The correct order of stability of following carbocations is : [figure]
- A > B > C > D
- C > B > A > D
- B > C > A > D
- C > A > B > D
Answer
(4) C > A > B > D
Solution
C is the tropylium (cycloheptatrienyl) cation: planar, cyclic, 6π electrons (4n + 2, n = 1) aromatic; the positive charge is spread over all seven carbons most stable.
A ( Ph3C ): the charge is delocalised into three benzene rings.
B ( Ph2CH ): delocalised into only two rings A > B.
D (sec-butyl cation): a 2° alkyl carbocation stabilised only by +I effect and hyperconjugation least stable.
C > A > B > D
Answer: (4)