19. Reactions of Aromatics: EAS and Beyond

In the context of nucleophilic aromatic substitution, why is the ${\mathrm{NO}}_2$ group considered a meta director when it comes to electrophilic aromatic substitution reactions?

Which of the following statements about nucleophilic aromatic substitution is true?

Show how the substituents containing the azo group (N=N) can facilitate both electrophilic and nucleophilic aromatic substitution.

(a)

Provide the structure of the product formed from the reaction of 1-bromo-2,4,6- trinitrobenzene with one equivalent of sodium methoxide. 

Provide the major organic product for the following reaction.

Provide the major organic product for the following reaction.

Which of the following compounds is most likely to undergo nucleophilic aromatic substitution via the addition-elimination pathway? 

Propose mechanisms and show the expected products of the following reactions.

(a) 2,4-dinitrochlorobenzene + sodium methoxide (NaOCH₃)

(b) 2,4-dimethylchlorobenzene + sodium hydroxide, 350 °C

Propose mechanisms and show the expected products of the following reactions.

(c) p-nitrobromobenzene + methylamine (CH₃–NH₂)

(d) 2,4-dinitrochlorobenzene + excess hydrazine (H₂N–NH₂)

Draw resonance contributors for the carbanion that would be formed if meta-chloronitrobenzene were to react with hydroxide ion. Why doesn't the reaction occur?

We have considered nucleophilic aromatic substitution of pyridine at the 2-position and 3-position but not at the 4-position. Complete the three possible cases by showing the mechanism for the reaction of methoxide ion with 4-chloropyridine. Show how the intermediate is stabilized by delocalization of the charge onto the nitrogen atom.

How do the mechanisms of the following reactions differ?

What are the products of the following reactions?

b.

Propose a mechanism for the following reaction: