In `S_(N^2)` reactions the sequence of bond breaking and bond formation is as follows

Options

A. bond breaking is followed by formation
B. bond formation is followed by breaking
C. bond breaking and formation occur simultaneously.
D. bond breaking and formation take place randomly.

Answer

To solve the question regarding the sequence of bond breaking and bond formation in \( S_N2 \) reactions, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding \( S_N2 \) Reactions:**
- \( S_N2 \) (Substitution Nucleophilic Bimolecular) reactions involve a nucleophile attacking an electrophile (usually an alkyl halide) to replace a leaving group (like a halide ion).

2. **Mechanism of \( S_N2 \) Reactions:**
- In an \( S_N2 \) reaction, the nucleophile approaches the electrophile from the side opposite to the leaving group. This is known as a backside attack.

3. **Simultaneous Bond Breaking and Formation:**
- As the nucleophile approaches, it begins to form a bond with the carbon atom of the alkyl halide. At the same time, the bond between the carbon and the leaving group (halide) begins to break.

4. **Transition State Formation:**
- During the reaction, a transition state is formed where the carbon is partially bonded to both the nucleophile and the leaving group. This state is often depicted as a pentacoordinate carbon.

5. **Final Product Formation:**
- The reaction completes when the bond to the leaving group is fully broken and the bond to the nucleophile is fully formed, resulting in the final product.

6. **Conclusion:**
- Therefore, in \( S_N2 \) reactions, the sequence of bond breaking and bond formation occurs simultaneously, which corresponds to the third option provided in the question.

### Final Answer:
The correct answer is that in \( S_N2 \) reactions, bond breaking and bond formation occur simultaneously.

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