旋光性聚{(+)-甲基丙烯酸-2,5-二[4′-((S)-2-甲基丁氧基)苯基]苄酯}的合成与表征

设计、合成了一个带有横挂三联苯侧基的手性乙烯基单体——(+)-甲基丙烯酸-2,5-二[4′-((S)-2-甲基丁氧基)苯基]苄酯,进行了普通自由基和原子转移自由基聚合反应.所得聚合物具有比单体低30°左右的比旋光度,且在侧基的紫外吸收处呈现明显不同于单体的Cotton效应,说明其主链可能形成了具有相反旋光方向的螺旋构象.在所研究范围内,聚合条件对聚合物的旋光度没有明显的影响.在分子量较小时,聚合物的比旋光度随着分子量的增加而降低,说明主链螺旋构象的贡献在增大,而当分子量达到一定值后,聚合物的比旋光度不再随分子量的增加而显著变化.     

蛋白质的检测方法与乳制品中蛋白含量测定

介绍5种常用的蛋白质检测方法,以及凯氏定氮法在食品,特别是乳制品蛋白含量测定中的应用和存在的问题,及其可能的解决方法。     

A versatile method for the synthesis of 3-alkoxycarbonyl beta-lactam derivatives

[reaction: see text] Ketene-imine cycloaddition reactions (the Staudinger reaction) of ethoxycarbonyl(phenylthio)ketene with various imines and subsequent desulfurization reactions were employed to synthesize 3-ethoxycarbonyl beta-lactam derivatives. The results indicate that the current approach provides a convenient, mild, and versatile method for synthesizing a variety of 3-alkoxycarbonyl trans-beta-lactam derivatives with good to excellent yields and diastereoselectivities.     

Thorpe-Ingold效应及其在有机成环反应中的应用

本文首先介绍了Thorpe-Ingold效应及其相关理论和实验研究进展,然后综述了近年来Thorpe-Ingold效应在形成三、四、五和六元环产物的环化反应中的应用。Thorpe-Ingold效应可以有效地促进分子内和分子间环化,提高环化的产率和速率。该效应主要通过空间效应、电子效应或者两者协同起作用,在某些情况下,该效应还会受催化剂和溶剂等影响。利用该效应可以促使一些难以发生的环化反应顺利进行,并能获得较好的产率。     

含邻手性碳原子双键亲电加成反应的立体选择性模型

本文主要介绍了预测邻位具有手性中心π体系亲电加成反应的立体选择性模型,尤其是α,β-不饱和羰基化合物亲核共轭加成形成的烯醇负离子及其类似物和硝基烯烃亲核加成形成的氮酸根类中间体的烷基化和动力学控制质子化反应的立体选择性模型。立体位阻效应控制的Zimmerman前过渡态模型主要适用于底物构象受限的环状或联烯型烯醇负离子的动力学质子化。对于构象转化相对灵活的直链底物,Houk基于量子化学计算研究提出了亲电试剂的进攻角度或接触角在经过环状过渡态时是锐角还是钝角决定了亲电加成反应的立体选择性控制(Houk模型)。而Fleming模型首次将烯丙基A-1,3张力引入各类烯醇负离子烷基化和质子化的过渡态。Mohrig模型在考虑A-1,3张力的基础上,将吸电子取代基与即将形成的σ键反式共平面,主要阐述了立体电子效应对酯的烯醇负离子动力学控制质子化立体选择性的影响,后来又提出了金属离子参与的立体电子效应控制的六元环状半椅式模型。本文希望对理解亲电加成反应的立体化学控制提供一些有用的信息。     

Experimental nibble for computational chemists: On the construction and CO2 capture by different zeolite imidazole ester framework-8 and ionic

The combination of zeolitic imidazolate framework-8 (ZIF-8) and ionic liquids (ILs) to create porous ionic liquids (PILs) is highly significant for efficient carbon dioxide (CO₂) capture and the advancement of carbon capture, utilization, and storage (CCUS) technologies. To further investigate the CO₂ capture characteristics of different PILs, two different-sized ZIF-8 structures and two functionalized ILs were prepared. Additionally, the enhancement factor of the reaction process was calculated using the dual-film theory and mass transfer coefficient. The results demonstrated that the original [PMIm]Cl had low CO₂ absorption capacity at ambient temperature and pressure, whereas the functionalized ILs had a maximum CO₂ capture capacity of approximately .31 mol/mol, with the 20 wt% concentration of tetraethylene pentamine-2-methylimidazole ([TEP][MIm]) exhibiting the highest CO₂ capture capacity of around 1.93 mol/mol. The synthesized PILs demonstrated a maximum CO₂ capture capacity of approximately 2.22 and 2.16 mol/mol at 20 and 10 wt% ionic concentrations, respectively, with a porous ionic liquid addition of 1.0/100 g. The corresponding enhancement factors were 1.53 and 1.59, respectively. These findings have significant implications for CCUS technology.     

Thermomechanical response of metallic sandwich tubes with prismatic cores considering active cooling

In this paper, the transient temperature distribution and the thermomechanical response of sandwich tubes with prismatic cores are analyzed considering active cooling. The effective thermal conductivities of prismatic cores with active cooling are derived. By using the effective thermal conductivities, the transient temperature fields of the tubes are predicted and are found to be very close to the results of finite element simulations, which confirms the correctness of the effective thermal conductivity. Based on the high-order sandwich shell theory, the thermal structural responses of sandwich structures are studied and compared with the results of finite element simulations. The reduction of the thermal structural responses as a result of active cooling is studied to demonstrate the advantages of prismatic cellular materials. The design of replacing the solid metal with cellular materials which has the capability of active cooling can reduce the temperature and the thermal structural response of the structure.     

手性氨基酸及其衍生物配体在酮不对称氢转移反应中的应用进展

前手性酮的不对称氢转移反应(ATH)是获得手性醇的重要方法.近年来氨基酸及其衍生物在金属Ru,Rh,Ir催化酮的ATH中的应用引起人们关注.就氨基酸、氨基酸酰胺、氨基酸硫代酰胺、氨基酸羟胺酸、氨基酸酰肼、氨基醇及氨基酸羟基酰胺等为配体的金属络合物在ATH中的催化性能进行了综述.     

氨基取代苯并咪唑衍生物的合成及在酮的氢转移反应中的应用

以α-氨基酸与邻苯二胺在微波辐射下反应合成了α-氨基取代苯并咪唑(1～5).1-(1H-苯并[d]咪唑-2-基)乙胺(1)与溴丁烷反应可形成单丁基、二丁基、三丁基取代产物1a～1d,1的氨基经Boc保护,N-烷基化后制备咪唑环上的N-烷基化产物1i～1g.制备的氨基取代咪唑与Ru(II)化合物原位组成催化体系,考察了其在取代苯乙酮的氢转移反应中的催化活性.结果表明RuCl2(PPh3)3与各配体组成的催化剂均有较好的催化活性,含有NH2基团的α-氨基取代苯并咪唑化合物参与的催化体系催化活性最好,TOF(Turnover frequency)可达到40200 h-1.     

Multivalent H-bonds for self-healing hydrogels

UPy is used as a reversible and dynamic crosslinker to prepare hydrogels that are injectable and undergo rapid self-healing in response to damage.