19. Reactions of Aromatics: EAS and Beyond

Propose a mechanism that shows why p-chlorotoluene reacts with sodium hydroxide at 350 °C to give a mixture of p-cresol and m-cresol.

Which is the major product for the following reaction?

Which is the major product for the following reaction?

The following compound reacts with a hot, concentrated solution of NaOH (in a sealed tube) to give a mixture of two products. Propose structures for these products, and give a mechanism to account for their formation.

The highly reactive triple bond of benzyne is a powerful dienophile. Predict the product of the Diels–Alder reaction of benzyne (from chlorobenzene and NaOH, heated) with cyclopentadiene.

Explain why the following compound is not stable:

What are the products of the following reactions?

d.

What are the products of the following reactions?

g.

Propose a mechanism for the following reaction:

One of the following compounds undergoes electrophilic aromatic substitution predominantly at C-3, and one undergoes electrophilic aromatic substitution predominantly at C-4. Which is which?

b. At what position does pyridine-N-oxide undergo electrophilic aromatic substitution?

Show how the following compounds can be prepared from the given starting material.

b.

Assume that H_a is the proton removed in the first step of the benzyne mechanism with p-chlorotoluene. Draw the benzyne intermediate and identify the two products that will result.

Predict the product(s) of the following nucleophilic aromatic substitution reactions occurring by the benzyne mechanism.

(b)

Addition by the benzyne mechanism is not usually regioselective. Explain the fact that the reaction shown is highly regioselective for the product shown.