IGCSE · Practice questions · Naming organic compounds

Count, then name.

Six original Cambridge-style questions on naming organic compounds and structural isomers.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Stem, number, ending.

Stems: meth 1, eth 2, prop 3, but 4 (count the −COOH carbon too).
Endings: -ane, -ene, -ol, -oic acid.
Extended: esters are alcohol-yl acid-oate: ethyl ethanoate.
Extended: isomers = same molecular formula, different structural formula.

Recall

[4 marks]

Name: (a) CH₃CH₂CH₂CH₃; (b) CH₃CH=CH₂; (c) CH₃CH₂OH; (d) HCOOH.

(a) butane. ✓
(b) propene. ✓
(c) ethanol. ✓
(d) methanoic acid. ✓

Apply

[2 marks]

Draw the displayed formula of propanoic acid.

CH₃−CH₂− chain with all C−H bonds drawn (3 H on the first carbon, 2 H on the second). ✓
Third carbon has C=O and C−O−H: every carbon has four bonds. ✓

Apply

[2 marks]

Give the structural formula and name of the alcohol with four carbon atoms and the −OH group on the end carbon.

CH₃CH₂CH₂CH₂OH. ✓
Butan-1-ol. ✓

Apply

[2 marks]

(Extended) Name the ester formed from methanol and ethanoic acid and give its structural formula.

Methyl ethanoate (alcohol part methyl, acid part ethanoate). ✓
CH₃COOCH₃. ✓

Explain

[2 marks]

(Extended) Define structural isomers and give the names of two structural isomers with formula C₄H₁₀.

Compounds with the same molecular formula but different structural formulae. ✓
Butane and methylpropane. ✓

Analysis

[2 marks]

(Extended) A student says CH₃CH₂CH₂OH and CH₃CH(OH)CH₃ are the same compound because both are C₃H₈O. Explain why the student is wrong and name both compounds.

The −OH group is on a different carbon atom, so the structural formulae differ: they are structural isomers, not the same compound. ✓
Propan-1-ol and propan-2-ol. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.