What will be 'A' in the following reaction?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(Sn/ dil. HCl\)
The reaction converts nitrobenzene into aniline, i.e., –\( \ce{NO2} \) → –\( \ce{NH2} \). This is a reduction, which is carried out with hydrogen and a metal catalyst or with a metal in acidic medium such as Sn/HCl or Fe/HCl:
\( \ce{C6H5NO2 + 6[H]} \xrightarrow{\ce{Sn/HCl}} \ce{C6H5NH2 + 2H2O} \)
Why the other options are incorrect
Option (1) C2H5−Na+/C2H5OH — Incorrect. Sodium ethoxide is a strong base used for elimination or Williamson synthesis; it does not reduce a nitro group.
Option (2) H+/H2O — Incorrect. Dilute acid alone supplies no electrons, so the nitro group stays unchanged.
Option (4) OH−/KOH — Incorrect. A base alone is not a reducing agent; nitrobenzene is not converted to aniline by alkali.
NCERT (2026-27 edition):
Reduction of Nitro Compounds – “Nitro compounds are reduced to amines by passing hydrogen gas in the presence of finely divided nickel, palladium or platinum and also by reduction with metals in acidic medium.”