Which one of the following reactions does not occur?

Aniline does not undergo Friedel-Crafts alkylation or Friedel-Crafts acylation.

This is because aniline reacts with the Lewis acid catalyst:

$$\mathrm{AlCl_3}$$

to form a salt.

$$\mathrm{C_6H_5NH_2 + AlCl_3 \longrightarrow C_6H_5NH_2^+AlCl_4^-}$$

Due to salt formation, the nitrogen atom acquires a positive charge.

$$\mathrm{-NH_2 \longrightarrow -NH_2^+}$$

The positively charged amino group becomes strongly electron-withdrawing and acts as a strong deactivating group.

Hence, the benzene ring becomes less reactive towards electrophilic substitution.

Therefore:

$$\mathrm{Friedel\text{-}Crafts\ Alkylation\ and\ Acylation\ do\ not\ occur}$$

However, other electrophilic substitution reactions such as:

$$\mathrm{Nitration,\ Halogenation,\ and\ Sulphonation}$$

can still take place under suitable conditions.

Thus, the right option is C.