L‐Proline–H2O2: A New Chemoselective Approach for Oxidation of Sulfides to Sulfoxides

A facile and selective oxidation of sulfides to sulfoxides using an L‐proline–H₂O₂ system for structurally divergent sulfide substrates with excellent yields at ambient conditions is reported.     

Analysis of Corrosion Products Formed on Cu-Ni Alloys Immersed in Sea Water

Abstract

A method was developed for separation and analysis of corrosion products formed on the surface of Cu-Ni alloys immersed in sea water polluted by sulphide ions. This method is based on the selective dissolution of oxidation compounds by suitable solvents dissolving the metal matrix only to a negligeable extent.

The following solvents were used: 1) methanol to dissolve Na⁺, Cu²⁺, Ni²⁺ chlorides and sulphates; 2) glycine to dissolve bivalent metal compounds - Cu²⁺, Ni²⁺ oxides, sulphides, oxysulphates, oxychlorides and oxycarbonates; 3) ammonia solution to dissolve Cu⁺ compounds (i.e. Cu₂O and CuCl); 4) potassium cyanide to dissolve CU⁺ sulphides.

Reasonable agreement between chemical and X-Ray analysis results was observed only for copper compounds, since nickel and iron compounds could not tie observed by X-Ray diffraction. The results of Auger and chemical analyses better agree with each other, yet no Fe compounds could be detected. This is to be attributed to the non-homogeneous corrosion layer which notably contains Fe compounds in the innermost region at a depth where Auger spectroscopy is unable to detect them, whereas their detection is possible by chemical analysis, since it is a bulk analysis.     

Thermally Rearranged Polymer Membranes Containing Tröger's Base Units Have Exceptional Performance for Air Separations

The influence of segmental chain motion on the gas separation performance of thermally rearranged (TR) polymer membranes is established for TR polybenzoxazoles featuring Tröger's base (TB) monomer subunits as exceptionally rigid sites of contortion along the polymer backbone. These polymers are accessed from solution‐processable ortho‐acetate functionalized polyimides, which are readily synthesized as high‐molecular‐weight polymers for membrane casting. We find that thermal rearrangement leads to a small increase in d‐spacing between polymer chains and a dramatic pore‐network reconfiguration that increases both membrane permeability and O₂/N₂ selectivity, putting its performance above the 2015 upper bound.     

基于半刚性配体的柔性超微孔金属有机骨架的合成及其尺度选择性二氧化碳捕获

基于半刚性的配体3′,5′-di(1H-1,2,4-triazol-1-yl)-(1,1′-biphenyl)-3,5-dicarboxylic acid (H₂DTBDA)和硝酸钴制备了一个柔性超微孔的金属有机骨架{[Co(DTBDA)]·4H₂O}_n (FJI-H35),并对该材料的结构进行了系统的表征。FJI-H35活化以后可以发生自适应的结构转变,使得孔径从0.43 nm收缩到0.37 nm。气体吸附测试表明FJI-H35可以从氮气和甲烷中选择性捕获二氧化碳,具有很高的吸附选择性和相对低的吸附焓。突破实验进一步证实FJI-H35可以从二氧化碳/氮气(15∶85,V/V)和二氧化碳/甲烷(50∶50,V/V)混合气中高效选择性捕获二氧化碳。     

多相催化生物甘油选择性氧化制取1,3-二羟基丙酮的研究进展北大核心CSCD

1,3-二羟基丙酮(DHA)是一种重要的化工原料,广泛应用于医药、化妆品及食品等领域.通过催化选择性氧化甘油制备DHA是一条高效、经济的工艺路线,而催化剂的种类及反应方式被证明对DHA的产率有较大影响.因此,结合近些年来相关文献,系统阐述了热、光和电这3种催化反应方式在甘油氧化制取DHA上的研究进展,并重点介绍了热催化路径中所选用的催化剂、相关研究实例及反应机理.最后,对甘油制备DHA的多路径选择性氧化的研究前景进行了展望.     

Bioassay-guided isolation of human carboxylesterase 2 inhibitory and antioxidant constituents from Laportea bulbifera: Inhibition interactions and molecular mechanism

