Question

Arrange carbocations in increasing order of stability.

• A. Tertiary < Secondary < Primary
• B. Primary < Secondary < Tertiary
• C. Secondary < Primary < Tertiary
• D. Primary < Tertiary < Secondary

Hint:

Carbocation stability generally follows: Tertiary \(>\) Secondary \(>\) Primary \(>\) Methyl due to increasing hyperconjugation and inductive effects.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Carbocations are organic intermediates with a positively charged carbon atom. Their stability is determined by how well the positive charge is dispersed or neutralized by neighboring groups.
Step 2: Detailed Explanation:
Carbocation stability is primarily influenced by two factors:
1. Inductive Effect (+I): Alkyl groups are electron-donating. They push electron density toward the positive carbon, helping to stabilize it. More alkyl groups mean more stabilization.
2. Hyperconjugation: The positive charge is stabilized by the overlap of sigma bonds (C-H) of adjacent alkyl groups with the empty p-orbital of the carbocation. More alpha-hydrogens result in higher stability.
Classification:
- Primary (\(1^\circ\)): One alkyl group attached to the positive carbon.
- Secondary (\(2^\circ\)): Two alkyl groups attached.
- Tertiary (\(3^\circ\)): Three alkyl groups attached.
Therefore, the order of stability is \(3^\circ>2^\circ>1^\circ\).
Step 3: Final Answer:
The increasing order of stability is Primary < Secondary < Tertiary.