auxiliary mediated acetate aldol reaction was explored in the enantioselective synthesis of (S)-dapoxetine (SSRI). The diastereoselective aldol adduct was transformed to highly enantiopure (S)-dapoxetine with overall good yield. 相似文献
95.
Kris Randell 《Journal of organometallic chemistry》2006,691(16):3411-3415
The attempted synthesis of bis(NHC)palladium complexes via the direct reaction of an imidazolium salt with palladium acetate results in the formation of a mixed NHC/aniline complex. The route by which the aniline is formed has not been completely elucidated, but it does originally derive from an imidazolium salt. 相似文献
96.
Anewphenolicglycoside1,anacardoside,1-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyloxy-3-hydroxy-5-methylbenzenewasrecentlyisolatedfromthefruitsofSemecarpusanacardium,whichhasbeenreportedtopossessanti-cancer,anti-inflammatory,anti-arihriticandanthelminticactivitiesz(2-8).Butthenaturalcontentofthenewphenolicglycosideisextremelysmall(0.0075%)andtheprocedureofextractionandseparationisverycomplicated'.Theimportantbiol0gicalimplication0ftheattachmentofsugarmoietiestoanaglyconaren0wbecondngmoreo… 相似文献
97.
Fused silica capillaries with surface-bonded sol–gel coatings containing covalently attached octadecyl, octyl, and methyl groups were prepared for capillary microextraction (CME) hyphenated on-line with high-performance liquid chromatography (HPLC). For this, octadecyltrimethoxysilane (C18TMS), octyltrimethoxysilane (C8TMS), or methyltrimethoxysilane (MTMS) was used as the respective sol–gel precursor. Hydrolytic polycondensation of these precursors led to the formation of surface-bonded sol–gel sorbents with pendant alkyl groups ready to serve as the extraction medium; no additional surface derivatization reactions were needed to anchor these ligands to the surface. Extraction behaviors of two sets of microextraction capillaries with alkyl-bonded sol–gel coatings were investigated: (a) capillaries prepared with a constant molar concentration of these precursors in the sol solution, and (b) capillaries prepared with varied molar concentrations of C8TMS in the sol solution. Among the capillaries prepared using sol solutions with the same molar concentration of sol–gel precursor, the detection limits for nonpolar and polar analytes ranged from 0.3 ng/L to 213.9 ng/L. The sol–gel octadecyl-coated capillaries were found to be the most efficient at extracting these analytes, followed by the sol–gel octyl-coated capillaries, followed by the sol–gel methyl-coated capillaries. The results of this study point to the possibility that polar analytes are extracted through synergistic molecular level interactions of the polar and nonpolar parts of the analyte molecules with the alkyl chains and silanol groups within the sol–gel coatings. These coatings also demonstrated run-to-run and capillary-to-capillary reproducibility, with HPLC peak area RSD values ranging from 1.1% to 9.6% and 1.3% to 10.0%, respectively. In the set of sol–gel octyl capillaries with varied molar concentrations, the capillaries prepared with 0.514 M concentration of C8TMS in the sol solution were most efficient in extracting nonpolar and polar analytes. When higher or lower concentrations of C8TMS were used in the sol solution, the resulting sol–gel coated capillaries were less efficient in extracting nonpolar and polar analytes. 相似文献
98.
Masako Fujiwara Takeshi Kobayashi Takahiro Jomori Yutaka Maruyama Yoshitomo Oka Hiroshi Sekino Yutaka Imai Kazuhisa Takeuchi 《Analytical and bioanalytical chemistry》2009,394(6):1655-1660
1H NMR spectroscopic and pattern recognition-based methods (NMR-PR) were applied to the metabolic profiling studies on hemodialysis
(HD). Plasma samples were collected from 37 patients before and after HD and measured by 600 MHz NMR spectroscopy. Each spectrum
was data-processed and subjected to principal component analysis for pattern recognition. Spectral patterns of plasma between
pre- and post-dialyses were clearly discriminated, together with significant fluctuations in the levels of creatinine, trimethylamine-N-oxide, glucose, lactate, and acetate, which were quantitated. We have first observed the significant elevation of lactate
levels in post-dialysis plasma. The present study has demonstrated the high feasibility of NMR-PR method for monitoring the
dialysis condition and comprehensive profiling of the change of low-molecular-weight metabolites in HD.
Figure PCA for 1H NMR spectra of plasma from HD patients 相似文献
99.
采用活性碳吸附,二硫化碳解吸进样,利用DB-1毛细管色谱柱采用恒温条件分离,以FID为检测器,同时测定空气或废气中乙酸乙酯、乙酸丁酯、环己酮、苯系物。结果表明,该方法分离效果好,精密度高,准确度高,分析时间短,适合空气或废气环境分析的要求,结果令人满意。 相似文献
100.