Question

Which is the correct decreasing order of boiling point for following amines?
Tertiary amine (I), Secondary amine (II), Primary amine (III)

• A. (I) \(>\) (II) \(>\) (III)
• B. (III) \(>\) (I) \(>\) (II)
• C. (II) \(>\) (I) \(>\) (III)
• D. (III) \(>\) (II) \(>\) (I)

Hint:

Boiling point follows the extent of intermolecular hydrogen bonding, which needs N-H bonds.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
For amines of similar molar mass, boiling point depends on intermolecular hydrogen bonding through N-H bonds.

Step 2: Compare the types
A primary amine has two N-H bonds and forms the most hydrogen bonds.
A secondary amine has one N-H bond and forms fewer.
A tertiary amine has no N-H bond, so it cannot hydrogen bond with its own molecules.

Step 3: Order
Boiling point order is primary > secondary > tertiary, that is (III) > (II) > (I).

Final Answer:
The order is primary > secondary > tertiary. \[ \boxed{\text{(D) }(\text{III}) > (\text{II}) > (\text{I})} \]