Question

The correct stability order of carbocations is

• A. $(\text{CH}_3)_3\text{C}^+ > \text{CH}_3 - \text{CH}_2 > (\text{CH}_3)_2\text{CH}^+ > \text{CH}_3 \\$
• B.

  

• C.
• D.

  

Answer 1

The Correct Option is B

Correct Order: The correct stability order of the carbocations is:

(CH₃)₃C⁺ > (CH₃)₂CH⁺ > CH₃–CH₂⁺ > CH₃⁺.

Thus, the correct order of stability for the given carbocations is:

(CH₃)₃C⁺ > (CH₃)₂CH⁺ > CH₃–CH₂⁺ > CH₃⁺.

Answer 2

The stability of carbocations is influenced by several factors, primarily the degree of substitution and the availability of hyper-conjugative hydrogens.

Stability Factors: Tertiary carbocations (three alkyl groups attached) are more stable than secondary (two alkyl groups), which in turn are more stable than primary (one alkyl group) and methyl (no alkyl groups). The order of stability due to hyperconjugation and inductive effects is:

Tertiary > Secondary > Primary > Methyl.

The stability of carbocations is a crucial concept in organic chemistry as it determines the ease of various reaction mechanisms such as SN1 reactions. Carbocations are positively charged species that contain a carbon atom with only six electrons in its outer shell, making it electron-deficient.

The stability of carbocations is influenced by several factors:

• Hyperconjugation: This refers to the delocalization of electrons in σ-bonds (such as C-H bonds) to the empty p-orbital of the carbocation. The more alkyl groups attached to the positively charged carbon, the greater the hyperconjugative stabilization.
• Inductive Effect: Electron-donating groups (such as alkyl groups) can push electron density toward the positively charged center, stabilizing it.
• Resonance: If a carbocation can be stabilized through resonance by delocalization of the positive charge over a pi system, it becomes more stable.

Considering these principles, the general order of stability for carbocations is as follows:

1. Tertiary carbocations - These are the most stable due to the maximum number of hyperconjugative and inductive effects.
2. Secondary carbocations - Less stable than tertiary but more stable than primary due to fewer hyperconjugative and inductive effects.
3. Primary carbocations - These have minimal stabilization.
4. Methyl carbocations - The least stable due to the absence of any inductive or hyperconjugative stabilization.

From the above discussion, the correct stability order of the given carbocations in the options is: \((\text{CH}_3)_3\text{C}^+ > (\text{CH}_3)_2\text{CH}^+ > \text{CH}_3\text{CH}_2^+ > \text{CH}_3^+\), which matches the correct answer image provided as Option 3.

In conclusion, the stability order of carbocations is primarily determined by hyperconjugation, inductive effects, and resonance, as seen in the above analysis.