Question

Note: Answer the question on the basis of information given below:

“Stability of carbocations depends upon the electron releasing inductive effect of groups adjacent to positively charged carbon atom involvement of neighbouring groups in hyperconjugation and resonance.”
Write structures of various carbocations that can be obtained from $2-$methylbutane. Arrange these carbocations in order of increasing stability.

Answer 1

Structures of $2-$Methylbutane is given below:



Structures of various carbocations that can be obtained from $2-$methylbutane are:





Carbocation is an electron deficient species. So, as the number of electrons releasing groups increases, the stability of carbocation increases.

$\text{Tertiary carbocation > secondary carbocation > primary carbocation}$

Carbocation $I$ is more stable than $IV$ because in carbocation $I,$ there are two $\alpha$ hydrogens while in $IV$ there is one $\alpha$ hydrogen due to which $I$ is more stabilised by hyperconjugation.

Thus, order of increasing stability:

$IV<I<II<III$