负载型钌催化剂催化对苯醌制对苯二酚的研究

采用浸渍法制备了负载型高分散纳米Ru催化剂,利用X射线衍射、X射线光电子能谱、透射电子显微镜、N2吸附-脱附实验对催化剂进行了表征,结果显示,Ru以高分散金属态存在,其平均粒径在5nm左右。考察了不同酸碱介质、催化剂与底物物质的量的比、反应温度、H2压力和反应时间对对苯二酚收率的影响。结果表明,以盐酸为反应介质,以5%Ru/AC为催化剂,nRu/AC∶n对苯醌=1∶100,反应温度30℃,H2压力3.0MPa,反应时间30min,对苯二酚的收率可达97.5%。     

复杂条件下高分子材料老化规律、寿命预测与防治研究新进展

复杂条件下有机高分子材料的老化、寿命预测和防治研究对满足相关行业发展的迫切需求,实现节能减排、环境保护及可持续发展等战略目标具有重大意义。本文重点综述了近年来针对聚烯烃、工程塑料、橡胶、涂料等大宗高分子材料在我国复杂大气环境中的自然老化及人工模拟加速老化研究的新进展,对材料老化失效基本规律和分子机理、老化数据库的建立及老化分级图谱的绘制进行了介绍,探讨了户外自然环境和人工模拟环境下材料老化失效规律的对应关系、服役寿命理论的预测模型及失效防治延寿新方法,并对其中存在的问题及下一步发展方向进行了展望。     

The synthesis of nebularine and its analogs via oxidative desulfuration in aqueous nitric acid

The synthesis of nebularine and its analogs has been achieved via oxidative desulfuration in H₂O for the first time. With 50% HNO₃ as an oxidant and solvent, 18 products were obtained in good yields (70%–94%). The oxidative desulfuration system could tolerate different functional groups including fluoro, chloro, amino, alkyl, allyl, ribosyl, deoxyribosyl, and arabinofuranosyl groups. More importantly, the drug nebularine could be obtained successfully on a 20 g scale, which made this route more attractive for industrial applications.     

Syntheses,crystal structures,electrochemical and photocatalytic properties of two mixed-ligand cobalt(II) coordination polymers based on flexible bis(2-methylbenzimidazole) dicarboxylic acid ligands

Two Co(II) coordination polymers (CPs), namely [Co(L)(tp)] _n (1) and [Co(L)_0.5(tbip)·H₂O] _n (2), (L = 1,6-bis(2-methylbenzimidazolyl) hexane, H₂tp = terephthalic acid, H₂tbip = 5-tert-butyl isophthalic acid), were hydrothermally synthesized and characterized by physicochemical and spectroscopic methods. CP 1 possesses a 2D (4,4) corrugated layer structure, which further extends into a 3D supramolecular framework by π–π stacking interactions, while CP 2 has a 1D ladder-like chain structure and combines into a 2D layer via O–H?O hydrogen-bonding interactions. The thermal stabilities, luminescence and electrochemical properties of both CPs, as well as photocatalytic activities for the decomposition of methylene blue, were presented. The photocatalytic mechanism was investigated by introducing t-butyl alcohol, EDTA-2Na and benzoquinone as ?OH, (hole)⁺ and ·O^2? scavengers, respectively.     

Ag@AgCl embedded on cellulose film: a stable,highly efficient and easily recyclable photocatalyst

In this work, cellulose–Ag@AgCl composite films have been fabricated directly through a one-step coagulation of a cellulose/1-butyl-3-methylimidazolium chloride (BmimCl) solution with AgNO₃ and PVP. The AgCl was formed upon the addition of AgNO₃ to a cellulose/BmimCl solution, and underwent further reaction with excess Cl^?, leading to the complete dissolution of AgCl. The AgCl crystals were regenerated on the cellulose matrix during the coagulation process. The AgCl was partial decomposed to Ag⁰ and formed Ag@AgCl under visible light irradiation. The morphology of Ag@AgCl in the cellulose matrix was controlled by varying the concentration of PVP. The addition of PVP enabled the formation of stable cellulose films embedded with Ag@AgCl. The composite film demonstrated efficient photodegradation of methyl orange, which was retained upon recycling. This work thus provides a simple pathway for the preparation of Ag@AgCl embedded on a polymer support via one-step coagulation.     

