The reagent which is used to distinguish between propene and propyne is

Options

A. Bromine
B. Alkaline `KMnO_4`
C. Ammoniacal `AgNO_3`
D. Ozone

Answer

To distinguish between propene (an alkene) and propyne (a terminal alkyne), we can use a specific reagent that selectively reacts with one of the compounds but not the other.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Propene (C3H6) is an alkene with a double bond.
- Propyne (C3H4) is a terminal alkyne with a triple bond.

2. **Understand the Reactivity**:
- Alkenes and alkynes can react with various reagents, but some reagents are selective.
- Both propene and propyne will react with bromine, so bromine is not a distinguishing reagent.

3. **Select a Suitable Reagent**:
- We need a reagent that will react with propyne but not with propene.
- The reagent known for this purpose is ammoniacal silver nitrate (Tollens' reagent), which specifically reacts with terminal alkynes.

4. **Conclusion**:
- The reagent used to distinguish between propene and propyne is ammoniacal silver nitrate (Tollens' reagent).

### Summary:
To distinguish between propene and propyne, the reagent used is ammoniacal silver nitrate (Tollens' reagent), as it selectively reacts with terminal alkynes like propyne.