a
In case of unsymmetrical ethers, the site of cleavage depends on the nature of alkyl group.

e.g., \(C{H_3} - O - {C_2}{H_5}\, + \,HI\,\xrightarrow{{373\,\,K}}C{H_3}I\, + \,{C_2}{H_5}OH\)

The alkyl halide is formed from the smaller alkyl group.

However, in case of tertiary alkyl ether following reaction occurs.

\(\mathop {C{H_3} - OC{{(C{H_3})}_3}}\limits_{ter - butyl\,\,methyl\,\,ether}  + \,HI\,\xrightarrow{{373\,\,K}}\)  \({(C{H_3})_3}C - I\, + \,C{H_3}OH\)

The alkyl halide is formed from the tertiary alkyl group and the cleavage of such ethers occurs by \(S_{N^1}\) mechanism as the product is controlled by the formation of more stable intermediate tertiary carbocation from orotonated ether.