11.2 Naming Organic Compounds

2026 Syllabus Objectives

  1. Core: Name and draw the displayed formulae of:

    • (a) methane and ethane
    • (b) ethene
    • (c) ethanol
    • (d) ethanoic acid
    • (e) the products of the reactions stated in sections 11.4–11.7
  2. Core: State the type of compound present, given a chemical name ending in -ane, -ene, -ol, or -oic acid or from a molecular formula or displayed formula

  3. Supplement: Name and draw the structural and displayed formulae of unbranched:

    • (a) alkanes
    • (b) alkenes, including but-1-ene and but-2-ene
    • (c) alcohols, including propan-1-ol, propan-2-ol, butan-1-ol and butan-2-ol
    • (d) carboxylic acids containing up to four carbon atoms per molecule
  4. Supplement: Name and draw the displayed formulae of the unbranched esters which can be made from unbranched alcohols and carboxylic acids, each containing up to four carbon atoms


Understanding Organic Nomenclature 🔑

The systematic naming of organic compounds follows specific rules based on the number of carbon atoms and the functional group present. This systematic approach allows chemists worldwide to understand the structure of a compound from its name alone.

Carbon Chain Prefixes

The prefixes in organic compound names indicate the number of carbon atoms in the main carbon chain:

Number of Carbon AtomsPrefix
1meth-
2eth-
3prop-
4but-

Important: These prefixes are universal across all homologous series. Any compound with two carbon atoms will have a name beginning with "eth-", regardless of whether it's an alkane, alkene, alcohol, or carboxylic acid.

Homologous Series Endings

Different homologous series have characteristic endings (suffixes) that identify the functional group:

Homologous SeriesSuffixFunctional Group
Alkanes-aneNone (saturated hydrocarbons)
Alkenes-eneC=C\text{C}=\text{C} (carbon-carbon double bond)
Alcohols-olOH-\text{OH} (hydroxyl group)
Carboxylic acids-oic acidCOOH-\text{COOH} (carboxyl group)

Key Term: A homologous series is a family of organic compounds that have the same functional group and similar chemical properties.

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