Question

Tertiary amines have the lowest boiling points because ,

• A. They possess polar N-C bonds
• B. They possess inter-molecular dipole-dipole attraction forces.
• C. They possess inter-molecular H-bonding
• D. They do not possess inter-molecular H- bonding

Hint:

Tertiary amines have no N-H bond, so they cannot hydrogen bond with each other.

Answer 1

The Correct Option is D

Step 1: Hydrogen bonding
Primary and secondary amines have N-H bonds and form intermolecular hydrogen bonds. Tertiary amines have no hydrogen on nitrogen.

Step 2: Result
Without intermolecular hydrogen bonding, only weaker dipole forces act, so the boiling point is the lowest.
Options (A) and (B) are true of tertiary amines but they do not explain the low boiling point.

Final Answer:
Tertiary amines lack intermolecular H-bonding. \[ \boxed{\text{(D)}\ \text{They do not possess inter-molecular H-bonding}} \]