What simple laboratory test could be performed to distinguish between `1`-pentyne and `2`-pentyne?

Options

A. the addition of `Ag^(+)` in ammonia
B. the addition of `H_(2)SO_(4)` in `Hg^(+2)`
C. the addition of `Br_(2)` in `C Cl_(4)`
D. the addition of `H_(2)` on a `Pt` catalyst.

Answer

To distinguish between 1-pentyne and 2-pentyne, we can perform a simple laboratory test using Tollens' reagent. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understand the Structures**:
- 1-pentyne (C5H10) is a terminal alkyne, meaning it has a triple bond at the end of the carbon chain.
- 2-pentyne (C5H10) is a non-terminal alkyne, meaning the triple bond is located between the second and third carbon atoms.

2. **Prepare Tollens' Reagent**:
- Tollens' reagent is a solution of silver nitrate (AgNO3) in ammonia (NH3). It is used to test for the presence of aldehydes and terminal alkynes.

3. **Perform the Test**:
- Take a small amount of the sample (either 1-pentyne or 2-pentyne) and add it to a test tube containing Tollens' reagent.

4. **Observe the Reaction**:
- If the sample is 1-pentyne, a silver mirror will form on the walls of the test tube due to the reduction of silver ions (Ag+) to metallic silver (Ag). This indicates a positive result.
- If the sample is 2-pentyne, no silver mirror will form, indicating a negative result.

5. **Conclusion**:
- The formation of a silver mirror indicates the presence of 1-pentyne (the terminal alkyne), while the absence of a silver mirror confirms the presence of 2-pentyne.