(a) Electron rich groups act as ortho and para directing groups as they increases electron density at these two positions. Out of the given groups, following are electron rich and deficient, Electron rich −OH,−OCH3,−NHCOCH3 Electron deficient −CN,−CO2H,−CHO Hence, −OH,−OCH3 and −NHCOCH3 acts as ortho and para-directing groups towards electrophilic substitution reactions.
