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901.
Masayuki Hoshi Souichi Suzuki Shingo Saitoh Mitsuhiro Okimoto Kazuya Shirakawa 《Tetrahedron letters》2007,48(1):119-124
A convenient, efficient and stereoselective synthesis of a range of bis(alk-3-en-1-ynyl)benzenes with E- and Z-configuration is described. The protocol involves Cu-mediated cross-coupling reaction of (E)- and (Z)-alk-1-enyldisiamylboranes with (trimethylsilyl)ethynyl bromide and Pd/Cu-catalyzed cross-coupling reaction with diiodobenzene. The sequential cross-coupling reaction proceeds readily under extremely mild conditions in a one-pot manner to afford bis(alk-3-en-1-ynyl)benzenes in good to excellent yields. The optical properties of the products are also described. 相似文献
902.
π‐Allyl (η3‐C3H5), a four‐electron donor, was used as a ligand model to replace η5‐C5Me4SiMe3 in DFT calculations on the tetranuclear yttrium polyhydrido complex (η5‐C5Me4SiMe3)4Y4H8 containing a Y4H8 tetrahedral core structure, which may separate the four π‐allyl groups and hence suppress the allyl ligand coupling during the computation. In terms of the calculated core geometry, isomerization energy barrier, charge population, and frontier orbital features of the complex, the η3‐C3H5 ligand model is comparable to η5‐C5H5. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
903.
The effect of the magnetic field on the electrokinetic transport coefficients (permeability coefficient and electro-osmotic permeability coefficient) of water and aqueous solutions of mercuric chloride and glycine through a sintered disc impregnated with cellulose acetate at different potentials, concentrations, and magnetic fields varying up to 21 kg/cm2 are reported at 308.15 K. The phenomenological coefficients characterizing the electro-osmotic flow and the membrane characteristics are also estimated for the various solutions with the object of determining the efficiencies of electrokinetic energy conversion and ζ potential. The effect of magnetic field has been attributed to the molecular orientation of dipoles in solutions and to the change in the structure of the membrane. 相似文献
904.
I. V. Ukrainets E. V. Mospanova L. V. Sidorenko 《Chemistry of Heterocyclic Compounds》2007,43(7):863-870
An improved method is reported for the synthesis of a series of 1-hydroxy-3-oxo-5,6-dihydro-3H-pyrrolo[3,2,1-ij]quinoline-2-carboxylic
acid hetarylamides. The antitubercular activity of all of the compounds prepared has been studied. The structure-biological
activity dependence revealed is discussed.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1023–1033, July, 2007. 相似文献
905.
Ewa?Cholewa Ian?Burgess Julia?Kunze Jacek?LipkowskiEmail author 《Journal of Solid State Electrochemistry》2004,8(10):693-705
Electrochemical measurements including cyclic voltammetry, differential capacity, and chronocoulometry have been used to characterize the adsorption behaviors of the zwitterionic surfactant
N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS) on the Au(111) electrode surface. The thermodynamics of the ideally polarized electrode have been employed to determine the Gibbs excess and the Gibbs energy of adsorption. The results show that the adsorption of DDAPS has a multistate character. The first two states are observed at potentials close to zero charge. At low bulk DDAPS concentrations, it corresponds to the formation of a film of nearly flat adsorbed molecules. At higher concentrations it is converted into a hemimicellar state. The second state is formed at negative potentials and charge densities close to 0 C cm–2. It corresponds to a film of tilted molecules oriented with the hydrocarbon tail towards the metal and the polar head toward the solution.Dedicated to Professor Zbigniew Galus on the occasion of his 70th birthday and in recognition of his many contributions to electrochemistry. 相似文献
906.
Dhanpat Rai Yuanxian Xia Linfeng Rao Nancy J. Hess Andrew R. Felmy Dean A. Moore David E. McCready 《Journal of solution chemistry》2005,34(4):469-498
The objectives of this study were to address uncertainties in the solubility product of (UO2)3(PO4)2⋅4H2O(c) and in the phosphate complexes of U(VI), and more importantly to develop needed thermodynamic data for the Pu(VI)-phosphate system in order to ascertain the extent to which U(VI) and Pu(VI) behave in an analogous fashion. Thus studies were conducted on (UO2)3(PO4)2⋅4H2O(c) and (PuO2)3(PO4)2⋅4H2O(am) solubilities for long-equilibration periods (up to 870 days) in a wide range of pH values (2.5 to 10.5) at fixed phosphate concentrations of 0.001 and 0.01 M, and in a range of phosphate concentrations (0.0001–1.0 M) at fixed pH values of about 3.5. A combination of techniques (XRD, DTA/TG, XAS, and thermodynamic analyses) was used to characterize the reaction products. The U(VI)-phosphate data for the most part agree closely with thermodynamic data presented in Guillaumont et al.,(1) although we cannot verify the existence of several U(VI) hydrolyses and phosphate species and we find the reported value for formation constant of UO2PO−4 is in error by more than two orders of magnitude. A comprehensive thermodynamic model for (PuO2)3(PO4)2⋅4H2O(am) solubility in the H+-Na+-OH−-Cl−-H2PO−4-HPO2−4-PO3−4-H2O system, previously unavailable, is presented and the data shows that the U(VI)-phosphate system is an excellent analog for the Pu(VI)-phosphate system. 相似文献
907.
