Synthesis of highly substituted pyrroles via oxidative free radical reactions of β-aminocinnamates

Oxidative free radical reactions of β-aminocinnamates are described. Imine radicals produced by tetra-n-butylammonium cerium(IV) nitrate (TBACN) oxidation of enamines undergo efficient addition to the C-C double bond of β-aminocinnamates. This TBACN mediated free radical reaction between β-aminocinnamates and enamines provides a novel method for the synthesis of highly substituted pyrroles. The direct TBACN oxidation of β-aminocinnamates gave the dimerization products effectively.     

噻吩甲酰三氟丙酮合铈(Ⅳ)的晶体结构和分子结构

3-(2′-噻吩甲酰)-1,1,1-三氟丙酮(HTTA)与铈(Ⅳ)形成Ce(TTA)₄配合物.本文报道其实验及测定结果.晶格属正交晶系,空间群Pc2₁b,晶体学常数a=10.699(2),b=17.436(5),c=20.680(2)Å.V=3847.1ų,Z=4,F(000)=1736,D_c=1.77g·cm^-3,.M_r=1028.82,μ=15.20cm^-1.CAD4衍射仪,Mo-Kα射线收集数据.结构由重原子法解出,全矩阵最小二乘法修正,各向同性热参数.偏离因子R=0.148.晶体中每个铈原子与四个TTA中的八个氧原子配位,其配位多面体为扭曲的四方反棱柱,铈(Ⅳ)处于四方反棱柱体的中心,Ce-O平均键长2.333Å,O-Ce-O平均键角70.5°,晶体中部分噻吩环与三氟甲基处于无序状态.     

Abtrennung von Ceriterden aus Gemischen mit Yttererden durch fraktionierte Kristallisation der Magnesiumdoppelnitrate in großem Maßstab

Summary The fractional crystallisation of magnesium double nitrates was used to separate cerium earths from 112 kg yttrium earth mixtures; they were recovered in three different fractions. By using excess magnesium nitrate the crystallisation could be extended at least to gadolinium without using HNO₃ as solvent. In the resulting solutions (69 kg oxide) there remained yttrium and nearly all erbium and heavy yttrium earths.

     

铈掺杂纳米ZnO结构与室温脱硫性能的相关性研究

Nano-ZnO desulfurizer doped with cerium was prepared by homogeneous precipitation. The bulk and surface structures were characterized by TG-DTA, XRD, XPS and TEM. The desulfurizing performance at ambient temperature was studied. The results show that at ambient temperature the desulfurizing activities of nano-Ce-ZnO desulfurizer are closely related to the particle size, the electron density on desulfurizer surface and the quantity of active sites. Compared with nano-ZnO, nano-Ce-ZnO desulfurizer calcined at 270 ℃ showed smaller particle size and higher surface electron density, which favored the adsorption and reaction of H₂S, resulting in improved desulfurizing activity at ambient temperature since the quantity of Zn^(2-δ)+ became greater by electron gain of zinc ion from cerium ion. The tendency for zinc and cerium to be separated out as individual oxide from Ce-ZnO desulfurizer would increase as the calcination temperature was raised. The enrichment of cerium on the surface of ZnO made decrease the active sites for H₂S adsorption, which led to the decrease in desulfurization activity at ambient temperature.     

f-Element/crown ether complexes. 27. The synthesis and crystal structure of [Ce(NO3)3 (OH2)(12-crown-4)] -12-crown-4

A unique cerium nitrate complex, [Ce(NO₃)₃(OH₂)(12-crown-4)]-12-crown-4, has been crystallized from the reaction of hydrated cerium nitrate and 12-crown-4. It crystallizes in the orthorhombic space group,Pnma, with (at –150°C)a = 22.901(5),b = 13.547(3),c = 8.422(1)Å, andD _x = 1.77 g cm^–3 forZ = 4 formula units. A finalR value of 0.048 was obtained utilizing 2059 unique observed [F _o 5(F _o)] reflections. The Ce atom resides on a crystallographic mirror plane and is 11-coordinate, coordinated to three bidentate nitrate groups, one water molecule and the four oxygens of one 12-crown-4 molecule. The water molecule hydrogen bonds a second 12-crown-4 unit. Both unique crown molecules and one of the nitrate anions are severely disordered.For part 26, see reference [1].     

