Question

Which among the following compounds is a primary amine?

• A. Ethyl methyl propyl amine
• B. Hexamethylene diamine
• C. Diphenyl amine
• D. N, N-Dimethyl aniline

Hint:

Look directly at the structural hydrogen count on the nitrogen. Any true primary amine structural suffix finishes or links with an unhindered $\text{-NH}_2$ group. Hexamethylene diamine retains both intact $\text{-NH}_2$ groups on its outer ends.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The problem requires us to classify the given amine compounds based on structural configuration and select the compound containing a primary amine functional cluster ($-\text{NH}_2$).

Step 2: Detailed Explanation:
Amines are classified as primary ($1^\circ$), secondary ($2^\circ$), or tertiary ($3^\circ$) depending on the total count of carbon substituents directly attached to the core nitrogen atom:

Primary ($1^\circ$) Amine: Nitrogen is bound to one carbon chain and two hydrogen atoms ($\text{R-NH}_2$).

Secondary ($2^\circ$) Amine: Nitrogen is bound to two carbon chains and one hydrogen atom ($\text{R}_2\text{-NH}$).

Tertiary ($3^\circ$) Amine: Nitrogen is bound to three carbon chains with no remaining hydrogens ($\text{R}_3\text{-N}$).
Let's evaluate the choices:

Ethyl methyl propyl amine: The central nitrogen is bound to an ethyl, a methyl, and a propyl group. It is a tertiary ($3^\circ$) amine.

Hexamethylene diamine: Structurally represented as $\text{H}_2\text{N-(CH}_2)_6\text{-NH}_2$. Both terminal nitrogen assemblies are bound to only one carbon chain link, making it a primary ($1^\circ$) diamine.

Diphenyl amine: The nitrogen is bound to two phenyl rings ($(\text{C}_6\text{H}_5)_2\text{NH}$), making it a secondary ($2^\circ$) amine.

N,N-Dimethyl aniline: The nitrogen atom is anchored to a phenyl ring and two methyl groups. It is a tertiary ($3^\circ$) aromatic amine.

Step 3: Final Answer: The single primary amine compound matches option (B).