Which of the following compounds undergo `E2 reaction with maximum rate?

Options

A. `CH_(3)C(CH_(3))(Br)CH_(2)CH_(3)`
B. `CH_(3)(CH_(2))_(2)CH_(2)Cl`
C. `CH_(3)(CH_(2))_(2)CH_(2)I`
D. `CH_(3)C(CH_(3))(I)CH_(2)CH_(3)`

Answer

To determine which of the given compounds undergoes an E2 reaction with the maximum rate, we need to consider two main factors: the leaving group ability and the stability of the alkene formed after the elimination reaction.

### Step-by-Step Solution:

1. **Identify the Leaving Groups**:
- In E2 reactions, the leaving group plays a crucial role. The order of leaving group ability is: Iodine (I) > Bromine (Br) > Chlorine (Cl) > Fluorine (F). This means that iodine is the best leaving group, followed by bromine and then chlorine.

2. **Analyze the Given Compounds**:
- We have four compounds to analyze. We need to check which ones have iodine as a leaving group since it has the highest leaving tendency.

3. **Elimination Reaction Mechanism**:
- In an E2 reaction, a base abstracts a proton (H) from the β-carbon (the carbon adjacent to the carbon bearing the leaving group), leading to the formation of a double bond (alkene) as the leaving group departs.

4. **Stability of the Alkene**:
- The stability of the alkene formed is also important. More substituted alkenes (those with more alkyl groups attached) are generally more stable due to hyperconjugation and the inductive effect. Therefore, the compound that forms a more substituted alkene will undergo the E2 reaction at a faster rate.

5. **Evaluate the Compounds**:
- For the compounds that contain iodine, analyze the structure to determine the substitution of the resulting alkene. The compound that leads to a more substituted alkene will be favored.

6. **Conclusion**:
- After analyzing the compounds, the one that has iodine as a leaving group and forms the most stable alkene (most substituted) will undergo the E2 reaction at the maximum rate.

7. **Final Answer**:
- Based on the analysis, the correct answer is the compound that leads to the most substituted alkene with iodine as the leaving group.