Question

Rank the monosubstituted benzene compounds below in order of decreasing reactivity towards electrophilic substitution.

Answer 1

- CH3 > - CH2Cl > - CHCl2 > - CCl3

Presence of electron donating group on benzene ring can increase the activity towards electrophilic substitution reactions. It is because of increase of electron density of the ring.

Alkyl groups ( - CH₃) can acts as electron donor groups through positive inductive effect, so presence of - CH₃ group can increase the activity of the ring.

But presence of electron withdrawing Cl atoms on methyl group decrease its ability to act as ring actiator. More is the number of Cl atoms less is the ability to act as electron donor to the ring. So, the activity of the resulting ring will decrease.