Question 13.23:-

Out of benzene, m–dinitrobenzene and toluene which will undergo nitration most easily and why?

The ease of nitration depends on the presence of electron density on the compound to form nitrates. Nitration reactions are examples of electrophilic substitution reactions where an electron-rich species is attacked by a nitronium ion (${{\mathrm{NO}}_{2}}^{-}$).
Now, ${{\mathrm{CH}}_{3}}^{-}$ group is electron-donating and ${{\mathrm{NO}}_{2}}^{-}$ is electron-withdrawing. Therefore, toluene
will have the maximum electron density among the three compounds followed by benzene.
On the other hand, m– Dinitrobenzene will have the least electron density. Hence, it will undergo nitration with difficulty. Hence, the increasing order of nitration is as follows: