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labile hydrogen
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  “labile hydrogen”译为未确定词的双语例句
     In the process, chloranil firstly was excited to singlet state and then a labile hydrogen abstraction interaction between singlet chloranil andβ-diketones was involved to form singlet stable neutral radical pairs (RP).
     光照作用下,四氯苯醌首先跃迁至单线态,然后夺取β二酮类化合物分子中的活泼氢,形成单线态中性自由基对。
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  相似匹配句对
     hydrogen britteness
     氢脆
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     METALLIC HYDROGEN
     金属氢
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     LABILE SPECIATION OF CADMIUM BY CAPILLARY ELECTROPHORESIS
     毛细管电泳用于镉易变形态分析
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     the heat-stable and the heat-labile antigens.
     同时还发现,有些菌株,耐热抗原相同,不耐热抗原不同;
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     Prgoress on Escherichia coli Heat Labile Enterotoxin
     大肠埃希菌不耐热肠毒素研究进展
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  labile hydrogen
Reactions of 5-cyano-1,4,6,9-trioxathia-5-phosphaspiro[4,4]nonanes with compounds containing a labile hydrogen atom
      
The reaction of nitriles, containing a labile hydrogen, with copper salts at 70-150? proceeds as an oxidation-reduction reaction of one-electron transfer from the nitrile to Cu2+.
      
Reactions of polyfluoronitroalkanes that contain a labile hydrogen atom
      
The salts of uracils react with the electrophilic phosphorus atom to give uracil phosphates, which function as phosphorylating agents toward compounds that contain a labile hydrogen atom.
      
The cleavage of the hydrogen proceeds selectively, and specifically from the methylene group that contains the most labile hydrogen atoms.
      
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The fragmentation mechanisms of a series of alkaloids isolated from Cephalotaxus, which is used for the treatment of some kinds of cancer, have been proposed based on the data of high resolution mass spectrometry. These compounds(1~9), according to their molecular skeleton, are divided into homoerythrina and cephalotaxine types.Three types of diagnostic ions are found in the spectra of homoerythrina series(compounds 1~3):(1) M-CH_3 is produced through hydrogen rearrangement and loss of C_4 in case of compounds...

The fragmentation mechanisms of a series of alkaloids isolated from Cephalotaxus, which is used for the treatment of some kinds of cancer, have been proposed based on the data of high resolution mass spectrometry. These compounds(1~9), according to their molecular skeleton, are divided into homoerythrina and cephalotaxine types.Three types of diagnostic ions are found in the spectra of homoerythrina series(compounds 1~3):(1) M-CH_3 is produced through hydrogen rearrangement and loss of C_4 in case of compounds possessing labile hydrogen at C_6(e. g., the rearranged molecular ion of 2). On the contrary, no M-15 is observed when a double bond is located between C_1 and C_6(compounds 1 and 3);(2)(RDA) and (RDA-H) ions resulting from the rupture of ring C(compounds 1 and 3); and(3) ion pairs of mass values 164,(M-164) and 151,(M-151) formed via ring B cleavage. These characteristic ions are useful in differentiating isomers with different substituents as well as positions of double bond in ring C.Compounds related to cephalotaxine undergo cleavage in a more complicated way, depending on the position of double bond in ring C, either via fission and recyclization of ring B and C(compounds 4~6), or through other pathways(compounds 7~9) giving rise to different key ions.The knowledge of mass spectral behaviors of these compounds will be helpful in structural elucidation of unknown alkaloids of these series.

本文用高分辨质谱法研究了由三尖杉属植物分得的高刺桐碱类和三尖杉碱类的质谱裂解规律.高刺桐类生物碱的质谱中有三类特征性离子:(1)(M-15)离子;(2)C环的(RDA)及(RDA-H)反应产生的离子;(3)B环裂解的产物离子.三尖杉碱类化合物则依C环上双键位置的不同,经不同的中间离子,再重排得相应的质谱峰.阐明这两类生物碱的质谱裂解规律,将有助于同类型未知生物碱的结构推断.

The ethy1-2-methyl-acetoacetate is prepared by methylation of ethylacetoacetate with Na and CH3I. The ethyl-O-acetyl-acetolactate is prepared by oxidation of the labile hydrogen of ethyl-2-methyl-acetoacetate with lead tetraacetate. a-Acetolactate is prepared by hydrolysis of ethyl-O-acethyl-acetolactate with NaOH.

由乙酰乙酸乙酯甲基化制奋α-甲基乙酰乙酸乙酯,用四乙酸铅氧化α-甲基乙酰乙酸乙酯生成α-乙酰氧基-α-甲基-乙酰乙酸乙酯,再经NaOH水解生成α-乙酰乳酸。

 
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