Which of the following most readily undergoes `E_(2)` elimination with a strong base?

Options

A. 2-bromopentane
B. 2-bromo-2-methylbutane
C. 1-bromo-2,2dimethyl propane
D. 2-bromo-3-methylbutane

Answer

To determine which compound most readily undergoes E2 elimination with a strong base, we need to analyze the provided options based on the stability of the resulting alkene, which is influenced by the number of beta hydrogens available for elimination.

### Step-by-Step Solution:

1. **Identify the Compounds**: The options given are:
- A) 2-bromo pentane
- B) 2-bromo-2-methylbutane
- C) 1-bromo-2,2-dimethylpropane
- D) 2-bromo-3-methylbutane

2. **Understand E2 Mechanism**: E2 elimination involves the removal of a beta hydrogen and the leaving of a leaving group (in this case, bromine) to form a double bond. The stability of the alkene formed is crucial for the reactivity of the alkyl halide.

3. **Analyze Each Compound**:
- **A) 2-bromo pentane**:
- Structure: CH3-CHBr-CH2-CH2-CH3
- Beta hydrogens: 5 (from the two CH2 and CH3 groups)
- Possible alkenes: 2-pentene and 3-pentene.

- **B) 2-bromo-2-methylbutane**:
- Structure: (CH3)2C(Br)CH2CH3
- Beta hydrogens: 9 (from the two CH3 groups and the CH2 group)
- Possible alkenes: 2-methylbutene (more substituted, more stable).

- **C) 1-bromo-2,2-dimethylpropane**:
- Structure: (CH3)3C(Br)CH3
- Beta hydrogens: 0 (no beta hydrogens available for elimination).
- E2 elimination is not possible.

- **D) 2-bromo-3-methylbutane**:
- Structure: CH3-CHBr-CH(CH3)-CH3
- Beta hydrogens: 5 (from the CH3 groups and one CH2 group).
- Possible alkenes: 2-methyl-2-butene and 3-methyl-1-butene.

4. **Compare Stability of Alkenes**:
- The stability of alkenes increases with the number of alkyl substituents. Therefore, the alkene formed from B (2-bromo-2-methylbutane) is more stable due to more alkyl groups compared to the others.
- B has 9 beta hydrogens, while A has 5, C has 0, and D has 5.

5. **Conclusion**:
- The compound that most readily undergoes E2 elimination with a strong base is **B) 2-bromo-2-methylbutane** because it has the highest number of beta hydrogens and forms the most stable alkene.

### Final Answer:
**B) 2-bromo-2-methylbutane**