HOFFMANN ELIMINATION REACTION

When a primary amine bearing one or more beta 

hydrogens is treated with methyl iodide, followed by 

aqueous silver oxide, followed by heat, the primary amine is

converted to an alkene.  This reaction is known as Hofmann

 elimination.

Elimination reactions of 4º-ammonium salts are termed Hofmann eliminations.Bimolecular Elimination of Quaternary Ammonium Ions is hofmann

elimination reaction .(E2)

 Since the counter anion in most 4º-ammonium salts is 

halide, this is often replaced by the more basic hydroxide ion

 through reaction with silver hydroxide (or silver oxide).

 The resulting hydroxide salt must then be heated (100 - 200

 ºC) to effect the E2-like elimination of a 3º-amine.

In an elimination reaction ,acidic hydrogen and the leaving group are at beta and alpha position.

The loss of the β-hydrogen occurs preferably from the most unhindered (least substituted) position [-CH₃ > -CH₂-R > -CH(R₂)].

The product alkene with fewer substitutents will predominate or is the major product.


Ester Pyrolysis also obeys this preference.