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221.
Hang GONG Nian Fa YANG? Wei Jun TANG Qing Hua FAN Li Wen YANG The College of Chemistry Xiangtan University Xiangtan Laboratory of Chemical Biology Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2005,16(8)
Among the reactions in which C-C bonds are formed, the Baylis-Hillman coupling of aldehydes with α, β-unsaturated carbonylic compounds is currently attracting much interest due to the atom economy, the mild conditions and the generation of functional groups1,2. Furthermore, compared to the Heck, Suzuki and other palladium catalyzed C-C bond forming reaction3, the Baylis-Hillman reaction can be promoted by using organic bases in the complete absence of any metal4. However, almost all the … 相似文献
222.
Wen Wei Lai Teh Chou Chang 《Journal of polymer science. Part A, Polymer chemistry》1995,33(7):1075-1083
A series of crosslinkable thermotropic liquid crystalline poly(ether-ester)s and copoly(ether-ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo-irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc. 相似文献
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An all-atom dimethyl sulfoxide (DMSO) model and a TIP5P water model have been adopted for molecular dynamics simulation. Two new qualities ηrelE and ηrel are introduced to describe the anomalous nonideal behaviors of DMSO–water mixtures. The simulation is compared with chemical shift and excess enthalpy of mixing, which shows good concentration dependences. In addition, our all-atom simulation also indicates that the C–H groups of DMSO may interact with the oxygen atoms of water and DMSO. The weak C–HO contacts and the strong O–HO hydrogen bonds represent the consistent concentration dependences, which exhibits the cooperation effect. 相似文献
226.
将快速 Monte Carlo方法与分子动力学方法相结合 ,研究了不同种类有机分子在 Al3P4 O3- 1 6 计量比的二维层状磷酸铝形成中的模板能力 .依据主 -客体之间非键相互作用能 (包括范德华能、氢键能和库仑能 ) ,可合理地解释已知实验现象 ,并能有效地预测出适于形成某一特定无机层结构的有机胺模板剂 .通过选择理论预测的有机胺分子作为模板剂 ,成功地合成了二维层状磷酸铝化合物 Al3P4 O1 6 · 1 .5 H3NC6 H1 0 NH3. 相似文献
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228.
Shou‐Ri Sheng Xiao‐Ling Liu Yong‐Fen Tong Lie Chen Hong‐Li Wen Cai‐Sheng Song 《中国化学会会志》2005,52(5):943-946
Several new methyl substituted poly(aryl ether ketone)s containing sulfone linkage with inherent viscosities of 0.62–0.84 dL/g have been prepared from 4,4′‐bis(2‐methylphenoxy)diphenylsulfone and 4,4′‐bis(3‐methylphenoxy)diphenylsulfone with terephthaloyl chloride and isophthaloyl chloride by electrophilic Friedel‐Crafts acylation in the presence of DMF with anhydrous AlCl3 as a catalyst in 1,2‐dichloroethane, respectively. These polymers having weight‐average molecular weight in the range of 71,000–49,000 are all amorphous and show high glass transition temperatures ranging from 167 °C to 191 °C, excellent thermal stability at temperatures over 400 °C in air or nitrogen, high char yields of 51–58% in nitrogen and good solubility in CHCl3 and polar solvents such as DMF, DMSO and NMP at room temperature. 相似文献
229.
This paper applies discrete wavelet transform (DWT) with various protein substitution models to find functional similarity of proteins with low identity. A new metric, 'S' function, based on the DWT is proposed to measure the pair-wise similarity. We also develop a segmentation technique, combined with DWT, to handle long protein sequences. The results are compared with those using the pair-wise alignment and PSI-BLAST. 相似文献