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31.
由手性配体α-D-葡萄糖衍生物5,6,7以及薄荷醇(8)和葑醇(9),经 Ulmann偶联反应得到光学活性的(R)-和(S)-6,6′-二硝基联苯-2,2′- 二甲酸(4a),(R)-6,6′-二甲基联苯-2,2′-二甲酸(4b),(R)-1,1′-联萘-2 ,2′-二甲酸(13)。以三个手性膦酰胺16,17,18和CuCl组成的手性络合物为 催化剂,通过2-萘酚直接氧化偶联得到(S)-2,2′-联萘酚(15)。产物4, 13,15具有中等ee值的光学活性。 相似文献
32.
Chronoamperograms for gold in solutions containing 0.1 M thiourea, 0.5 M H2SO4, and catalytically active sulfide ions at the concentration c 1 from 1 × 10?5 to 4 × 10?5 M are obtained at different potentials with the aid of an automated setup intended for renewing the electrode surface directly in the solution by cutting off a thin surface layer of the metal. It is shown that the results of measurements of the current practically coincide at a constant value of the product c 1 t, where t is the time period elapsed after the renewal of the electrode surface. Such a coincidence testifies to a diffusion nature of processes that hamper accumulation of sulfide ions at the gold surface. This fact permitted the use of a procedure developed previously for the calculation of polarization curves at constant values of surface coverage θ by catalytically active ions. At θ = const, the voltammetric curves for gold in sulfide-containing thiourea solutions are shown to correspond to the Tafel equation. With the surface coverage increasing, the effective values of the exchange current i 0, transfer coefficient α, and anodic reaction order with respect to thiourea P a increase from the values i }~ 10?5 A cm?2, α }~ 0.12, and P a = 0.2, which are characteristic of pure solutions, to 2 × 10?4 A cm?2, α }~ 0.5, and P a = 1.1 (at θ }~ 0.5). An interpretation to the established regularities is given. 相似文献
33.
薄层扫描法测定冬眠过程中刺猬活性组织酶的周期变化冯金城(天津师范大学天津300074)孙金生(天津水产研究所天津300221)1前言为了跟踪观察刺猬在冬眠过程中体内乳酸脱氢酶的周期性变化,利用薄层扫描仪测定了其相关的组织同工酶的差异。实践证明,此法简... 相似文献
34.
旋光性高分子的合成(下)刘引烽,华家栋(上海科技大学化学系,上海,201800)4不对称聚合由外消旋手性单体制备旋光性高分子必须通过选择性聚合才能实现。选择性聚合是指外消旋的两个对映异构单体进行聚合时,由于体系中存在着某种不对称的诱导因素,其中之一比... 相似文献
35.
Tsutomu Oishi Kensoh Kagawa Minoru Fujimoto 《Journal of polymer science. Part A, Polymer chemistry》1995,33(8):1341-1352
Two types of optically active N-[N′-(α-methylbenzyl)amino/carbonyl-n-alkyl]maleimides (MBAC) were synthesized from maleic anhydride, 6-amino-n-caproic acid (or 12-amino-n-dodecanoic acid), and (R)-(+)-α-methylbenzylamine. Radical homopolymerizations of MBAC were performed in several solvents at 60 and 110°C for 24 h to give optically active polymers. Radical copolymerizations of MBAC were performed with styrene (ST) and methyl methacrylate (MMA) in dioxane at 60°C. The monomer reactivity ratios and the Alfrey-Price Q-e values were determined. Chiroptical properties of the polymers and copolymers were investigated. © 1995 John Wiley & Sons, Inc. 相似文献
36.
David M. Rogers Claire Wells Melanie Joseph Vanessa J. Boddington Joseph J.W. McDouall 《Journal of Molecular Structure》1998,434(1-3):239-245
We describe a procedure which may be used to aid selection of the active space in multiconfigurational self-consistent field (MCSCF) calculations for general chemical systems. Starting from a restricted Hartree-Fock calculation, we define a hierarchy of interacting virtual orbitals for every occupied orbital. The most strongly interacting orbitals are then taken to constitute the active space in a configuration interaction (CI) calculation. The natural orbital occupation numbers obtained from the CI calculation are then used to choose the active space to be used in a subsequent MCSCF calculation. We illustrate our method on a number of systems (Li2, B2, C2, carbonyl oxide and the transition state for oxidation of H2S by dioxirane). In all these cases, ‘intuitive’ active spaces are inadequate, as are active spaces derived from the natural orbitals of unrestricted Hartree-Fock calculations. 相似文献
37.
The reducing system NiCl2·2H2O—Li—arenecat (cat is catalyst) was proposed for use to reduce a wide range of organic compounds, including alkenes, alkynes, carbonyl compounds, imines, halogenated derivatives, sulfonates, aromatic compounds, hydrazines, azo and azoxy compounds, N-oxides, and nitrones. The degree of reduction can be controlled for some substrates. Deuterium can be incorporated in the reaction products using nickel chloride deuteriohydrate. Nitrones, N-alkoxyamides, and acyl azides are also reduced with the Li—arenecat system containing no nickel salt. 相似文献
38.
39.
A need for an elaboration of the methods for synthesis and characterization of activated carbons with a requisite porous structure has existed for a long time. One of the methods giving possibility for creating controlled mesopore and micropore structures deals with the steam gasification of various carbon materials. In this work the effects of calcium catalyst on the catalytic steam gasification of active carbons from plum stones and porous polymers are presented. Determination of micropores capacity and specific adsorption in mesopores have been performed by means of the
s
method, but adsorption on the heterogeneous solids was described by the integral equation with various local isotherms. This equation has been solved by the regularization method. Based on this method the changes in structural parameters of active carbons depending on the amount of calcium catalyst were estimated.Nomenclature
d
width of slit-like micropore
-
F(x)
distribution function of the half-width
-
p
vapor pressure of sorbate
-
p/p
N
relative pressure
- PSAC
Plum Stone Active Carbon
-
average pore radius, nm
-
S
1
relative limit of the validity of experimental point on the adsorption isotherm in the computations by means of regularization method
- SAC
Synthetic Active Carbon
-
S
BET
specific surface area calculated by means of BET method, m2/g
-
S
mes
mesopore surface area, m2/g
-
S
mic
micropore surface area, m2/g
-
T
absolute temperature, K
-
V
mes
sorption capacity of mesopores, cm3/g
-
V
mic
sorption capacity of micropores, cm3/g
-
V
p
sorption capacity of pores, cm3/g
- w/w
weight in weight concentration
-
x
half-width of slit-like micropore, nm
-
x
1
maximum of half-width of micropore slit, nm
-
average half-width of slit-like micropore, nm
-
X
min-X
max
integration limits of thex
Greek Letters Greek Letters
variance of average half-width of slit-like micropore, nm2
-
local relative filling of micropores
-
total relative filling of micropores 相似文献
40.