Nucleophilic addition

• When does nucleophilic addition occur?


  When a ketone or aldehyde reacts.
• What happens in nucleophilic addition?


  Nucleophile joins onto carbonyl group
• Why does nucleophilic addition occur?


  As the carbon on the carbonyl group is positive as the oxygen is more electronegative.
• Reduction to form alcohols?


  Reagent: NaBH4

  
• Producing hydroxynitriles?


  Reagents: KCN and dilute acid in water.

  
• Risk assessment of using KCN?


  It is toxic and produces HCN so do in fume cupboard.

  Organic products are flammable so heat in water bath.
• Why is KCN used over HCN?


  As HCN is a weaker acid so only partially dissociates into a low amount of CN- ions.
• How does nucleophilic addition reactions produce a racemate?


  CN- can attack planar C=O bond equally on either side, producing a racemate.