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JEE Main levelSingle correct optionDifficulty 2 of 3hc191

Cyclopenta-1,3-diene reacts with maleic anhydride at room temperature. The major (kinetic) product is:

AThe endo adduct, with the anhydride ring oriented towards the new $C = C$ bridge side
BThe exo adduct, with the anhydride ring oriented towards the $CH X_{2}$ bridge
CAn equimolar mixture of endo and exo adducts
DNo adduct, since the diene is cyclic

Answer: A

The endo rule says the substituents of the dienophile lie under the diene pi system in the transition state because of favourable secondary orbital overlap. The endo adduct is therefore the kinetic product. Cyclic dienes are locked in s-cis form and react very readily.

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