In which of the following C-Cl Bond ionisation shall give most stable ion ?

Options

A.
B.
C.
D. `Ph-CH_(2)-Cl`

Answer

To determine which C-Cl bond ionization gives the most stable ion, we will analyze the stability of the resulting carbocations formed from each compound.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We need to identify the compounds in question that contain the C-Cl bond. Let's assume we have four different compounds with varying structures.

2. **Understand the Ionization Process**:
When the C-Cl bond is broken, a carbocation is formed. The stability of this carbocation is influenced by the surrounding groups attached to the carbon atom that loses the chlorine atom.

3. **Analyze the First Compound**:
In the first compound, when the C-Cl bond breaks, a phenyl carbocation is formed. This carbocation can stabilize itself through resonance due to the presence of the benzene ring. This resonance allows the positive charge to be delocalized, making the carbocation relatively stable.

4. **Analyze the Second Compound**:
The second compound has three phenyl groups attached to the carbon. When the C-Cl bond breaks, a carbocation is formed that can utilize resonance from all three phenyl groups. This extensive delocalization of the positive charge makes this carbocation the most stable among the options.

5. **Analyze the Third Compound**:
The third compound has only one phenyl group. While it can still stabilize the carbocation through resonance, it is less stable than the carbocation formed in the second compound due to the lack of additional resonance contributors.

6. **Analyze the Fourth Compound**:
The fourth compound is a benzyl carbocation, which has one phenyl group. It is more stable than a simple alkyl carbocation but less stable than the carbocation formed in the second compound with three phenyl groups.

7. **Conclusion**:
Based on the analysis, the carbocation formed from the second compound, which has three phenyl groups, is the most stable due to the maximum resonance stabilization.

### Final Answer:
The C-Cl bond ionization that gives the most stable ion is from the **second compound** with three phenyl groups.