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Beckmann Rearrangement

Definition: What is Beckmann Rearrangement?

Beckmann rearrangement is an acid-catalyzed reaction of ketoximes into amides. The yield of this reaction increases at elevated temperatures. The reaction is named after German pharmacist and chemist Ernst Otto Beckmann [1-2].

Beckmann Rearrangement

Examples of Beckmann Rearrangement

Beckmann rearrangement is used in the conversions of benzophenone oxime to benzanilide and cyclohexanone oxime to caprolactam [3].

Beckmann Rearrangement Benzophenone Oxime
Beckmann Rearrangement Cyclohexanone Oxime

Mechanism of Beckmann Rearrangement

The mechanism of the Beckmann rearrangement follows the same pattern as a pinacol reaction. The acid converts the oxime OH into a leaving group, and an alkyl group migrates on to the nitrogen as water departs. The product cation is then trapped by water to give an amide [4-8].

Beckmann Rearrangement Mechanism

Applications of Beckmann Rearrangement

  • In the synthesis of caprolactam, which is used in the production of nylon 6
  • For the synthesis of paracetamol by converting a ketone to a ketoxime with the help of hydroxylamine
  • In the synthesis of various steroids and drugs
  • In the production of some of the chloro bicyclic lactams

References

  1. Definition and example – Chem.libretexts.org
  2. Definition – Researchgate.net
  3. Example – Pubs.acs.org
  4. Mechanism – Adichemistry.com
  5. Mechanism – Chemtube3d.com
  6. Mechanism – Synarchive.com
  7. Mechanism – Name-reaction.com
  8. Mechanism – Nature.com

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