Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.
The preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method because the reaction follows S_N1 pathway for these alcohols. In this pathway, elimination competes over substitution, and as a consequence, alkenes are easily formed instead of the desired ethers.
This method is suitable only for the preparation of ethers having primary alkyl groups where the alkyl group is unhindered and temperature is kept low. Otherwise, the reaction favours the formation of alkene.
Explanation
According to the textbook context, the dehydration of secondary and tertiary alcohols to give corresponding ethers is unsuccessful because elimination competes over substitution. The reaction follows S_N1 pathway when the alcohol is secondary or tertiary, leading to alkene formation. The method is suitable only for primary alcohols with unhindered alkyl groups at low temperatures.