Which of the following compound give solvolysis reaction with slowest rate ?

Options

A. `P-overset(o+)(N)R_(3)-C_(6)H_(4)-CH_(2)-Br`
B. `p-C Cl_(3)-C_(6)H_(4)-CH_(2)-Br`
C. `P-N equiv C-C_(6)H_(4)-CH_(2)-Br`
D. `C_(6)H_(5)-CH_(2)-Br`

Explanation

To determine which of the given compounds undergoes solvolysis at the slowest rate, we need to analyze the stability of the carbocations formed during the solvolysis reaction. The stability of the carbocation is crucial because a more stable carbocation will lead to a faster reaction rate.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have four compounds with a common structure: C6H4CH2Br. The variations are:
- Compound 1: C6H4CH2Br with a PNr3+ group.
- Compound 2: C6H4CH2Br with a PCCl3 group.
- Compound 3: C6H4CH2Br with a PNCBC group.
- Compound 4: HC6H4CH2Br (no additional group).

2. **Understanding Solvolysis**:
Solvolysis involves the reaction of a substrate with a solvent, typically resulting in the formation of a carbocation intermediate. The rate of solvolysis is influenced by the stability of this carbocation.

3. **Analyzing Carbocation Stability**:
- **Compound 1 (PNr3+)**: The presence of a positively charged phosphorus group can stabilize the carbocation through resonance or inductive effects.
- **Compound 2 (PCCl3)**: Similar to Compound 1, the phosphorus group can provide some stabilization, but chlorine is more electronegative and can withdraw electron density, which may destabilize the carbocation slightly.
- **Compound 3 (PNCBC)**: The presence of a triple bond (PN≡C) is likely to destabilize the carbocation significantly due to the strong electronegativity of the nitrogen and the nature of the triple bond, which pulls electron density away from the carbocation.
- **Compound 4 (HC6H4CH2Br)**: This compound does not have any additional groups that would destabilize the carbocation, making it relatively stable.

4. **Conclusion**:
Among the four compounds, Compound 3 (C6H4CH2Br with PNCBC) will give the solvolysis reaction with the slowest rate due to the destabilizing effect of the PN triple bond, which decreases the stability of the carbocation formed during the reaction.

### Final Answer:
The compound that gives the solvolysis reaction with the slowest rate is **Compound 3 (C6H4CH2Br with PNCBC)**.