Reactions with Alkenes

This topic is part of F322 AS OCR A Chemistry. There are five different reactions that you need to know involving the reaction with alkenes.

I have summarised all the reactions in this diagram/mind map I made below:

 

 

1. Reaction with halogens/ Halogen addition reactions

 

- Electrophilic Addition

- This is a test for unsaturation.

- The observation: decolourisation.

- Unsaturated hydrocarbons decolourise bromine water.

 

2. Reaction with a halogen halide

 

- e.g. HCl

- Electrophilic Addition

 

3. Reaction with Hydrogen / Hydrogenation

 

- A Nickel (Ni) Catalyst is used

- Requires High temperatures and pressures (About 150°C)

- Used in the manufacture of margarine from animal or vegetable fats and oils.

 

4. Reaction with water

 

- The water must be in gaseous state - H₂O (g) - Steam

- High Temperatures

- Catalyst: Phosphoric Acid (H₃PO₄)

- Product: An Alcohol

 

5. Addition Polymerisation

 

- Many monomers (unsaturated), bond together by the double bond.

- The double bond opens up and joins to other monomers to form ONE large molecule called a POLYMER.