Alcohol Dehydration: Acid and Heat

If you see heat and acid with an alcohol… your professor wants an ALKENE. Alcohol dehydration

is an elimination reaction where an –OH leaves as water, forming an alkene. Here’s the key setup:

Reagents: strong acid like H₂SO₄ or H₃PO₄ + heat What’s happening: you’re removing

H and OH → H₂O leaves Mechanism depends on the alcohol: 3° and 2° alcohols: go through E1

Protonate OH Water leaves → carbocation Alkene forms 1° alcohols: usually E2

No stable carbocation Happens in one concerted step Regioselectivity matters:

Product usually follows Zaitsev’s rule → more substituted alkene wins Big exam tip:

If you see acid + heat + alcohol, think dehydration = elimination, not substitution.