Question

Which of the following alcohols gives the best yield of dialkyl ether on being heated with a trace of sulphuric acid?
(a) 2-Pentanol
(b) Cyclopentanol
(c) 2-Methyl-2-butanol
(d) 1-Pentanol

Answer 1

(c) 2-Methyl-2-butanol

Answer 2

Answer: (d) 1-Pentanol is the correct answer.

Explanation:

Ethers are obtained when alcohols react with carboxylic acids, acid chlorides and acid anhydrides.

When excess alcohol is reacted with concentrated sulphuric acid it gives dialkyl ether.

In this process two equal portions of alcohol and sulphuric acid are taken

Alkyl hydrogen sulphate is formed.

Then excess alcohol is added to give dialkyl ether.

This reaction gives two types of products

1) dialkyl ether

2) alkenes

The above method is suitable for preparation of ethers only with primary alcohols.

Hence, (d) 1-Pentanol is the correct answer.

This is substitution reaction.

Dehydration of secondary and tertiary alcohols is elimination reaction.