Question

Which one of the carbocations from the following is most stable?

• A.
• B.
• C.
• D.

Hint:

Carbocations are stabilized by resonance and electron-donating groups, while electron-withdrawing groups tend to destabilize them. Look for conjugated systems or groups that can delocalize the positive charge to predict carbocation stability.

Answer 1

The Correct Option is B

Carbocation Stability 

Given:

- The carbocation intermediate is stabilized by the following effects: - **Inductive Effect (+I)**: Electron-withdrawing groups stabilize the carbocation. - **Resonance Effect (+M)**: Groups with lone pairs can donate electron density through resonance to stabilize the carbocation. - **Hyperconjugation**: Delocalization of electrons from adjacent C-H bonds to the empty p-orbital of the carbocation center stabilizes the carbocation.

Step 1: Analysis of Option 2

In **Option 2**, the carbocation is conjugated with a stronger +M group \( -OCH_3 \), which provides resonance stabilization to the positive charge on the carbocation. \[ \text{Resonance Effect:} \quad -OCH_3 \text{ provides electron density through resonance}. \] This leads to increased stabilization of the carbocation in **Option 2** compared to others.

Final Conclusion:

The carbocation in **Option 2** is the most stable due to the resonance stabilization provided by the \( -OCH_3 \) group.