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951.
结合三维静电势参数研究二取代苯的定量结构-疏水性关系 总被引:1,自引:0,他引:1
对含有常见取代基的92个二取代苯化合物进行了结构优化和静电势及其导出参数的计算,运用多元线性回归方法对化合物的疏水常数与分子的结构参数进行了关联.结果表明,分子表面负静电势的加和ΣV-S、分子空间内最负的静电势Vmin、表面最大静电势Vs,max以及分子体积V、极性表面积APS和分子的偶极密度μ/V这六个参数,可以很好地用于表达这些化合物疏水性与分子结构间的定量关系,而不用具体考虑分子中极性基团间的相互作用.用建立起来的QSPR(quantitative structure-property relationship)关系式对111个类似化合物的疏水性进行了预测,获得了满意的结果. 相似文献
952.
含苯氧基萘并萘醌和偶氮苯双变色基化合物的合成和性质 总被引:2,自引:0,他引:2
通过6-氯-5,12-萘并萘醌与4-羟基偶氮苯及其衍生物的反应合成了3种含苯氧基萘并萘醌和偶氮苯光致变色基的双变色基化合物,6-[4-(苯偶氮基)苯氧基]-5,12-萘并萘醌(5),6-[4-(p-乙氧基苯偶氮基)苯氧基]-5,12-萘并萘醌(6)和6-[4-(p-硝基苯偶氮基)苯氧基]-5,12-萘并萘醌(7).这些化合物的苯氧基萘并萘醌变色基的UV诱导光致变色性较弱;基于氨与苯氧基萘并萘醌ana显色体的不可逆反应,化合物5和6DMSO溶液在365nm紫外光辐照光稳态(PSS)下的ana醌式摩尔分数估计分别为22%和17%.这些结果说明,苯偶氮基对苯氧基萘并萘醌变色基的光致变色性质有着极强的影响.另一方面,与4-羟基偶氮苯母体不同,这些双变色基化合物在DMSO中偶氮苯变色基的顺式异构体是相对稳定的 相似文献
953.
116例冠心病患者血清中钙镁钡铝锶含量的研究 总被引:1,自引:0,他引:1
测定116例冠心病患者血清中钙,镁,钡,铝和锶的含量并与正常值比较,常量元素钙,镁和微量元素锶降低,而微量元素钡和铝升高,它们之间的差异都有显著或高度显著性。P〈0.05或P〈0.01。 相似文献
954.
955.
Yang HH Zhang SQ Yang W Chen XL Zhuang ZX Xu JG Wang XR 《Journal of the American Chemical Society》2004,126(13):4054-4055
In this study, we report a simple procedure for applying molecular imprinting functional groups to the inner surfaces of the template-synthesized sol-gel nanotubes for chemical separation of estrone. The silica nanotubes were synthesized within the pores of nanopore alumina template membranes using a sol-gel method by simultaneous hydrolysis of a silica monomer-imprinted molecule complex and tetraethoxysilane (TEOS). A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of the isocyanate group of 3-(triethoxysilyl)propyl isocyanate and a phenol moiety of estrone to form a thermally cleavable urethane bond. This allowed us to remove the imprinted estrone by simple thermal reaction and to simultaneously introduce functional groups into the cavity formed by the silica nanotubes. Experiments indicated that estrone could be bound selectively by such an approach and have a binding affinity of 864 +/- 137 (n = 3). 相似文献
956.
957.
David Wei Wang Michael M. Fisher 《Journal of polymer science. Part A, Polymer chemistry》1983,21(3):671-677
A two-phase polycondensation reaction was used to prepare high molecular weight linear poly-(amino-s-triazine)s from aminodichloro-s-triazines and diamines. These polymers contain a high concentration of melamine-type units in the polymer backbone. Molded specimens exhibited good mechanical properties and resistance to organic solvents. Dimethyl substitution at the exocyclic amino group led to a significant reduction in indentation resistance, strength, and modulus. 相似文献
958.
Wei Q Nieuwenhuyzen M Meunier F Hardacre C James SL 《Dalton transactions (Cambridge, England : 2003)》2004,(12):1807-1811
The metal-organic framework [Co(INA)(2)]x0.5EtOH (INA = isonicotinate, NC(5)H(4)-4-CO(2)(-)), was synthesised under solvothermal conditions. Its X-ray crystal structure shows channels containing ethanol guests which are hydrogen-bonded to carboxylate oxygens of the framework. The pyridyl rings of the framework alternate between 'open' and 'closed' positions along the channels resulting in large variation in the channel cross-sectional area from ca. 1.4 by 2.3 A at the narrowest point to 4.9 by 5.3 A at the widest. Despite the very small windows, the ethanol guests (of van der Waals diameter ca. 4.2-6.1 A) may be reversibly desorbed and sorbed into the structure quantitatively, as shown by in situ variable-temperture IR spectroscopy and XRPD. The single-crystal structure of the desolvated form [Co(INA)(2)] shows that there is no change in the overall connectivity on desolvation, but the rotational positions of the pyridine rings are altered. This suggests that pyridyl rotation may occur to allow guests to pass in and out. When the synthesis was conducted in 1-propanol solvent [Co(INA)(2)]x0.5Pr(n)OHxH(2)O, was obtained, and a single-crystal X-ray structure revealed the same overall connectivity as in but with pyridine rings disordered over closed and open positions. There was no evidence of included guests from X-ray crystallography, suggesting that they are also highly disordered. Variable-temperature XRPD performed on bulk samples showed peaks which were unsymmetrical and exhibited shoulders, suggesting that for each pattern obtained the material actually consisted of several closely-related phases. The movements of the peaks during desolvation showed the presence of intermediate phases before the final desolvated product was formed. The peak positions of the intermediate phases matched more closely with the calculated pattern for than with or, suggesting that they may have disordered structures similar to. The results also suggest that the intermediate phase represents an initial increase in volume before a larger decrease in volume occurs to give the final desolvated material. 相似文献
959.
Discharge performance of K2FeO4 electrode under different conditions was studied by the constant electric current discharge method. The electrochemical characteristics of K2FeO4 electrode were investigated for the first time by means of cyclic voltammetry. The results show that the K2FeO4 electrode made at moderate pressure (20MPa) and discharged at lower current has better discharge performance. It is also found that K2FeO4 electrode is significantly rechargeable. 相似文献
960.
Norikazu Nishiyama Yong-Rong Dong Tao Zheng Yasuyuki Egashira Korekazu Ueyama 《Journal of membrane science》2006,280(1-2):603-609
Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO2, O2, N2, CF4, n-C4H10 and i-C4H10, as well as binary mixtures of CH4/n-C4H10 and N2/CF4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH4/n-C4H10 mixtures and higher than 8100 for the N2/CF4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines. 相似文献