Which of the following isomer having molecular formula `C_(6)H_(14)` will give minimum number of mono-chloro derivatives?

Options

A. Hexane
B. 2-Methylpentane
C. 3-Methylpentane
D. 2, 3-Dimethyl butane

Answer

To determine which isomer of the molecular formula \( C_6H_{14} \) gives the minimum number of monochloro derivatives, we need to analyze each isomer and count the number of unique hydrogen atoms that can be replaced by chlorine.

### Step-by-Step Solution:

1. **Identify the Isomers**:
The given isomers are:
- Hexane
- 2-Methylpentane
- 3-Methylpentane
- 2,3-Dimethylbutane

2. **Count Unique Hydrogen Atoms**:
The number of monochloro derivatives depends on the number of unique hydrogen atoms that can be replaced by chlorine. This is determined by the number of different types of carbon atoms in each structure.

3. **Analyze Each Isomer**:
- **Hexane**:
- Structure: \( CH_3-CH_2-CH_2-CH_2-CH_3 \)
- All carbon atoms are equivalent (primary).
- Number of unique hydrogen atoms: 3 (from the terminal CH3) + 2 (from each of the 4 CH2) = 3 + 8 = 11.
- Unique types of hydrogen: 2 types (from CH3 and CH2).
- Total monochloro derivatives: 3 (from CH3) + 8 (from CH2) = 11.

- **2-Methylpentane**:
- Structure: \( CH_3-CH(CH_3)-CH_2-CH_2-CH_3 \)
- Types of carbon: 1 (from CH3) + 1 (from CH) + 2 (from CH2) = 4 unique types.
- Total monochloro derivatives: 5.

- **3-Methylpentane**:
- Structure: \( CH_3-CH_2-CH(CH_3)-CH_2-CH_3 \)
- Types of carbon: 1 (from CH3) + 1 (from CH) + 2 (from CH2) = 4 unique types.
- Total monochloro derivatives: 4.

- **2,3-Dimethylbutane**:
- Structure: \( CH_3-CH(CH_3)-C(CH_3)-CH_3 \)
- Types of carbon: 1 (from CH3) + 1 (from CH) + 1 (from CH) = 3 unique types.
- Total monochloro derivatives: 2.

4. **Conclusion**:
After analyzing all the isomers, we find that **2,3-Dimethylbutane** has the least number of monochloro derivatives, which is 2.

### Final Answer:
**2,3-Dimethylbutane** gives the minimum number of monochloro derivatives.