Question

Which of the following methods gives better yield of p-nitrophenol?

• A. Phenol [20^∘C]dil. HNO₃ p-Nitrophenol
• B. Phenol (i) NaNO₂ + H₂SO₄ (ii) HNO₃ p-Nitrophenol
• C. Phenol (i) NaOH (ii) conc. HNO₃
• D. None of the three

Hint:

To increase para substitution: • Block ortho positions temporarily • Use stepwise functional group transformations

Answer 1

The Correct Option is B

Step 1: Direct nitration of phenol gives a mixture of o- and p-nitrophenols.
Step 2: In method (b), phenol is first converted into phenyl nitrite which rearranges (via nitrosation–oxidation) to give predominantly p-nitrophenol.
Step 3: Para product is favoured due to steric hindrance at ortho position.