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Beckmann rearrangement

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mahrooshabbasi1

The Beckmann rearrangement is an acid-catalyzed reaction where an oxime is converted to an amide. Specifically, the reaction involves the migration of an acyl group from carbon to nitrogen on the oxime. This rearrangement allows the conversion of ketones and aldehydes to amides. Common catalysts used include sulfuric acid, phosphorus pentachloride, and hydrochloric acid. The reaction proceeds through an oxonium ion intermediate.

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Beckmann Rearrangement PRESENTED BY: MAHROOSH ABBASI
Beckmann rearrangement
Rearrangement: When carbon skeleton of the molecule is rearranged to give a structural isomer of original molecule Migration of group from one to another atom either within same molecule or to another molecule definitions
Radical rearrangements Nucleophillic rearrangements Electrophillic rearrangements Types of rearrangements
Beckmann rearrangement: History: Ernst Beckmann Definition: “The acid catalyzed conversion of Oximes to N-substituted Amides is called Beckmann rearrangement’’
General reaction: Ketone Oxime Amides
Aldehyde Hydroxyl Amine Aldoxime Ketone Hydroxyl Amine Ketoxime
Aliphatic oximes Aliphatic Amides Cyclic oximes Cyclic amides
Reactant and Product: Ph H N H N NOH NOH NOH H N O O O Ph
H2SO4 PCl5 HClH3PO 4 SiO2 Catalysts
How to form Oxime:
Stereoselect -ive Concerted Group ANTI to l.g migrates Retention of configurati on of M.G Stereochemistry:
Migratory aptitude: H Ph 3˚C 2˚C 1˚C ≫ > > >
Mechanism with Acid: +H + + H2O _R H2O H + H + ←← Oxime Oxonium ion + + N-Subs Amides + + = → Tautomerize -
Mechanism with PCl5: -H –OPCl4 H2O
Chiral migrating group:
EWG with migrating group:
Applications Caprolactam Isoquinoline Paracetamol
Formation of NYLON: BaseH2SO4 Mechanism N-hydroxylamines Caprolactam Nylon
Formation of Isoquinoline:
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Beckmann rearrangement