Free Radical Stability

Free Radicals are trivalent carbon species with one unpaired electron. They are stabilized similarly to carbocations:

• Order: $3^{\circ }>2^{\circ }>1^{\circ }>\text{Methyl}$.
• Reasons:

1. Hyperconjugation: Delocalization of the unpaired electron into adjacent $\sigma -C-H$ bonds. More $\alpha -H$ (found in $3^{\circ }$) leads to more stable radical structures.
2. Resonance: If a radical is adjacent to a double bond (Allylic) or benzene ring (Benzylic), it is exceptionally stable due to delocalization.