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hofmann elimination
相关语句
  hofmann消除反应
     An improved method for preparing quaternary ammonium salt using p-methyl-benzyl chloride and trimethylamine and preparing [2,2]-paracyclophane by Hofmann elimination was developed. The influences of solvent,reaction time,reaction temperature,etc. ,on the yield and purification of two products were investigated.
     用对甲基氯苄和三甲胺合成季铵盐及利用Hofmann消除反应制备了[2,2] 对二甲苯环二体,讨论了溶剂、反应时间、反应温度等工艺条件对两步反应物产率、纯度的影响,确定了适宜的合成工艺条件,制备季铵盐的最佳条件为:n(对甲基氯苄)∶n(三甲胺)=1∶1 1,乙醇为溶剂,反应时间2h,反应温度45℃。
短句来源
     In the previous work,a conformational rule was proposed for Hofmann elimination of quaternary ammonium hydroxides.
     本文合成了12种含环戊基或环己基的第四级铵碱,使之发生Hofmann消除反应
短句来源
  霍夫曼消除反应
     A synthetic method for the preparation of [2,2]-paracyclophane by hofmann elimination was proposed.
     研究了季铵盐经霍夫曼消除反应制备[2,2]-对二甲苯环二体的合成方法。
短句来源
  “hofmann elimination”译为未确定词的双语例句
     A Study of the Thermal Elimination of Quaternary Ammonium Hydroxides——On the Conformation Rule for Hofmann Elimination
     第四级铵氢氧化物的Hofmann消除反应的研究——关于Hofmann消除反应的构象规则
短句来源
     THE CONFORMATIONAL ANALYSIS AND REACTION MECHANISM FOR HOFMANN ELIMINATION OF QUATERNARY AMMONIUM HYDROXIDES
     第四级铵氢氧化物Hofmann消除反应的构象分析及反应机理
短句来源
     Studies of the Thermal Elimination of Quaternary Ammonium Hydroxides Ⅱ On the Conformational Rule for Hofmann Elimination
     第四级铵碱Hofmann消除反应的研究Ⅱ.——关于Hofmann消除反应的构象规则
短句来源
     Studies on the Thermal Elimination of Quaternary Ammonium Hydroxides Ⅲ On the Conformational Rule for Hofmann Elimination
     第四级铵碱Hofmann消除反应的研究Ⅲ关于Hofmann消除反应的构象规则
短句来源
     The ring enlargement of N-heterocycles might be performed if the N-ylide intermediates can be generated. In compounds containing a β -hydrogen atom, Hofmann elimination may compete and in many cases provides the major product. It is difficult to Perform ring enlargement of N-heterocycles containing a β -hydrogen atom.
     N-杂环季胺盐的反应的意图是通过生成N-ylide从而导致扩环,一般而言如果季胺盐有β氢存在,进行Hofmann降解反应,对于具有β氢的饱和氮杂环化合物,直接通过氮原子来改造环的大小是较为困难的。
短句来源
更多       
  相似匹配句对
     HARMONICS AND ELIMINATION
     谐波与抑制
短句来源
     Fluorosis and its Elimination
     氟中毒及其治理
短句来源
     THE CONFORMATIONAL ANALYSIS AND REACTION MECHANISM FOR HOFMANN ELIMINATION OF QUATERNARY AMMONIUM HYDROXIDES
     第四级铵氢氧化物Hofmann消除反应的构象分析及反应机理
短句来源
     A synthetic method for the preparation of [2,2]-paracyclophane by hofmann elimination was proposed.
     研究了季铵盐经霍夫曼消除反应制备[2,2]-对二甲苯环二体的合成方法。
短句来源
     Hofmann Rearrangement in Pazufloxacin Synthesis
     帕珠沙星合成中的Hofmann重排反应
短句来源
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  hofmann elimination
(a) Acrylate derived base-labile linker yielded α-aminonitriles with N-alkylated piperazines via Hofmann elimination after quarternisation with an alkyl halide.
      
This behavior, is well known and characteristic of the Hofmann elimination reaction.
      
Trans-2-aryl-3-hydroxymethyl-1-methylpyrrolidines suffer an unusual Hofmann elimination when treated withp-toluensulfonyl chloride in basic medium at room temperature.
      
The Hofmann elimination pathway accounts for 77% of total body clearance of cisatracurium.
      
Organ-independent Hofmann elimination appears to be the predominant pathway for the elimination of cisatracurium besylate.
      


It is known that there are many examples of the thermal elimination of quaternary ammonium hydroxides which do not follow the Hofmann rule. Ye Xiulin et al. proposed the "conformation rule" for the elimination of quaternary ammonium hydroxides, and then, eight quaternary ammonium hydroxides were synthesised and subjected to the elimination. The results show that the conformational rule is superior and acceptable.DPCILO and CNDO/2 methods were used to calculate the conformational energy...

It is known that there are many examples of the thermal elimination of quaternary ammonium hydroxides which do not follow the Hofmann rule. Ye Xiulin et al. proposed the "conformation rule" for the elimination of quaternary ammonium hydroxides, and then, eight quaternary ammonium hydroxides were synthesised and subjected to the elimination. The results show that the conformational rule is superior and acceptable.DPCILO and CNDO/2 methods were used to calculate the conformational energy of some quaternary ammonium cations with different conformations and the distribution of charge for studying the mechanism of Hofmann elimination reaction.The results show that the conformational rule, based on the conformational energy, can be used to explain the Hofmann elimination reaction well, but the elimination of straight chain alkyl groups other than the ethylic groups should follow cis-E2 elimination mechanism instead of trans-E2 one proposed by Ye Xiulin.

