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991.
992.
Sn基合金负极材料具有高达990 mAh·g-1的理论比容量,但其也存在因脱嵌锂过程发生巨大的体积变化而导致循环性能较差的问题. 本文以Sn、Fe、石墨为原料利用简易的高能球磨法成功制备了具有核壳结构的FeSn2-C复合物,系统研究了球磨时间、FeSn2相含量对材料物相结构及电化学性能的影响,并分析了电极的失效机理. 研究表明,球磨时间的增加有利于FeSn2金属间化合物相的形成及材料颗粒的细化,进而有利于材料比容量的增加及循环性能的提升;FeSn2相含量的增加能够提高FeSn2-C材料的比容量,但会降低FeSn2-C电极的循环稳定性. 经工艺优化及组分调节,球磨24 h合成的Sn20Fe10C70材料具有最优的电化学性能,材料的比容量在540 mAh·g-1左右,并能稳定循环100次,是一种非常有发展前途的锂离子电池高比容量负极材料. 相似文献
993.
《Tetrahedron letters》2004,45(10):2141-2145
Treatment of hydroxythiol 4 with α,α-diethoxyacetophenone at room temperature yielded a mixture of epimeric S,O-acetals 6 and 7 (1:4, 92% yield), which were efficiently separated by flash chromatography. The OTBS derivatives 8 and 9 were treated with several Grignard reagents to afford carbinols 10 and 13 respectively (85-99% yield, >95% dr). After successive hydrolysis and reduction of 10 and 13 it is possible to obtain either enantiomer of diols 16 in high optical purity (>95% er). 相似文献
994.
Simultaneous detection with a 700-A Hall? and an NPD detector is an effective technique for characterizing chloro-and chloronitroanilines in highly complex Publicly Owned Water Treatment Works (POTW) sludges. The utilization of a modified Varian effluent splitter and a SE-54 fused silica capillary column permitted the detection of mid-picogram quantities of the polar chloroanilines without sacrificing peak shape. The response of the Hall? detector in the halogen mode was roughly proportional to the number of chlorine atoms present, while the response of the Hall? in the nitrogen mode and the NPD was less predictably influenced by the presence of one or more nitro groups. When combined with retention time data, the ratio of the NPD response to the Hall? response has been found to substantiate the presence of chloro- and chloronitroanilines in sludge extracts. 相似文献
995.
The catalytic system composed of CuCl2 and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC) was found to be highly efficient for the selective α-oxidation of internal alkynes to the corresponding α,β-acetylenic ketones, with aqueous tert-butyl hydroperoxide under mild conditions. For the first time, full conversions of alkynes were reached with excellent selectivities, and propargylic tert-butylperoxy ethers were observed and suggested as the reaction intermediates. In the case of terminal alkynes, the oxidations are sluggish and low yields ranging from 32% to 40% were obtained. 相似文献
996.
Stereochemistry of 7-aryl-1,7,8,8a-tetrahydro-3(2H)-indolizinones was studied by1H and13C NMR. Complete assignment of1H NMR signals and analysis of1H-1H coupling constants were performed using the iterative PANIC program. Values of3
J
6,7,3
J
7,8endo, and4
J
5,7 allow one to unambiguously identify the correspondingexo- andendo-stereoisomers. For stereoisomers with exo-orientation of H(7), complete assignment of13C NMR signals was performed on the basis of analysis of the13C-1H coupling constants using two dimensional heteronuclear shift-correlating spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 591–593, March, 1996. 相似文献
997.
Ab initio calculations ofp-dichlorobenzene molecule were carried out using the Hartree-Fock method in the 6–31 G* valence-split basis set. The molecule was also calculated by the MNDO method in the valence sp-basis set for comparison. The populations of the valent p-orbitals of the C and CI atoms were analyzed. The optimized geometry of the molecule as well as its35Cl NQR frequency and the asymmetry parameter of the electric field gradient at the35CI nuclei calculated using the populations of the less diffuse components of the valent p-orbitals of the Cl atoms are in agreement with the corresponding experimental values for the -modification of 1,4-Cl2C6H4.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2177–2179, September, 1996. 相似文献
998.
V. G. Avakyan L. E. Gusel’nikov S. L. Gusel’nikov V. F. Sidorkin 《Russian Chemical Bulletin》2005,54(9):2013-2022
The effect of the nature of substituents at sp2-hybridized silicon atom in the R2Si=CH2 (R = SiH3, H, Me, OH, Cl, F) molecules on the structure and energy characteristics of complexes of these molecules with ammonia, trimethylamine,
and tetrahydrofuran was studied by the ab initio (MP4/6-311G(d)//MP2/6-31G(d)+ZPE) method. As the electronegativity, χ, of the substituent R increases, the coordination bond
energies, D(Si← N(O)), increase from 4.7 to 25.9 kcal mol−1 for the complexes of R2Si=CH2 with NH3, from 10.6 to 37.1 kcal mol−1 for the complexes with Me3N, and from 5.0 to 22.2 kcal mol−1 for the complexes with THF. The n-donor ability changes as follows: THF ≤ NH3 < Me3N. The calculated barrier to hindered internal rotation about the silicon—carbon double bond was used as a measure of the
Si=C π-bond energy. As χ increases, the rotational barriers decrease from 18.9 to 5.2 kcal mol−1 for the complexes with NH3 and from 16.9 to 5.7 kcal mol−1 for the complexes with Me3N. The lowering of rotational barriers occurs in parallel to the decrease in D
π(Si=C) we have established earlier for free silenes. On the average, the D
π(Si=C) energy decreases by ∼25 kcal mol−1 for NH3· R2Si=CH2 and Me3N·R2Si=CH2. The D(Si←N) values for the R2Si=CH2· 2Me3N complexes are 11.4 (R = H) and 24.3 kcal mol−1 (R = F). sp2-Hybridized silicon atom can form transannular coordination bonds in 1,1-bis[N-(dimethylamino)acetimidato]silene (6). The open form (I) of molecule 6 is 35.1 and 43.5 kcal mol−1 less stable than the cyclic (II, one transannular Si←N bond) and bicyclic (III, two transannular Si←N bonds) forms of this molecule, respectively. The D(Si←N) energy for structure III was estimated at 21.8 kcal mol−1.
Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1952–1961, September, 2005. 相似文献
999.
S. S. Shukurov M. A. Kukaniev I. M. Nasyrov K. S. Zakharo R. A. Karakhanov 《Russian Chemical Bulletin》1993,42(11):1874-1878
Reactions of 2-bromo-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidine with sodium derivatives of pentane-2,4-dione, malonodinitrile, Meldrum acid, acetoacetic, cyanoacetic and malonic esters have been shown to give the respective substituted derivatives. Azinyl-ylidene tautomerism has been found to be characteristic of these compounds, the latter existing mainly in the ylidene form. The acid hydrolysis of pentane-2, 5-dione and cyanoacetic and malonic esters derivatives has been investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1961, November, 1993 相似文献
1000.
Structures with AIB2? and BaAl4?type Units. I The Compounds Sr4Pd5P5 and Sr2Pd3P3 Sr4Pd5P5 (Cmcm, a = 4.177(1) Å, b = 31.377(5) Å, c = 8.581(2) Å, Z = 4) und Sr2 Pd3P3(Pmmm, a = 4.199(1) Å, b = 4.212(1) Å, c = 34.227(4) Å, Z = 4) have been prepared by heating the elements. Both structures contain exclusively units characteristic for the AIB2? and BaAl4?type. The ratio between isolated P-atoms and P2?pairs is interpreted with an ionic splitting of the formulas. 相似文献