Hoffmann Elimination is a reaction in which an amine containing β-hydrogens is converted into an alkene under heating conditions, using iodomethane, water, and silver oxide. It is named after the German chemist August Wilhelm von Hofmann.
The Hofmann elimination offers an efficient method for synthesizing alkenes from amines, especially when conventional approaches (such as E1 or E2) are hindered by steric factors or otherwise unsuitable. Unlike a typical E2 reaction that follows Zaitsev's rule, the Hofmann elimination favors formation of the less substituted alkene—this can prove highly valuable in certain synthetic designs.
Reagents: Methyl Iodide, Silver Oxide, Water
Reactants: Amine with β-Hydrogen
Products: Alkene
Reaction Type: Elimination reaction
Experimental Tips:
-
Suitable solvents include ethanol and acetonitrile.
-
Use an excess amount of methyl iodide to make sure all of the amine is converted into the quaternary ammonium salt.
-
Typically, heat the mixture evenly between 100–200°C using an oil bath
-
Caution: Methyl iodide is toxic and a potential carcinogen. Always handle it inside a fume hood with appropriate safety measures.
Reaction Mechanism:
Original Literature:
Top Citations：
-
Elimination Reactions. II. Hofmann Elimination in Bicyclic Compounds. J. Am. Chem. Soc. 1967, 89 (25), 6701–6704.
-
Olefins from Amines: The Hofmann Elimination Reaction and Amine Oxide Pyrolysis. In Organic Reactions American Cancer Society, 2011; pp 317-493.
- Dimethylenedihydroheteroaromatic Compounds and Heterocyclophanes by 1,6-Hofmann Elimination Reactions. J. Am. Chem. Soc. 1960,82 (6), 1428–1435.
艳 李
