weirdfacts
Year 12 / IUPAC names and branching

Give every carbon an address.

Find the longest appropriate chain containing the principal functional group or multiple bond. Number it to give that feature its lowest permitted locant, then place and name substituents. Common roots run meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non-, dec-.

CH₃CH(OH)CH₂CH₃ is butan-2-ol. CH₃COCH₂CH₃ is butan-2-one. A terminal –CHO gives an aldehyde name ending -al. For esters, name the alcohol-derived alkyl group first, followed by the acid-derived alkanoate.

Primary, secondary and tertiary describe how many other carbon atoms attach to the carbon bearing OH or the halogen. They do not describe the total number of carbon atoms in the molecule.

INTERACTIVE MODEL

Spot the functional group

CH₃CH₂OHEthanol
Hydroxyl → alcohol · C₂H₆O

Condensed structural diagrams. Bonds show connectivity, not measured bond angles. Compare the molecular formula with the arrangement of atoms.

CH₃COOCH₂CH₃ → ethyl ethanoate
Assumed knowledge

A displayed or condensed structure can be traced carbon by carbon.

Learning checkpoints & sourceYOUR SYLLABUS CHECKPOINT
  • Name chains up to ten carbons with simple branches.
  • Assign functional-group and substituent positions.
  • Classify alcohol and haloalkane carbons.
QCAA Chemistry 2025 v1.3 · p. 39
READY TO TRY IT?

Turn the idea into an answer.

Loading progress…