To determine which of the given amines has the lowest boiling point, we need to understand the relationship between the structure of amines and their boiling points. Boiling points are influenced by hydrogen bonding, molecular weight, and molecular structure.
1. Hydrogen Bonding:
- Primary amines (R-NH₂) have two hydrogen atoms attached to the nitrogen and can form hydrogen bonds with other amine molecules.
- Secondary amines (R₂-NH) have one hydrogen atom attached to the nitrogen and can also form hydrogen bonds, but less efficiently than primary amines.
- Tertiary amines (R₃-N) do not have any hydrogen atoms attached to the nitrogen and therefore cannot form hydrogen bonds with other molecules, resulting in lower boiling points compared to primary and secondary amines.
2. Types of Amines in the Options:
- (A) C₂H₅-NH₂: Ethylamine is a primary amine.
- (B) (C₂H₅)₃N: Triethylamine is a tertiary amine.
- (C) (C₂H₅)₂NH: Diethylamine is a secondary amine.
- (D) CH₃-NH₂: Methylamine is a primary amine.
3. Analysis of the Boiling Points:
- Among these identified types, tertiary amines have the lowest boiling points because they cannot form hydrogen bonds.
- Hence, (B) Triethylamine ((C₂H₅)₃N) is a tertiary amine and expected to have a lower boiling point than the primary and secondary amines listed.
Therefore, the amine expected to have the lowest boiling point among the options provided is:
(B) [tex]$\left( C _2 H _5\right)_3 N$[/tex]
