Which of the following combinations is correctly matched?

Options

A. `H_(3)C-underset(D)underset(|)overset(H)overset(|)C-Cl,S_(N)2` Walden inversion
B. `H_(3)C-underset(D)underset(|)overset(H)overset(|)C-Cl,S_(N)1` Waldem inversion
C. `H_(5)C_(6)-underset(CH_(3))underset(|)overset(C_(2)H_(5))overset(|)C-Cl,S_(N)1` only retension
D. `H_(5)C_(6)-underset(CH_(3))underset(|)overset(C_(2)H_(5))overset(|)C-Cl,S_(N)1` only inversion

Answer

To determine which combination is correctly matched, we need to analyze the mechanisms of SN1 and SN2 reactions and their characteristics.

### Step-by-Step Solution:

1. **Understanding SN1 Mechanism:**
- In an SN1 reaction, the nucleophile attacks after the leaving group departs, leading to the formation of a carbocation intermediate.
- The stability of the carbocation is crucial: tertiary carbocations are more stable than secondary, which are more stable than primary.
- Since the nucleophile can attack from either side of the planar carbocation, a racemic mixture of products (both R and S configurations) is formed.

**Hint:** Remember that SN1 reactions lead to racemic mixtures due to the planar nature of the carbocation.

2. **Understanding SN2 Mechanism:**
- In an SN2 reaction, the nucleophile attacks the substrate from the opposite side of the leaving group, resulting in a single transition state.
- The nucleophile attacks the less hindered side, making primary substrates more favorable for SN2 reactions.
- The result of this backside attack is inversion of configuration at the carbon center, known as Walden inversion.

**Hint:** SN2 reactions are characterized by a backside attack and result in inversion of configuration.

3. **Analyzing the Options:**
- **Option 1:** SN2 leads to Walden Inversion at a primary carbon.
- This is correct because SN2 reactions occur predominantly with primary carbons and result in inversion of configuration.
- **Option 2:** SN1 leads to a mixture of products.
- This is also correct, but it does not specify the configuration or the type of product formed, making it less specific than the first option.

**Hint:** Compare the specificity of the options. The first option clearly states the mechanism and outcome.

4. **Conclusion:**
- The first option (SN2 Walden Inversion at primary carbon) is correctly matched.
- The second option is misleading as it does not specify the nature of the mixture produced in SN1.

### Final Answer:
**The correctly matched combination is: SN2 Walden Inversion at a primary carbon.**