Return to Contents Chapter 15: Alcohols, Diols and Thiols Ch 15 contents
Dehydration of Alcohols
(review of Chapter 5)
Dehydration Reaction
Reaction type: 1,2- or b-Elimination


Related Reactions
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.
E1 mechanism for ROH
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:
An acid/base reaction. Deprotonation by a base (a water molecule) from a C atom adjacent to the carbocation center leads to the creation of the C=C

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© Dr. Ian Hunt, Department of Chemistry, University of Calgary