Which one of the following gives only one monochloro derivative?

Options

A. n-hexane
B. 2-methylpentane
C. 2,3-dimethylpentane
D. neo-pentane

Answer

To determine which compound gives only one monochloro derivative, we need to analyze the structure of each compound and identify the types of carbon atoms present. A monochloro derivative means that only one type of chlorine substitution can occur due to the symmetry of the compound.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We need to consider the four compounds given in the question. Let's denote them as Compound A, Compound B, Compound C, and Compound D.

2. **Analyze Compound A (n-Hexane)**:
- Structure: CH₃-CH₂-CH₂-CH₂-CH₂-CH₃
- Carbon Types: All carbon atoms are connected in a straight chain, but they are not identical. There are three types of carbon atoms (primary, secondary, and tertiary).
- Conclusion: This compound can give multiple monochloro derivatives due to the presence of different types of carbon atoms.

3. **Analyze Compound B (2,3-Dimethylpentane)**:
- Structure: CH₃-CH(CH₃)-CH(CH₃)-CH₂-CH₃
- Carbon Types: There are several types of carbon atoms due to the branching (methyl groups).
- Conclusion: This compound can also give multiple monochloro derivatives.

4. **Analyze Compound C (Pentane)**:
- Structure: CH₃-CH₂-CH(CH₃)-CH₂-CH₃
- Carbon Types: Similar to Compound B, there are multiple types of carbon atoms due to branching.
- Conclusion: This compound can also give multiple monochloro derivatives.

5. **Analyze Compound D (Neopentane)**:
- Structure: (CH₃)₄C
- Carbon Types: All four carbon atoms are equivalent due to the symmetrical structure.
- Conclusion: Since all carbon atoms are identical, substituting chlorine at any position will yield the same compound. Therefore, only one monochloro derivative can be formed.

6. **Final Answer**:
Based on the analysis, **Compound D (Neopentane)** gives only one monochloro derivative.