Question

What is the stability order of carbocation?

Answer 1

Stability order of carbocation:

1. So actually, carbocation is a molecule in which there is a presence of positive charge on the carbon atom and three bonds attached basically they are the carbon cations.
2. They are planar in structure as the trivalent Carbon is ${\mathrm{sp}}^2$ hybridized.
3. So, only 6 valence electrons are present on Carbon which are actually used up in the making of sigma bonds, and also the p-orbital that is extending above and below the plane is just unoccupied.
4. The stability of carbocation depends upon the Inductive effect and the Hyperconjugation effect.
5. According to the Inductive effect when the electrons in covalent bonds are shifted towards a nearby atom with a higher electronegativity, then the positively charged carbocation will draw in the electron density from the surrounding substituents thereby gaining stabilization.
6. Also the alkyl groups are more effective at inductively donating electron density than Hydrogen because they are larger and more polarizable and also contain more bonding electrons.
7. So, the more alkyl groups attached to a carbocation the more would be the inductive effect and so the carbocation becomes stable.
8. Hyperconjugation is basically an electron donation that occurs from the parallel overlap of the p-orbitals with the adjacent hybridized orbitals participating in the sigma bonds.
9. So, in this also as the number of alkyl substituents increases, the number of sigma bonds available for hyperconjugation also increases and the carbocation becomes more stable.
10. Therefore, Stability of Tertiary carbocation > Secondary carbocation > Primary carbocation > Methyl.