有机化学/烯烃

烯烃为不饱和烃，其结构特征是分子中含有C=C双键，公式为C_nH_2n

烯类命名

特性

反应

制备

制备烯烃有几种不同方式。下面有的方式（像是威悌反应）我们这边只简短介绍，后面会更详细的说明。

目前只需要知道这些是制备烯的方式就好。

卤代烷（Haloalkanes）的脱卤化氢（Dehydrohalogenation）

用脱卤化氢的方式合成烯烃

威悌反应（Wittig Reaction）

威悌反应是醛酮类与三苯基磷𬭩内盐（威悌试剂）作用生成烯烃和三苯基氧膦的一类有机化学反应

透过威悌反应合成烯烃

马尔科夫尼科夫规则（Markovnikov's Rule）

Before we continue discussing reactions, we need to take a detour and discuss a subject that's very important in Alkene reactions, "Markovnikov's Rule." This is a simple rule stated by the Russian Vladmir Markovnikov in 1869, as he was showing the orientation of addition of HBr to alkenes.

His rule states:"When an unsymmetrical alkene reacts with a hydrogen halide to give an alkyl halide, the hydrogen adds to the carbon of the alkene that has the greater number of hydrogen substituents, and the halogen to the carbon of the alkene with the fewer number of hydrogen substituents" (This rule is often compared to the phrase: "The rich get richer and the poor get poorer." Aka, the Carbon with the most Hydrogens gets another Hydrogen and the one with the least Hydrogens gets the halogen)

This means that the nucleophile of the electophile-nucleophile pair is bonded to the position most stable for a carbocation, or partial positive charge in the case of a transition state.

取代和消除反应机制

消除反应（Elimination Reactions）

E1 vs E2

查依采夫规则（Zaitsev's Rule）

查依采夫规则，也称作扎伊采夫规则或扎伊切夫规则，是指醇或卤代烃在进行消除反应时，主要生成物会是碳碳双键上取代基较多的烯烃（最稳定的烯烃）。

例如，2-丁醇进行消除反应时，主要生成物是2-丁烯，1-丁烯只是次要生成物。