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排序方式: 共有261条查询结果,搜索用时 265 毫秒
1.
Szabolcs Cserényi 《Journal of fluorine chemistry》2006,127(7):850-853
The Perkin reaction of the activated aromatic ketones (2,2,2-trifluoroacetophenone and its 4′-phenyl-derivative) with various condensing agents (acetic anhydride, propionic anhydride, phenylacetic acid/acetic anhydride) gives the title compounds in good or moderate yields, and high E-stereoselectivity. For some derivatives an appreciable amount of the Z isomer was also formed. Several of the resulting butenoic acids and their methyl esters are synthesised and characterised for the first time. 相似文献
2.
3.
The ultraviolet photoelectron spectra of mono and binuclear cyclooctatetraene (COT) complexes (CO)3FeCOT (I) [(CO)3Fe]2COT (II), CpCrCOT (Cp: 1,3 cyclopentadienyl) (III) and (CpCr)2COT (IV) are reported. The interpretation of the low energy part of the spectra is followed by a discussion concerning the metal–ligand (COT) and metal–metal interactions. The calculated gas phase structure of CpCrCOT is presented and its main features are discussed. 相似文献
4.
Szöllosi G Bucsi I Cserényi S Bartók M 《Rapid communications in mass spectrometry : RCM》2005,19(24):3743-3748
We have studied the adsorption on a platinum (Pt) catalyst of two compounds utilizable as a chiral basic catalyst and a chiral modifier, dihydrocinchonidine (DHCD), and a new cinchona alkaloid derivative containing a bulky group, the Ph3SiO-DHCD molecule. The method of choice was the detection by electrospray ionization (ESI) ion-trap tandem mass spectrometry (MS/MS) of hydrogen/deuterium (H/D) exchange at room temperature, in tetrahydrofuran, at a D2 pressure of 1 bar. Based on the ESI-MS/MS spectrum of the new compound, we propose a mechanism for the formation of the silatropylium cation containing a Si-O bond. From the fragmentation pattern of Ph3SiO-DHCD it was confirmed that ESI-ion-trap MS/MS can be used to study the adsorption processes of complicated carbon compounds by investigating their H/D exchange reactions. In the case of Ph3SiO-DHCD, the results demonstrate that H/D exchange takes place mainly on the quinoline skeleton. However, the strong pi-bonded adsorption of the quinoline skeleton parallel with the imaginary plane of Pt is not preferred because the bulky Ph3Si group inhibits the multiple pi-bonded adsorption of the Ph3SiO-DHCD. Because of this hindrance the molecule was adsorbed tilted via the nonbonding electron pair of the N atom and C2' atom of the quinoline skeleton; consequently, mainly alkaloid-d1 and alkaloid-d2 are formed. 相似文献
5.
Werner Bihlmaier Rolf Huisgen Hans-Ulrich Reissig Sabine Vass 《Tetrahedron letters》1979,20(28):2621-2624
Whereas diazomethane cycloadditions are only accelerated by electron-attracting substituents in the olefinic or acetylenic dipolarophile, the cycloadditions of diazoacetic, diazomalonic and diazo(phenylsulfonyl)acetic ester show in accordance with the PMO treatment U-shaped activity functions when log k2 is plotted versus the lowest IP of the dipolarophiles. 相似文献
6.
Sz. Vass 《Chemical physics letters》1980,70(1):135-137
The small number of reagents solubilized in a micelle prohibits the use of conventional reaction kinetics. In order to describe the kinetics of the reaction A + B ? AB proceeding in a micellar phase, a stochastic model is evaluated. The deviation of these results from those obtained by conventional kinetics may be as high as 20%. 相似文献
7.
Vass S Grimm H Bányai I Meier G Gilányi T 《The journal of physical chemistry. B》2005,109(24):11870-11874
Slowly diffusing water molecules were found by quasi-elastic neutron scattering (QENS) in a sodium dodecyl sulfate (SDS) micellar solution, and both their diffusion coefficient (4.33 x 10(-6) cm2 x s(-1)) and mole fraction (0.057) were determined. After successfully checking the mean slowing down of solvent molecules by the gradient compensated stimulated spin-echo (GCSTE) pulse sequence NMR method, a similar effect was observed with this technique in the solvent phase of dodecyl trimethylammonium bromide (DTAB) and differing chain length (X = 12, 20, 30, and 40) ethoxylated nonyl phenol (9NX) micellar systems. Following the literature, the experimental results are qualitatively explained by assuming that, apart from ionic hydration, H-bonds may form between the solvent molecules and the O or N atoms present in the hydrophilic (head)groups of the micelle-forming monomers. 相似文献
8.
Results are presented concerning the role of oxalic acid, salicylic acid and glycine as coimpregnation ingredients in preparation of Pd/Al2O3 catalysts from PdCl
4
2–
and PdBr
4
2–
solutions.
, , , Pd/Al2O3 PdCl 4 2– PdBr 4 2– .相似文献
9.
Using preilluminating flashes at 2°C prior to continuous excitation of isolated chloroplasts at -80°C, a period-four oscillation with maxima at the 0th, 4th and 8th flashes was observed in the amplitude of the thermoluminescence band Zv . Inactivation of the water-splitting system by hydroxylamine- or Tris-treatments greatly diminished the Zv band. On the other hand, its amplitude was not considerably affected by the addition of inhibitory concentration of DCMU. On the basis of the results, the possible origin of the Zv band is discussed. 相似文献
10.
The state of art of the various preparative planar liquid chromatographic (PLC) methods is summarized, especially for off-line and on-line sample application. The sample purification possibilities for PLC techniques are discussed. Purification and isolation strategies using forced-flow planar chromatographic techniques, such as overpressured layer chromatography and rotation planar chromatography, are suggested in the form of flow charts. 相似文献