Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.

Explanation

Acid catalysed dehydration of primary alcohols to ethers occurs by `SN_(2)` reaction involving nucleophilic attack by the alcohol molecule on the protonal molecule.

Under these condition, `2^(@)` and `3^(@)` alcohols, however, give alkenes rather than ethers. The reason being that due to steric hindrance, nucleophilic attack by the alcohols molecule on the protonated alcohol molecule does not occur. Instead protonated `2^(@)` and `3^(@)` alcohols lose a molecule of water to form stable `2^(@)` and `3^(@)` carbocation. These carbocations prefer to lose a proton to form alkenes rather than undergoing nucleophilic attack by alcohol molecules to form ethers.