Nitration of Aniline

Direct Nitration (Anomalous Yields due to Anilinium Ion):

$$\begin{aligned}\text{C}_6\text{H}_5\text{NH}_2 \xrightarrow{\text{Conc. HNO}_3 + \text{Conc. H}_2\text{SO}_4, \, 288\text{ K}} p\text{-Nitroaniline } (51\%) + m\text{-Nitroaniline } (47\%) + o\text{-Nitroaniline } (2\%)\end{aligned}$$

(Key Point: In strongly acidic medium, aniline gets protonated to form the meta-directing anilinium ion $$[\text{C}_6\text{H}_5\text{NH}_3]^+$$, yielding $$47\%$$ meta-product)

Controlled Nitration (for $$p$$-Nitroaniline): Acetylate first using $$(\text{CH}_3\text{CO})_2\text{O}$$, nitrate, then hydrolyze.