Which among the following will yield 2,2-dibromo butane?

Options

A. `HC-=CH+2HBrrarr`
B. `CH_(3)C-=CH+2HBr rarr`
C. `CH_(3)-CH=CH-CH_(3)+2HBrrarr`
D. `CH_(3)-CH_(2)-C-=CH+2HBr rarr`

Answer

To determine which reaction will yield 2,2-dibromobutane, we need to analyze the given options step by step.

### Step 1: Understand the Structure of 2,2-Dibromobutane
2,2-Dibromobutane has the following structure:
- It consists of 4 carbon atoms (butane).
- There are two bromine atoms attached to the second carbon atom.

The structure can be represented as:
```
Br
|
CH3-CH-CH2-CH3
|
Br
```

### Step 2: Analyze Each Reaction Option

**Option 1: CH≡C + 2 HBr**
- The reactants consist of 2 carbon atoms (alkyne).
- The product will have 4 carbon atoms, which is not possible since we started with only 2.
- **Conclusion:** This option is incorrect.

**Option 2: CH3C≡CH + 2 HBr**
- The reactants consist of 3 carbon atoms (alkyne).
- Again, the product will have 4 carbon atoms, which cannot be achieved from 3.
- **Conclusion:** This option is also incorrect.

**Option 3: CH3-CH=CH-CH3 + 2 HBr**
- The reactants consist of 4 carbon atoms (alkene).
- Electrophilic addition occurs, where HBr adds across the double bond.
- The product formed will be 2-bromobutane (only one bromine atom added).
- **Conclusion:** This option is incorrect as it does not yield 2,2-dibromobutane.

**Option 4: CH3-CH2-C≡CH + 2 HBr**
- The reactants consist of 4 carbon atoms (alkyne).
- Electrophilic addition occurs, following Markovnikov's rule.
- The first HBr adds to the carbon with fewer hydrogen atoms, leading to the formation of an intermediate.
- The second HBr adds, resulting in the addition of bromine to the carbon with fewer hydrogens.
- The final product is 2,2-dibromobutane.
- **Conclusion:** This option is correct.

### Final Answer
The correct option that yields 2,2-dibromobutane is **Option 4: CH3-CH2-C≡CH + 2 HBr**.

---