Substrate that show E1 reaction

Options

A. `CH_3CH_2I`
B.
C. `CH_3-undersetunderset(CH_3)(|)oversetoverset(CH_3)(|)C-CH_2-I`
D.

Answer

To determine which substrate shows an E1 reaction, we need to identify the stability of the carbocation formed during the reaction. E1 reactions involve the formation of a carbocation intermediate, and the stability of this carbocation is crucial for the reaction to proceed.

### Step-by-Step Solution:

1. **Understanding E1 Mechanism**:
- E1 stands for unimolecular elimination. It involves two steps: the formation of a carbocation intermediate and the elimination of a leaving group to form a double bond.

2. **Identify the Stability of Carbocations**:
- Carbocation stability increases in the following order: primary < secondary < tertiary. Therefore, substrates that can form tertiary carbocations are more likely to undergo E1 reactions.

3. **Analyzing the Options**:
- **Option 1**: This substrate will lead to the formation of a primary carbocation. (Not favored for E1)
- **Option 2**: This substrate will also lead to a primary carbocation. (Not favored for E1)
- **Option 3**: This substrate will again lead to the formation of a primary carbocation. (Not favored for E1)
- **Option 4**: This substrate will lead to the formation of a tertiary carbocation after the leaving group departs. (Favored for E1)

4. **Conclusion**:
- Among the given options, the substrate in **Option 4** is the one that will show an E1 reaction because it forms the most stable carbocation (tertiary).

### Final Answer:
The substrate that shows E1 reaction is **Option 4**.

---