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排序方式: 共有220条查询结果,搜索用时 0 毫秒
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Beker H Boggild H Boissevain J Cherney M Dodd J Esumi S Fabjan CW Fields DE Franz A Hansen KH Holzer EB Humanic TJ Jacak BV Jayanti R Kalechofsky H Kobayashi T Kvatadze R Lee YY Leltchouk M Lörstad B Maeda N Medvedev A Miake Y Miyabayashi A Murray M Nagamiya S Nishimura S Noteboom E Pandey SU Piuz F Polychronakos V Potekhin M Poulard G Sakaguchi A Sarabura M Shigaki K Simon-Gillo J Sondheim W Sugitate T Sullivan JP Sumi Y van Hecke H Willis WJ Wolf K Xu N 《Physical review letters》1995,74(17):3340-3343
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Mass-spectral and n.m.r. analysis of thiophenes labeled by exchange with deuteriosulfuric acid establishes that exchange at the 2 and 5 positions is essentially complete before any deuterium is incorporated at positions 3 and 4. Thus, such exchange is a satisfactory procedure for position-specific labeling. Mass spectra of the labeled thiophenes show that about 60% of the [CHS]+ ion yield is derived from molecular ions that have not undergone prior rearrangement. The remaining 40% arises by a path or paths in which the four hydrogen atoms lose position identity. Other decomposition paths contributing to the mass spectrum are characterized by more nearly complete scrambling of hydrogens. 相似文献
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Fluorine-containing nitrogen compounds—VI Sulfur tetrafluoride fluorination of aliphatic nitro acids
Sulfur tetrafluoride converts aliphatic nitro acids to the corresponding trifluoromethyl compounds. The yield is poor with primary nitro acids; but high yields of fluoronitrocarbons, otherwise difficult to obtain, are produced from certain γ-substituted butyric acids and from substituted acrylic acids. Eleven new fluoronitrocarbons are described. 相似文献
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9-Borabicyclononane (9-BBN) has been utilized to protect functionalized amino acids for potential chemoselective side chain manipulation. The 9-BBN group imparts organic solubility to otherwise hydrophilic molecules and is tolerant of a wide range of reaction conditions. The high degree of solubility of these molecules in THF is particularly noteworthy. It is cleaved with either aqueous HCl or by exchange with ethylenediamine in methanol. [reaction: see text] 相似文献
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C. Kourkoumelis L. K. Resvanis T. A. Filippas E. Fokitis A. M. Chops S. Iwata R. B. Palmer D. C. Rahm P. Rehak I. Stumer C. W. Fabjan T. Fields D. Lissauer I. Mannelli P. Mouzourakis A. Nappi W. J. Willis 《Zeitschrift fur Physik C Particles and Fields》1980,5(2):95-104
The inclusive cross-section for π0 production near 90° inpp collisions at the CERN Intersecting Storage Rings has been studied for thep T range 3<p T <16GeV/c at four different centre-of-mass energies ( \(\sqrt s = 30.6\) , 44.8, 52.7, and 62.8 GeV). In this experiment the two photons from the π0→yy decay were resolved and measured separately forp T values up to 10 GeV/c. Results indicate an agreement with thep T ?8 behaviour for the lower values ofp T and a slower decrease of the cross-section for the higher values ofp T . The high-p T data deviate from the scaling expressionp T ?n F(x T ), which holds for the lowerp T values (p T <8GeV/c). 相似文献
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J.Michael Birchall Roy Fields Robert N. Haszeldine Reginald J. McLean 《Journal of fluorine chemistry》1980,15(6):487-495
Thermolysis of hexafluorocyclopropane in the presence of ethylene, propene, vinyl chloride, and vinyl bromide gives good yields of the corresponding 1,1-difluorocyclopropanes, formed by addition of difluorocarbene to the olefin. The tetrafluoroethylene formed dimerises to octafluorocyclobutane, co-dimerises with the olefin, or survives, depending on the reaction conditions. With allene, hexafluorocyclopropane gives 1-(difluoromethylene)cyclopropane, 2,2,3,3-tetrafluorospiropentane, and products derived from tetrafluoroethylene and allene. 相似文献