Question

Which one of the following carbocation violates Bredt's rule?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

According to Bredt's rule, bicyclic molecule having bridge can not have bridge head C as $s{p}^2$ C. A multiple bond, carbocation, transition state and, to a lesser degree, free radicals cannot be placed at the bridgehead of a bridged ring system (unless the rings are large enough).
This is not valid for fused ring systems or rings with 8 or more carbon atoms.