Question

In order to distinguish between $C_{2}H_{5}NH_{2}$ and $C_{6}H_{5}NH_{2}$ which of the following reagents is useful?

• A. Hinsberg test
• B. $\beta$-Naphthol
• C. $CHCl_3/KOH$
• D. $NaOH$

Hint:

Azo-dye Test: Aromatic $1^\circ$ Amine $\rightarrow$ Colored Dye; Aliphatic $1^\circ$ Amine $\rightarrow$ No Dye.

Answer 1

The Correct Option is B

Step 1: Concept
To distinguish an aliphatic primary amine from an aromatic primary amine, the Azo-dye test is used.
Step 2: Analysis
Aromatic amines like Aniline ($C_6H_5NH_2$) react with $NaNO_2/HCl$ at $0-5^\circ C$ to form stable diazonium salts, which then react with $\beta$-naphthol to form a brightly colored dye.
Step 3: Comparison
Aliphatic amines ($C_2H_5NH_2$) form unstable diazonium salts that decompose immediately, releasing Nitrogen gas and failing to form a dye.
Step 4: Conclusion
Hence, $\beta$-naphthol is the correct reagent for the Azo-dye test.
Final Answer:(B)