Nitration is the process of introducing a nitro group (-NO2) into an organic compound. Benzene, chlorobenzene, and toluene are aromatic hydrocarbons that can undergo nitration. However, the ease of nitration depends on the nature of the substituent present in the molecule.



Benzene is a highly stable aromatic compound due to the presence of delocalized electrons in the ring. However, it can undergo nitration in the presence of a mixture of concentrated nitric acid and concentrated sulfuric acid. Nitration of benzene leads to the formation of nitrobenzene.



Chlorobenzene is less reactive than benzene towards electrophilic substitution reactions due to the electron-withdrawing effect of the chlorine substituent. The chlorine atom withdraws electron density from the ring, making it less nucleophilic and less susceptible to attack by electrophiles. Hence, chlorobenzene undergoes nitration at a slower rate than benzene.



Toluene is more reactive than benzene towards electrophilic substitution reactions due to the presence of a methyl group (-CH3) as a substituent. The methyl group is electron-donating and increases the electron density on the ring, making it more nucleophilic and more susceptible to attack by electrophiles. Hence, toluene undergoes nitration more easily than benzene.



In summary, of benzene, chlorobenzene, and toluene, toluene undergoes nitration more easily due to the presence of a methyl group as a substituent. Benzene can also undergo nitration, but chlorobenzene is less reactive towards electrophilic substitution reactions due to the electron-withdrawing effect of the chlorine substituent.