Reaction of Phenol with conc. \( HNO_3 \) gives
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Picric Acid
The –OH group strongly activates the benzene ring towards electrophilic substitution and directs to the ortho and para positions. With dilute nitric acid at 298 K, phenol gives a mixture of o- and p-nitrophenol. With concentrated nitric acid, all three positions are nitrated and 2,4,6-trinitrophenol is formed, commonly known as picric acid:
\( \displaystyle \ce{C6H5OH + 3HNO3} \xrightarrow{\text{conc.}} \ce{C6H2(NO2)3OH + 3H2O} \)
Three electron-withdrawing nitro groups make picric acid a strong acid.
Why the other options are incorrect
Option (1) Citric acid — Incorrect. Citric acid is a tricarboxylic acid found in citrus fruits; it has no benzene ring and is not made from phenol.
Option (3) Nitrobenzene — Incorrect. Nitrobenzene, \( \ce{C6H5NO2} \), is made by nitrating benzene; nitration of phenol keeps the –OH group.
Option (4) o-Nitrobenzene — Incorrect. There is no such compound: an ortho prefix needs two groups on the ring, and nitrobenzene has only one.
NCERT (2026-27 edition):
Nitration – “With dilute nitric acid at low temperature (298 K), phenol yields a mixture of ortho and para nitrophenols. … The ortho and para isomers can be separated by steam distillation. o-Nitrophenol is steam volatile due to intramolecular hydrogen bonding while p-nitrophenol is less volatile due to intermolecular hydrogen bonding which causes the association of molecules.
With concentrated nitric acid, phenol is converted to 2,4,6-trinitrophenol. The product is commonly known as picric acid. The yield of the reaction product is poor.”