Criteria for Nucleophilic Aromatic Substitution

In the previous chapter, we learned all about electrophilic aromatic substitution reactions. 

In this short chapter, we will look at the flipside is it possible for an aromatic ring to function as an electrophile and react with a nucleophile In other words, is it possible for the aromatic ring to be so electron-poor that it is subject to attack by a nucleophile The answer is yes. 

But in order to observe this kind of reaction, called nucleophilic aromatic substitution, we will need to meet three very specific criteria. Let s look closely at each one of these criteria  

The ring must have a very powerful electron-withdrawing group. The most common example is the nitro group  

We saw in the previous chapter that the nitro group is a strong deactivator toward electrophihc aromatic substitution because the nitro group very powerfully withdraws electron density from the ring (by resonance). This causes the electron density in the ring to be very poor  

---