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A Levels Chemistry (9701)•9701/12/O/N/22
Question 37 from 9701/12/O/N/22

Explanation

Nitrile hydrolysis to acid, then reduction to alcohol for esterification

Steps:

  • Hydrolyze propanenitrile (CH3CH2CN) with NaOH(aq) to propanoate salt, acidify to propanoic acid (X = CH3CH2COOH).
  • Reduce X with LiAlH4 to propan-1-ol (Y = CH3CH2CH2OH).
  • React Y with X under acidic conditions to form propyl propanoate (CH3CH2COOCH2CH2CH3).
  • Confirms three-step synthesis using only propanenitrile-derived compounds.

Why B is correct:

  • NaOH(aq) hydrolyzes nitriles to carboxylates (R-CN + 2H2O + OH- → R-COO- + NH3), and LiAlH4 reduces carboxylic acids to primary alcohols (RCOOH + 4[LiH] → RCH2OH + ...).

Why the others are wrong:

  • A: HCl(aq) hydrolyzes nitrile but conc. H2SO4 dehydrates amides, not reducing acid to alcohol.
  • C: Option incomplete, lacks valid reagents.
  • D: NaBH4 reduces aldehydes/ketones but not carboxylic acids or nitriles effectively.

Final answer: B

Topic: Organic synthesis

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