Assertion:`S_(N)2` reactions proceed with inversion of configuration
Reason: `S_(N)2` reactions oC Cur in one step .

Answer

To analyze the given assertion and reason, we will break down the concepts involved in \( S_N2 \) reactions step by step.

### Step 1: Understanding the Assertion
The assertion states that \( S_N2 \) reactions proceed with inversion of configuration.

**Explanation**:
In \( S_N2 \) reactions, a nucleophile attacks the electrophilic carbon atom from the side opposite to the leaving group. This back-side attack leads to the inversion of configuration at the carbon center. For example, if the carbon is initially in an R configuration, after the reaction, it will be in an S configuration (or vice versa).

**Hint**: Remember that the nucleophile approaches from the opposite side of the leaving group, causing the inversion.

### Step 2: Understanding the Reason
The reason states that \( S_N2 \) reactions occur in one step.

**Explanation**:
The \( S_N2 \) mechanism is a concerted process, meaning that the bond formation and bond breaking occur simultaneously in a single step without any intermediates. The nucleophile attacks the substrate, and the leaving group departs at the same time, leading to the inversion of configuration.

**Hint**: Focus on the term "concerted" which indicates that the reaction happens in one continuous motion without any intermediate stages.

### Step 3: Evaluating the Relationship Between Assertion and Reason
Now, we need to evaluate whether the reason provided explains the assertion.

**Explanation**:
While both the assertion and reason are true statements, the reason does not directly explain why \( S_N2 \) reactions result in inversion of configuration. The inversion is a consequence of the back-side attack of the nucleophile, not merely because the reaction occurs in one step.

**Hint**: Consider whether the reason provides a direct explanation for the assertion. If not, they may be independent.

### Conclusion
Based on the analysis:
- Both the assertion and the reason are true.
- However, the reason does not explain the assertion.

Thus, the correct answer is that both statements are true, but the reason is not a valid explanation for the assertion.

**Final Answer**: Both the assertion and reason are true, but the reason does not explain the assertion.