Identify A in the following reaction.

The reaction shown is oxidation of aniline.

Aniline reacts with a strong oxidising agent:

$$\mathrm{K_2Cr_2O_7/H^+}$$

The amino group:

$$\mathrm{-NH_2}$$

strongly activates the benzene ring, making it highly susceptible to oxidation.

Thus, oxidation affects the entire aromatic ring system rather than only the nitrogen atom.

The reaction proceeds through multiple intermediates and finally forms:

$$\mathrm{p\text{-}Benzoquinone}$$

also called:

$$\mathrm{1,4\text{-}Benzoquinone}$$

The product contains:

1. Two carbonyl groups

2. Two conjugated double bonds

3. Carbonyl groups at the para positions

Overall reaction:

$$\mathrm{C_6H_5NH_2 \xrightarrow{K_2Cr_2O_7/H^+} p\text{-}Benzoquinone}$$

Hence, the correct structure is:

$$\mathrm{Option\ D}$$