查询词典 carbanions

Formylation and diformylation of dithieno [2,3-b:3',2'-d] thiophene were prepared by two methods. Firstly, aromatic carbanions were prepared by 1 Br/Li exchange of bromo dithieno[2,3-b:3',2'-d]thiophene with n-BuLi in THF at low temperature; 2 deprotonation of dithieno[2,3-b:3',2'-d]thiophene with LDA.

二噻吩并[2，3-b：3'，2'-d]噻吩单醛与双醛的制备首先通过两种方法产生芳基负离子：1溴代并三噻吩在四氢呋喃中与正丁基锂发生的溴锂交换；2用LDA对二噻吩并[2，3-b：3'，2'-d]噻吩去质子化作用。

How can we solve this problem? First, we must find a way to let the oxygen activated; secondly, let the H atom cleavage from the methyl, and turn to carbanions; finally, the activated dioxygen react with carbanions, so the problem of oxidizate nitrotoluene is sloved in the end.

因此，在较温和的条件下高选择性氧化硝基甲苯制备硝基苯甲酸是一个具有重要理论意义和实用价值的研究课题。

Can induce the reaction of cleavage H atom from methyl on the ring of deactivated toluenes,such as nitrotoluene. The carbanions caused by base are the very important reaction intermediums, which determined the reaction rate and reaction effect.

该反应体系中，NaOH的加入对此催化反应起着相当关键的作用，研究表明强碱也能像温度一样促进苯环卜甲基的摘氢速度，使底物形成相应的硝基苯甲基阴离子，稳定的硝基苯甲基阴离子是氧化反应进行的重要中间体。

An important condition for enhancing the reaction in this mechanism is the presence of H2S and the formation of carbenium ions or carbanions.

一个重要条件，为提高反应在这一机制是存在的硫化氢和形成的碳离子或离子carbanions 。

The effects of the a-positively charged groups on thethermodynamic stabilities of sixteen Ylide carbanions and the corresponding Ylide-l...

根据这些PKa和BDE数据，对16个Ylide前体化合物的C－H键的均裂能和异裂能进行了比较，并讨论了a-杂正离子取代基对相关的Ylide和类-Ylide自由基的热力学稳定性的影响及结构效应

Product studies combined with ESR and IR detns. strongly support that the reactions involve an initial electron-transfer step from carbanions to BPO.

用ESR和IR研究的结果表明反应包含一个从碳阴离子到BPO的电子转移过程。

Under alkaline catalyst , active methylene compounds were changed into carbanions, the carbanions make nucleophilic reagent to take place many chemical reaction.

它在碱的作用下，生成碳负离子，碳负离子作为亲核试剂，可以发生一系列化学反应，最典型的例子是与卤代烃发生亲核取代反应。

These novel reagents were treated with base to produce polystyrene-supported a-seleno carbanions, which reacted with alkyl halides, followed by stereospecific selenoxide syn-elimination to give 2i-vinylphosphonates and is-vinylsulfones respectively.

它们在碱的作用下形成α—硒基碳负离子，然后与卤代烃发生烷基化反应，烷基化后的树脂可以通过温和条件下的氧化消除以良好产率和较高纯度分别合成了烯基磷酸酯和烯基砜。

This novel reagent was treated with LDA to produce polystyrene-supported a-seleno carbanions, which reacted with alkyl halides and epoxides, followed by stereospecific selenoxide syn-elimination to give olefins and allylic alcohols respectively.

它与LDA反应形成α—硒基稳定的碳负离子，再与卤代烃或环氧化合物发生α—烷基化反应，烷基化后的树脂可以在30%的双氧水中进行氧化-消除，以良好产率和较高纯度合成了取代烯烃或烯丙基醇。

But we don't care about Battlegrounds.

但我们并不在乎沙场中的显露。

Ah! don't mention it, the butcher's shop is a horror.

啊！不用提了。提到肉，真是糟透了。