CBSE Class 12-science Answered

Some functional groups promote substitution at the ortho or para positions and are called ortho or para directing groups. These groups with unshared pairs of electrons are strongly activating and electron donating groups. These groups add electron density to the p system making it more nucleophilic.

Common ortho, para directing groups:

While the other groups that increase substitution at the meta position are called meta directing groups. These groups draw substantial electron density from the pi system making it less nucleophillic. These are strongly deactivating groups. These meta directing groups are electron withdrawing groups.

Common meta directing groups: