Identify a reagent from the following list which can easily distinguish between 1-butyne and 2-butyne.

Options

A. (a) Bromine, `C Cl_4`
B. (b) `H_2`, Lindlar's catalyst
C. (c) Dilute `H_2SO_4`, `HgSO_4`
D. (d) Ammoniacal `Cu_2Cl_2` solution

Explanation

To solve the problem of distinguishing between 1-butyne and 2-butyne, we need to understand the structural differences between these two compounds and the reagents that can react differently with them.

### Step-by-Step Solution:

1. **Identify the Structures**:
- 1-butyne (C4H6) is a terminal alkyne, meaning it has a triple bond at the end of the carbon chain.
- 2-butyne (C4H6) is an internal alkyne, meaning the triple bond is located between two carbon atoms, not at the end.

2. **Understand the Reactivity**:
- Terminal alkynes (like 1-butyne) can react with certain reagents that can distinguish them from internal alkynes (like 2-butyne).
- Internal alkynes do not react with these reagents.

3. **Identify the Reagents**:
- Tollens' reagent (Ag(NH3)2+) and Fehling's solution (Cu2+) are two reagents that can be used for this purpose.
- When 1-butyne is treated with Tollens' reagent, it gives a white precipitate, indicating a positive reaction.
- In contrast, 2-butyne does not react with Tollens' reagent, resulting in no precipitate.

4. **Conclusion**:
- Since 1-butyne gives a positive test with Tollens' reagent while 2-butyne does not, we can use this reagent to distinguish between the two compounds.
- Therefore, the correct reagent from the list that can easily distinguish between 1-butyne and 2-butyne is **Tollens' reagent**.

### Final Answer:
The reagent that can easily distinguish between 1-butyne and 2-butyne is **Tollens' reagent**.