E2+reaction

The E2 reaction mechanism is a one-step, concerted reaction where a strong, sterically hindered base (see below) is used to remove a proton adjacent to a leaving group to form an alkene.

The mechanism involves a transition state, similar in concept to what happens in the S N 2 reaction.

In the mechanism shown below, the base (CH 3 O - ) is removing a proton adjacent to the leaving group (Cl) in a concerted (all one step) reaction:



The alkene is formed when the reaction is complete.

Some sterically hindered bases used in E2 reactions as reagents include:
 * the tert-butoxide ion
 * TEA (triethylamine)
 * LDA (lithium diisopropylamide)
 * pyridine

Here is an animation of the E2 mechanism.

And another.

The hydrogen being removed must be in the same plane as the leaving group. Newman projections will help visualize this requirement of the E2 mechanism.

Here is a good visual of what it means to have the H and L in the same plane (periplanar).