Skip to content
qorganica.es qorganica.comOrganic Chemistry made transparent Course map Español

Elimination of alcohols (dehydration)

The elimination of alcohols (dehydration) is a good method to get alkenes:

Dehydration of cyclohexanol to cyclohexene with H₃PO₄ and heat

Elimination reactions are usually carried out at high temperatures.

If the elimination goes through an E1 mechanism, which is quite usual, the reaction produces carbocations which can lead to surprising results due to rearrangements. Look!

2-Methyl-2-pentanol and 4-methyl-2-pentanol give the same olefin, 2-methyl-2-pentene, with H₂SO₄ at 80 °C

The simplified mechanism, that explains the production of the very same olefin from the two different alcohols, is as follows:

E1 mechanism with hydride shifts: the initial secondary carbocation rearranges to another secondary one and then to the tertiary one, which loses a proton to give the most substituted olefin