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

Explanation

Acid-catalysed dehydration of `1^(@)` alcohols to ethers occurs by `S_(N)2` reaction involving nucleophilic attack by the alcohol molecule on the protonated alcohol molecule.

Under these conditions, `2^(@) and 3^(@)` alcohols, however, give alkenes rather than ethers. the reason being that due to sterric hindrance, nucleophilic attack by the alcohol 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^(@)` carbocations. these carbocations prefer to loss a proton to form alkenes rather than undergoing nucleophilic attack by alcohol molecule to form ethers.