Reaction of Ether with Hydrogen Iodide (HI)

Chemical properties of Ethers (With HI)

On heating with concentrated Hydrogen iodide (HI) the C-O bond in ethers breaks forming alcohol and alkyl iodide. For example,

C₂H₅ -O-C₂H₅ + HI ------------> C₂H₅ - I + C₂H₅OH

On boiling with excess of concentrated Hydrogen iodide (HI), Alkyl iodide is formed.


C₂H₅ -O-C₂H₅ + 2HI ------------> 2C₂H₅I + H₂O

In the case of mixed ethers with two different alkyl groups, the site of cleavage and hence the alcohol and alkyl iodide that form depend on the nature of the alkyl groups.

When one group is methyl and the other is primary or secondary alkyl group, it is the lower alkyl group that forms alkyl iodide due to steric factors.
For Example,









When one group is methyl and the other alkyl group is a tertiary group, the halide formed is a tertiary group, the halide formed is a tertiary halide.
For Example,






It is because the attack by I- takes place at that carbon of alkyl group, which has a greater electron pushing inductive effect and a lower electron density.

Phenolic ethers react with HI to form phenol and alkyl iodide. This can be attributed to the resonance and steric effects of the benzene ring.


For more about chemical reaction of ether visit http://entrancechemistry.blogspot.in/2012/07/chemical-properties-of-ether.html