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硼氢化反应作为烯烃的主要化学性质之一在国内外有机化学教科书中均有论述,但对反应机理的描述却众说纷纭,概括起来有如下几种观点: 观点一认为硼氢反应经历了一个正碳离子过程,如下所示: 硼烷作亲电试剂进攻双键含氢较多碳,双键另一碳变成正离子,硼烷上的一个氢异裂下来与正碳离子结合,形成顺式加成产物. 观点二认为反应历程不经过形成正碳离子中间体这一步,硼烷中的硼极化带正电荷,硼与氢加在双键的同一边,各碳原子上原子或取代基仍保持原来的相对位置,整个分子的几何形状不发生改变,保持原来构型
As one of the main chemical properties of olefins, the hydroboration of hydroboration has been discussed in the textbooks of organic chemistry both at home and abroad. However, there are many different opinions on the reaction mechanism. To sum up, there are several opinions as follows: Ion process, as follows: Borane as electrophilic reagent attack Double bond hydrogen more carbon, double bond another carbon becomes positive ion borane hydrogens on the crack with a combination of carbon ions to form cis Addition product point of view two view that the reaction does not go through the process of forming a positive carbon ion intermediates, boron borane polarization with a positive charge, boron and hydrogen added on the same side of the double bond, atoms or substituents on each carbon atom Still maintain the original relative position, the entire molecular geometry does not change, maintain the original configuration