Definition: What is Hofmann elimination?

The Hofmann elimination, or Hofmann’s rule, is an elimination reaction used to synthesize alkenes by eliminating parts of an amine that have β-hydrogen. When alkyl amines react with methyl halides, they form an alkylammonium salt. The salt is treated with silver oxide or a strong base (e.g., silver hydroxide) to produce an alkene. With asymmetrical amines, the most favored alkene product is the one that is least substituted. ^[1-4]

Example of Hofmann Elimination ^[1]

Mechanism of Hofmann Elimination ^[3-7]

FAQs

Q.1. How does Zaitsev’s rule differ from Hofmann’s rule?

Ans. Unlike the Hofmann rule, Zaitsev’s rule follows the principle that the original alkene product is the one that is highly substituted and the most stable.

Q.2. Can cyclic amines undergo Hofmann elimination?

Ans. Although rare, cyclic amines having a β-hydrogen (e.g., pyrrolidines and piperidines) may undergo Hofmann elimination.

Q.3. Does Hofmann elimination take place in the body?

Ans. Yes. Non-depolarizing muscle relaxants like atracurium and cisatracuriumbesilate (Nimbex©) are removed from the body through Hofmann elimination.