Question: Using resonance structures, explain why a nitroso group (-NO) is an ortho, para director that deactivates a benzene ring toward electrophilic attack.

The Lewis structures used to represent the movement of electrons in a pi bonded system are named resonance structures.

Electrophiles are electron-deficient species that get attracted to electron-rich centers.

The presence of electron-withdrawing groups on a system decreases their reactivity towards electrophiles.

The nitroso group (-NO) on a benzene ring acts as a deactivating group. It pulls the pi-electron density from the ring, generating electron deficiencies (indicated using the positive charge) on ortho and para positions.

Resonance structures of nitrosobenzene

Since the presence of the nitroso group reduces the electron density of the ring, it deactivates the benzene ring towards electrophilic attack.