The dienophile shown is heated with each of the dienes in the options. Which diene essentially fails to give a Diels-Alder adduct because its s-cis conformation is severely destabilised by steric clash between the inner substituents of its two terminal carbons?

AStructure A
BStructure B
CStructure C
DStructure D

Answer: B

The compound shown is maleic anhydride, a good dienophile. A diene must adopt the s-cis conformation to react. In (2Z,4Z)-hexa-2,4-diene the two methyl groups point inward in the s-cis form and clash, so the diene hardly reacts. The (2E,4E) isomer has outward methyls, cyclopentadiene is locked s-cis, and 2,3-dimethylbutadiene is unhindered.

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The dienophile shown is heated with each of the dienes in the options. Which diene essentially fails to give a Diels-Alder adduct because its s-cis conformation is severely destabilised by steric clash between the inner substituents of its two terminal carbons?

Answer: B

More questions on Alkyne hydration, hydroboration and Diels-Alder products