Hofmann elimination

Hofmann elimination converts a quaternary ammonium compound into an alkene and a tertiary amine by removing a β-hydrogen and expelling a tertiary amine.

E2 reaction: A bimolecular elimination in which a base removes a β-hydrogen as a leaving group departs in one concerted step. Hofmann elimination follows this concerted pathway, with a quaternary ammonium group as the leaving group.
Hofmann exhaustive methylation: A sequence that converts an amine into a quaternary ammonium salt by repeated methylation. It commonly prepares the quaternary ammonium substrate used in classical Hofmann elimination.
Zaitsev's rule: A rule predicting that elimination often favors the more substituted alkene. Its usual product prediction contrasts with Hofmann elimination's preference for the less substituted alkene.
Hofmann degradation: A classical sequence of exhaustive methylation and elimination used to degrade amines. Repeated application can reveal structural information about an amine's carbon framework.
Hofmann product: The less substituted alkene favored in certain elimination reactions. This is the characteristic alkene product when competing β-hydrogens can be removed.
Quaternary ammonium hydroxide: A quaternary ammonium cation paired with hydroxide as its counterion. Heating this salt enables hydroxide to act as base in the elimination.
Hofmann rule: The tendency of some elimination reactions to favor the less substituted alkene. This product-selection principle describes the characteristic outcome of Hofmann elimination.
Hofmann rearrangement: A reaction that converts a primary amide into an amine with one fewer carbon atom. It shares Hofmann's name but is a distinct reaction, not an alkene-forming elimination.
Quaternary ammonium compound: A positively charged nitrogen compound bonded to four carbon-containing groups. It supplies the nitrogen-containing leaving group that becomes a tertiary amine.
β-Hydrogen: A hydrogen attached to a carbon adjacent to a functional group or reaction center. Its availability and accessibility determine which alkene can form.

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