Question

The order of boiling point of the following amines is (i) Butan-1-amine
(ii) N-Ethylethanamine
(iii) N,N-Dimethylethanamine

• A. (i) > (iii) > (ii)
• B. (i) > (ii) > (iii)
• C. (iii) > (ii) > (i)
• D. (iii) > (i) > (ii)
• E. (ii) > (i) > (iii)

Hint:

The boiling point of amines decreases as the number of alkyl groups on nitrogen increases because the ability to form hydrogen bonds decreases.

Answer 1

The Correct Option is B

The boiling point of amines is influenced by the type of intermolecular forces present, specifically hydrogen bonding and the size of the molecule. - Butan-1-amine (i): This is a primary amine, which can form hydrogen bonds with other molecules, leading to a higher boiling point compared to secondary and tertiary amines. - N-Ethylethanamine (ii): This is a secondary amine, which can also form hydrogen bonds but less effectively than primary amines because there is one alkyl group replacing a hydrogen on nitrogen. Therefore, its boiling point is lower than that of butan-1-amine. - N,N-Dimethylethanamine (iii): This is a tertiary amine, which has no hydrogen atoms attached to the nitrogen, so it cannot form hydrogen bonds, leading to the lowest boiling point among the three. Thus, the correct order of boiling points is (i) > (ii) > (iii). Thus, the correct answer is (B) (i) > (ii) > (iii).