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

Explanation

Acid-catalyod dehydration of `1^(@)` alcohols to others take place by `S_(N)2` reaction involving nucleophilic attack by the alcohol molecule on the potente alebo molecule as :

However, under these conditions, `2^(@)` and `3^(@)` alcohols give alenes rather than others. This is because of the serie hindrance nucleophilic attack by the alcohol on the protonated alcohol molecule do not take place. Instead of this, the protonated `2^(@)` and `3^(@)` alcohol lose a molecule of water to form stable and carbonations. These carbonations the prefer to lose a proton to formlenes rather than undergoing sucophile attack by alcohol molecule to form ethers.

Similary `3^(@)` alcohols give alkenes.
`CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)C-OH underset(-H^(+)) overset(H^(+))hArr CH_(3)-underset(CH_(3))underset(|)overset(CH_(2))overset(|)C-OH_(2)- underset(-H_(2)O)to CH_(3)-underset("tert-Butyl Carbocation")underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C^(+))overset(-H^(+))to underset("2-Methylprop-1-ene")(CH_(3)-overset(CH_(3)) overset(|)C=CH_(2))`