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: Understand the question.
We must pick the primary amine. A primary amine has its nitrogen joined to just one carbon group and two hydrogen atoms, written $\text{R-NH}_2$.

Step 2: Recall the classes.
Primary means one carbon on nitrogen, secondary means two carbons, and tertiary means three carbons on nitrogen. We count carbons attached to nitrogen.

Step 3: Check ethyl methyl propyl amine.
Here nitrogen carries an ethyl, a methyl, and a propyl group, so three carbon groups. That makes it tertiary, not primary.

Step 4: Check diphenyl amine and N,N-dimethyl aniline.
Diphenyl amine has two phenyl rings on nitrogen, so it is secondary. N,N-dimethyl aniline has one phenyl plus two methyl groups on nitrogen, so it is tertiary. Neither is primary.

Step 5: Check hexamethylene diamine.
Its structure is $\text{H}_2\text{N-(CH}_2)_6\text{-NH}_2$. Each nitrogen is joined to just one carbon chain and carries two hydrogens. So both ends are primary amine groups.

Step 6: Pick the answer.
The primary amine is hexamethylene diamine, which is option 2.
\[ \boxed{\text{Hexamethylene diamine}} \]