Which of the following is not true for `S_(N^(1))` reaction ?

Options

A. Ethyl chloride
B. Isopropyl chloride
C.
D.

Answer

To determine which statement is not true for an \( S_N^1 \) reaction, we need to analyze the characteristics and requirements of \( S_N^1 \) reactions.

### Step-by-Step Solution:

1. **Understanding \( S_N^1 \) Reaction**:
- \( S_N^1 \) stands for unimolecular nucleophilic substitution. The term "unimolecular" indicates that the rate-determining step involves only one molecule, which is the substrate undergoing substitution.

2. **Mechanism of \( S_N^1 \)**:
- The \( S_N^1 \) reaction occurs in two steps:
- **Step 1**: Formation of a carbocation intermediate after the leaving group departs (e.g., Cl⁻).
- **Step 2**: Nucleophilic attack on the carbocation by a nucleophile.

3. **Carbocation Stability**:
- The stability of the carbocation formed is crucial for the \( S_N^1 \) reaction to proceed. The order of stability is:
- Tertiary carbocation > Secondary carbocation > Primary carbocation > Methyl carbocation.
- Therefore, substrates that can form stable carbocations are more likely to undergo \( S_N^1 \) reactions.

4. **Analyzing Given Compounds**:
- **Ethyl Chloride (CH₃CH₂Cl)**: Forms a primary carbocation, which is less stable. Thus, it is not favorable for \( S_N^1 \).
- **Isopropyl Chloride (CH₃CHClCH₃)**: Forms a secondary carbocation, which is stable and can undergo \( S_N^1 \).
- **Bridged Compound**: The carbocation formed at the bridgehead position is unstable and will not form, making this compound unreactive for \( S_N^1 \).
- **Another Compound with Cl**: If it forms a primary carbocation that is stable, it can undergo \( S_N^1 \).

5. **Conclusion**:
- The statement that is not true for \( S_N^1 \) reactions is related to the compound that cannot form a stable carbocation. In this case, the bridged compound is the one that will not undergo \( S_N^1 \) due to the instability of the carbocation formed.

### Final Answer:
The option that states the bridged compound will undergo \( S_N^1 \) reaction is **not true**.