Question

Why primary amines have higher boiling points than tertiary amines?

Hint:

More N-H bonds = More hydrogen bonding = Higher boiling point. Order of boiling points: $1^\circ \gt 2^\circ \gt 3^\circ$.

Answer 1

Step 1: Concept
Intermolecular forces and their effect on boiling points.

Step 2: Meaning
Stronger intermolecular forces (like hydrogen bonding) require more thermal energy to overcome, leading to higher boiling points.

Step 3: Analysis
Primary amines ($R-NH_2$) possess two hydrogen atoms directly bonded to the highly electronegative nitrogen atom.
This allows them to form extensive intermolecular hydrogen bonds with other primary amine molecules.
Tertiary amines ($R_3N$), however, lack any hydrogen atoms directly attached to the nitrogen,
completely preventing them from forming intermolecular hydrogen bonds with each other.

Step 4: Conclusion
The presence of strong hydrogen bonding network in primary amines dictates their higher boiling point.

Final Answer: Primary amines have two hydrogen atoms directly attached to the nitrogen, allowing them to form strong intermolecular hydrogen bonds. Tertiary amines have no hydrogen atoms attached to the nitrogen and cannot form intermolecular hydrogen bonds, resulting in a lower boiling point.