which are meta ortho and para generating groups?
|Electron withdrawing groups (EWG) with p bonds to electronegative atoms (e.g. -C=O, -NO2) adjacent to the p system deactivate the aromatic ring by decreasing the electron density on the ring through a resonance withdrawing effect. The resonance only decreases the electron density at the ortho- and para- positions. Hence these sites are less nucleophilic, and so the system tends to react with electrophiles at the meta sites.|