In which of the following compounds , the C - Cl bond ioniosation shall give most stable carbonium ion ?

Options

A.
B.
C.
D.

Answer

To determine which compound will produce the most stable carbonium ion (carbocation) upon ionization of the C-Cl bond, we need to analyze the stability of the resulting carbocations formed from each compound. The stability of carbocations is influenced by the degree of substitution (primary, secondary, tertiary) and resonance effects.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Let's denote the compounds as A, B, C, and D. We need to analyze the C-Cl bond in each compound and the carbocation that forms upon ionization.

2. **Understand Carbocation Stability**:
- The stability of carbocations follows this order:
- Tertiary (3°) > Secondary (2°) > Primary (1°) > Methyl (CH3+).
- Tertiary carbocations are stabilized by hyperconjugation and inductive effects from adjacent alkyl groups.

3. **Analyze Each Compound**:
- **Compound A**: When C-Cl bond breaks, it forms a primary carbocation (1°).
- **Compound B**: When C-Cl bond breaks, it forms a secondary carbocation (2°).
- **Compound C**: When C-Cl bond breaks, it forms a tertiary carbocation (3°).
- **Compound D**: When C-Cl bond breaks, it forms a benzyl carbocation, which is stabilized by resonance.

4. **Compare Stability**:
- **Tertiary Carbocation (Compound C)**: Highly stable due to three alkyl groups donating electron density.
- **Benzyl Carbocation (Compound D)**: Stabilized by resonance, but less stable than a tertiary carbocation due to the lack of hyperconjugation.
- **Secondary Carbocation (Compound B)**: Less stable than tertiary and benzyl.
- **Primary Carbocation (Compound A)**: Least stable.

5. **Conclusion**:
- The most stable carbocation is formed from **Compound C**, which is a tertiary carbocation.

### Final Answer:
The compound that will give the most stable carbonium ion upon C-Cl bond ionization is **Compound C**.