22.7 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 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.