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51.
Flavone ( 1 ) was easily reduced by using the electrochemical method to give two hydrodimers of 2,2′‐biflavanone(racemate) ( 5a ) and 2,2′‐biflavanone(meso) ( 5b ) and one reductive product of flavanone ( 6 ). Their yields were dependent on the nature of electrodes, the kinds of supporting electrolytes and the reaction temperature. They were found to afford higher yields of 2,2′‐biflavanone(racemate) ( 5a ) and 2,2′‐biflavanone (meso) ( 5b ) (32.4% and 24.8%, 35.8% and 13.4%, respectively,) in the reaction conditions of Pb(‐)/C(+)‐H2SO4‐7F/mol and C(‐)/C(+)‐H2SO4‐5F/mol. 相似文献
52.
Swee-Ping Chia 《Physics letters. [Part B]》1990,240(3-4):465-470
The flavour-changing radiative decay b→sγ is analysed, and is found to be sensitive to the WWγ coupling. QCD corrections are found to play an important role. A good measurement of the branching ratio for B→K*γ may allow us to test the gauge coupling for WWγ of the standard model. 相似文献
53.
P. F. Wu J. B. Shi Y. C. Chang M. Z. Tsai Chia‐Tze Kao F. C. Cheng H. W. Lee M. Y. Chen Y. J. Huang R. Y. Huang S. K. Lin 《Crystal Research and Technology》2014,49(11):873-877
Large area and uniform nanosheets Co3O4 have been fabricated by thermal annealing of cobalt thin film under the DC magnetron sputtering method. The synthesis is based on controlling the simple thermal oxidative formation of precursor Co films. The Co films were heated at 300, 400, and 500 °C for two hours in a pure oxygen atmosphere. At 300 °C, CoO and Co3O4 phases appear to survive together. An amount of pure polycrystalline Co3O4 nanosheets were observed at 400 °C. The structural and morphological properties of the nanosheets Co3O4 were characterized by means of transmission electron microscopy (TEM) and Raman spectroscopy. 相似文献
54.
BH+2与C2H2反应势能面的量子化学研究 总被引:3,自引:0,他引:3
用B3LYP/6-311G(d,p) 密度泛函方法和高级电子相关的CCSD(T)/6-311G(2df,p)偶合簇法研究BH+2与C2H2反应势能面. 结果表明 该势能面上存在(a) H2B+*C2H2, (b) HBCHCH2+, (c) H2BCCH+2和(d) H2*BHCCH+四种异构体, 其中(b)能量最低且在动力学上最稳定, (a), (c)和(d)在动力学上均不稳定; BH+2通过对C2H2的分步亲电加成以及随后的氢迁移和H2消除等反应形成离解产物HBCCH++H2, 该反应不需要活化能且大量放热. 计算结果有助于深入了解BH+2等缺电子硼氢正离子的反应行为. 相似文献
55.
The new tetracyclic 9H,10H-indolizino[1,2-b]indole-1-one derivatives (7a-d, 7ea, 7eb) have been synthesized by modified Fischer indole synthesis from the enol ether of 2,5-dihydroxy-7-methyl-6-cyano-indolizine (3) and arylhydrazines (4a-g). Attempted N-methylation of 7a-d produced a series of autoxidized products including 10-hydroperoxy-1-methoxyindolizino[1,2-b]indole (9a-d) as the major product accompanied with methylperoxides (10a-d and 11a-d) and 2-formyl-3-(pyridine-2-yl)indole (12a, 12c) derivatives as the minor products. A plausible mechanism of the autoxidation is postulated based on the isolation of some intermediates. The reaction is thought to proceed through azaenolate/enamine intermediates following a novel type of autoxidation. 相似文献
56.
Thirteen specimens of Heteroscyphus coalitus were chemically examined. Among the isolated compounds, 1‐hydroxyaromadendr‐4‐en‐3‐one has not been reported previously. A third new chemotype with kauranoids as the major constituents for the liverwort H. coalitus was identified. 相似文献
57.
C.M. Lin C.T. Chia V. I. Mashanov H.H. Cheng 《光散射学报》2005,17(3):283-284
pacc:7830,7850C Wepresentthemicro-Ramanstudyof curvedGexSi1-x/GeySi1-yheterostructure,and foundthestrainofthecurvedthinlayerispropor tionaltothecurvature,i.e.inverselyproportional tothediameter.TheopticalandelectricpropertiesofSi1-x GexalloygrownonSisubst… 相似文献
58.
A new, reliable method for the introduction of an amine group at positions 2 or 6 of β-cyclodextrin and permethyl-β-cyclodextrin is described. It involves selective tosylation followed by azide substitution and almost quantitative reduction with triphenylphosphine followed by hydrolysis of the phosphinimine intermediate. 相似文献
59.
The effects of power ultrasound on four metal-nonmetal powdered systems: copper-sulphur iron-sulphur, zinc-sulphur and magnesium-sulphur in various solvents, such as hexane and carbon disulphide, are briefly examined here. For each system, a sonication time of 30 min was affected. The sonicated products are analysed by X-ray diffraction, X-ray fluorescence and atomic absorption spectrophotometry to determine their qualitative and quantitative compositions and the percentage yields of the products obtained are then compared and discussed. 相似文献
60.
G. L. Chia 《Journal of Graph Theory》1995,19(2):251-261
A graph is chromatically unique if it is uniquely determined by its chromatic polynomial. Let G be a chromatically unique graph and let Km denote the complete graph on m vertices. This paper is mainly concerned with the chromaticity of Km + G where + denotes the join of graphs. Also, it is shown that a large family of connected vertextransitive graphs that are not chromatically unique can be obtained by taking the join of some vertex-transitive graphs. © 1995 John Wiley & Sons, Inc. 相似文献