Hofmann elimination

In the Hofmann elimination (also Hofmann degradation ) is a name reaction in organic chemistry, which was named after the German chemist August Wilhelm von Hofmann. In the Hofmann elimination of amines obtained from amines by quaternization ( = Per- alkylation) of the nitrogen and a subsequent elimination reaction alkenes.

Overview reaction

Wherein Hofmann elimination is an amine is converted to an alkene, wherein the nitrogen atom and a vicinal protons are eliminated.

Mechanism

In the first step an amine with an alkylating agent is " exhaustive " alkylated (for example, methyl iodide ); i.e., the amine is transferred in excess of CH3I in the quaternary ammonium compound. The ammonium salt ( counter ion: iodide) is converted with silver (I ) oxide, which serves as a base in aqueous solution in the ammonium salt with the counter ion hydroxide. By evaporation of the aqueous solution or by heating the latter then decays in a E2 reaction to form the corresponding alkene.

When a plurality of β - hydrogen atoms are present, different olefins may occur. In many cases is followed by the elimination of the Hofmann rule, that is, it is formed preferably, the alkene with the least number of alkyl groups.

Importance

The Hofmann -amine degradation was an important tool for structure elucidation of nitrogenous natural products ( alkaloids).

An example is the degradation of 1,3,5,7- cyclooctatetraene to pseudopelletierine by Richard Willstätter (Munich, 1905).

Importance in medicine

In anesthesiology is the Hofmann elimination with respect to the inactivation of certain muscle relaxants of Meaning: The muscle relaxants atracurium and cisatracurium are degraded independent organ in the body: they decay pH - and temperature-dependent. Although laudanosine and acrylate also arise as degradation products, but by an alternative pathway: hydrolysis by non-specific plasma.

Source

• Organikum, German VEB Verlag der Wissenschaften, Berlin 1976.