Step 1:
An acid/base reaction. Protonation of the alcoholic oxygen to make a
better leaving group. This step is very fast and reversible. The
lone pairs on the oxygen make it a Lewis base.
Step 2:
Cleavage of the C-O bond allows the loss of the good leaving group,
a neutral water molecule, to give a carbocation intermediate. This is
the rate determining step (bond breaking is endothermic)
Step 3:
Attack of the nucleophilic bromide ion on the electrophilic carbocation
creates the alkyl bromide.
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