On chiral centre there is always ........... in `S_(N)^(1)` reaction

Options

A. 100% retention
B. 100% inversion
C. 100% recenisation
D. inversion is more than retention leading to recenisation

Answer

To answer the question regarding what happens at a chiral center during an \( S_N1 \) reaction, we can break down the process into clear steps:

### Step-by-Step Solution:

1. **Understanding \( S_N1 \) Mechanism**:
- The \( S_N1 \) (Substitution Nucleophilic Unimolecular) reaction involves two main steps: the formation of a carbocation intermediate and the nucleophilic attack.

2. **Formation of Carbocation**:
- In the first step, the leaving group departs, resulting in the formation of a planar carbocation. This carbocation has a trigonal planar geometry, making it symmetrical.

3. **Nucleophilic Attack**:
- The nucleophile can attack the carbocation from either side (front or back) due to its planar structure. This leads to two possible outcomes:
- **Inversion**: If the nucleophile attacks from the opposite side of the leaving group, it results in inversion of configuration.
- **Retention**: If the nucleophile attacks from the same side as the leaving group, it results in retention of configuration.

4. **Resulting Configurations**:
- Since both inversion and retention are possible, the product will be a mixture of both configurations. This phenomenon is known as **racemization**.

5. **Conclusion**:
- Therefore, at a chiral center during an \( S_N1 \) reaction, there is always **inversion and retention leading to racemization**.

### Final Answer:
On a chiral center, there is always **inversion and retention leading to racemization** in an \( S_N1 \) reaction.

---