Question

The major product formed in the following reaction is 

• A. (A)
• B. (B)
• C. (C)
• D. (D)

Hint:

When analyzing cycloaddition reactions, always consider the types of bonds being formed and the reactivity of the starting materials.

Answer 1

The Correct Option is C

Reaction type: This is a Diels-Alder reaction between cyclopentadiene (diene) and dimethyl maleate (dienophile).

Reactants:

• Diene: Cyclopentadiene (5-membered ring with conjugated double bonds)
• Dienophile: Dimethyl maleate (cis-alkene with two CO₂CH₃ groups)

Diels-Alder mechanism:

• [4+2] cycloaddition reaction
• Creates a 6-membered ring
• Stereospecific: cis substituents on dienophile remain cis in product
• Endo rule: dienophile orients with electron-withdrawing groups under the diene

Product structure:

1. Cyclopentadiene provides 4 π electrons (diene)
2. Dienophile provides 2 π electrons
3. Forms bicyclic structure with 6-membered ring fused to 5-membered ring
4. Two CO₂CH₃ groups maintain cis relationship
5. Endo approach places CO₂CH₃ groups on the same side as the bridging methylene

Analyzing options:

(A): Shows two CO₂CH₃ groups on different positions - incorrect orientation

(B): Shows bicyclic structure but wrong CO₂CH₃ positioning - exo product

(C): Shows correct bicyclic norbornene structure with two CO₂CH₃ groups in endo, cis positions (both pointing toward the bridge) - CORRECT 

(D): Shows CO₂CH₃ groups on bridgehead positions - structurally incorrect

Answer: (C)