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71.
介绍一个面向高年级本科生的计算化学实验。通过利用量子化学计算,确定嘧啶碱基的酸碱性质以及它们与水分子之间的相互作用能,构建氢键复合物分子间相互作用与分子酸碱性之间的定量关系,使学生对分子的酸碱性、分子间相互作用、分子识别之间的关系有一定的直观认识。该实验有助于学生梳理课堂学到的碎片化知识,提升学生逻辑分析及创新能力。 相似文献
72.
Rongjun Zhang Dehua He Innovative Catalysis Program Key Lab of Organic Optoelectronics Molecular Engineering 《天然气化学杂志》2012,(1):1-6
A series of ZrO2 catalysts were prepared by treating ZrO(OH)2 hydrogel with different alcohol solvents (C2-C4 alcohols) and calcining under N2 flow at 773 K for 3 h. The obtained ZrO2 catalysts were systematically characterized by the methods of N2 adsorption-desorption, powder X-ray diffraction, NH3 temperature-programmed desorption, and CO2 temperature-programmed desorption. The catalytic performance of each catalyst was evaluated in the selective synthesis of iso-C4 (isobutene and isobutane) and light olefins (C2= ~C4= ) from CO hydrogenation. The specific surface area increased for the ZrO2 catalysts obtained by treating ZrO(OH)2 hydrogel with different alcohol solvents. The amounts of both acidic and basic sites on the catalyst surface increased obviously. The catalytic activity (CO conversion) of ZrO2 catalysts also increased after the treatment with different alcohol solvents. The highest activity was obtained over the catalyst which was pretreated with isopropanol. However, alcohol solvent treatment retarded the transformation of ZrO2 crystal structure from tetragonal phase to monoclinic phase, and subsequently resulted in the decrease of monoclinic phase in ZrO2, which led to the decrease of olefin selectivity in corresponding hydrocarbon products (C2=~C4= /CH). 相似文献
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针对高职学生理论基础薄弱、对课堂传授知识的学习积极性不高等普遍现象,在酸碱滴定之后的电位分析学习过程中,通过教学改革增设综合性强的系列实验项目,如酸碱滴定理论突跃曲线(pH-V曲线)验证实验,滴定终点与化学计量点比较实验,不同方法测定水溶液酸度的比较实验等。以实验贯通酸碱滴定和电位分析重要核心内容,利用一个体系,通过几种分析方法进行比较教学,将现学的知识与已学过的知识相互连接起来,并让学生通过实验亲自动手验证理论,在熟练掌握分析操作技能的基础上提升了理论知识。 相似文献
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首次提出并研究了一种基于光纤折射率传感原理的新颖的化学酸碱滴定分析方法, 为光纤传感技术在化学滴定分析的新应用作出了有意义的尝试. 实验结果表明: 此方法适应于酸碱互滴, 只需少量样品; 在待测样品浓度较低时, 采用浓度高的滴定剂效果更佳, 可测量浓度低至0.001 mol/L 的溶液; 与传统的pH滴定方法等比较, 本方法无需添加终点指示剂, 可实现实时监控; 在二元酸碱的滴定中, 化学计量点指示更明确, 精度更高; 稳定性和准确性测试效果良好, 对HNO3, NaOH进行测定RSD分别为0.23%和0.28%. 相似文献
78.
Lakshmikumar Pillai Roger D. Boss Mark S. Greenberg 《Journal of solution chemistry》1979,8(9):635-646
The macroscopic and microscopic acid-base chemistry of a series of sulfhydryl and ammonium-containing amino acids HS–R–NH3 [R=–CH2CH(COOH)–, cysteine (CYS); R=–C(CH3)2CH(COOH)–, penicillamine (PEN); R=–CH(COOH)CH2CH2CONHCH(–CH2)CONHCH2COOH, glutathione (GSH)] was characterized in water and its binary mixtures with acetonitrile (16.3, 34.2, and 53.9 mass % acetonitrile). Macroscopic acid dissociation constants were obtained by potentiometric titration using the glass-calomel electrode pair. Microscopic acid dissociation constants were calculated from ultraviolet absorption measurements at ca. 232 nm where the deprotonated sulfhydryl group absorbs. The macroscopic constants decrease uniformly as the solvent becomes enriched in acetonitrile. The microscopic constants, which characterize the relative concentrations of the two monoprotonated tautomers of the molecules (I and II)
reveal that as the solvent becomes enriched in acetonitrile, the fraction of molecules existing as highly charged tautomer I decreases for CYS (0.68–0.40), PEN (0.85–0.34), and GSH (0.61–0.30). These results are related to the decreasing concentration of water as the solvent becomes enriched in acetonitrile. 相似文献
79.
80.
F. I. Bel'skii G. V. Bodrin Yu. M. Polikarpov M. I. Kabachnik 《Russian Chemical Bulletin》1998,47(9):1741-1743
A derivative of dibenzo-18-crown-6 containing dihydroxyphosphorylmethyl groups in the 4, 5, 4′, and 5′ positions of the benzene
ring has been synthesized. Unlike dibenzo-18-crown-6, its phosphorylated derivative does not form stable complexes with cations
of alkali and alkaline-earth metals. Complexes with transition metals are water-insoluble in most cases.
Deceased.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1789–1791. September, 1998. 相似文献