The structure of picric acid is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 2,4,6-trinitrophenol
Picric acid is the common name of 2,4,6-trinitrophenol: a phenol with nitro groups at both ortho positions and the para position. It is formed when phenol is treated with concentrated nitric acid:
\( \displaystyle \ce{C6H5OH + 3HNO3} \xrightarrow{\text{conc.}} \ce{C6H2(NO2)3OH + 3H2O} \)
The three electron-withdrawing –\( \ce{NO2} \) groups stabilise the phenoxide ion strongly, so picric acid is a strong acid, much stronger than phenol, which explains the name "acid" for a phenol.
Why the other options are incorrect
Option (1) 4-hydroxybenzoic acid — Incorrect. It carries a carboxyl group para to –OH and no nitro group.
Option (2) 4-nitrophenol — Incorrect. It has only one nitro group; picric acid has three.
Option (3) 4-methylphenol (p-cresol) — Incorrect. It carries an electron-releasing methyl group and is even less acidic than phenol.
NCERT (2026-27 edition):
Nitration – …
