Overview:
The general
form of the E2 mechanism is as follows:
B:
= base
X = leaving group (usually halide or tosylate)
In the
E2 mechanism, a base abstracts a proton neighboring the leaving
group, forcing the electrons down to make a double bond, and,
in so doing, forcing off the leaving group. When numerous
things happen simultaneously in a mechanism, such as the E2
reaction, it is called a concerted step.
An example
of the E2 reaction:
Base
Strength: A strong base is required since the base is
involved in the rate-determining step.
Leaving
groups: A good leaving group is required, such as a halide
or a tosylate, since it is involved in the rate-determining
step.
Stereochemistry
requirements:
Must occur with antiperiplanar stereochemistry.
|