How do you determine which molecule has greater liability of undergoing Electrophillic substitution reactions.

Example question: Arrange in order of increasing Electrophillic substituion reactions: Benzene, Nitro Benzene, Toulene

Dear student,
electrophillic substitution rtn. occurs only when the electron loving electrophile attacks an electron rich substrate. the electrophiles hunt for electron rich substrate
In this case we can see that, toluene has -CH₃group attached to benzene ring which has +I effect which is electron donating group hence it increases electron density on the benzene ring , rendering it more prone to attack by electrophile.

In Nitrobenzene, -NO₂group, has -I/-M effect which is electron withdrawing and it reduces electron density on the benzene ring thus making it less reactive to electrophillic subs titution retn.

benzene’s suceptibility to electrophillic subs. is in between the other two comp. since no substituents are attached to the benzene ring to increase or decrease electron density .

rate of electro. subs. – toluene>benzene>nitrobenzene