In electrophilic aromatic substitution, which statement about the mechanism is true?

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Multiple Choice

In electrophilic aromatic substitution, which statement about the mechanism is true?

In electrophilic aromatic substitution, the ring first sacrifices aromatic stability to attach the electrophile. The electrophile adds to the ring to form a sigma complex (an arenium ion), which is not aromatic. This intermediate is higher in energy because it lacks the delocalized pi system. Then a base removes the attached proton, restoring the planar, conjugated pi system and reestablishing aromaticity to give the substituted benzene. This restoration of aromaticity is the driving force behind the reaction. Why the other ideas aren’t correct here: the ring does not gain aromaticity during the reaction; it loses it temporarily and then regains it. The mechanism isn’t SN2 on an sp3 carbon, since the key step involves electrophilic attack on an sp2 carbon of the aromatic ring, not a backside displacement on an sp3 center. And it isn’t a radical polymerization process, which would involve radical species and polymer growth rather than a single-step substitution on an aromatic ring.

In electrophilic aromatic substitution, the ring first sacrifices aromatic stability to attach the electrophile. The electrophile adds to the ring to form a sigma complex (an arenium ion), which is not aromatic. This intermediate is higher in energy because it lacks the delocalized pi system. Then a base removes the attached proton, restoring the planar, conjugated pi system and reestablishing aromaticity to give the substituted benzene. This restoration of aromaticity is the driving force behind the reaction.

Why the other ideas aren’t correct here: the ring does not gain aromaticity during the reaction; it loses it temporarily and then regains it. The mechanism isn’t SN2 on an sp3 carbon, since the key step involves electrophilic attack on an sp2 carbon of the aromatic ring, not a backside displacement on an sp3 center. And it isn’t a radical polymerization process, which would involve radical species and polymer growth rather than a single-step substitution on an aromatic ring.

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