Describe the rules used to name organic compounds from the homologous series of alkanes and alcohols, using examples to support your answer.

Cambridge International IGCSE Chemistry (0620) — 11.2 Naming organic compounds · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

The prefix (meth-, eth-, prop-, but-) shows the number of carbon atoms in the longest chain. The suffix -ane is used for alkanes, indicating only single C–C bonds. The suffix -ol is used for alcohols, indicating the presence of an –OH group. For example, propane is a three‑carbon alkane, and propanol is the corresponding alcohol with the same carbon chain length.

Examiner tips

  • Use the correct prefix for the chain length
  • Add -ane for alkanes and -ol for alcohols
  • Give a matching pair of examples
  • Keep the answer concise

Common mistakes

  • Using the wrong suffix (e.g. -ene for alkanes)
  • Mixing up the order of prefix and suffix
  • Failing to give both an alkane and its alcohol example

Mark scheme (4 marks)

  1. The prefix (meth-, eth-, prop-, but-) indicates the number of carbon atoms in the longest carbon chain
  2. The suffix -ane indicates the compound is an alkane (single / no carbon–carbon double bonds)
  3. The suffix -ol indicates the compound is an alcohol / contains an –OH (hydroxyl) group
  4. Correct named example of an alkane AND a corresponding alcohol with the same carbon chain length, e.g. propane / propanol or ethane / ethanol

Key terms in this question

homologous series · alkane · alcohol

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