1-bromopropane can react with ethanolic potassium hydroxide to produce an alkene. Explain what happens during this reaction, including the type of reaction, the bonds broken and formed, and the name of the organic product.

WJEC A-Level Chemistry (Wales) — 2.6 Halogenoalkanes · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

The reaction is an elimination (E2) reaction.
1. The C–Br bond of 1‑bromopropane is broken.
2. A C–H bond on an adjacent carbon is also broken.
3. A C=C double bond is formed.
4. The organic product is propene.

Examiner tips

  • Use the term "elimination (E2) reaction" to show understanding of the mechanism.
  • Mention both bonds broken and the bond formed explicitly.
  • State the product name (propene) clearly.
  • Keep the answer concise and use correct UK spelling.

Common mistakes

  • Calling the reaction a substitution instead of elimination.
  • Omitting the breaking of the C–H bond.
  • Giving the wrong product name such as propyl chloride or propanol.

Mark scheme (5 marks)

  1. The reaction is an elimination reaction
  2. The C–Br bond is broken
  3. A C–H bond is also broken
  4. A C=C double bond is formed
  5. The organic product is propene

Key terms in this question

alkene

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