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A2 · Practice questions · A Level organic reactions

Label every reaction.

Six original Cambridge-style questions on A Level organic reaction types.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

What attacks, what is lost.

01
Recall
[4 marks]

State the type of reaction: (a) benzene with Br2 and FeBr3; (b) ethanoyl chloride with ethanol; (c) ethanamide heated with NaOH(aq); (d) nitrobenzene with Sn and concentrated HCl.

  • (a) electrophilic substitution. ✓
  • (b) addition-elimination (also a condensation, as HCl is lost). ✓
  • (c) hydrolysis. ✓
  • (d) reduction. ✓
02
Calculation
[3 marks]

15.6 g of benzene is nitrated and 18.45 g of nitrobenzene is collected. Calculate the percentage yield.

  • n(benzene) = 15.6 ÷ 78.0 = 0.200 mol. ✓
  • Maximum nitrobenzene = 0.200 × 123.0 = 24.6 g. ✓
  • Yield = 18.45 ÷ 24.6 × 100 = 75.0%. ✓
03
Explain
[3 marks]

Explain the meaning of the term addition-elimination, using the reaction of ethanoyl chloride with water.

  • A lone pair on the water O attacks the δ+ carbon of C=O: addition. ✓
  • The C=O reforms and Cl− leaves, then H+ is lost: elimination. ✓
  • Overall CH3COCl + H2O → CH3COOH + HCl. ✓
04
Recall
[2 marks]

Write a balanced equation using [O] for the oxidation of methylbenzene to benzoic acid.

  • C6H5CH3 + 3[O] → C6H5COOH + H2O. ✓
  • Reagent: hot alkaline KMnO4, then acidify. ✓
05
Calculation
[2 marks]

Calculate the atom economy for making N-ethylethanamide (Mr 87.0) from ethanoyl chloride (78.5) and ethylamine (45.0).

  • Total mass of reactants = 78.5 + 45.0 = 123.5. ✓
  • Atom economy = 87.0 ÷ 123.5 × 100 = 70.4%. ✓
06
Explain
[2 marks]

Explain the difference between a condensation reaction and a hydrolysis reaction.

  • Condensation: two molecules join together and a small molecule (H2O or HCl) is released. ✓
  • Hydrolysis: a bond is broken by reaction with water, so water is a reactant; it is the reverse of condensation. ✓

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