CIE A Level Chemistry复习笔记3.3.3 Elimination Reactions of Halogenoalkanes

Category: A-level课程, 教材笔记, 福利干货 Date: 2022年8月12日下午4:45

Halogenoalkanes: Elimination Reactions

In an elimination reaction, an organic molecule loses a small molecule
- In the case of halogenoalkanes this small molecule is a hydrogen halide (eg. HCl)
The halogenoalkanes are heated with ethanolic sodium hydroxide causing the C-X bond to break heterolytically, forming an X- ion and leaving an alkene as an organic product
- For example, bromoethane reacts with ethanolic sodium hydroxide when heated to form ethene

3.3-Halogen-Compounds-Elimination Hydrogen bromide is eliminated to form ethene

Exam Tip

The reaction conditions in a reaction are extremely important.If NaOH(ethanol) is used, an elimination reaction takes place to form an alkene from a halogenoalkane.If NaOH(aq) is used, a nucleophilic substitution reaction takes place to form an alcohol from a halogenoalkane.

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