Diels–Alder reaction between butadiene and ethene yields which ring system?

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Multiple Choice

Diels–Alder reaction between butadiene and ethene yields which ring system?

Diels–Alder is a [4+2] cycloaddition that builds a six-membered ring by combining a conjugated diene with a dienophile in a single concerted step. Here, butadiene provides the four π electrons and ethene provides two, so the resulting ring is six atoms in size. The product retains one C=C double bond in the ring, giving cyclohexene. The other options don’t fit because cyclohexane would be fully saturated, cyclohexadiene would have two double bonds in the ring, and benzene would be aromatic—not produced by this simple Diels–Alder with ethene.

Diels–Alder is a [4+2] cycloaddition that builds a six-membered ring by combining a conjugated diene with a dienophile in a single concerted step. Here, butadiene provides the four π electrons and ethene provides two, so the resulting ring is six atoms in size. The product retains one C=C double bond in the ring, giving cyclohexene. The other options don’t fit because cyclohexane would be fully saturated, cyclohexadiene would have two double bonds in the ring, and benzene would be aromatic—not produced by this simple Diels–Alder with ethene.

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