Nucleophilic addition-elimination

• When does nucleophilic addition-elimination occur?


  Reactions with acyl chlorides/ acid anhydrides
• What happens during nucleophilic addition-elimination?


  Nucleophile attacks and joins onto positive carbon. Part of the organic molecule leaves.
• Why does nucleophilic addition-elimination occur?


  Carbon on carbonyl group is positive as oxygen is more electronegative.
• What are the nucleophiles?


  Ammonia, amine, water, alcohol.
• Nucleophilic addition-elimination general mechanism?

  
• Why is acid anhydride better than acyl chloride?


  It is cheaper, less corrosive, doesn't produce toxic HCl fumes and reacts less vigorously with water.
• What does HCl produce?


  Misty white fumes.