镧和铈改性对氧化铝性质的影响

 以拟薄水铝石为前驱物，采用溶胶法制备了γ－Al2O3，在制备 初期添加硝酸镧或硝酸铈对氧化铝进行改性，并使用红外光谱、氮物理 吸附和X射线衍射等方法对样品进行了表征．实验表明，稀土添加物覆 盖了部分氧化铝的表面羟基．在1000℃下对样品烧结行为的考察发现， 添加镧或铈化合物都能提高γ－Al2O3的抗烧结性能和高温稳定性，镧 改性样品的效果略优于铈改性样品．烧结动力学研究发现，制备的氧化 铝的烧结机理为体相扩散，加入稀土有效地阻止了氧化铝颗粒内的体相 扩散．用微反装置测定了改性样品的反应性能，发现铈改性样品有一定 的裂化性能和脱氢性能，而镧改性样品几乎无催化活性．     

氟、铈对磷酸三钙水解过程及其产物抗酸性的影响

研究了不同浓度的F- 和Ce3 +对磷酸三钙 (Ca3 (PO4) 2 ,TCP)的水解过程和水解产物的影响。XRD及IR实验结果表明 ,TCP在NaF溶液中的水解产物为羟基磷灰石 (Ca1 0 (PO4) 6(OH) 2 ,HAP)和氟基磷灰石 (Ca1 0 (PO4) 6F2 ,FAP)的混合物。氟离子浓度越高 ,FAP的含量越多。TCP水解过程的pH值变化随氟离子的起始浓度不同而不同。氟离子浓度越高 ,pH值越低。TCP在CeCl3 溶液中的水解产物为铈取代的羟基磷灰石 (CexCa1 0 -y(PO4) 6-z(OH) 2 ,Ce HAP)。溶解实验表明 ,氟处理比铈处理更有效地增强了TCP水解产物的抗酸性。当F -浓度为 0 1%或Ce3 +浓度为 5× 10 - 2 %时 ,TCP水解产物的抗酸性最强     

一个新的超大铈锑钨酸盐阴离子Ce_3Sb_4W_2O_8(H_2O)_(10)(SbW_9O_(33))_4~(19-)

合成了一超大铈锑钨酸盐[Ce3Sb4W2O8（H2O）10（SbW9O33）4]（NH4）19·48H2O,用X射线单晶衍射法及元素分析确定了其结构.其晶胞参数为:α=1.890 8（6）nm,b=2.003 2（14）nm,c=2.865 3（12）nm,α=86.95（6）°,β=75.68（3）°,γ=67.52（5）°,υ=9.706（9）nm3,空间群P1.在杂多阴离子Ce3Sb4W2O8（H2O）10（SbW9O33）419-中,四个β-B-（SbW9O33）9-是通过一个大的中心集团[Ce3Sb4W2O8（H2O）10]17+连接起来的,中心集团中含有两个桥连{WO2-（H2O）}基,三个Ce（Ⅲ）离子和一个{Sb4O4}基团.三个Ce（Ⅲ）离子的配位数均为9,Ce（1）和 Ce（3）的配位环境相同,但不同于Ce（2）的配位环境,四个{SbW9O33}中的三个参与了向 Ce（Ⅲ）的配位.两个{SbW9O33}中的四个氧,三个水分子中的三个氧,{Sb4O4}中的一个氧及一个桥连{WO2（H2O）}中的一个氧向Ce（1）[或Ce（3）]配位;两个{SbW9O33}中的四个氧,两个水分子中的两个氧,{Sb4O4}中的一个氧及两个桥连{WO2（H2O）}中的两个氧向Ce（2）配位.在{Sb4O4}中,四个Sb原子的中心构成了一四面体.该离子属Cs点群,Sb（5）,Sb（8）和Ce（2）所在的平面是其对称面.     

邻苯二酚衍生物与希土元素的配位反应Ⅱ．铈(Ⅳ)配合物显现颜色机理的探讨

用实验与量化计算对邻苯二酚类衍生物与铈（Ⅳ）生成的配合物显现颜色的机理进行了探讨，认为是由配体上大π键电子向中心金属离子跃迁所产生的Ｌ→Ｍ荷移所致     

纳米CeO_2/PMMA杂化材料的制备与表征

采用在位分散聚合法制备了纳米CeO2 /PMMA杂化材料.XRD分析表明,杂化材料是无定形的.SEM分析表明,杂化材料中CeO2 含量不同,材料的断面形貌明显不同,随CeO2 含量的增加,杂化材料由韧性断裂向脆性断裂转变.EDS面分析表明,Ce在杂化材料中分布均匀.实验表明,随CeO2 含量的增加,杂化材料的透过率和溶解性降低