Which of the following will give 2,2-dibromopropane on reaction with HBr?

Options

A. `CH_(2)-CH=CH_(2)`
B. `CH_(3)C-=CH`
C. `CH_(3)CH=CHBr`
D. `CH-=CH`

Explanation

To determine which of the given compounds will yield 2,2-dibromopropane upon reaction with HBr, we need to analyze the addition of HBr to different alkenes or alkynes according to Markovnikov's rule.

### Step-by-Step Solution:

1. **Identify the Reactants**:
We need to analyze the given options (alkenes or alkynes) to see how they will react with HBr.

2. **Understand Markovnikov's Rule**:
According to Markovnikov's rule, when HBr adds to an alkene, the hydrogen (H) will attach to the carbon with the greater number of hydrogen atoms already attached, while the bromine (Br) will attach to the other carbon.

3. **Analyze Each Option**:
- **Option A**: If we assume this is an alkene like propene (CH3-CH=CH2), H will attach to the carbon with more hydrogens (the terminal carbon), and Br will attach to the other carbon, resulting in CH3-CHBr-CH3 (not 2,2-dibromopropane).
- **Option B**: If this is 2-butene (CH3-CH=CH-CH3), H will attach to the carbon with more hydrogens (the second carbon), and Br will attach to the first carbon, leading to CH3-C(Br)-C(Br)-CH3, which is 2,2-dibromopropane. This is the correct option.
- **Option C**: If this is 1-butyne (CH≡C-CH2-CH3), the addition of HBr will lead to the formation of a product that does not yield 2,2-dibromopropane.
- **Option D**: If this is 2-butyne (CH3-C≡C-CH3), the reaction with HBr will also not yield 2,2-dibromopropane.

4. **Conclusion**:
After analyzing all options, we find that only **Option B** (2-butene) will give 2,2-dibromopropane when reacted with HBr.

### Final Answer:
The correct option that will give 2,2-dibromopropane on reaction with HBr is **Option B**.