JEE Main 2025 Apr 8 Shift 2, Chemistry Q3: Carboxylic Acid Derivatives

Step 1: Identification of A

A positive Lassaigne's test for nitrogen indicates the presence of nitrogen. The molar mass is 121 g mol⁻¹, which matches benzamide.

$\boxed{A={\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CON}{\mathrm{H}}_2}$

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Step 2: Identification of B

On treatment with NaOH followed by ${\mathrm{H}}_3{\mathrm{O}}^{+}$, an amide undergoes hydrolysis to form the corresponding carboxylic acid.

$\mathrm{C_6H_5CONH_2} \xrightarrow[\mathrm{H_3O^+}]{\mathrm{NaOH}} \mathrm{C_6H_5COOH}$

The product benzoic acid reacts with $\mathrm{NaHC}{\mathrm{O}}_3$ to liberate $\mathrm{C}{\mathrm{O}}_2$, producing brisk effervescence, which matches the given observation.

$\boxed{B={\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}}$

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Step 3: Identification of C

Benzoic acid undergoes Fischer esterification with ethanol in the presence of ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ and heat to form an ester.

$\mathrm{C_6H_5COOH+C_2H_5OH} \xrightarrow[\Delta]{\mathrm{H_2SO_4}} \mathrm{C_6H_5COOC_2H_5+H_2O}$

The ester ethyl benzoate has a pleasant fruity odour, which agrees with the given description.

$\boxed{C={\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COO}{\mathrm{C}}_2{\mathrm{H}}_5}$

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Conclusion

$\boxed{ A=\mathrm{C_6H_5CONH_2},\quad B=\mathrm{C_6H_5COOH},\quad C=\mathrm{C_6H_5COOC_2H_5} }$

Hence, the correct answer is Option (1).