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].

Examples of Beckmann Rearrangement

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

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].

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