New reactivities of deltaline analogs: an efficient O-demethylation at C-1 and an unusual extrusion of the C-14 atom

O-Demethylation at C-1 in the C₁₉-diterpenoid alkaloids is very challenging. In this paper, it was firstly observed that 10-OH group in deltaline (1) is a determining factor for the O-demethylation reaction. After removal of this hydroxyl group, 1-O-methyl group in the corresponding deltaline analogs can be readily removed by treatment with HBr–HOAc. Meanwhile, the C-14 atom in bromides 18 or 20 can be extruded under basic condition probably via a sequence, including Grob fragmentation, aerobic oxidation, deformylation, and S_N2 nucleophilic substitution, to give enone 21 (70%) and oxetane 22 (14%). The structure of compound 22 was confirmed by X-ray crystallographic analysis of its derivative 21.     

Polystyrene-bound diethanolamine based ionic liquids for chemical fixation of CO2

Polystyrene-bound diethanolamine based ionic liquids (PS-DHEEAB and PS-THEAB) were synthesized and applied for the chemical fixation of CO₂ into cyclic carbonates without any additional co-catalyst and solvent. The effect of the catalysts with different number of hydroxyl group in the cation of the IL on the reaction was systematically investigated. Highest activity and selectivity were achieved in the presence of polystyrene supported diethanolamine ethyl bromide (PS-DHEEAB) in comparison with other catalysts employed. The catalyst was tough in stability and also found to be extended to a variety of terminal epoxides and aziridines. The relationship between high catalytic reactivity and the –OH functional groups was proposed.     

Effect of Vacancy Defects on the Young's Modulus and Fracture Strength of Graphene: A Molecular Dynamics Study

The Young's modulus of graphene with various rectangular and circular vacancy defects is investigated by molecular dynamics simulation. By comparing with the results calculated from an effective spring model, it is demonstrated that the Young's modulus of graphene is largely correlated to the size of vacancy defects perpendicular to the stretching direction. And a linear reduction of Young's modulus with the increasing concentration of mono‐atomic‐vacancy defects (i.e., the slope of ?0.03) is also observed. The fracture behavior of graphene, including the fracture strength, crack initiation and propagation are then studied by the molecular dynamics simulation, the effective spring model, and the quantized fracture mechanics. The blunting effect of vacancy edges is demonstrated, and the characterized crack tip radius of 4.44 Å is observed.     

Polypropylene/poly(butyl methacrylate) blends prepared by diffusion and subsequent polymerization of butyl methacrylate in isotactic polypropylene pellets

Polypropylene/poly(butyl methacrylate)(PP/PBMA) blends were prepared by diffusion and subsequent polymerization of butyl methacrylate(BMA) in commercial isotactic polypropylene(iPP) pellets.The diffusion kinetics,diametrical distribution of PBMA in a pellet and phase morphology of a typical PP/PBMA blend were investigated.     

An environmentally benign benzylic oxidation catalyzed by hypervalent iodine intermediate in water

An effective and environmentally benign benzylic oxidation for transition of alkylarenes into the corresponding carbonyl compounds was reported.Alkylarenes were mixed and stirred with potassium bromide,m-chloroperbenzoic acid and a catalytic amount of iodobenzene in water at 60 8C for several hours,a series of the corresponding carbonyl compounds was obtained in moderate to good yields.In the reaction,iodobenzene was first oxidized by m-chloroperbenzoic acid into the hypervalent iodine intermediate which then reacted with potassium bromide to form the key radical initiator for the benzylic oxidation.     

焊接接头和U型试样中的氢分布

本文作者利用自行研制的激光测氢装置,测量了焊接接头和U型试样中的氢分布,并且推导了U型试样弯曲部分(塑性变形区)的应变、残余应力计算公式。结果表明:在焊接接头中,1.沿熔深方向上,氢分布是不均匀的。最高氢含量在熔合线附近;2.氢的具体分布情况,取决于焊缝金属和母材原始含氧量,以及金相组织。在U型试样中,1.计算应变的公式和应力公式可以用来计算无明显反弹的U型试样弯曲部分的应变量和残余应力值。1Cr18Ni9Ti(C.R.)钢的F=990MPa、n=0.146;2.氢分布明显受应力和应变的影响。应力、应变值愈大,含氢量愈高。     

关于多值映象连续性的两个例子

本文在R²中构造了两个十分简单的多值映象的例子:第一个说明准上半连续(?)上半连续;第二个说明弱上半连续(?)准上半连续。     

S空位调节扶手型二硫化钼纳米带的电子性质

二硫化钼纳米带按边界结构特征可分为锯齿型和扶手型,在制备过程中,不可避免地会存在一定的缺陷,其中硫空位(VS)最为常见,它将改变纳米结构,进而影响其电子性质。本文采用密度泛函理论来研究S空位对扶手型二硫化钼纳米带性质的影响。计算结果表明：纯扶手型二硫化钼纳米带（AMoS2NRs）为非磁性半导体,但其物性受S空位的位置及浓度所调制。当S空位出现在纳米带内部时,其性质不变。但当S空位在纳米带边缘时,AMoS2NRs被调节成半金属;并随着S空位的浓度的增加,其物性从半金属转变为稀磁半导体。这一有趣的发现将使得低维MoS2纳米材料在自旋电子学上有更宽广的应用。