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Cambridge IGCSE Chemistry · 0620

Chapter 11: Organic Chemistry — Part 2

Topic 11.2 · Naming organic compounds

Naming Rules

The name of an organic compound is determined by the number of carbon atoms (prefix) and the functional group present (suffix).

No. of Carbons Prefix Alkane Name
1 meth- Methane
2 eth- Ethane
3 prop- Propane
4 but- Butane
5 pent- Pentane
6 hex- Hexane
7 hept- Heptane
8 oct- Octane

Identifying Functional Groups by Name

  • -ane: Indicates an alkane (e.g., ethane).
  • -ene: Indicates an alkene (e.g., ethene). Numbers are used to show the position of the double bond (e.g., but-1-ene).
  • -ol: Indicates an alcohol (e.g., ethanol). Numbers show the position of the hydroxyl group (e.g., propan-1-ol).
  • -oic acid: Indicates a carboxylic acid (e.g., ethanoic acid). The -COOH group is always at the end.
  • -oate: Indicates an ester (e.g., methyl ethanoate).

Exam Traps

  • Do not use −ane for alkenes or −ene for alkanes — the suffix must match the functional group present.
  • Do not place −COOH in the middle of a name — carboxylic acids always have the carboxyl group at carbon 1.

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