Maleic anhydride does not react with but-2-ene but reacts rapidly with 2,3-dimethylbuta-1,3-diene under thermal conditions. Why do these observations occur under thermal conditions?

• A. Maleic anhydride does not react with but-2-ene under thermal conditions because it would undergo antarafacial ring closure that is not possible in the formation of a four-membered ring. While, it reacts rapidly with 2,3-dimethylbuta-1,3-diene under thermal conditions because it would undergo suprafacial ring closure.
• B. Maleic anhydride does not react with but-2-ene under thermal conditions because it would undergo suprafacial ring closure that is not possible in the formation of a four-membered ring. While, it reacts rapidly with 2,3-dimethylbuta-1,3-diene under thermal conditions because it would undergo antarafacial ring closure.
• C. Maleic anhydride does not react with but-2-ene under thermal conditions because it would undergo antarafacial ring closure that is not possible in the formation of a five-membered ring. While, it reacts rapidly with 2,3-dimethylbuta-1,3-diene under thermal conditions because it would undergo antarafacial ring closure.
• D. Maleic anhydride does not react with but-2-ene under thermal conditions because it would undergo suprafacial ring closure that is not possible in the formation of a five-membered ring. While, it reacts rapidly with 2,3-dimethylbuta-1,3-diene under thermal conditions because it would undergo suprafacial ring closure.

Answer: (A)