The group which increases the electron density at ortho and para positions are called as ortho-para directors,
Example:
-OH. -NH2 -NHR. -OCH3 , -CH3 , -C2H5 etc.
Let us consider the directive influence of phenolic group. Phenol is the resonance hybrid of the following structures:
In these resonance structures, the negative charge residue in the present at orilio and para positions of the ring structure. h is quite evident that the lone pair of electrons on the atom which is attached lo the ring is involved in resonance and it makes the ring more electron rich than benzene.
The electron density at oriho and para position increases as compared to the meta position. Therefore phenolic group activates the benzene ring for electrophilic attack at oriho and para positions. Hence 01-1 group is an orilio para director and activator
