Overview:
The general
form of the E1 mechanism is as follows:
B:
= base
X = leaving group (usually halide or tosylate)
In the
E1 mechanism, the the first step is the loss of the leaving
group, which leaves in a very slow step, resulting in the
formation of a carbocation. The base then attacks a neighboring
hydrogen, forcing the electrons from the hydrogen-carbon bond
to make the double bond. Since this mechanism involves the
formation of a carbocation, rearangements can occur.
An example
of the E1 reaction:
Base
Strength: A strong base not required, since it is not
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.
Rearangements:
Since the mechanism goes through a carbocation intermediate,
rearangements can occur.
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