Which of the following reagents would convert but-2-yne to but-1-yne?

Options

A. `HgSO_4`,`H_2SO_4`
B. Ethanilic KOH, heat
C. `NaNH_2` in mineral oil, heat
D. Ammoniacal `AgNO_3`

Explanation

To convert but-2-yne to but-1-yne, we need to identify the appropriate reagent from the given options. Here’s a step-by-step solution:

### Step 1: Understand the Structures
- **But-2-yne** has the structure: CH₃-C≡C-CH₃ (triple bond between the second and third carbon).
- **But-1-yne** has the structure: CH≡C-CH₂-CH₃ (triple bond between the first and second carbon).

### Step 2: Identify the Type of Reaction Needed
To convert an internal alkyne (but-2-yne) to a terminal alkyne (but-1-yne), we need a reagent that can facilitate this transformation.

### Step 3: Analyze the Reagents
1. **HgSO₄ (Oxymercuration)**: This reagent would add a hydroxyl group and does not convert but-2-yne to but-1-yne. It typically forms a ketone.
2. **Ethanolic KOH**: This reagent is used for elimination reactions and would not convert but-2-yne to but-1-yne.
3. **NaNH₂ in mineral oil (heat)**: This reagent is a strong base and can deprotonate terminal alkynes. It can convert internal alkynes to terminal alkynes by forming a carbanion and then allowing for protonation to yield the terminal alkyne.
4. **Ammonical AgNO₃**: This reagent is used for differentiating between terminal and internal alkynes but does not facilitate the conversion from but-2-yne to but-1-yne.

### Step 4: Conclusion
The reagent that would successfully convert but-2-yne to but-1-yne is **NaNH₂ in mineral oil (heat)**. This reagent allows the transformation of an internal alkyne to a terminal alkyne.

### Final Answer
The correct answer is **C: NaNH₂ in mineral oil (heat)**.

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