An alkyl bromide produces a single alkene when it reacts with sodium ethoxide and ethanol. This alkene undergoes hydrogenation and produces 2-methylbutane. What is the alkybromide ?

Options

A. 1-bromo-2-methylbutane
B. 1-bromobutane
C. 1-bromo-2,2-dimethylpropane
D. 2-bromo-2-methylbutane

Answer

To determine the alkyl bromide that produces a single alkene upon reaction with sodium ethoxide and ethanol, which subsequently undergoes hydrogenation to yield 2-methylbutane, we can analyze the options provided step by step.

### Step 1: Analyze the Reaction Conditions
The reaction involves an alkyl bromide reacting with sodium ethoxide in ethanol. Sodium ethoxide is a strong base that promotes elimination reactions (dehydrohalogenation) to form alkenes.

### Step 2: Identify the Alkene Formation
The problem states that the alkyl bromide produces a single alkene. This means that the structure of the alkyl bromide must allow for only one beta hydrogen to be available for elimination.

### Step 3: Evaluate the Options
We have four options to consider:

1. **1-bromo-2-methylbutane**
2. **1-bromobutane**
3. **1-bromo-2,2-dimethylpropane**
4. **2-bromo-2-methylbutane**

#### Option 1: 1-bromo-2-methylbutane
- Structure:
- This compound has a beta hydrogen that can participate in elimination.
- It can produce one alkene (2-methylbutene) upon elimination.

#### Option 2: 1-bromobutane
- Structure:
- This compound has two beta hydrogens (at the 2nd carbon).
- It can produce two different alkenes (1-butene and cis/trans-2-butene), which does not satisfy the condition of producing a single alkene.

#### Option 3: 1-bromo-2,2-dimethylpropane
- Structure:
- This compound has no beta hydrogens available for elimination.
- Therefore, it cannot form any alkene.

#### Option 4: 2-bromo-2-methylbutane
- Structure:
- This compound has no beta hydrogens available for elimination.
- Therefore, it cannot form any alkene.

### Step 4: Conclude the Alkyl Bromide
From the analysis:
- **Option A (1-bromo-2-methylbutane)** is the only option that can produce a single alkene (2-methylbutene) upon reaction with sodium ethoxide.
- This alkene can undergo hydrogenation to yield 2-methylbutane.

Thus, the correct alkyl bromide is **1-bromo-2-methylbutane**.

### Final Answer
**The alkyl bromide is 1-bromo-2-methylbutane.**