Concept:The concentration of the nitrating agent determines the degree of substitution on the highly activated phenol ring.
Formula:$$ \text{C}_6\text{H}_5\text{OH} + 3\text{HNO}_3\text{(conc.)} \xrightarrow{\text{H}_2\text{SO}_4} \text{C}_6\text{H}_2(\text{NO}_2)_3\text{OH} + 3\text{H}_2\text{O} $$
Solution:- Dilute \(\text{HNO}_3\) yields a mixture of ortho- and para-nitrophenol (mono-substitution).
- Concentrated \(\text{HNO}_3\) (often with concentrated sulfuric acid) forcefully nitrates all available activated positions (both ortho positions and the para position).
- This yields 2,4,6-trinitrophenol, commonly known as picric acid.
Why other options are incorrect:Options B and C are the products formed only when reacting with
dilute nitric acid.
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