Question

Arrange the following in the increasing order of boiling point.

• A. $n-\mathrm{Butylamine}$
• B. $\mathrm{Diethylamine}$
• C. $\mathrm{Dimethylethylamine}$
• D. $n-\mathrm{Butanol}$

Answer 1

Boiling point of aliphatic amines increases in the order:
primary > secondary > tertiary
Primary and secondary amines are having intermolecular associations due to hydrogen bonding between nitrogen of one molecule and hydrogen of its neighbouring molecule. Intermolecular hydrogen bonding is greater in primary amines than secondary because of the availability of two hydrogen atoms for hydrogen bond formation and thus primary amines have higher boiling points than secondary and tertiary amines. Hydrogen bonding in alcohols is stronger than that of amines having comparable molar mass.