Explain the stability order of free radicals.

Explanation

The stability order of free radicals is as follows:
Tertiary free radical `gt` Secondary free radical `gt` Primary free radical
It can be explained on the basis of hyperconjugation. The presence of the alkyl group attached to carbon atom leads to hyperconjugation. The greater the number of alkyl groups present, the more will be the hyperconjugated structures. Thus, greater will be the stability of free radical.
`H-underset("radical " (1^@))underset("Methyl free")underset(H)underset(|)overset(H)overset(|)(Ccdot) lt H-underset("radical " (2^@))underset("Ethyl free")underset(H)underset(|)overset(H)overset(|)(Ccdot) lt H_3C-underset("radical " (2^@))underset("Isopropyl free")underset(H)underset(|)overset(CH_3)overset(|)(Ccdot) lt H_3C-underset("radical " (3^@))underset("Teritiary-butyl free")underset(H)underset(|)overset(H)overset(|)(Ccdot)`