有機化學/烯烴

烯烃为不饱和烃，其结构特征是分子中含有C=C双键，公式為C_nH_2n

反應

製備

製備烯烴有幾種不同方式。下面有的方式（像是威悌反應）我們這邊只簡短介紹，後面會更詳細的說明。

目前只需要知道這些是製備烯的方式就好。

鹵代烷（Haloalkanes）的脫鹵化氫（Dehydrohalogenation）

用脫鹵化氫的方式合成烯烴

威悌反應（Wittig Reaction）

威悌反應是醛酮類與三苯基磷鎓內鹽（威悌試劑）作用生成烯烴和三苯基氧膦的一類有機化學反應

透過威悌反應合成烯烴

馬爾科夫尼科夫規則（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.

取代和消除反應機制

消除反應（Elimination Reactions）

E1 vs E2

查依采夫規則（Zaitsev's Rule）

查依采夫规则，也稱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，主要生成物會是碳碳双键上取代基較多的烯烃（最穩定的烯烃）。

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。