L. I. Belen’kii A. V. Kolotaev V. Z. Shirinyan M. M. Krayushkin Yu. P. Strokach T. M. Valova Z. O. Golotyuk V. A. Barachevskii 《Chemistry of Heterocyclic Compounds》2005,41(1):86-92
The polar [4+2] cycloaddition reaction of 1,2-bis(2,5-dimethyl-3-thienyl)acetylene with thiobenzamide and certain aldehydes of the thiophene and furan series catalyzed by boron trifluoride etherate gives the corresponding 4-hetaryl-5,6-di(2,5-dimethyl-3-thienyl)-2-phenyl-4H-1,3-thiazines. The photochromic properties of the products have been studied.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 100–106, January, 2005. 相似文献
908.
Tetsuji Yano Makoto Ebizuka Hiroyuki Yamamoto Shuichi Shibata Masayuki Yamane 《Journal of Sol-Gel Science and Technology》2000,19(1-3):845-849
Na2O-B2O3-SiO2 (NBS) gels containing a large amount of CdS quantum-dots (10 wt%) were densified using the hot press (HP) sintering method. By HP treatment, full-densification temperature could be lowered by about 40°C than that of the normal non-pressing (NP) heat treatment. Exciton absorption of CdS quantum-dots in HP-sample showed a large blue shift compared with that in the NP sample, and the size-distribution of CdS dots remained very sharp, with a mean particle diameter d = 3.66 nm and a standard deviation of = 0.72. HP pressure had a large effect on the reduction of sintering temperature and time, resulting in the suppression of the aggregation and growth of CdS quantum-dots in NBS glasses. 相似文献
909.
Jing-kun Xu Gao-quan Shi Feng-en Chen Xiao-yin Hong Department of Chemistry Bio-organic Phosphorous Chemistry Laboratory Tsinghua University Beijing China 《高分子科学》2002,(5):425-430
The Raman spectra of poly(3-methylthiophene) (PMeT) films with different thicknesses, which have beenelectrochemically deposited on a flat stainless steel electrode surface by direct oxidation of 3-methylthiophene in borontrifluoride diethyl etherate (BFEE) at a constant applied potential of 1.38 V (versus SCE), have been investigated byexcitation with a 633-nm laser beam. The spectroscopic results demonstrated that the doping level of PMeT film wasincreasing during film growth. This finding was also confirmed by electrochemical examination. Moreover, the Raman bandsassigned to radical cations and dications in doped PMeT films were found approximately at 1420 and 1400 cm~(-1),respectively. Radical cations and dications coexist on the backbone of PMeT as conductive species and their concentrationsincrease with the increase of doping level. Successive cyclic voltammetry was proved to be an effective approach toimproving the doping level of as-grown thin compact PMeT film. 相似文献
910.
The potential energy surface (PES) for the CF3CFHO2+HO2 reaction has been theoretically investigated using the DFT [B3LYP/6‐311G(d,p)] and B3LYP/6‐311++G(3df,3pd)//B3LYP/6‐311G(d,p) levels of theory. Both singlet and triplet PESs are investigated. The reaction mechanism on the triplet surface is simple. It is revealed that the formation of CF3CFHOOH+3O2 is the dominant channel on the triplet surface. On the basis of the ab initio data, the total rate constants for the reaction CF3CFHO2+HO2 in the T = 210–500 K range have been computed using conventional transition state theory with Wigner's tunneling correction and have been fitted by a rate constant expression as k = 1.04 ×10?12(cm3 molecule?1 s?1) exp (700.33/T). Calculated transition state rate constants with Wigner's tunneling correction for the reaction CF3CFHO2+HO2 are in good agreement with the available experimental values. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献