Activating + ortho/para directors: -OH, -OR, -NH2, -NHR, -NR2, -NHCOR, -R (alkyl)

• These donate electron density into the ring (by +M or hyperconjugation)
• Sigma complex at ortho/para has a resonance structure with positive charge on the carbon bearing the substituent — directly stabilized by electron donation

Deactivating + ortho/para directors: -F, -Cl, -Br, -I

• -I (deactivating) > +M (weak), but +M places electron density at o/p positions

Deactivating + meta directors: -NO2, -CN, -COR, -CHO, -COOH, -COOR, -SO3H

• These withdraw electrons from the ring
• At o/p attack, the sigma complex has positive charge directly on the C bearing the withdrawing group (very unstable). Meta avoids this.

When two groups conflict: The more activating (stronger +M) group controls direction. If both are deactivating, the weaker deactivator controls.