`C_(5)H_(11)Br+ NaCN rarr A overset(H_(3)O^(+))(rarr) B + "NaOH" overset("CaO")(rarr) `C
C' has the formula `C_(5)H_(12)` which can give four structural isomeric monochloro derivative . What is the structure of `C_(5)H_(11) Br` ?

Options

A. `CH_(3)- underset(CH_(3))underset(|)(CH) - CH_(2) CH_2- `Br
B. `CH_(3) - CH_(2) - overset(Br)overset(|)(CH) - CH_(2) - CH_(5)`
C. `CH_(5) - CH_(2) - CH_(2) - underset(Br)underset(|)(CH) - CH_(3)`
D. `CH_(2) - underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C ) - CH_(2) - `Br

Answer

To solve the problem, we need to identify the structure of the compound \(C_5H_{11}Br\) based on the given reactions and the final product \(C\) with the formula \(C_5H_{12}\).

### Step-by-Step Solution:

1. **Identify the Final Product:**
The final product \(C\) has the formula \(C_5H_{12}\). This indicates that it is a saturated hydrocarbon (alkane) with 5 carbon atoms.

2. **Determine the Isomeric Nature of \(C_5H_{12}\):**
The problem states that \(C\) can give four structural isomeric monochloro derivatives. This suggests that the structure of \(C_5H_{12}\) must have at least four different positions where a chlorine atom can be substituted.

3. **Possible Structures of \(C_5H_{12}\):**
The possible structural isomers of \(C_5H_{12}\) that can yield four different monochloro derivatives are:
- **n-Pentane:** \(CH_3-CH_2-CH_2-CH_2-CH_3\)
- **Isopentane (2-Methylbutane):** \(CH_3-CH(CH_3)-CH_2-CH_3\)
- **Neopentane (2,2-Dimethylpropane):** \(C(CH_3)_4\) (This will not yield four isomers)
- **3-Methylbutane:** \(CH_3-CH_2-CH(CH_3)-CH_3\)

The structure that can give four distinct monochloro derivatives is **2-Methylbutane**.

4. **Relate \(C_5H_{12}\) Back to \(C_5H_{11}Br\):**
Since \(C_5H_{11}Br\) is the brominated precursor to \(C_5H_{12}\), we can deduce that the bromine atom is likely attached to a carbon that allows for the formation of the isomers.

5. **Propose the Structure of \(C_5H_{11}Br\):**
Given that the final product \(C_5H_{12}\) is 2-Methylbutane, the structure of \(C_5H_{11}Br\) can be proposed as:
- **2-Bromopentane:** \(CH_3-CH(CH_2Br)-CH_2-CH_3\) or
- **1-Bromopentane:** \(CH_3-CH_2-CH_2-CH_2-CH_2Br\) (but this will not yield four isomers).

The most likely structure for \(C_5H_{11}Br\) that leads to 2-Methylbutane upon hydrolysis is **1-Bromo-2-methylbutane**.

### Final Structure:
The structure of \(C_5H_{11}Br\) is:
\[ CH_3-CH(CH_3)-CH_2-CH_2Br \]