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971.
Reaction of Adipic Acid Diamide with Phosphorus Pentachloride The reaction of adipamide (I) with phosphorus pentachloride in a solvent leads to (Cl3P?NCCl2CCl2CH2)2 (II). The stages of the reaction are: 1. chlorination of the keto and methylen groups 2. formation of the ? N?PCl3 group. This result is a supplement of the existing conception about the course of the reaction of carboxylic acid amides with phosphorus pentachloride. The reaction of (I) with PCl5 without any solvent has been reproduced and the course of reaction has also been investigated. This reaction gives mainly NC(CH2)4CN. The resulting product of a careful hydrolysis of (II) is (Cl2OPN?CClCl2CH2)2. A total hydrolysis gives back (I). 相似文献
972.
Morikawa T Narita S Klein DJ 《Journal of chemical information and computer sciences》2004,44(6):1891-1896
This article first revises graph-theoretical (local aromaticity and overall molecular) indices, introduced by M. Randi? in 1975, for benzenoid hydrocarbons and somewhat improves them for computer enumeration. This goes beyond total Kekulé structure enumeration, yielding an index calculation useful for the quantitative estimation of localization of different Kekuléan substructures (including ethylene-, benzene-, annulene-, and radialene-units). This may be viewed as a "molecules-in molecule" approach to polycyclic aromatic hydrocarbons within the context of graph theoretical partitioning. 相似文献
973.
The reaction of titanocene dichloride with disodium fumarate in the two-phase system H2O/CHCl3 yields bis(μ-fumarato)bis[di(π-cyclopentadienyl)titamum(IV)]. Crystal data for the pure compound (IIIa): monoclinic, P21/n, a 18.558(5), b 9.076(5), c 7.559(2) Å, β 101.69(2)°; Z = 2. Crystal data for a phase containing chloroform of crystallization (CHCl3/Ti = ) (IIIb): triclinic, P, a 20.439(11), b 10.269(5), c 8.858(3) Å, α 112.18(3), β 93.93(5), γ 91.63(7)°; Z = 2 × 1. The three independent [(π-C5H5)2TiOCOCHHOCO]2 molecules differ in the puckering of their 14-membered rings and the geometry of their TiOC units. 相似文献
974.
J. Zechner G. Köhler N. Getoff I. Tatischeff R. Klein 《Photochemistry and photobiology》1981,34(2):163-168
Abstract— The two main primary photoprocesses (electron ejection and H-atom release) for indole, 5-methoxyindole and N-methylindole in various polar and nonpolar solvents were studied as a function of the excitation energy and were correlated with the corresponding fluorescence quantum yields. In hydrocarbon solvents, N–H bond cleavage is the main primary photoprocess from the 1 Bb band of the substrates with the exception of N-methylindole. In alcohols, both processes are of negligible importance. Hydrated electrons (e− aq ) are ejected from the relaxed singlet states of all three compounds in aqueous solutions with a similar yield for excitation at 280 and 254 nm (1 La and 1 Lb states). The yield increases when the excitation is into the 1 Bb band. The quantum yields of the two primary processes from the higher excited states are generally lower than the fraction of molecules not converting to the fluorescent state. This is explained by an efficient back reaction in competition with a thermally activated radical release from an intermediate state or radical pair formed from the S2 (1 Bb ) state. The non-occurrence of a photoionization energy threshold is discussed. 相似文献
975.
The separation of initially induced ion pairs into free ions in solution is discussed theoretically by means of numerical calculations of the partial differential equation for diffusion in a Coulomb field. The theory is compared with simple approximation formulae and previously published experimental data. 相似文献
976.
Rigid, microporous silica rods, prepared previously by the sol-gel process, were infiltrated with three triacrylate monomers to give sequential interpenetrating networks (IPNs). The three commercially available triacrylate monomers are glycerol propoxy triacrylate (GPTA), trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA). Each solution containing a photoinitiator was allowed to infiltrate the silica rod, after which the sample was UV irradiated to polymerize the triacrylate monomer. Emphasis was placed on establishing the infiltration and polymerization conditions leading to optically transparent composites. For comparison, one of the triacrylates (GPTA) was introduced into a hydrolyzing sol-gel formulation containing TEOS, ethanol, water and acid catalyst, to effect a simultaneous IPN. The sequential IPN and the simultaneous IPN samples gave similar transmission curves, despite differences in skeletal density.1992 Fulbright Visiting Scholar, on leave from Marie Curie Sklodowska University, Lublin, Poland. 相似文献
977.
