导数示波极谱法测定废水中微量对硝基乙苯

研究了导数示波极谱法测定废水中微量对硝基乙苯。在０．０１５ｍｏｌ·Ｌ－１乙二胺０．０１０ｍｏｌ·Ｌ－１ＥＤＴＡ底液中，对硝基乙苯产生一灵敏的二阶导数极谱峰，峰电位为－０．５４Ｖ（ｖｓＳＥＣ）。对硝基乙苯浓度在１．００×１０－７～７．００×１０－５ｍｏｌ·Ｌ－１范围内，浓度与峰电流成线性关系。检测限为１．００×１０－７ｍｏｌ·Ｌ－１。该法用于氯霉素药厂废水中对硝基乙苯的测定，取得满意的结果。     

Lewis-Br(o)insted复合碱性离子液体的合成及其在催化Knoevenagel缩合反应中溶剂效应的研究

合成了同时含有Lewis碱和Br(o)nsted碱的复合碱性离子液体,研究了其在Knoevenagel缩合反应中的催化性能.结果表明,它们对醛/酮与氰乙酸乙酯的缩合具有很好的催化活性.芳香醛的反应收率可达85%～99%.考察了它们催化Knoevenagel缩合反应的溶剂效应,发现质子溶剂可以促进缩合反应,这一促进作用可能是由于质子溶剂通过氢键活化反应底物的羰基而降低了反应能垒所造成的.该离子液体可以循环使用3次,反应活性没有下降.     

Inclusion complexes of $$\hbox{cholesteryl-(}\varepsilon\hbox{-caprolactone})_{\overline{10}}$$ functionalized polymer with γ-cyclodextrin

An inclusion complex (IC) of γ-cyclodextrin with biodegradable \(\hbox{cholesteryl-(}\varepsilon\hbox{-caprolactone})_{\overline{10}}\) \(\hbox{(Chol-(CL)}_{\overline{10}})\) functionalized polymer was prepared by using a general method of mixing solution. The formation of \(\gamma \hbox{-CD-Chol-(CL)}_{\overline{10}}\) IC was determined by Fourier transform infrared (FTIR),¹H-NMR, differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD), respectively. The results indicated that the \(\hbox{oligo}(\varepsilon\hbox{-CL})_{\overline{10}}\) blocks as well as the end cholesteryl moiety of the functionalized polymer were included and covered by γ-CD in a single-stranded mode in the \(\gamma \hbox{-CD-Chol-(CL)}_{\overline{10}}\) ICs. Moreover, the \(\gamma \hbox{-CD-Chol-(CL)}_{\overline{10}}\) ICs had a channel-type crystalline structure similar to that formed between the poly(propylene glycol) (PPG) and γ-CD. Finally, TGA revealed that the ICs had better thermal stability than their free components due to the inclusion complexation.     

Metastable Tetragonal Cu2Se Hyperbranched Structures: Large‐Scale Preparation and Tunable Electrical and Optical Response Regulated by Phase Conversion

Despite the promising applications of copper selenide nanoparticles, an in‐depth elucidation of the inherent properties of tetragonal Cu₂Se (β‐Cu₂Se) has not been performed because of the lack of a facile synthesis on the nanoscale and an energy‐intensive strategy is usually employed. In this work, a facile wet‐chemical strategy, employing HCOOH as reducing agent, has been developed to access single‐crystalline metastable β‐Cu₂Se hyperbranched architectures for the first time. The process avoids hazardous chemistry and high temperatures, and thus opens up a facile approach to the large‐scale low‐cost preparation of metastable β‐Cu₂Se hyperbranched architectures. A possible growth mechanism to explain the formation of the β‐Cu₂Se dendritic morphology has been proposed based on time‐dependent shape evolution. Further investigations revealed that the metastable β‐Cu₂Se can convert into the thermodynamically more stable cubic α‐Cu_2?xSe maintaining the dendritic morphology. An increase in electrical conductivity and a tunable optical response were observed under ambient conditions. This behavior can be explained by the oxidation of the surface of the β‐Cu₂Se hyperbranched structures, ultimately leading to solid‐state phase conversion from β‐Cu₂Se into superionic conductor α‐Cu_1.8Se, which has potential applications in energy‐related devices and sensors.     

