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Preparation of aldehydes and ketones sheet
5-mark answer frame

Write one equation each, with reagents and conditions, to prepare: (i) an aldehyde from an acyl chloride (ii) an aldehyde from a nitrile (iii) benzaldehyde from toluene (iv) benzaldehyde from benzene (v) a ketone from benzene.

How to lay out the answer. Follow the frame, then write it in your own words.

  1. 1 · Rosenmund reduction. C₆H₅COCl + H₂ → (Pd-BaSO₄) C₆H₅CHO + HCl.
  2. 2 · Stephen reaction. RCN → (SnCl₂ + HCl) RCH=NH → (H₃O⁺) RCHO.
  3. 3 · Etard reaction. C₆H₅CH₃ → (CrO₂Cl₂ in CS₂) chromium complex → (H₃O⁺) C₆H₅CHO.
  4. 4 · Gattermann-Koch reaction. C₆H₆ + CO → (HCl, anhydrous AlCl₃ or CuCl) C₆H₅CHO.
  5. 5 · Friedel-Crafts acylation. C₆H₆ + CH₃COCl → (anhydrous AlCl₃) C₆H₅COCH₃ + HCl.
  6. 6 · Link to real life. Benzaldehyde, the flavour of bitter almonds, is made in industry from toluene.
  7. 7 · Close in one line. So each named reaction is fixed by its starting compound and its reagent.

Scoring tip: Write the reagent above the arrow and the condition (catalyst, solvent, hydrolysis step) below it. A missing reagent costs the mark even if the product is right.