A combined treatment of hydration and dynamical effects for the modeling of host–guest binding thermodynamics: the SAMPL5 blinded challenge

As part of the SAMPL5 blinded experiment, we computed the absolute binding free energies of 22 host–guest complexes employing a novel approach based on the BEDAM single-decoupling alchemical free energy protocol with parallel replica exchange conformational sampling and the AGBNP2 implicit solvation model specifically customized to treat the effect of water displacement as modeled by the Hydration Site Analysis method with explicit solvation. Initial predictions were affected by the lack of treatment of ionic charge screening, which is very significant for these highly charged hosts, and resulted in poor relative ranking of negatively versus positively charged guests. Binding free energies obtained with Debye–Hückel treatment of salt effects were in good agreement with experimental measurements. Water displacement effects contributed favorably and very significantly to the observed binding affinities; without it, the modeling predictions would have grossly underestimated binding. The work validates the implicit/explicit solvation approach employed here and it shows that comprehensive physical models can be effective at predicting binding affinities of molecular complexes requiring accurate treatment of conformational dynamics and hydration.     

[C_2mim][Ala]丙氨酸离子液体水溶液粘滞流动的活化参数

在288.15-328.15 K温度范围内,测量了不同浓度的氨基酸离子液体[C_2mim][Ala]水溶液的密度和粘度,根据J ones-Dole方程得到了较大正值的粘度B系数并且dB/dT0。借助Feakins理论,计算了溶质对溶液粘滞流动活化自由能贡献Δμ_2~(≠0),根据Δμ_2~(≠0)随温度的线性变化,进而得到流动活化熵ΔS_2~(≠0)和活化焓ΔH_2~(≠0);在E yring液体粘度的过渡态理论基础上,提出了预测离子液体[C_2mim][Ala]水溶液粘度的半经验新方法,其预测值与相应的实验值很好的一致。     

4′-{2-[5-(4-羧基苯基)呋喃基]}-2,2′:6′,2″-三联吡啶的合成——推荐一个大学有机化学实验

介绍一个面向大学高年级本科生的综合性有机化学实验——4′-{2-[5-(4-羧基苯基)呋喃基]}-2,2′:6′,2″-三联吡啶的合成与结构表征。以糠醛、对氨基苯甲酸为原料经低温条件下的偶联反应制备5-(4-羧基苯基)呋喃-2-甲醛,并以其和2-乙酰基吡啶为原料,在碱性条件下以氨水为氮源合成目标产物。通过熔点测定、红外光谱和核磁共振氢谱对其结构进行表征。该实验合成路线成熟,包括芳环偶联、α,β-不饱和酮的合成、Michael加成等内容,能达到多方面对学生进行锻炼之目的,是一个值得推荐的有机化学实验。     

Estimated conditional score function for missing mechanism model with nonignorable nonresponse

Missing data mechanism often depends on the values of the responses, which leads to nonignorable nonresponses. In such a situation, inference based on approaches that ignore the missing data mechanism could not be valid. A crucial step is to model the nature of missingness. We specify a parametric model for missingness mechanism, and then propose a conditional score function approach for estimation. This approach imputes the score function by taking the conditional expectation of the score function for the missing data given the available information. Inference procedure is then followed by replacing unknown terms with the related nonparametric estimators based on the observed data. The proposed score function does not suffer from the non-identifiability problem, and the proposed estimator is shown to be consistent and asymptotically normal. We also construct a confidence region for the parameter of interest using empirical likelihood method. Simulation studies demonstrate that the proposed inference procedure performs well in many settings. We apply the proposed method to a data set from research in a growth hormone and exercise intervention study.     

A linear-time algorithm for the trust region subproblem based on hidden convexity

We present a linear-time approximation scheme for solving the trust region subproblem (TRS). It employs Nesterov’s accelerated gradient descent algorithm to solve a convex programming reformulation of (TRS). The total time complexity is less than that of the recent linear-time algorithm. The algorithm is further extended to the two-sided trust region subproblem.