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81.
Qing LI Hui LI Bin SU Xiang Bao MENG Meng Shen CAI Zhong Jun LI* Department of Chemical Biology School of Pharmaceutical Sciences National Research Laboratory of Natural Biomimetic Drugs Peking University Beijing 《中国化学快报》2002,13(4):303-305
Our previous paper1,2reported the results of selective synthesis of mannose type glycosides and their dimers in our attempt to synthesize derivatives of N-acetyllacto- samine, which could have potential activity of anti-metastasis3. Further studies on the glycosylation of the accepters exploiting glycosyl nitrate instead of the acetate as donor showed interesting chemoselectivity between the two kinds of donor, namely, the glucose type and the mannose type. The reactivity difference of the t… 相似文献
82.
Lanying?Yang Yi?Zhang Qingqi?Chen Jin Shi?MaEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(2):223-229
Summary. 1-(Dipyrrin-2-yl)-1-(dipyrrin-3-yl)methane, the N-confused analog of biladiene-ac, is prepared by condensation of 2,3-dipyrromethane with two molecules of 2-formylpyrrole in dichloromethane in the presence of hydrogen bromide. Self-assembly of the ligand with Zn(II) in dichloromethane and methanol offers a dinuclear dimeric complex with a ligand:metal ratio of 2:2. X-Ray crystal structure analysis reveals two ligands bound through a head-to-tail pattern to two zinc centers to form a severely distorted helical conformation, which has the shape of a rectangle. 相似文献
83.
The influence of microporous carbon surface oxidation on energetics of methane adsorption at 308 K is discussed. Obtained adsorption heats and integral molar entropies of the adsorbate show that microporous carbon surface oxidation changes the methane adsorption process. This is probably resulted by the existence of an endothermic effect during adsorption in oxidized carbon micropores. 相似文献
84.
从TGEV 3CL蛋白酶二聚体结构出发,研究了TGEV 3CL蛋白酶二聚体单体之间的静电和疏水相互作用.蛋白质的静电相互作用通过有限差分方法求解Poisson-Boltzmann方程得到,疏水相互作用通过分析溶剂可及性表面模型得到.考察了不同pH值对TGEV 3CL蛋白酶二聚体静电和疏水相互作用的影响,在pH值为5.5~8.5时,二聚体静电相互作用能、静电去溶剂化能和疏水自由能都较小,表明在该条件下静电和疏水相互作用有利于二聚体的稳定存在,这符合实验结晶所需条件.pH值对静电去溶剂化能的影响大于疏水自由能,表明静电作用是造成强酸或强碱条件下二聚体不能稳定存在的主要原因. 相似文献
85.
La-Ba系氧化物催化剂用于甲烷氧化偶联 总被引:1,自引:0,他引:1
以La_2O_3为基础,碱土金属作为第二组分的二元氧化物催化剂均具有较高的生成C_2活性,特别是La-Ba-O系催化剂具有优良的甲烷氧化偶联活性和稳定性,当La/Ba原子比为2.5时,C_2收率可达20.3%。第三组分的添加有助于提高C_2选择性,特别是添加碱金属,可以抑制完全氧化反应,并提高乙烯/乙烷比。在La:Ba:Na=2.5:1:0.1的催化剂上进行了500/小时的寿命实验,在整个反应期间,催化剂的活性和选择性相当稳定。X-射线物相分析表明,新鲜催化剂除有少量的碳酸钡外,主要是氧化镧和氧化钡的混合物。500小时后的物相基本上是氧化镧和碳酸钡。使用前后催化剂的比表面积及表面La和Ba的分布均无改变。较高的CH_4/O_3比对提高C_2选择性有利,当CH_4:O_2=4:1时,C_2选择性和收率分别为65.1%和19.1%。 相似文献
87.
YipingZhang DongjieWang JinhuaFei XiaomingZheng 《天然气化学杂志》2003,12(2):145-149
Mo/HZSM-5 is a good catalyst for methane aromatization, and the reaction performance of Mo/HZSM-5 and Cu modified Mo/HZSM-5 catalysts under various pretreatment conditions has been studied. The results indicate that the catalyst presented a distinguished catalytic activity, benzene selectivity and a high stability when the bed temperature was raised in N2 atmosphere. 相似文献
88.
R. G. Bulgakov Yu. G. Ponomareva Z. S. Muslimov F. G. Valyamova R. A. Sadykov R. F. Tuktarov 《Russian Chemical Bulletin》2007,56(2):211-219
Fullerenyl radicals (FR) RC60
· and chemiluminescence (CL) are generated in the presence of O2 in C60—R3Al (R = Et, Bui) solutions in toluene (T = 298 K). The FR are formed due to the addition of the R· radical, which is an intermediate of R3Al autooxidation, to C60. Mass spectroscopy and HPLC were used to identify EtnC60Hm (n, m = 1–6), EtpC60 (p = 2–6), and dimer EtC60C60Et as stable products of FR transformations. As found by ESR, the EtC60
· radical (g = 2.0037) is also generated by photolysis of solutions obtained after interaction in the (C60— R3Al)—O2 system. In the presence of dioxygen, the FR is not oxidized but yields complexes with O2, which appear as broadening of the ESR signals. Chemiluminescence arising in the (C60—R3Al)—O2 system is much brighter (I
max = 1.86·108 photon s−1 mL−1) than the known background CL (I
max = 6.0·106 photon s−1 mL−1) for the autooxidation of R3Al and is localized in a longer-wavelength spectral region (λmax = 617 and 664 nm). This CL is generated as a result of energy transfer from the primary emitter 3CH3CHO* to the products of FR transformation: RnC60Hm, RpC60, and EtC60C60Et.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 205–213, February, 2007. 相似文献
89.
Xiao‐Yan Chen Peng Cheng Shi‐Ping Yan Dai‐Zheng Liao Zong‐Hui Jiang 《无机化学与普通化学杂志》2005,631(15):3104-3107
A novel two‐dimensional cobalt complex, [Co(btrm)2(dca)]ClO4 ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R1 = 0.0784, wR2 = 0.2041. The cobalt atom involves a six‐coordinated CoN6 environment, with a distorted octahedral coordination. Two btrm ligands connect the CoII atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated. 相似文献
90.
B. Michalkiewicz 《Chemical Papers》2006,60(5):371-374
The reactions taking place during methane esterification in oleum were investigated. It was found that the primary products
were methyl bisulphate and formaldehyde, which was subsequently oxidized to carbon dioxide. The catalyst, Pd or PtCl4, was needed to activate methane and for its oxidation to the primary products. The formation of CO2 was not a catalytic process. It was found that the addition of either carbon dioxide or ester into the reaction mixture did
not slow down the reactions. Methane oxidation in oleum is an irreversible process, during which water is produced and subsequently
consumed to give sulphuric acid by the reaction with sulphur trioxide.
Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May
2006. 相似文献