Addition Reactions of Alkenes

Part of Alkenes · Section 6 of 14

Deep DiveUnit: Organic ChemistryGCSE

This deep dive covers Addition Reactions of Alkenes within Alkenes for GCSE Chemistry. Revise Alkenes in Organic Chemistry for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 6 of 14 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.

⚗️ Addition Reactions of Alkenes

Alkenes undergo addition reactions — atoms ADD ACROSS the double bond, breaking it and forming two single bonds.

1. Addition of Hydrogen (Hydrogenation)

Ethene + Hydrogen → Ethane
C₂H₄ + H₂ → C₂H₆
Conditions: Ni catalyst, 150°C

2. Addition of Bromine (Bromination)

Ethene + Bromine → 1,2-dibromoethane
C₂H₄ + Br₂ → C₂H₄Br₂
Room temperature, no catalyst needed

3. Addition of Water (Hydration)

Ethene + Water → Ethanol
C₂H₄ + H₂O → C₂H₅OH
Conditions: Phosphoric acid catalyst, 300°C, 70 atm pressure
Key Pattern: In ALL addition reactions, the C=C double bond breaks and becomes a C-C single bond, with new atoms adding to each carbon.

Practice questions for Alkenes

What is the general formula for alkenes?

  • A. CnH2n+2
  • B. CnH2n-2
  • C. CnH2n
  • D. CnH4
1 markfoundation

Explain what is meant by the term 'unsaturated' when applied to alkenes.

2 marksstandard

Quick recall flashcards

How are alkenes produced?
By cracking long-chain alkanes from crude oil
What are alkenes?
Unsaturated hydrocarbons containing a C=C double bond

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