Cope Reaction
When
tertiary amine oxides are heated to about 150°C, they undergo thermal
elimination to form alkenes. This reaction is known as the Cope
Reaction.
·
The reaction involves the formation of an alkene
and hydroxylamine as products.
Example:
This
reaction may also be carried out in dimethyl sulfoxide (DMSO)
or tetrahydrofuran (THF) at room temperature.
(iii)
Hofmann Elimination:
The
Hofmann elimination involves the thermal decomposition of quaternary
ammonium hydroxides. This reaction results in the formation of an
alkene, with the least substituted alkene (anti-Zaitsev product)
usually being the major product due to steric effects.
Reaction:
If
β-hydrogen is available at more than one position, a mixture of alkenes is
obtained. However, unlike eliminations with alkyl halides, the Hofmann
elimination predominantly forms the least substituted alkene due to
steric reasons.
Example:
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