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)`

Explanation

To distinguish between 1-butyne and 2-butyne, we can use a reagent that reacts differently with each compound. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Structures
1. **Identify the structures of 1-butyne and 2-butyne**:
- **1-butyne** has the structure: CH≡C-CH2-CH3 (a terminal alkyne).
- **2-butyne** has the structure: CH3-C≡C-CH3 (a non-terminal alkyne).

### Step 2: Identify the Reagents
2. **Consider the reagents**:
- The question asks which reagent can distinguish between the two alkynes. We will analyze the effects of different reagents.

### Step 3: Analyze NaNH2
3. **Test with NaNH2**:
- **1-butyne**: When NaNH2 is added, it reacts with the terminal hydrogen of 1-butyne, forming a sodium acetylide (CH≡C-Na).
- **2-butyne**: There is no terminal hydrogen in 2-butyne, so NaNH2 does not react.
- **Conclusion**: NaNH2 can distinguish between 1-butyne (reacts) and 2-butyne (does not react).

### Step 4: Analyze HCl
4. **Test with HCl**:
- **1-butyne**: HCl adds across the triple bond according to Markovnikov's rule, resulting in a product where Cl attaches to the more substituted carbon.
- **2-butyne**: HCl also adds across the triple bond, but since 2-butyne is symmetrical, it does not provide a distinct product.
- **Conclusion**: HCl does not distinguish between the two.

### Step 5: Analyze O2
5. **Test with O2**:
- Both 1-butyne and 2-butyne do not react with O2.
- **Conclusion**: O2 cannot distinguish between the two.

### Step 6: Analyze Br2
6. **Test with Br2**:
- Both alkynes react with Br2, resulting in dibrominated products.
- **Conclusion**: Br2 does not distinguish between the two.

### Final Conclusion
The only reagent that can distinguish between 1-butyne and 2-butyne is **NaNH2**. Therefore, the answer is **A: NaNH2**.

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