Name reaction · mechanism

Baeyer–Villiger Oxidation

The Baeyer–Villiger oxidation inserts an oxygen atom between a carbonyl carbon and one of its neighbours, turning ketones into esters and cyclic ketones into lactones. A peroxyacid adds to the carbonyl to give the Criegee intermediate; the group best able to carry positive charge migrates to oxygen as a carboxylate leaves.

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Baeyer–Villiger Oxidation mechanism: Peracetic acid adds to acetophenone (Criegee intermediate); the phenyl group, the better migrating group, moves to oxygen to give phenyl acetate.
Baeyer–Villiger oxidation: overall reaction, every curly-arrow step and key points. Click to open and edit it in MolDraw.

Overall reaction

Acetophenone + CH₃CO₃H (or mCPBA) → phenyl acetate

A peroxyacid inserts an oxygen next to the carbonyl: ketone → ester.

Mechanism step by step

  1. Addition. The peroxyacid OH attacks the carbonyl carbon
  2. Proton transfer. The Criegee intermediate
  3. Migration (slow). Phenyl moves to O as acetate leaves
  4. Deprotonation. Acetate takes the proton

Each step is checked electron by electron: the curly arrows give exactly the structures drawn.

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Key points

  • Migratory aptitude: tertiary alkyl > secondary alkyl ≈ phenyl > primary alkyl > methyl.
  • The migrating group keeps its configuration.
  • Cyclic ketones give lactones (cyclohexanone → ε-caprolactone).
  • Aldehydes give carboxylic acids (H migrates).

For JEE and NEET

  • Migratory aptitude: 3° alkyl > 2° alkyl ≈ phenyl > 1° alkyl > methyl (H high for aldehydes).
  • Acetophenone gives phenyl acetate (phenyl migrates, not methyl).
  • Cyclohexanone gives ε-caprolactone.
  • The migrating carbon keeps its configuration.

FAQ

Which group migrates in the Baeyer–Villiger oxidation?

The group best able to stabilise positive charge in the transition state: tertiary > secondary ≈ aryl > primary > methyl.

What is the Criegee intermediate?

The tetrahedral adduct of the peroxyacid and the ketone, R₂C(OH)–O–O–C(O)R′.

What does an aldehyde give?

Usually the carboxylic acid (H migrates); some electron-rich aryl aldehydes give formate esters (Dakin-type).

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