排序方式: 共有12条查询结果,搜索用时 156 毫秒
1.
p palan BS 《Physical review letters》1987,58(16):1597-1599
2.
Molar extinction coefficients of some carbohydrates viz. l-arabinose (C5H10O5), d-glucose (C6H12O6), d-mannose (C6H12O6), d-galactose (C6H12O6), d(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a
narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter
polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying
within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well. 相似文献
3.
Back Cover: Selective Aromatic Hydroxylation with Dioxygen and Simple Copper Imine Complexes (Chem. Eur. J. 33/2015) 下载免费PDF全文
4.
van Eis MJ van Der Linde BS de Kanter FJ de Wolf WH Bickelhaupt F 《The Journal of organic chemistry》2000,65(14):4348-4354
In contrast to the terminal phosphinidene complex PhPW(CO)(5) (2), which adds to [5]metacyclophane (1) in a 1,4-fashion, dichlorocarbene preferentially adds in a 1,2-fashion to the formal "anti-Bredt" type double bond of the aromatic ring of 1 to afford the norcaradiene 11b, which immediately rearranges to the bridged cycloheptatriene 12b and further by a [1,5] sigmatropic chlorine migration to the isomeric 13b as the first observable product. More slowly, the latter isomerizes via a dissociative mechanism to give 15b. A computational study supports the notion that the [1,5] chlorine migration in the rearrangement 12b --> 13b, for which an activation barrier of 70.2 kJ mol(-)(1) was calculated, is essentially concerted with minor charge separation. In contrast, the analogous [1,5] chlorine migration in the flat model compound 7,7-dichlorocycloheptatriene (12a) displays features of a dissociative pathway. 相似文献
5.
6.
7.
An isocratic, reversed-phase HPLC assay has been developed for the separation of the enantiomers of four lipoxygenase metabolites, without the need for a derivatization step. Separation of the enantiomers was studied on a polysaccharide type chiral stationary phase column. Upon determination of suitable mobile phase composition, the assay was evaluated at various temperatures. In all cases the R enantiomer eluted before the S enantiomer. The best separations were observed at 0 degrees C. 相似文献
8.
Thermodynamics of Chromium(VI) Anionic Species Sorption onto Surfactant-Modified Montmorillonite Clay 总被引:3,自引:0,他引:3
Batch sorption experiments performed on Cr(VI) species sorption showed a significantly enhanced removal of inorganic hexavalent chromium anionic species from aqueous solution by montmorillonite clays modified with quaternary amine, hexadecyltrimethylammonium (HDTMA) bromide. Unmodified clay had no affinity for chromium(VI) species. The sorption of Cr(VI) species has been carried out as a function of pH, contact time, adsorbate concentration (4.14x10(-5) to 8.62x10(-3) M), and temperature (5-45 degrees C). The surfactant-modified clay surface was stable when exposed to extremes in pH. The optimum pH for maximum sorption of Cr(VI) species was found to be at pH 1 and was constant between pH 2 and pH 6. The sorption data obtained was well described by DKR and Langmuir sorption isotherms. Sorption energy (E) for (i) surfactant sorption by montmorillonite clay and (ii) sorption of chromium(VI) species by surfactant modified clay have been computed from the DKR equation. Sorption energy evaluated for the sorption of both surfactant and Cr(VI) species showed that an ion-exchange mechanism was operative. The mechanism of retention appears to be replacement of counterion of the surfactant by Cr(VI) anionic species. Adsorbent capacity for the sorption of Cr(VI) species has been evaluated from the Langmuir sorption isotherm data. Thermodynamic parameters (Delta H degrees, Delta S degrees and Delta G degrees ) for surfactant sorption on montmorillonite clay and Cr(VI) sorption by modified clay have been evaluated. The specific rate constant for sorption of Cr(VI) species on modified montmorillonite was rapid during the first 10 min and equilibrium was found to be attained within 30 min. The sorption of Cr(VI) species onto modified montmorillonite clay followed first-order rate kinetics. Copyright 2000 Academic Press. 相似文献
9.
Jonathan Becker Puneet Gupta Dr. Friedrich Angersbach Prof. Dr. Felix Tuczek Prof. Dr. Christian Näther Prof. Dr. Max C. Holthausen Prof. Dr. Siegfried Schindler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11735-11744
The formation of a bis(μ‐oxido)dicopper complex with the ligand 2‐(diethylaminoethyl)‐6‐phenylpyridine (PPN) and its subsequent hydroxylation of the pendant phenyl group (studied earlier by Holland et al., Angew. Chem. Int. Ed. 1999 , 38, 1139–1142) has been reinvestigated to gain a better understanding of such systems in view of the development of new synthetic applications. To this end, we prepared a simple copper imine complex system that also affords selective o‐hydroxylation of aromatic aldehydes by using dioxygen as the oxidant: Applying the ligand N′‐benzylidene‐N,N‐diethylethylenediamine (BDED), salicylaldehyde was prepared in good yields and we show that this reaction also occurs through an intermediate bis‐μ‐oxido copper complex. The underlying reaction mechanism for the PPN‐supported complex was studied at the BLYP‐D/TZVP level of density functional theory and the results for representative stationary points along reaction paths of the BDED‐supported complex reveal a closely related mechanistic scenario. The results demonstrate a new facile synthetic way to introduce OH groups into aromatic aldehydes. 相似文献
10.