有机化学反应图与反应构图教学探索

反应图是一种呈现有机物间相互转化关系的网络示意图,学生制作反应图的过程称作反应构图。在界定反应图和说明其特点、分类和制作步骤的基础上,提出开展反应构图教学活动的设计理念和实践思路。通过教学实践和态度问卷调查,了解该教学活动的实际成效,并对活动期间出现的问题进行了讨论。     

Stereoselective synthesis of 2-substituted 6-[1-(2,6-difluorophenyl)ethyl]-5-methylpyrimidin-4(3<Emphasis Type="Italic">H</Emphasis>)-ones

A procedure has been proposed for the synthesis of 2-(cyclopentylsulfanyl)-6-[(1R)-1-(2,6-difluorophenyl) ethyl]-5-methylpyrimidin-4(3H)-one through intermediate (3R)-4,4-dimethyl-2-oxotetrahydrofuran-3-yl (2R)-2-(2,6-difluorophenyl)propanoate which was obtained from prochiral 2-(2,6-difluorophenyl)prop-1-en-1-one generated in situ. The proposed procedure may be regarded as stereoselective route to 6-[(1R)-1-(2,6- difluorophenyl)ethyl]-5-methylpyrimidin-4(3H)-one derivatives.     

Lévy-frailty copulas

A parametric family of n-dimensional extreme-value copulas of Marshall–Olkin type is introduced. Members of this class arise as survival copulas in Lévy-frailty models. The underlying probabilistic construction introduces dependence to initially independent exponential random variables by means of first-passage times of a Lévy subordinator. Jumps of the subordinator correspond to a singular component of the copula. Additionally, a characterization of completely monotone sequences via the introduced family of copulas is derived. An alternative characterization is given by Hausdorff’s moment problem in terms of random variables with compact support. The resulting correspondence between random variables, Lévy subordinators, and copulas is studied and illustrated with several examples. Finally, it is used to provide a general methodology for sampling the copula in many cases. The new class is shown to share some properties with Archimedean copulas regarding construction and analytical form. Finally, the parametric form allows us to compute different measures of dependence and the Pickands representation.     

乙二醛在Ti/纳米TiO2-Pt修饰电极上的电催化氧化

采用溶胶.凝胶和电沉积法制备Ti基纳米TiO2-Pt(Ti/纳米TiO2-Pt)修饰电极.X射线衍射(XRD)表明纳米TiO2为锐钛矿型,扫描电镜(SEM)显示Pt纳米粒子在纳米TiO2多孔膜的表面呈现簇分散状态,平均粒径约25nm.通过循环伏安(CV)和计时电流法研究了Ti/纳米TiO2-Pt修饰电极对乙二醛直接电氧化的电催化活性,结果表明,修饰电极对乙二醛的直接电氧化呈现良好的催化活性,在0.60和1.23 V(vs SCE)出现两个氧化峰,二者电流密度分别为16和42 mA·cm2,约为纯Pt电极的2倍和1.5倍,反应过程受浓差扩散控制.     

Synthesis and characterization of a novel molecularly imprinted polymer for simultaneous extraction and determination of water-soluble and fat-soluble synthetic colorants in chilli products by solid phase extraction and high performance liquid chromatography

A sorbent was synthesized and investigated for molecularly imprinted solid phase extraction (MISPE). Molecularly imprinted polymers (MIP) were synthesized via precipitation polymerization procedure, where 4-vinyl pyridine (4-VP) was used as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The imprinting effect of the MISPE was evaluated by elution experiments. The resulting MISPE showed high extraction selectivity to water-soluble and fat-soluble synthetic colorants. The determination of multi-residue for three kinds of water-soluble and six kinds of fat-soluble synthetic colorants in chilli products was also investigated by HPLC coupled with MISPE. The mean recoveries calculated by solvent calibration curve for water-soluble and fat-soluble synthetic colorants were from 72.1% to 95.6% for chilli spice and 72.1% to 92.3% for chilli powder. The decision limit (CCα) and the detection capability (CCβ) obtained for water-soluble and fat-soluble synthetic colorants were in the range of 1.2–1.6 and 1.9–2.4 μg kg⁻¹ in chilli spice and chilli powder. The resulting MISPE was successfully used off-line for the determination of nine kinds of synthetic colorants in chilli products.     

Crystal structures of (azido)(pentamethylcyclopentadienyl)iridium(III) complexes containing various types of bidentate ligands

