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91.
92.
Yong Ding Baochun Ma Qiang Gao Guixian Li Liang Yan Jishuan Suo 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):121-128
The epoxidation of cyclopentene with hydrogen peroxide catalyzed by 12-heteropolyacids of molybdenum and tungsten (H3PMo12−nWnO40, n = 1–11), 12-tungstophosphoric acid and 12-molybdophosphoric acid combined with cetylpyridinium bromide as a phase transfer reagent was carried out in acetonitrile. Among 13 heteropolyacids investigated, catalyst of H3PMo6W6O40 showed the highest activity, giving a conversion of 60% and a selectivity of 95% in the epoxidation of cyclopentene. The fresh catalysts and the catalysts under reaction condition were characterized by UV–vis, FT-IR and 31P NMR spectroscopy, which has revealed that all of the molybdotungstophosphoric acids were degraded in the presence of hydrogen peroxide to form a considerable amount of phosphorus-containing species. The active species resulted from H3PMo6W6O40 are new kinds of phosphorus-containing species, which is different from {PO4[WO(O2)2]4}3−. 相似文献
93.
The first examples of mononuclear, structurally characterized triarylphosphine complexes of zirconium and hafnium are reported. The metathetical reactions of MCl4(THF)2 (M = Zr, Hf) with [iPrNP]Li(THF)2 ([iPrNP]- = N-(2-(diphenylphosphino)phenyl)-2,6-diisopropylanilide) or [MeNP]Li(THF)2 ([MeNP]- = N-(2-(diphenylphosphino)phenyl)-2,6-dimethylanilide) in toluene at -35 degrees C produced the corresponding [iPrNP]MCl3(THF) and [MeNP]2MCl2, respectively, in high yield. In contrast, attempts to prepare [MeNP]MCl3(THF) and [iPrNP]2MCl2 led to the concomitant formation of mono- and bis-ligated complexes, from which purification proved rather ineffective. The solution and solid-state structures of [iPrNP]MCl3(THF) and [MeNP]2MCl2 were studied by multinuclear NMR spectroscopy and X-ray crystallography. The geometry of these six-coordinate complexes is best described as a distorted octahedron in which the chloride ligands in [iPrNP]MCl3(THF) adopt a virtually meridional coordination mode whereas those in [MeNP]2MCl2 are trans to each other. 相似文献
94.
甲醇与乙醇一步合成异丁醛用CuO-ZnO/Al2O3催化剂 总被引:20,自引:0,他引:20
在CuO-ZnO/Al2O3催化剂上,甲醇与乙醇在常压和210 ̄360℃温度下一步反应合成异丁醛。利用正交设计方法,研究了CuO-ZnO/Al2O3体系催化剂组成和制备条件等因素对催化剂催化性能的影响。结果表明,催化剂中CuO含量对催化剂的催化活性影响最大,而ZnO含量则主要影响催化剂对异丁醛的选择性。催化剂制备条件,如沉淀温度、陈化时间等,也不同程度也影响催化剂的催化性能。XRD和BET表征结果 相似文献
95.
Diastereoselective allylation of imine derived from N‐glyoxyloyl camphorpyrazolidinone and amines was treated with allyltributylstannane in the presence of triflic acid. The corresponding optically enriched homoallylic amines were obtained in reasonable to high material yields and with practical levels of stereoselectivity in 10 min at ambient temperature. 相似文献
96.
Studies on fluorenscence resonance energy transfer between CdS nanoparticles and DOCAI dyes 总被引:1,自引:0,他引:1
Lun Wang Yan Liu Hong Qi Chen A Ni Liang Fa Gong Xu 《中国化学快报》2007,18(3):369-372
The water-soluble CdS nanoparticles were synthesized in aqueous solution. A novel fluorescence resonance energy transfer (FRET) system with CdS nanoparticles as energy donors and 3,30-diethyl-oxadicarbocyanine iodide (DOCAI) dyes as energy accepter has been developed. 相似文献
97.
The total synthesis of a didemnin B analogue containing a conformationally constrained replacement for the isostatine moiety is reported. Synthetic highlights include an improved preparation of 2-hydroxy-3-cyclohexenecarboxylic acid and a new strategy for accessing the macrocycle. 相似文献
98.
Molecularly imprinted polymer membranes containing artificial recognition sites for 4-aminopyridine have been prepared by photopolymerization using 4-aminopyridine as template. Reference membranes were prepared with the same monomer mixture but in the absence of the template. The binding characteristics of the imprinted polymer membrane were investigated by a batch method and the transport properties of the membranes were investigated using diffusion chambers. The results showed that the binding amount of 4-aminopyridine is higher than that of 2-aminopyridine whereas the latter can transport the 4-aminopyridine imprinted polymer membrane faster than 4-aminopyridine. 相似文献
99.
Ag2C4, the second silver carbide to be fully characterized, has been synthesized as a light-gray powder (contaminated with metallic silver) that is explosive at high temperature (130 degrees C) and sensitive to mechanical shock, rather like the well-known prototype Ag2C2. In the pair of hydrated double salts Ag2C4.6AgNO3.nH2O (n = 2, 3), the nearly linear, centrosymmetric 1,3-butadiyne-1,4-diyl dianion C42-exhibits an unprecedented mu8-coordination mode, each terminal being capped by four sigma-bonded silver(I) atoms with pi-interaction to one of them. 相似文献
100.