Ethanol (C₂H₅OH) and 1-bromopropane (CH₃CH₂CH₂Br) are both organic compounds. Describe the key structural features that make each compound belong to its respective homologous series, and explain what type of chemical is produced when the bromine atom in 1-bromopropane is replaced by a hydroxyl group.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Ethanol is widely used as a solvent and in alcoholic drinks. 1-Bromopropane is a halogenoalkane used in industrial synthesis.
Model answer (5 marks)
Ethanol contains a hydroxyl (–OH) functional group.
The –OH group attached to a carbon chain makes ethanol an alcohol.
1‑Bromopropane has a bromine atom bonded to a carbon chain.
The presence of the halogen (bromine) bonded to the carbon chain makes 1‑bromopropane a halogenoalkane.
Replacing the bromine atom with a hydroxyl (–OH) group produces an alcohol (propan‑1‑ol).
The –OH group attached to a carbon chain makes ethanol an alcohol.
1‑Bromopropane has a bromine atom bonded to a carbon chain.
The presence of the halogen (bromine) bonded to the carbon chain makes 1‑bromopropane a halogenoalkane.
Replacing the bromine atom with a hydroxyl (–OH) group produces an alcohol (propan‑1‑ol).
Examiner tips
- Use the exact terms – ‘hydroxyl group’, ‘halogen atom’, ‘alcohol’, ‘halogenoalkane’.
- Show the structural feature first, then explain its significance.
- Remember the product is propan‑1‑ol, not just ‘an alcohol’.
- Keep the answer concise – one sentence per point.
Mark scheme (5 marks)
- Ethanol contains a hydroxyl (–OH) functional group
- The presence of the hydroxyl group makes ethanol an alcohol
- 1-Bromopropane contains a halogen atom (bromine) bonded to a carbon chain
- The presence of the halogen (bromine) bonded to the carbon chain makes 1-bromopropane a halogenoalkane
- Replacing the bromine atom with a hydroxyl (–OH) group produces an alcohol (propan-1-ol)
Key terms in this question
hydroxyl group · homologous series
Related
- All WJEC A-Level Chemistry (Wales) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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