can u plz tell me what is beckmann reaction and curtius reaarangement?

can u plz tell me what is beckmann reaction and curtius reaarangement?


1 Answers

bhanuveer danduboyina
95 Points
12 years ago

Beckmann Rearrangement

An acid-induced rearrangement of oximes to give amides.

This reaction is related to the Hofmann and Schmidt Reactions and the Curtius Rearrangement, in that an electropositive nitrogen is formed that initiates an alkyl migration.

Mechanism of the Beckmann Rearrangement

Oximes generally have a high barrier to inversion, and accordingly this reaction is envisioned to proceed by protonation of the oxime hydroxyl, followed by migration of the alkyl substituent "trans" to nitrogen. The N-O bond is simultaneously cleaved with the expulsion of water, so that formation of a free nitrene is avoided.

Curtius Rearrangement

The Curtius Rearrangement is the thermal decomposition of carboxylic azides to produce an isocyanate. These intermediates may be isolated, or their corresponding reaction or hydrolysis products may be obtained.

The reaction sequence - including subsequent reaction with water which leads to amines - is named the Curtius Reaction. This reaction is similar to the Schmidt Reaction with acids, differing in that the acyl azide in the present case is prepared from the acyl halide and an azide salt.

Mechanism of the Curtius Rearrangement

Preparation of azides:


Reaction with water to the unstable carbamic acid derivative which will undergo spontaneous decarboxylation:

Isocyanates are versatile starting materials:

Isocyanates are also of high interest as monomers for polymerization work and in the derivatisation of biomacromolecules.



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