Hofmann elimination



Hofmann elimination (also known as exhaustive methylation) is a process where an amine is reacted to create a tertiary amine and an alkene by treatment with excess methyl iodide followed by treatment with silver oxide, water, and heat (Fig. 1).

After the first step, a quartenary ammonium iodide salt is created as can be seen in the exact reaction mechanism in Figure 2. The major alkene product is the least substituted and generally the least stable, an observation known as the Hofmann rule. This is in direct contrast to normal elimination reactions where the more substituted, stable product is dominant (Zaitsev's rule).



The reaction is named after its discoverer: August Wilhelm von Hofmann.