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61.
Lämmerhofer M 《Journal of chromatography. A》2005,1068(1):3-30
Enantiomer separations by CE employing nonaqueous conditions are reviewed. The general focus of this article is directed towards solvent effects on chiral recognition and the separation mechanism. After a general discussion of solvent effects on the individual processes involved in CE enantiomer separation, specifics for various selector classes are discussed together with a few applications of enantioselective nonaqueous CE. 相似文献
62.
Solvent effects in a carbenoid N-H insertion route to triarylamines via 2-diazo-1,3-cyclohexanedione
Peter Livant 《Tetrahedron letters》2005,46(12):2113-2116
The Rh-carbenoid derived from 2-diazo-1,3-cyclohexanedione inserts into the N-H bond of arylalkylamines and diarylamines. A solvent for this reactive carbenoid is suggested. The insertion products undergo a Pd-mediated aromatization to afford alkyldiarylamines and triarylamines. 相似文献
63.
64.
Poly(ethylene glycol) (PEG 3400) was used as a soluble polymeric support for the synthesis of a series of novel benzazepines. The key step for the preparation of these heterocycles was a phosphine-free palladium-catalyzed Heck reaction. Palladium nanoparticles formed during the course of the reaction were characterized. The presence of PEG 3400 influenced the outcome of the reaction in terms of selectivity. 相似文献
65.
Toshio Fuchigami 《Journal of fluorine chemistry》2007,128(4):311-316
Recent studies on solvent effects on electrochemical partial fluorination are reviewed. At first, the historical background and some problems of electrochemical fluorination in organic solvents like acetonitrile (MeCN) are briefly mentioned. Ethereal solvents like dimethoxyethane (DME) and a mixture of DME and MeCN were found to improve both the yield and current efficiency for electrochemical fluorination since these solvent systems effectively suppress anode passivation and overoxidation of fluorinated products once formed during the electrolysis. It was also found that DME stabilizes radical cationic intermediates of 4-arylthio-1,3-dioxolan-2-ones and 3-phenylthiophthalide leading to α-fluorination while dichloromethane (CH2Cl2) destabilizes them leading to fluorodesulfurization. On the other hand, imidazolium ionic liquids and liquid fluoride salts like Et4NF·4HF and Et3N·5HF exhibited similar effects to CH2Cl2. Selective fluorination of hardly oxidizable phthalide was also achieved using a combination of two kinds of ionic liquids (imidazolium triflate and liquid fluoride salts). 相似文献
66.
In developing a method for possible low level isotopic enrichment, which uses to advantage the equilibrium isotope effect
observed during U(1V)-U(VI) electron exchange reaction in sulphate solutions, details of a solvent extraction process involving
high concentration of a mixture of U(IV) and U(VI) and at low acid concentrations, are described. The extraction behaviour
of uranium under these conditions is discussed. During the extraction with amines, U(IV) tended to get oxidised in sulphate
solutions. 相似文献
67.
萃取有机相中微乳液的稳定性研究 总被引:3,自引:0,他引:3
赊P507钾盐外,PSO7理、钠、按盐和P204的理、钠、钾、按以及有机接盐等与醇一油一水在一定条件下都能形成微乳液.因此,进一步搞清这些体系形成微乳液的结构、性质和稳定性,对革取化学研究是十分重要的.我们曾对PSO7(K)一醇一正庚烷一水四组分体系的结构参数[’j和物理化学性质[’]进行过研究,观察到辅助表面活性剂性质和含水量对微乳液结构有重要的影响·本文采用测定微乳液电导的变化,研究含有不同醇和不同量水时,P507(K)在革取有机相中形成微乳液颗粒的活化能(凸E),并用凸E的大小来描述和比较微乳液的界面膜强度… 相似文献
68.
Summary Two epimers of the mycotoxin chlamydosporol were separated by HPLC on an RP-18 column using a quaternary mobile phase consisting of water (79.1%), methanol (10.0%), acetonitrile (10.4%) and tetrahydrofuran (0.5%), with a flow rate of 1 ml min–1. This optimal composition of mobile phase, with which the resolution value for the two epimers (1 and2) was 2.73 with retention times of 5.88 and 7.12 min, respectively, was achieved by the application of Philips Solvent Optimisation Software PU 6100. The presence of free silanols on the stationary phase was shown to be an essential requirement for the separation of the chlamydosporol epimers. 相似文献
69.
The model of Onsager in which a polar molecule undergoes a reaction field due to the polarization of the molecular surroundings is used to evaluate by a S.C.F. calculation (CNDO/2 approximation) the modifications of a molecular structure in the liquid state.Application to water molecule and to three polar dimers for values of the dielectric constant varying between 3 and 78, shows that most of geometric parameters and dipoles moments vary of few per cent when the molecule is inserted in a liquid. In the liquid state dipole moments do not depend very much on the dielectric constant but energies and relative stabilities of isomers are strongly dependent on the medium.[/p] 相似文献
70.
Y. Marcus 《Journal of solution chemistry》1991,20(9):929-944
Taft and Kamlet's -scale of solvent hydrogen bond donation ability is reexamined with regard to its correlations with three widely used polarity scales: Dimroth and Reichardt's E
T
(30), Kosower's Z and Mayer's A
N
, as well as with the m values of the solvents when present as monomeric solutes. The correlation with E
T
serves to extend the solvent -scale according to the expression:
相似文献 |