Question

The products P and Q formed in the reaction are 

• A. A
• B. B
• C. C
• D. D

Hint:

Singlet carbenes react stereospecifically with alkenes to give syn cyclopropanes. Triplet carbenes, in contrast, give mixtures due to stepwise radical addition.

Answer 1

The Correct Option is B

Step 1: Type of reaction.
A carbene (:CFCI) in the singlet state undergoes stereospecific cycloaddition to alkenes, forming cyclopropane derivatives.
Step 2: Mechanistic pathway.
- Singlet carbenes add to the same face of the double bond (syn addition).
- The product retains the stereochemistry of the alkene substituents.
- Here, isobutene reacts to form a cyclopropane ring substituted with –Cl and –F atoms on the same carbon.
Step 3: Conclusion.
The major product corresponds to structure (A).