Which of the following reagents will be able to distinguish between `1-`butyne and `2-`butyne ?

Options

A. `NaNH_(2)`
B. HCl
C. `O_(2)`
D. `Br_(2)`

Answer

To distinguish between 1-butyne and 2-butyne, we can follow these steps:

### Step 1: Identify the Structures
1. **Draw the structures of both compounds:**
- **1-butyne (C₄H₆)**: The structure is CH₃C≡C−H. The triple bond is between the first and second carbon atoms, making it a terminal alkyne.
- **2-butyne (C₄H₆)**: The structure is CH₃C≡CCH₃. The triple bond is between the second and third carbon atoms, making it a non-terminal alkyne.

### Step 2: Choose a Suitable Reagent
2. **Select a reagent that can distinguish between terminal and non-terminal alkynes:**
- Sodium amide (NaNH₂) is a suitable reagent because it reacts with terminal alkynes to produce hydrogen gas.

### Step 3: Perform the Reaction
3. **Conduct the reaction with NaNH₂:**
- When 1-butyne (the terminal alkyne) is treated with NaNH₂, it will react and produce hydrogen gas (H₂) due to the acidic hydrogen present at the terminal position.
- The reaction can be represented as:
\[ \text{NaNH}_2 + \text{CH}_3C≡C−H \rightarrow \text{CH}_3C≡C−Na + \text{H}_2 \uparrow \]
- In contrast, 2-butyne (the non-terminal alkyne) will not react with NaNH₂ because it does not have an acidic hydrogen:
\[ \text{NaNH}_2 + \text{CH}_3C≡CCH_3 \rightarrow \text{No Reaction} \]

### Step 4: Conclusion
4. **Interpret the results:**
- The evolution of hydrogen gas indicates the presence of a terminal alkyne (1-butyne), while no gas evolution indicates a non-terminal alkyne (2-butyne). Thus, NaNH₂ can effectively distinguish between 1-butyne and 2-butyne.

### Final Answer
The reagent that can distinguish between 1-butyne and 2-butyne is **Sodium amide (NaNH₂)**.

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