Question

What product is formed when Phenol reacts with concentrated Nitric acid?

• A. Nitrobenzene
• B. o-Nitrophenol
• C. Picric acid
• D. Benzoic acid

Hint:

Phenol reacts with dilute nitric acid to form o-nitrophenol and p-nitrophenol, but with concentrated nitric acid it forms picric acid.

Answer 1

The Correct Option is C

Concept: Phenol is highly reactive toward electrophilic substitution reactions because the hydroxyl group \((-OH)\) strongly activates the benzene ring. When phenol reacts with concentrated nitric acid, multiple nitration reactions occur. The nitro groups are introduced at the ortho and para positions of the benzene ring. This leads to the formation of 2,4,6-trinitrophenol, commonly known as picric acid. The reaction can be represented as: \[ Phenol + HNO_3 \rightarrow 2,4,6\text{-trinitrophenol} \]

Step 1: Activation of benzene ring.
The hydroxyl group increases electron density on the ring.

Step 2: Electrophilic substitution.
Nitro groups \((-NO_2)\) are introduced at ortho and para positions.

Step 3: Final product formation.
After three nitrations, the product formed is picric acid.