Statement-I: Nucleophilic substitution reaction on an optically active alkyl halide gives a mixture of enantiomers.
Because Statement-II: The reaction occurs by `S_(N^(1))` mechanism.

Options

A. Statement-I is True, Statement-II is True, Statement-II is a correct explanation for Statement-I
B. Statement-I is True, Statement-II is True, Statement-II is NOT a correct explanation for Statement-I
C. Statement-I is True, Statement-II is False.
D. Statement-I is False, Statement-II is True.

Answer

To solve the question, we need to analyze both statements provided:

**Statement I:** Nucleophilic substitution reaction on an optically active alkyl halide gives a mixture of enantiomers.

**Statement II:** The reaction occurs by the SN1 mechanism.

### Step-by-Step Solution:

1. **Understanding Optically Active Alkyl Halides:**
- An optically active alkyl halide has a chiral carbon, which means it has four different substituents attached to it. This chirality allows the compound to exist in two non-superimposable mirror images known as enantiomers.

2. **Identifying the Type of Alkyl Halide:**
- Optically active alkyl halides are typically secondary (2°) or tertiary (3°) alkyl halides. Primary (1°) alkyl halides are generally not optically active because they do not have a chiral center.

3. **Mechanism of Nucleophilic Substitution:**
- The SN1 mechanism involves two steps:
- First, the alkyl halide undergoes ionization to form a carbocation.
- Second, the nucleophile attacks the carbocation. Since the carbocation is planar, the nucleophile can attack from either side, leading to the formation of both enantiomers.

4. **Formation of Enantiomers:**
- In the case of an optically active alkyl halide undergoing an SN1 reaction, the nucleophile can attack from either the front or the back of the plane of the carbocation. This results in a mixture of products: one retaining the original configuration and the other inverting it, thus producing a racemic mixture (equal amounts of both enantiomers).

5. **Conclusion:**
- Since the nucleophilic substitution reaction on an optically active alkyl halide indeed gives a mixture of enantiomers and this occurs via the SN1 mechanism, both statements are true. Furthermore, Statement II correctly explains Statement I.

### Final Answer:
- **Both Statement I and Statement II are true. Statement II is the correct explanation for Statement I.**

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