Question

Choose the correct stability order of the given free radicals. 

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

Hint:

Free radicals are more stable when they have resonance stabilization and hyperconjugation.

Answer 1

The Correct Option is B

Step 1: Understanding Free Radical Stability Factors
The stability of free radicals is influenced by: 1. Resonance stabilization
2. Hyperconjugation
3. Inductive effects
Step 2: Evaluating Stability of Each Compound
Free radicals (II) and (I) have stabilizing effects from resonance and hyperconjugation.
Free radical (III) has a strong $-I$ effect from $-NO_2$, which destabilizes it.
Free radical (IV) has a weak electron-withdrawing effect from $-CN$, making it more stable than (III).
Step 3: Ranking Stability Order
The stability order follows: $$II>I>IV>III$$ Thus, the correct answer is (B).