Cope Elimination
Treatment of a tertiary amine with hydrogen peroxide results in a two-electron oxidation of the amine to an amine oxide.
When an amine oxide with at least one beta-hydrogen shown in red is heated, it undergoes thermal decomposition to form an alkene and an N,N-dialkylhydroxylamine.
Thermal decomposition of an amine oxide to an alkene is known as a Cope
Elimination after its discoverer, Arthur C. Cope, of MIT.
All experimental evidence indicates that the Cope elimination is syn stereoselective and concerted. As shown in the following mechanism, the transition state involves a planar or nearly planar arrangement of the five participating atoms and a cyclic flow of three pairs of electrons.
Cope elimination is regioselective. Unlike
intermolecular E2 reactions, it does not
follow Zaitsevs rule; the major product is always the
least stable alkene, i.e., the alkene with the least
highly substituted double bond
intermolecular E2 reactions, it does not
follow Zaitsevs rule; the major product is always the
least stable alkene, i.e., the alkene with the least
highly substituted double bond
Sir I want to know when a reaction is said to be concerted??
ReplyDeleteIn the final step , yes.a tertiary amine oxide after it is formed will be concerted.Cope elimination begins here.please remember that a concerted reaction proceeds via a transition state .
ReplyDelete