Describe three methods of preparing alcohols, with equations. Write the mechanism of the acid-catalysed hydration of ethene.

1. 1 · Name the three methods. Hydration of alkenes, reduction of carbonyl compounds and acids, and Grignard reagents with carbonyl compounds.
2. 2 · Hydration, with mechanism.
   • CH₂=CH₂ + H₃O⁺ → CH₃CH₂⁺ + H₂O (protonation)
   • CH₃CH₂⁺ + H₂O → CH₃CH₂O⁺H₂ (attack by water)
   • CH₃CH₂O⁺H₂ + H₂O → CH₃CH₂OH + H₃O⁺ (deprotonation)
3. 3 · Hydroboration-oxidation. Propene + B₂H₆, then H₂O₂/NaOH → propan-1-ol.
4. 4 · Reduction. RCHO + H₂ (Pd) → RCH₂OH; RCOR' + H₂ → RCH(OH)R'; RCOOH + 4[H] → RCH₂OH + H₂O, using LiAlH₄.
5. 5 · Grignard route. CH₃COCH₃ + CH₃MgBr → (CH₃)₃COMgBr; (CH₃)₃COMgBr + H₂O → (CH₃)₃COH + Mg(OH)Br.
6. 6 · Link to real life. Propan-2-ol for sanitisers and injection swabs is made by hydrating propene.
7. 7 · Close in one line. So the method you choose decides whether you get a 1°, 2° or 3° alcohol.

Scoring tip: In the mechanism, put the + charge on the correct carbon and show H₃O⁺ given back at the end.