Simultaneous qualitative assessment and quantitative analysis of flavonoids in various tissues of lotus (Nelumbo nucifera) using high performance liquid chromatography coupled with triple quad mass spectrometry

Flavonoid composition and concentration were investigated in 12 different tissues of ‘Ti-1’ lotus (Nelumbo nucifera) by high performance liquid chromatography equipped with photodiode array detection tandem electrospray ionization mass spectrometry (HPLC-DAD-ESI-MSⁿ). A total of 20 flavonoids belonging to six groups (myricetin, quercetin, kaempferol, isohamnetin, diosmetin derivatives) were separated and identified. Myricetin 3-O-galactoside, myricetin 3-O-glucuronide, isorhamnetin 3-O-glucuronide and free aglycone diometin (3′,5,7-trihydroxy-4′-methoxyflavone) were first reported in lotus. Flavonoid composition varied largely with tissue type, and diverse compounds (5–15) were found in leaf and flower stalks, flower pistils, seed coats and embryos. Flower tissues including flower petals, stamens, pistils, and, especially, reproductive tissue fruit coats had more flavonoid compounds (15–17) than leaves (12), while no flavonoids were detectable in seed kernels. The flavonoid content of seed embryos was high, 730.95 mg 100 g⁻¹ DW (dry weight). As regards the other tissues, mature leaf pulp (771.79 mg 100 g⁻¹ FW (fresh weight)) and young leaves (650.67 mg 100 g⁻¹ FW) had higher total flavonoid amount than flower stamens (359.45 mg 100 g⁻¹ FW) and flower petals (342.97 mg 100 g⁻¹ FW), while leaf stalks, flower stalks and seed coats had much less total flavonoid (less than 40 mg 100 g⁻¹ FW).     

Stereochemistry as a tool in deciphering the processes of a tandem iminium cyclization and Smiles rearrangement

To understand the detailed mechanism of a recently reported tandem iminium cyclization and Smiles rearrangement, the reaction processes of a chiral substrate were investigated by monitoring its stereochemical courses. Under the tandem reaction conditions, chiral aldehyde 1 derived from l-prolinol led to two surprising results. First, the iminium cyclization gave a diastereomeric mixture with the cis-configured product as the predominant one. Second, Smiles rearrangement of both cis- and trans-2 led to the same product 3a directly derived from the trans isomer. The former was rationalized by the postulation of a Cram's chelate transition state leading to the cis product as kinetically favored. The latter was due to the equilibration between the trans/cis pair involving a carbocation intermediate and the steric hindrance, which prevented the cis isomer from undergoing the intramolecular nucleophilic substitution. This hypothesis was further supported by the results of a competition experiment in which the addition of 1 equiv of p-methoxyaniline in the rearrangement step led to a significant amount of anilinyl-exchanged rearrangement product.     

不等式约束优化一个新型可行QP-free算法

本文对非线性不等式约束优化问题提出了一个新的可行 QP-free 算法. 新算法保存了现有算法的优点, 并具有以下特性: (1) 算法每次迭代只需求解三个具有相同系数矩阵的线性方程组, 计算量小; (2) 可行下降方向只需通过求解一个线性方程组即可获得, 克服了以往分别求解两个线性方程组获得下降方向和可行方向, 然后再做凸组合的困难;(3) 迭代点均为可行点, 并不要求是严格内点; (4) 算法中采用了试探性线搜索,可以进一步减少计算量; (5) 算法中参数很少,数值试验表明算法具有较好的数值效果和较强的稳定性.     

A one‐pot procedure for ring enlargement of α‐chloromethyl N‐containing heterocycles

A simple one‐pot procedure for ring enlargement of α‐chloromethyl N‐containing heterocycles has been developed. By reaction of chloromethyl tetrahydroisoquinoline and its thieno analog with benzyl or allyl bromide under basic conditions, ring expansion and N‐substitution were achieved simultaneously. The key to the transformation was proposed to involve the formation of aziridinium salt and subsequent bond breaking between the nitrogen and tertiary carbon atoms.     

Investigation of the beam propagation in a pumped laser rod

A method investigating the beam propagation in a pumped laser rod is proposed. In this method, the pumped laser rod in a resonator is evenly divided into N segments along the laser rod axis, and each segment is considered as a small thermal lens with thermal focus length of f. Accordingly, the beam radius distributions in the laser rod for the symmetric and asymmetric resonators are thus calculated, respectively. The beam radius distribution in the whole resonator is also calculated. Moreover, the calculated beam distribution in the whole resonator and in the rod is also described in detail.