Gold‐Catalyzed Tandem Cycloisomerization–Halogenation of Chiral Homopropargyl Sulfonamides

Two new gold‐catalyzed tandem cycloisomerization–halogenation reactions of chiral homopropargyl sulfonamides have been developed. Various enantioenriched 3,3‐diiodopyrrolidin‐2‐ols and 3‐fluoropyrrolidin‐2‐ols were obtained in moderate‐to‐good yields with excellent enantio‐ and diastereoselectivity.     

Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst

Selective hydrogenation of α, β-unsaturated aldehydes with modified Pd/C catalyst was developed.The reduction of C=O bond could be efficiently inhibited by the addition of carbonates,and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions.This protocol provides an alternative for efficient preparation of saturated aldehydes.     

不同磁路下微型ECR中和器电子引出的模拟研究

电子回旋共振(ECR)中和器是微型ECR离子推力器的重要组成部分,其引出的电子用于中和ECR离子源的离子束流,避免了航天器表面电荷堆积,并且电子引出性能对推力器的整体性能起着重要作用.为了分析影响微型ECR中和器电子引出的因素,本文建立了二维轴对称PIC/MCC计算模型,通过数值模拟研究不同磁路结构对中和器的电子引出,及不同腔体长度对壁面电流损失的影响.计算结果表明, ECR区位置和引出孔附近磁场构型对中和器的电子引出性能至关重要.当ECR区位于天线上游,电子在迁移扩散中易损失,并且电子跨过引出孔前电势阱所需的能量更高.如果更多磁力线平行通过引出孔,中和器引出相同电子电流所需电压较小.当ECR区被天线切割或位于下游时,电子更易沿磁力线迁移到引出孔附近,从而降低了收集板电压.研究了同一磁路结构下不同腔体长度对电子引出的影响,发现增加腔体长度,使得更多平行轴线的磁力线通过引出孔从而避免电子损失在引出板表面,增加了引出电子电流.研究结果有助于设计合理的中和器磁路和腔体尺寸.     

Temperature memory effect and its stability revealed via differential scanning calorimetry in ethylene‐vinyl acetate within glass transition range

In this article, we reveal the temperature memory effect (TME) in a commercial thermoplastic polymer, namely ethylene‐vinyl acetate (EVA), within its glass transition range via a series of differential scanning calorimeter (DSC) tests. In addition, we investigate the influence of heating holding time and also compare the observed TME in current study with that of shape memory alloys (SMAs). It is concluded that the TME via DSC (without any macroscopic shape change) is achievable within the glass transition range of a polymer. Conversely, although the observed TME shares the many similar features as those in SMAs, due to the nature of micro‐Brownian motion in the glass transition of polymers, the resulted TME is strongly affected by the heating holding time. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1731–1737     

Sonochemical coating of magnetite nanoparticles with silica

Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating.     

TMEDA-CATALYZED SYNTHESIS OF N-ARYL-N′-ETHOXYCARBONYL THIOUREA AND ARENE (OR POLYMETHYLENE)-BIS-ETHOXYCARBONYLTHIOUREA DERIVATIVES

A novel and efficient method for synthesis ethoxycarbonyl isothiocyanate and ethoxycarbonyl thioureas catalyzed by TMEDA is reported. A series of N-aryl-N′-ethoxycarbonyl thioureas and arene (or polymethylene)-bis-ethoxycarbonyl thiourea derivatives have been synthesized in good-to-excellent yields via this method at room temperature.     

Cobalt(III) Supramolecuar Complex: Synthesis,Crystal Structure and Anions Recognition Properties of 6,7-Dinitroquinoxaline-2,3-dione

A 3D supramolecular complex [Co(III)(Phen)₂Cl₂][DNQ]Cl·H₂O (DNQ = 6,7-dinitroquinoxaline-2,3-dione) has been synthesized and determined by single-crystal X-ray analysis. Anion binding studies carried out using ¹H NMR and UV-visible revealed that a genuine hydrogen bond interaction between anion receptor 2 and Cl^?  can be detected, but fluoride is deprotonating the anion receptor 2. X-ray analysis results show that it is not possible for the two amide nitrogen atoms of anion receptor to form hydrogen bonds to a chloride ion in the presence of small aliquots of water.     

CCQM-K74国际比对中二氧化氮浓度的测量

介绍了国际比对样品中10μmol/mol NO2气体浓度精确分析方法的建立过程。该方法的建立包括标准物质的制备、分析仪器的选择和测量结果的不确定度3个主要的方面。标准物质的制备及其量值的不确定度评价采用了气体标准物质定值的基准方法——称量法。对傅立叶变换红外光谱法(FTIR)和化学发光光谱法进行了比较研究。确定了更适合于本次国际比对样品的分析方法为化学发光光谱法,测量结果的相对扩展不确定度为1.0%(k=2)。本次比对的最终结果报告显示,所建立的分析方法准确可靠。