19. Reactions of Aromatics: EAS and Beyond

Which of the following correctly arranges the compounds $toluene$, $benzene$, and $nitrobenzene$ in order of decreasing reactivity toward electrophilic aromatic substitution?

In the general mechanism for electrophilic aromatic substitution, what is the first step?

In the context of electrophilic aromatic substitution, which position on a benzene ring substituted with a nitro group (${\mathrm{NO}}_2$) is most likely to act as an electrophilic site?

In the context of electrophilic aromatic substitution, which position on a benzene ring is most susceptible to attack by an electrophile?

What is the major product formed when isopropylbenzene (cumene) undergoes electrophilic aromatic substitution with ${\mathrm{Br}}_2$ in the presence of ${\mathrm{FeBr}}_3$?

In the nitration of benzene, which species acts as the electrophile during the electrophilic aromatic substitution reaction?

In the context of electrophilic aromatic substitution, how many electrophilic centers are present in acetyl chloride (${\mathrm{CH}}_3\mathrm{COCl}$)?

Which of the following species is commonly used as an electrophile in electrophilic aromatic substitution reactions?

During the electrophilic aromatic substitution of $\mathrm{isopropylbenzene}$ (cumene) with ${\mathrm{Br}}_2$ in the presence of a Lewis acid catalyst, which position on the benzene ring is most likely to be brominated?

Sort the following compounds in order of increasing reactivity toward electrophilic aromatic substitution: $t-\mathrm{Bu}-\mathrm{Ph}$ (tert-butylbenzene), $\mathrm{Ph}-{\mathrm{NO}}_2$ (nitrobenzene), $\mathrm{Ph}-{\mathrm{OCH}}_3$ (anisole), and $\mathrm{Ph}$ (benzene). Which sequence is correct?

Furan undergoes electrophilic aromatic substitution more readily than benzene; mild reagents and conditions are sufficient. For example, furan reacts with bromine to give 2-bromofuran.

b. Explain why furan undergoes bromination (and other electrophilic aromatic substitutions) primarily at the 2-position.

Furan undergoes electrophilic aromatic substitution more readily than benzene; mild reagents and conditions are sufficient. For example, furan reacts with bromine to give 2-bromofuran.

a. Propose mechanisms for the bromination of furan at the 2-position and at the 3-position. Draw the resonance forms of each sigma complex, and compare their stabilities.

Styrene (vinylbenzene) undergoes electrophilic aromatic substitution much faster than benzene, and the products are found to be primarily ortho- and para-substituted styrenes. Use resonance forms of the intermediates to explain these results.

What products would you expect from the following coupling reactions?

(b)

What products would you expect from the following coupling reactions?

(a)