Laportea bulbifera (Sieb. et. Zucc.) Wedd has long been utilized in Traditional Chinese Medicines (TCM) for the treatment of rheumatoid arthritis. However, the study of systematic anti-inflammatory chemical constituents in L. bulbifera has never been reported. Thus, bioassay-guided isolation for its roots part led to 46 compounds, including 38 phenolic derivatives. Their structures were determined on the basis of ¹H and ¹³C NMR and MS spectra. All compounds were isolated from L. bulbifera for the first time except for 13 compounds. Most of the compounds showed good COX-2 inhibitory activity (IC₅₀: 0.13–3.94 μM) and DPPH radical-scavenging activity (IC₅₀: 1.57–9.55 μM). Four compounds (4, 17, 35, and 43) with different skeletons showed preferential COX-2 over COX-1 inhibition with selective indices ranging from 12 to 171. High content active compounds are important for elucidating the basis of the active substance of TCM. Compound 4 (COX-2, IC₅₀ 0.24 μM), a high content compound, represented one of the best selective COX-2 inhibitors. Another high content active compound (35) with a different skeleton might have different mechanism. Further study for the inhibition kinetics against COX-2 indicated compounds 4 and 35 were noncompetitive and competitive COX-2 inhibitors, respectively. Moreover, molecular docking and molecular dynamics simulation data further indicated that compound 4 could bind in the cavity of COX-2 and interacted with key residues VAL-538, PHE-142, and GLY-225 of COX-2 through hydrogen bonds. The results indicated that L. bulbifera roots could be applied as antioxidant and anti-inflammatory agents due to their potent selective COX-2 inhibitory and antioxidant activity of phenolic compounds.     

Revealing the Reaction and Fading Mechanism of FeSe2 Cathodes for Rechargeable Magnesium Batteries

Rechargeable Mg batteries (RMBs) are advantageous large-scale energy-storage devices because of the high abundance and high safety, but exploring high-performance cathodes remains the largest difficulty for their development. Compared with oxides and sulfides, selenides show better Mg-storage performance because the weaker interaction with the Mg²⁺ cation favors fast kinetics. Herein, nanorod-like FeSe₂ was synthesized and investigated as a cathode for RMBs. Compared with microspheres and microparticles, nanorods exhibit higher capacity and better rate capability with a smaller particle size. The FeSe₂ nanorods show a high capacity of 191 mAh g⁻¹ at 50 mA g⁻¹ and a good rate performance of 39 mAh g⁻¹ at 1000 mA g⁻¹. Ex situ characterizations demonstrate the Mg²⁺ intercalation mechanism for FeSe₂, and a slight conversion reaction occurs on the surface of the particles. The capacity fading is mainly because of the dissolution of Fe²⁺, which is caused by the reaction between Fe²⁺ and Cl⁻ of the electrolyte during the charge process on the surface of the particles. The surface of FeSe₂ is mainly selenium after long cycling, which may also dissolve in the electrolyte during cycling. The present work develops a new type of Mg²⁺ intercalation cathode for RMBs. More importantly, the fading mechanism revealed herein has considered the specificity of Mg battery electrolyte and would assist a better understanding of selenide cathodes for RMBs.     

Enthalpies of aqueous solution of noble gases at 25°C

The standard enthalpies of solution of rare gases (helium, neon, argon, krypton, and xenon) in water at 25°C have been measured by a high precision steady-state calorimetric method. The aqueous solvation process is energetically favorable at 25°C for the gases studied. Values of the standard free energy, enthalpy, and entropy changes are found to be well correlated with cavity surface areas and the number of water molecules in the first solvation shell. Also, the values of the standard enthalpy and entropy of solution for the rare gases are found to have the same dependence on the number of solvation shell water molecules as inorganic and hydrocarbon gases. These results imply that the dominant source of enthalpy and entropy change resides in the first solvation shell.     

锆氢化反应研究 Ⅰ.酯类及双官能团化合物的锆氢化反应

本工作以一氯一氢二茂锆为还原试剂,对苯甲酸苯乙酯和苯甲酸甲酯进行还原,对还原的条件及水解产物的分离鉴定进行了研究。并对同时含酯基与其它官能团的几种化合物进行了选择性还原,列出了官能团还原先后的顺序,对结果进行了讨论。     

离子选择电极阵列土壤中硝态氮测定

土壤硝态氮反映土壤短期氮素供应水平,实时了解土壤硝态氮的含量为精准农业和农业面源污染防控提供支撑,因此,在线实时检测土壤硝态氮方法突破就显得十分迫切。土壤硝态氮中的硝酸根离子在土壤中的高水溶性和流动性为全固态硝酸根离子选择电极高敏感检测土壤中硝态氮提供了条件,固态硝态氮离子选择电极的离子选择膜反应硝酸根离子在被测溶液中的浓度。采用全固态硝酸根离子选择电极,且与温度电极和pH电极融合组成电极阵列对土壤饱和溶液中的硝态根离子进行检测。设计了高输入阻抗运算放大电路对电极信号进行采集,并通过微处理控制蠕动泵完成土壤硝态氮待测溶液连续流动测量及实时传输结果。实验结果表明,电极响应时间≤15 s,斜率-51.63 mV/decade,线性范围10-5-10-2.2 mol/L,最低检测限10-5.23 mol/L。相对标准差在0.78%-4.47%范围内,加标回收率均在90%-110%以内。与国家标准紫外可见分光光度法测试结果相比,相关系数（R2）为0.9952,为土壤硝态氮在现场检测奠定技术基础。