Axel Klein Prof. Dr. Natascha Hurkes André Kaiser Wolfram Wielandt 《无机化学与普通化学杂志》2007,633(10):1659-1665
The red colour of the novel organonickel complex [(dppz)Ni(Mes)Br] (dppz = dipyrido[3,2‐a:2′,3′‐c]phenazine, Mes = 2,4,6‐trimethylphenyl) originates from long‐wavelength MLCT/L′LCT charge transfer bands. However, luminescence in dilute solution comes presumably from the 3π‐π* (phenazine) excited state. The red‐shifted emission exhibited in concentrated solutions is assigned to dimers. In the solid state emission is quenched. The crystal structure reveals two different types of π‐π stacking along the crystallographic a axis. 相似文献
978.
Summary We consider the determination of the behavior of a distribution function F at its endpoints in terms of the behavior of its Laplace-Stieltjes transform at the limits of its interval of convergence. The results extend various known strong and weak results to a larger class of distributions via a relatively straightforward technique based on the weak convergence of suitably normalized associated distributions. An application and examples are considered briefly.Research supported by Technion VPR Fund-Lawrence Deutsch Research Fund 相似文献
979.
Bernd Mayer Giancarlo Marconi Christian Klein Gottfried Köhler Peter Wolschann 《Journal of inclusion phenomena and macrocyclic chemistry》1997,29(1):79-93
Complexation trajectories and the variation ofinduced circular dichroism are calculated for thedocking of phenol and 2,4,6-trimethyl-phenol with-cyclodextrin. The results are compared toexperimental chirality data to elucidate themechanism of nonspecific molecular recognitionprocesses in aqueous solution. Large geometricalchanges along nearly isoenergetic Dynamic Monte Carlotrajectories show the conformational flexibility ofsuch host–guest systems. This proves diffuseintermolecular interactions, van der Waals orelectrostatic in nature, as the main contributions to thebinding energy. The number and position of the methylsubstituents of the guest reduces the complexityof the conformational space as the guests positionbecomes fixed by steric constraints.The solvation free energy is calculated from thesolvent accessible surface area weighted byrespective atomic solvation parameters. Consideringthe solvation term in the dynamic simulationsrestricts the conformational flexibility of themacromolecular system. The relative importance ofvarious contributions to the solvation energy isdiscussed and it is shown that those terms arisingfrom the interaction of hydrophobic groups with theaqueous environment are essential for thedetermination of the complex structure. Consideringthese terms in the dynamic simulation model, the signand strength of the calculated rotatory strength isin perfect agreement with induced circular dichroismobtained from experimentally determined averagedspectra. The results demonstrate the accuracy of thegeometrical properties of host–guest systems obtainedfrom these simulations. 相似文献
980.
Emmanuel Ngameni Yves Le Mest Maurice L'Her James P. Collman Neil H. Hendricks Kimoon Kim 《Journal of Electroanalytical Chemistry》1987,220(2)
Adsorbed on graphite electrodes, Co2FTF4 in a potent catalyst for O2 reduction by a four-electron mechanism. The two observable redox surface waves have been previously assigned to the two cobalt centres. Using differential pulse polarography (DPP), the behaviour of this dicobalt cofacial dimer was re-examined at different pH values in aqueous solutions and in the presence of potential axial ligands for cobalt. From these observations and from a comparison with other adsorbed porphyrins it can be concluded that (a) the porphyrins are probably adsorbed by strong interactions between graphite and the aromatic rings, and (b) the more negative surface wave is cobalt-based but the more positive one is instead a porphyrin ring oxidation. This implies that the catalyst is in the CoIICoIIIFTF4 state when catalytic oxygen reduction begins. 相似文献