Question

The correct order of stability of given carbocations is:

• A. $I>IV>III>II$
• B. $I>IV>II>III$
• C. $IV>I>III>II$
• D. $IV>I>II>III$

Answer 1

The correct option is B $I>IV>II>III$

The stability order is explained on the basis of Meromeric effect, Inductive effect and Hyperconjugation.

In these effects, we have to follow following order for stabler.

$MeromericEffect$>$Hyperconjugation$>$InductiveEffect.$

$-OC{H}_3$ is ${}^{\prime }+M^{\prime }$ group.

The cation which is in resonance with $-OC{H}_3$ is more stable.

So $\left(I\right)$ and $\left(IV\right)$ are more stable than $\left(II\right)$ and $\left(III\right)$.

Between $\left(I\right)$ and $\left(IV\right)$, ${}^{\prime }{I}^{\prime }$ is more stable because of Inductive effect as carbon atoms are more in $I$.

Between $\left(II\right)$ and $\left(III\right)$, $II$ is more stable because of $9$ hyper conjugative structure of $II$ than ${}^{\prime }{4}^{\prime }$ hyper conjugative structure of $III$.

So stability order is $I>IV>II>III$