# Reactions of alcohol/ethers with hydrogen halides [duplicate]

General equation -

Alcohol - $\ce{ROH + HX -> RX + H2O}$

Ethers - $\ce{ROR + HX -> RX + ROH}$

I've been told that X = $\ce{Cl-}$ , $\ce{Br-}$ , $\ce{I-}$

Then I wonder ...

• How Cl , Br and I nucleophile is going to Attack OH ?

All of the 3 are weaker nucleophile than OH as well as a better leaving group. So ...

• How does it replace and substitute OH ?

Or

• OR (with ethers)?

## marked as duplicate by Mithoron, Pritt Balagopal, Buttonwood, Jon Custer, jerepierreJun 26 '17 at 15:45

• Is it $\ce{OH-}$ that leaves? – Pritt Balagopal Jun 25 '17 at 4:38
This reaction generally takes place in an environment where there are free $\ce{H3O+}$ ions. The oxygen atom in the alcohol or ether takes up $\ce{H+}$ from these ions. Now the leaving group is $\ce{H\bond{-}O+\bond{-}H}$ or $\ce{H\bond{-}O+\bond{-}R}$ which are much better leaving groups than $\ce{O\bond{-}H}$ or $\ce{O\bond{-}R}$. This makes the substitution of the halide ions easier.