本文用DPCILO,CNDO程序分别计算了一些第四级铵离子不同构象的能量及电荷密度,探讨Hofmann消除反应的机理,结果表明构象规则能较好地说明Hofmann消除反应的机理,只是“直链型”烷基的消除反应应按顺式E2机理进行。

Seven quaternary ammonium hydroxides iso-Hex-NMe2-R OH-, in which the R group equals to Et, n-Pr, iso-Pr, n-Bu, iso-Bu, sec-Bu and iso-Am respectively, were prepared and subjected to Hofmann Elimination. It can be seen from Table Ⅱ that:(1) Et, n-Pr, iso-Pr, sec-Bu and n-Bu are the alkyl groups eliminated easier than iso-Hex group, while iso-Bu and iso-Am are the alkyl groups eliminated more difficult than iso-Hex group. This result means that iso-Hex group can be put in the Reactivity Sequence for Alkyl...

Seven quaternary ammonium hydroxides iso-Hex-NMe2-R OH-, in which the R group equals to Et, n-Pr, iso-Pr, n-Bu, iso-Bu, sec-Bu and iso-Am respectively, were prepared and subjected to Hofmann Elimination. It can be seen from Table Ⅱ that:(1) Et, n-Pr, iso-Pr, sec-Bu and n-Bu are the alkyl groups eliminated easier than iso-Hex group, while iso-Bu and iso-Am are the alkyl groups eliminated more difficult than iso-Hex group. This result means that iso-Hex group can be put in the Reactivity Sequence for Alkyl Groups proposed for the Conformational Rule and can be considered as "a primary alkyl group with a remote side alkyl group".(2) The fact that iso-Hex group eliminated easier than iso-Am group implicates that the elimination of iso-Am and iso-Hex groups tends to the trans E2 mechanism rather than to the cis one, since it has been shown by calculation that via the trans, mechanism the energy of the needed conformation for iso-Hex group is lower than that for iso-Am group, while via the cis mechanism the situation is just opposite.

本文制备了七个各含有一个异己基的第四级铵碱,并使之发生Hofmann消除反应。目的是为了给异己基在Hofmann消除反应的构象规则消除易度序列中确定其位置,并探索异己基在该消除反应中的机理倾向。气相色谱分析的结果表明异己基比异戊基和异丁基容易消除,属于“含侧链较远的第一级烷基”,并且其反应过程倾向于反式E_2机理。

In the previous work,a conformational rule was proposed for Hofmann elimination of quaternary ammonium hydroxides.Thus,the different types of alkyl group were put in a sequence with decreasing reactivity of the alkyl groups eliminat-ed to olefins,but in this sequence no position was assigned for the eyclo-alkyl group such as cyclo-pentyl and cyclo-hexyl groups.For the purpose of remedy this shortage,twelve quaternary ammonium hydLox-ides,six cyclo-Hex-NMe_2-R OH ̄-and six cyclo-Pent-NMe_2-R OH ̄-,in which...

In the previous work,a conformational rule was proposed for Hofmann elimination of quaternary ammonium hydroxides.Thus,the different types of alkyl group were put in a sequence with decreasing reactivity of the alkyl groups eliminat-ed to olefins,but in this sequence no position was assigned for the eyclo-alkyl group such as cyclo-pentyl and cyclo-hexyl groups.For the purpose of remedy this shortage,twelve quaternary ammonium hydLox-ides,six cyclo-Hex-NMe_2-R OH ̄-and six cyclo-Pent-NMe_2-R OH ̄-,in which the two R groups both equal to iso-pr,tert-Bu,Sec-Bu,n-Bu,iso-Bu,and iso-Am groups respectively,were prepared and subjected to the thermal elimination. It could be seen from the data listed in Table Ⅱ that:(1) All the"ethylic groups"(iso-pr,tert-Bu,sec-Bu)and the n-alkyl group (n-Bu)were eliminated easier than cyclo-Hex and cyclo-Pent groups,while iso-Bu and iso-Am groups were eliminated more difficuIt than these cyclo-alkvl groups.Therefore,cyclo-Hex and cyclo-Pent groups could be acceptably put in thereactivity sequence as the"other socondary alkyl groups".( 2)From the alike pairs of the cyclo-Hex-NMe_2-R OH ̄- and cyclo-Pent-NMe_2-R OH ̄-(1 and 7,2and8,3and9,4 and10,5 and11,6and12),it could be seen thatall the pairs,with one exception(5 and 11),showed that in which cyclo-Pent groupwas eliminated easier than or comparable to cyclo-Hex group. Therefore,in mostcases cyclo-Pent group should occupy a position prior to cyclo-Hex group in the re-actlvity sequence.

本文合成了12种含环戊基或环己基的第四级铵碱,使之发生Hofmann消除反应。利用气相色谱法分析其产物,以检验构象规则对含脂环基的第四级铵碱消除反应的适应性,并确定了环戊基和环己基在Hofmann消除反应的构象规则中消除易度序列的位置。研究结果表明:含环戊基和环己基的第四级铵碱所发生的Hofmann消除反应能很好地符合构象规则。环戊基和环己基在该消除易度序列中属于"其它第二级烷基"一类;在大多数的例子中,环戊基比环己基容易消除。

 
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