Which of the following ethers cannot be prepared by bimolecular dehydration of alcohol?

(A) 2-Methoxy-2-methylpropane
(B) 2-Methoxy propane
(C) 1-Propoxypropane
(D) 2-Ethoxy butane

Choose the correct answer from the options given below:

(A), (B) and (D) only

The correct answer is Option (1) → (A), (B) and (D) only

Ethers can be prepared by bimolecular dehydration of alcohols using concentrated acid at about 413 K.

General reaction: 2R–OH → R–O–R + H₂O This reaction proceeds mainly through an SN2 mechanism, so it works best with primary alcohols. Secondary and tertiary alcohols tend to undergo elimination to form alkenes instead of ethers. Therefore, this method mainly produces symmetrical ethers from primary alcohols.

(A) 2-Methoxy-2-methylpropane

This is tert-butyl methyl ether. Formation would require a tertiary alcohol, which under acidic conditions forms alkenes rather than ethers. Thus, it cannot be prepared by bimolecular dehydration

(B) 2-Methoxypropane

This ether would involve a secondary alcohol, which prefers elimination reactions instead of ether formation. Thus, it cannot be prepared by bimolecular dehydration.

(C) 1-Propoxypropane

This is a symmetrical ether derived from 1-propanol (a primary alcohol). Two molecules of 1-propanol can undergo dehydration to form this ether. Thus, it can be prepared by bimolecular dehydration.

(D) 2-Ethoxybutane

This ether involves a secondary alcohol, which again favors elimination rather than ether formation. Thus, it cannot be prepared by bimolecular dehydration.