A DFT study on the double bond migration of butene catalyzed by ionic pair of 1-ethyl-3-methyl-imidazolium fluoride

The double bond migration of butene catalyzed by 1-ethyl-3-methyl-imidazolium fluoride (EmimF) has been studied using quantum chemical method. The geometries of reactant, transition state and product for the isomerization have been optimized by density functional theory (DFT) at the B3PW91/6-31G(d,p), 6-311++G(d,p) and aug-cc-PVDZ levels. The computed results show that the 4-H atom on imidazole ring of EmimF has a good catalytic activity to the double bond migration of butene and the catalytic reaction of 1-butene to 2-butene is a synergetic and elementary process. The apparent activation energy of isomerization is about 197 kJ/mol.     

Adsorption Behavior of a Water-soluble Porphyrin at the Glass-water Interface as Studied by Synchronous Total Internal Reflection Fluorescence Spectroscopy

Total imernal reflection fluorescence spectroscopy (TIRF) and synchronous scanning technique were combined to study the adsorption behavior of the meso-tetrakis (4-sulfonatophenyl)porphyrin (TPPS) at the glass-water interface without any surfactant. The pH dependence of synchronous fluorescence signal at the interface was analyzed. Both unprotonated (TPPS^4-) and diprotonated (H2TPPS^2-) forms of TPPS were observed at the interface. But the interface favored the adsorption of. The apparent estimated pKa2 value shifted from 5.00 in the bulk solution to 2.7 at the interface. STIRF provides a good technique to study multi-component systems at the interface.     

Ge—132对小鼠H22肝癌移植瘤的影响

Ｇｅ－１３２对小鼠Ｈ２２肝癌移植瘤的实验研究证明：１．Ｇｅ－１３２对Ｈ２２肝癌移植瘤有一定的抑制作用，３００ｍｇ／ｋｇ体重剂量抑瘤率达到３６．１９％；２．增强机体的抗氧化作用，抑制脂质的过氧化物水平；３．促进免疫功能，当Ｇｅ－１３２和环磷酰胺联合使用时，可抵抗环磷酰胺的免疫抑制作用，而且并不减弱其抑制瘤作用。     

硒与消化系统癌关系的探讨

据不同地貌、地质条件在30个县市按剖面、同步、随机取土壤样品372份．测定硒等微量元素含量．作等级相关分析显示。土壤硒含量与消化系统癌呈负相关关系．作相对危险度、剂量-效应及多因素分析,认为此负相关关系并非偶然现象．     

Baker''''s yeast mediated reduction of substituted acenaphthenequinones: Regio-and enantioselective preparation of mono-hydroxyacenaphthenones

Baker's yeast mediated reduction of acenaphthenequinone within 4-10 h afforded mono-hydroxyacenaphthenone mainly with low enantioselectivity, the substrate and mono-hydroxyacenaphthenone product almost converted to dihydroxyacenaphthene after 48 h. By control of the reaction time and in the presence of DMF as co-solvent, the reduction of 6-substituted acenaphthenequinones under vigorous agitation afforded the corresponding 2-hydroxyacenaphthenones in 24-84% yields with 10-93% ee.     

Synthesis of diethers derived from furoin by phase transfer catalysis under microwave irradiation

A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (>75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.     

Preparation and characterization of trans-RhCl(CO)(TPPTS)2-intercalated layered double hydroxides

trans-RhCl(CO)(TPPTS)₂ (TPPTS=tris(m-sulfonatophenyl)phosphine) has been intercalated into Zn-Al layered double hydroxides (LDHs) by the method of ion exchange. The structure, composition and thermal stability of the composite material have been characterized by powder X-ray diffraction, Fourier transform infrared and ³¹P solid-state magic-angle spinning nuclear magnetic resonance spectroscopy, elemental analysis, thermogravimetry, and differential thermal analysis. The geometry of trans-RhCl(CO)(TPPTS)₂ was fully optimized using the PM3 semiempirical molecular orbital method, and a schematic model for the intercalated species has been proposed. The thermal stability of trans-RhCl(CO)(TPPTS)₂ is significantly enhanced by intercalation, which suggests that such materials may have prospective application as the basis of a supported catalyst system for the hydroformylation of higher olefins.     

扫描近场光学显微镜对纳米结构的观察

光学显微镜在人们认识微观世界的过程中一直扮演着非常重要的角色．随着认识的深入，对空间分辨率的要求也越来越高．但是众所周知，普通光学显微镜（远场情况下）的分辨率受光的衍射效应所限制，一般可表达为0．61A／N．A．（约等于A／2，A为照射光的波长，N．A．为数值孔径）     

How can enzymes be so efficient?

Dudley Williams and his colleagues discuss how ligands can gain binding energy to their receptors, and substrate transition states to their enzymes, by tightening the protein structures, with a decrease in their dynamic behaviour.     

Anionic templating: synthesis,structure, and characterization of novel three-dimensional mixed-metal oxychlorides Te(4)M(3)O(15).Cl (M = Nb(5+) or Ta(5+))

Two new three-dimensional oxychlorides are reported, Te(4)M(3)O(15).Cl (M = Nb(5+) or Ta(5+)). The isostructural materials were synthesized by chemical transport reactions utilizing TeO(2), M(2)O(5), and MCl(5) (M = Nb(5+) or Ta(5+)) as reagents. The compounds exhibit a three-dimensional cationic tunnel framework, with Cl(-) anions occupying the tunnels. Crystal data: monoclinic, space group C2/c, a = 18.9944(7) A, b = 7.8314(3) A, c = 21.1658(8) A, beta = 116.6400(10) degrees, Z = 8 (T = 295 K).