排序方式: 共有15条查询结果,搜索用时 15 毫秒
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Sosale Chandrasekhar 《Research on Chemical Intermediates》2005,31(9):779-783
The 'duplication' strategy for the further enrichment of an already enantiomerically-enriched mixture consists of the formation
of all the three possible 'dimeric' diastereomers, i.e., (R)–X–(R), (R)–X–(S) and (S)–X–(S), where X is an appropriate spacer that can be readily cleaved to yield the original enantiomers. The mixture of (R)–X–(R) and (S)–X–(S) thus obtained would be of higher enantiomeric excess (e.e.) as compared to the original mixture, on the basis of a simple
kinetic scheme. The success of the strategy is experimentally well-established, but is apparently based on the (unproven)
assumption that the theoretically-derived rate ratios are identical to the experimentally observed product ratios. Although
the detailed kinetic treatment for a system such as the above is extremely complex, it is possible to show (mathematically)
that the above assumption is indeed justified when all the three diastereomers are formed without chiral discrimination (as
assumed in the strategy). 相似文献
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Hussain Al-Qassem 《分析论及其应用》2004,20(2):99-112
In this paper, we study the mapping properties of singular integral operator along surfaces of revolution. We prove Lp bounds (1 < p < ∞) for such singular integral operators as well as for their corresponding maximal truncated singular integrals if the singular kernels are allowed to be in certain block spaces. 相似文献
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研究AgCl-CS(NH_2)_2-H_2O三元体系,对于用硫脲溶解、分离角银矿(AgCl)中的金、银显然是有意义的.但有关该三元体系的文献很少.等结合折光指数认为在AgCl-CS(NH_2)_2-KCl-H_2O系统中只生成配合物Ag[CS(NH_2)]_2Cl.我们的研究工作也证明可生成Ag[Cs(NH_2)_2]_2Cl.我们研究了AgCl-CS(NH_2)_2-H_2O三元体系在20℃及30℃时的溶度和折光指数.由于两个温度的溶度图图形基本相仿,故本文只报道30℃的工作. 相似文献
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宽广温度范围的水离子积是在理论上和实际应用上涉及面很广的重要物理化学性质之一.傅培鑫,Quist及Marshall等在总结实验数据的基础上提出了相应的计算水离子积的经验公式;Taylor还用热力学方法进行了计算.在饱和蒸气压及0~800℃范围内,以Marshall-Franck的经验公式准确度为最高,并由国际蒸气性质协会(IAPA)于1980年公布为计算宽广温度范围的水离子积公式.但是在温度较高(200~300℃)时,此公式的计算值与实验值之间的误差随温度升高而逐渐增大,平均误差为0.033pK_w单位. 相似文献
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本文研究了一个钡-钙-茜素配合剂(ALC)新体系的极谱波及其机理,此极谱波是一种双金属三元配合物吸附波,是由钡-钙-ALC配合物在电极上吸附还原而产生的,配合物的组成为:Ba:Ca:ALC=1:2:5,此方法可应用于硫酸钡溶积度的测定。 相似文献
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Huoxiong Wu Shanzhi Yang 《分析论及其应用》2007,23(4):389-400
In this paper, the authors establish Lp boundedness for several classes of multiple singular integrals along surfaces of revolution with kernels satisfying rather weak size condition. The results of the corresponding maximal truncated singular integrals are also obtained. The main results essentially improve and extend some known results. 相似文献
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