22.7 Cope Elimination

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Cope Elimination

The Cope Elimination is an elimination reaction specifically for tertiary amines for which the major organic product is an alkene.  The leaving group involved (a hydroxyl amine) is a moderate base and therefore is not a good leaving group.  As a result, the major product is the Hofmann product (a.k.a. anti-Zaitsev product--the least substituted alkene).  An explanation for why a poor leaving group results in the Hofmann product can be found here:  7.7b Exceptions to Zaitsev’s Rule for E2 Reactions.

Cope Elimination

Cope Elimination Mechanism

The Cope Elimination occurs over the course of two steps:

  • Step 1 - Oxidation -- The oxidation of a tertiary amine to an amine oxide using hydrogen peroxide.
  • Step 2 Elimination - The amine oxide produced in step 1 undergoes E2 elimination.  This step is unique in that the oxide portion of the leaving group serves as the base involved in the elimination reaction.
Cope Elimination Mechanism