Sunday 30 June 2013

Beckmann rearrangement




The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is an acid-catalyzed rearrangement of an oxime to an amide. Cyclic oximes yield lactams.
The Beckmann Rearrangement

 
This example reaction starting with cyclohexanone, forming the reaction intermediate cyclohexanone oxime and resulting in caprolactam is one of the most important applications of the Beckmann rearrangement, as caprolactam is the feedstock in the production of Nylon 6.
The Beckmann solution consists of acetic acid, hydrochloric acid and acetic anhydride, and was widely used to catalyze the rearrangement. Other acids, such as sulfuric acid or polyphosphoric acid, can also be used. sulfuric acid is the most commonly used acid for commercial lactam production due to its formation of an ammonium sulfate by-product when neutralized with ammonia. Ammonium sulfate is a common agricultural fertilizer providing nitrogen and sulfur.

The Beckmann rearrangement is an organic reaction used to convert an oxime to an amide under acidic conditions. The reaction begins by protonation of the alcohol group forming a better leaving group. The R group trans to the leaving group then migrates to the nitrogen, resulting in a carbocation and the release of a water molecule. This trans [1-2]-shift allows for the prediction of the regiochemistry of this reaction. The water molecule then attacks the carbocation and after deprotonation and tautomerization results in the final amide product.





Beckmann rearrangement mechanism



lactam, a monomer for the production of Nylon 12.



Beckmann reaction

SEE BELOW ILLUSTRATION IN

http://www.mdpi.com/1420-3049/17/11/13662

 Upon treatment with phenyl dichlorophosphate (PhOP=OCl2) in acetonitrile at ambient temperature, a variety of ketoximes underwent a Beckmann rearrangement in an effective manner to afford the corresponding amides in moderate to high yields.

Saturday 22 June 2013

1,3 cyclohexane dione

1,3 cyclohexane dione
some reactions you may like?????????????
 
synthesis and reactions
 insert a methyl group
 
 

Saturday 15 June 2013

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