Phenol reacts with conc. \(\mathrm{HNO_3}\) to form :
Phenol reacts with conc. \(\mathrm{HNO_3}\) to form :
Show Hint
- Salicylic acid
- Picric acid
- Benzoic acid
- Phthalic acid
The Correct Option is B
Solution and Explanation
The -OH group in phenol is strongly activating and directs the incoming group to the ortho and para positions. This makes the ring very easy to substitute (electrophilic aromatic substitution).
Step 2: Reaction with conc. nitric acid.
With dilute \(\mathrm{HNO_3}\) at low temperature, phenol gives a mixture of o-nitrophenol and p-nitrophenol. With conc. \(\mathrm{HNO_3}\) (usually with conc. \(\mathrm{H_2SO_4}\)), all three activated positions (2, 4 and 6) are nitrated.
\[ \mathrm{C_6H_5OH} + 3\mathrm{HNO_3} \xrightarrow{\text{conc.}} \mathrm{C_6H_2(NO_2)_3OH} + 3\mathrm{H_2O} \]
The product is 2,4,6-trinitrophenol, called picric acid.
Step 3: Why the other options are wrong.
Salicylic acid (o-hydroxybenzoic acid) is formed by the Kolbe reaction, using \(\mathrm{NaOH}\), \(\mathrm{CO_2}\) and then acid. Benzoic acid comes from oxidation of toluene or from benzaldehyde. Phthalic acid comes from oxidation of o-xylene or naphthalene. None of these forms from phenol and nitric acid.
Final Answer:
Phenol with conc. \(\mathrm{HNO_3}\) gives picric acid, which is option (B).
\[ \boxed{\text{Picric acid}} \]
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