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19.22: Amines to Alkenes: Hofmann Elimination

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Organic Chemistry

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Amines to Alkenes: Hofmann Elimination

19.22: Amines to Alkenes: Hofmann Elimination

Alkenes can be obtained from amines via an E2 elimination. The amine is first converted into a good leaving group, such as a quaternary ammonium salt. This is accomplished by treating the amine with an excess of alkyl halide, which results in a halide salt. Next, the halide salt is transformed into a hydroxide salt that functions as a base to enable elimination.

Under thermal conditions, the hydroxide can abstract a proton from the β carbon; this generates an alkene with the simultaneous release of a neutral amine molecule. This elimination process is called the Hofmann elimination. For the elimination to occur, the β proton and tertiary amine group must be positioned opposite or anti-periplanar to each other. This reaction yields the less substituted alkene as the major product, also known as the Hofmann product.


Amines Alkenes Hofmann Elimination E2 Elimination Quaternary Ammonium Salt Alkyl Halide Halide Salt Hydroxide Salt Base Thermal Conditions & 946; Carbon Alkene Neutral Amine Molecule Hofmann Product

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