Optically active alkyl halides under going `S_N 1` mechanism leads to:

Options

A. retention of configuration
B. racemisation
C. inversion of configuration
D. both (a) and (c)

Explanation

To solve the question about optically active alkyl halides undergoing an SN1 mechanism, we can break it down into several steps:

### Step 1: Understand the SN1 Mechanism
The SN1 mechanism involves two main steps:
1. Formation of a carbocation after the leaving group departs.
2. Nucleophilic attack on the carbocation.

### Step 2: Identify the Starting Material
We start with an optically active alkyl halide. This means the carbon attached to the halide (e.g., Cl) is a chiral center, having four different groups attached to it.

### Step 3: Formation of the Carbocation
When the alkyl halide undergoes the SN1 reaction, the leaving group (Cl) departs, forming a carbocation. This carbocation is planar and can be attacked by a nucleophile from either side.

### Step 4: Nucleophilic Attack
The nucleophile can attack the carbocation from two different orientations:
- From above the plane of the carbocation.
- From below the plane of the carbocation.

### Step 5: Resulting Products
The two different orientations of attack will lead to two different products:
1. One product will have the nucleophile (e.g., OH) on the wedge (indicating it is above the plane).
2. The other product will have the nucleophile on the dash (indicating it is below the plane).

### Step 6: Analysis of the Products
Since the original compound was chiral, and the nucleophile can attack from both sides, we end up with a racemic mixture of two enantiomers (one R and one S configuration).

### Step 7: Conclusion
The overall result of the reaction leads to a racemic mixture, which is a 1:1 mixture of the two enantiomers. This process is called racemization.

### Final Answer
The answer to the question is that optically active alkyl halides undergoing SN1 mechanism leads to **racemization**.

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