Question

Which of the following gives the decreasing order of stability of carbocation?

A) $IV>III>II>I$

B) $IV>III>I>II$

C)$IV>I>II>III$

Mark your answer as A, if the order given in A is correct.

Answer 1

In the carbocation, $\left(IV\right)$, the oxygen atom of the alkoxy group attached is electronegative which stabilizes the aryl group carbon atom. It is also stabilized by conjugated double bonds. Hence, it is the most stable.

Adjacent carbon-carbon pi bond stabilizes carbocations in $\left(III\right)$ is a $3^o$ carbocation and so, $\left(III\right)$ is more stable than $\left(I\right)$ at meta position which is stabler than the $\left(II\right)$ carbocation as it is least stable because of pi bond on the same carbocation carbon.

Therefore, the order of stability is as follows: $IV>III>I>II$

So, the correct answer is ( B )