Alcohol dehydration
An alcohol loses water to give an alkene. The more substituted alkene is the one that forms.
What it needs, and what it gives
- Reaction class
- Elimination
- Concentrated acid and heat.
- balanced — the co-products are written out, not dropped
- Mechanism
- Unimolecular elimination, 3 steps
How it is thought to happen
Acid turns the hydroxyl into a good leaving group, it leaves on its own, and the cation then loses a proton to give the alkene.
- Acid protonates the hydroxyl
- Water leaves on its own
- A base takes a proton from the next carbon
Try it on your own structures
Enter your reactants in the Reaction Lab. If this transformation matches what you drew, it is applied and the outcome is shown next to the records that back it — with the count of documented reactions doing the same thing on substrates like yours, rather than a confidence score.
Other elimination transformations
Elimination with a small base
The base takes a hydrogen next to the leaving group. A small base reaches the more crowded position, so the more substituted alkene forms.
Elimination with a bulky base
A bulky base cannot reach the crowded hydrogen, so it takes one from the least hindered position and the less substituted alkene forms.