Several (azido)iridium(III) complexes having a pentamethylcyclopentadienyl (Cp∗) group, [Cp∗Ir(N₃)₂(Ph₂Ppy-κP)] (1: Ph₂Ppy = 2-diphenylphosphinopyridine), [Cp∗Ir(N₃)(Ph₂Ppy-κP,κN)]CF₃SO₃ (2), [Cp∗Ir(N₃)(dmpm)]PF₆ (3: dmpm = bis(dimethylphosphino)methane), [Cp∗Ir(N₃)(Ph₂Pqn)]PF₆·$·$CH₃OH (4·$·$CH₃OH: Ph₂Pqn = 8-diphenylphosphinoquinoline), and [Cp∗Ir(N₃)(pybim)] (5: Hpybim = 2-(2-pyridyl)benzimidazole) have been prepared and their crystal structures have been analyzed by X-ray diffraction. In complex 1, the Ph₂Ppy ligand is only coordinated via the P atom (-κP), while in 2 it acts as a bidentate ligand through the P and N atoms (-κP,κN) to form a four-membered chelate ring. Comparing the structural parameters of the chelate ring in 2 with those of a similar five-membered chelate ring formed by Ph₂Pqn in 4, it became apparent that the angular distortion in the Ph₂Ppy-κP,κN ring was remarkable, although the Ir–P and Ir–N bonds in the Ph₂Ppy-κP,κN ring were not elongated very much from the corresponding bonds in the Ph₂Pqn-κP,κN ring. In the pybim complex 5, the five-membered chelate ring was coplanar with the pyridine and benzimidazolyl rings. With the related (azido)iridium(III) complexes analyzed previously, comparison of the structural parameters of the Ir–N₃ moiety in [Cp∗Ir^III(N₃)(L–L′)]^+/0 complexes reveals an anomalous feature of the 2,2′-bipyridyl (bpy) complex, [Cp∗Ir(N₃)(bpy)]PF₆.     

固相萃取-毛细管电泳法测定免血清中的山茛菪碱对映体

建立一种可用于定量的毛细管电泳法分离山莨菪碱对映体.系统研究了三种手性选择剂:羟丙基-β-环糊精(HP-β-CD),甲基-β-环糊精(Me-β-CD),羧甲基-β-环糊精(CM-β-CD)及其浓度、缓冲溶液浓度和pH对山莨菪碱拆分的影响.在110 mmol/L Tris-H3PO4缓冲液中加入20.0 mg/mL HP-β-CD和5.0 mg/mL CM-β-CD(pH 4.0)条件下,山莨菪碱的4个对映体达到基线分离.血清样品通过崮相萃取预处理和浓缩,对映体的固相萃取回收率在82.9%～90.7%,相对标准偏差RSD%均小于7%.山莨菪碱的4个对映体血标准溶液浓度与电泳峰面积在77.86～0.39μg/mL范围内呈良好的线,r≥0.999,检出限(S/N=3)为0.08 μg/mL.平均日内和日间精密度(RSD%)分别小于4.2%和6.5%,方法回收率为95.1%和105%.建立的方法准确、可靠,应用于监测兔连续3 d口服75 mg山莨菪碱后血清中山莨菪碱的血药浓度,结果满意.     

Dynamics of wicking in silicon nanopillars fabricated with interference lithography and metal-assisted chemical etching

The capillary rise of liquid on a surface, or "wicking", has potential applications in biological and industrial processes such as drug delivery, oil recovery, and integrated circuit chip cooling. This paper presents a theoretical study on the dynamics of wicking on silicon nanopillars based on a balance between the driving capillary forces and viscous dissipation forces. Our model predicts that the invasion of the liquid front follows a diffusion process and strongly depends on the structural geometry. The model is validated against experimental observations of wicking in silicon nanopillars with different heights synthesized by interference lithography and metal-assisted chemical etching techniques. Excellent agreement between theoretical and experimental results, from both our samples and data published in the literature, was achieved.     

Concordance between antioxidant activities in vitro and chemical components of Radix Astragali (Huangqi)

Five Radix Astragali (RA) extracts were prepared and their antioxidant activities were measured in vitro using ABTS [2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid diammonium salt)], DPPH?·?(1,1-diphenyl-2-picrylhydrazyl radical), reducing power, ?O?? and ?OH assays. Their chemical contents were then determined, including total phenolics, total flavonoids, total saponins and total sugars. The 1/IC?? values of the various antioxidant assays were used to evaluate the level of antioxidant activity of the RA extracts (plot showing 1/IC?? values vs. chemical contents), and the average R values (correlation coefficients) of total phenolics and total flavonoids were 0.762 and 0.638. In contrast, the average R values of the total saponins and total sugars were -0.0386 and -0.132, respectively. This large difference clearly demonstrates that the antioxidant effects of RA in vitro might be generally considered to be a result of the presence of phenolic compounds (including flavonoids) but not astragalosides and polysaccharides.     

Crystallization and melting behavior of PP/nano-CaCO<Subscript>3</Subscript> composites with different interfacial interaction

The effect of different interfacial interaction on the crystallization and melting behavior of PP/nano-CaCO₃ composites was investigated using differential scanning calorimetry, X-ray diffraction and polarized optical microscope. The results indicated that nano-CaCO₃ acted as heterogeneous nuclei for PP crystallization. There existed a synergistic effect of heterogeneous nucleation between nano-CaCO₃ and compatibilizer for PP crystallization, which was proved by increasing the crystallization rate and decreasing the fold surface free energy as well as favoring the formation of β-crystal of PP. However, this synergistic effect was dependent on the interfacial interaction between PP and compatibilizer. The increased miscibility between compatibilizer and PP favored this synergistic effect.