Question

Which among the following decreasing order of boiling points is correct for amines?

• A. Ethyl dimethylamine \(>\) Diethylamine \(>\) n-Butylamine
• B. Diethylamine \(>\) Ethyl dimethylamine \(>\) n-Butylamine
• C. n-Butylamine \(>\) Ethyl dimethylamine \(>\) Diethylamine
• D. n-Butylamine \(>\) Diethylamine \(>\) Ethyl dimethylamine

Hint:

For amines of similar molar mass: Primary \(>\) Secondary \(>\) Tertiary in boiling point due to hydrogen bonding.

Answer 1

The Correct Option is D

Step 1: Factors affecting boiling point of amines.
Boiling points of amines depend on hydrogen bonding, molecular mass, and branching. Primary amines show stronger hydrogen bonding than secondary and tertiary amines.

Step 2: Nature of given amines.
n-Butylamine is a primary amine with maximum hydrogen bonding.
Diethylamine is a secondary amine with moderate hydrogen bonding.
Ethyl dimethylamine is a tertiary amine with least hydrogen bonding.

Step 3: Arrange in decreasing order.
Stronger hydrogen bonding leads to higher boiling point. Thus: \[ \text{n-Butylamine}>\text{Diethylamine}>\text{Ethyl dimethylamine} \]

Step 4: Conclusion.
Option (D) correctly represents the decreasing order of boiling points.