Question

Rank the following carbocations in order of stability ($1=$ most stable)

• A. $A\to 2,B\to 1,C\to 3,D\to 4$
• B. $A\to 4,B\to 2,C\to 1,D\to 3$
• C. $A\to 4,B\to 3,C\to 2,D\to 1$
• D. $A\to 1,B\to 2,C\to 3,D\to 4$

Answer 1

Answer: (A)

A $-2[3^{\circ }$ carbocation with cross conjugation $]$
B $-1[2^{\circ }$ carbocation with extended conjugation ]
C - $3[3$ carbocation with $4$ hyperconjugations and $+1$ of $3$ alkyl groups $]$
D - $4[2^{\circ }$ carbocation with $2$ hyperconjugations and $+I$ of $2$ alkyl groups]
So order will be
$A\to 2,B\to 1,C\to 3,D\to 4$