Benzene in electrophilic aromatic

Another drawback to the use of amino-substituted benzenes in electrophilic aromatic substitution reactions is that Friedel-Crafts reactions are not successful (Section 16.3). The amino group forms an acid-base complex with the AICI3 catalyst, which prevents further reaction from occurring. Both drawbacks can be overcome, however, b3 carrying out electrophilic aromatic substitution reactions on the corresponding amide rather than on the free amine. 

Explain why pyridine is less reactive than benzene in electrophilic aromatic substitution reactions. 

The alkenes most reactive to cationic polymerization contain electron-donating functional groups that can stabilize the carbocation intermediate. The reactivity order of substituents in cationic polymerization is similar to the reactivity order of substituted benzenes in electrophilic aromatic substitution reactions. 

The reaction of quinoline (78) with bromine and sulfuric acid gives a bromi-nated quinoline derivative via reaction with Br+, but where Note that quinoline is a base, and it will react with sulfuric acid to form an ammonium salt. Remember that pyridine is much less reactive than benzene in electrophilic aromatic substitution reactions. Therefore, assume that the ring containing nitrogen is much less reactive. This leaves C5-C8 as potential sites for electrophilic substitution. Indeed, 78 reacts with bromine and srdfuric acid to give a mixture of 5-bromoquinoline and 8-bromoquinoline, with 5-bromoquinoline being the major product. ... 

For each N-substituted benzene, predict whether the compound reacts faster than, slower than, or at a similar rate to benzene in electrophilic aromatic substitution. Then draw the major product(s) formed when each compound reacts with a general electrophile E. ... 

Since pyridine is less reactive than benzene in electrophilic aromatic substitution reactions, it should not be surprising that pyridine is more reactive than benzene in nucleophilic aromatic substitution reactions. The electron-withdrawing nitrogen atom that destabilizes the intermediate in electrophilic aromatic substitution stabilizes the intermediate in nucleophilic aromatic substitution. Notice that, in nucleophilic aromatic substitution reactions, the ring has a leaving group that can be replaced by a nucleophile. 

Electron-donating groups make the compound more reactive than benzene in electrophilic aromatic substitution. Electron-withdrawing groups make the compound less reactive than benzene in electrophilic aromatic substitution. 

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