Reagents which cannot be used to distinguish allyl bromide from n-propyl bromide are

Answer

To solve the question of which reagents cannot be used to distinguish allyl bromide from n-propyl bromide, we will analyze the reactivity of both compounds with various reagents.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **Allyl Bromide (C3H5Br)**: The structure is CH2=CH-CH2Br. It has a double bond (C=C) adjacent to the carbon attached to bromine.
- **n-Propyl Bromide (C3H7Br)**: The structure is CH3-CH2-CH2Br. It is a straight-chain alkane with bromine attached to the terminal carbon.

2. **Reagent 1: Bromine in CCl4**:
- **Test**: When bromine in CCl4 is added to an alkene, it reacts with the double bond and decolorizes the reddish-brown solution.
- **Result**: Allyl bromide will decolorize the bromine solution due to its unsaturation (double bond), while n-propyl bromide will not react.
- **Conclusion**: This reagent can distinguish between the two compounds.

3. **Reagent 2: Aqueous AgNO3**:
- **Test**: Allyl bromide is more reactive and will react with AgNO3 to form a yellow precipitate of AgBr. n-Propyl bromide is less reactive and will not form a precipitate.
- **Result**: Allyl bromide gives a yellow precipitate, while n-propyl bromide does not.
- **Conclusion**: This reagent can also distinguish between the two compounds.

4. **Reagent 3: Boiling with Aqueous KOH followed by Acidification with Dilute HNO3 and Addition of AgNO3**:
- **Test**: Both allyl bromide and n-propyl bromide will undergo nucleophilic substitution with KOH to form alcohols. Upon acidification and addition of AgNO3, both will produce AgBr precipitate.
- **Result**: Both compounds will yield a yellow precipitate of AgBr after the reaction.
- **Conclusion**: This reagent cannot distinguish between allyl bromide and n-propyl bromide.

5. **Final Answer**:
- The reagent that cannot be used to distinguish allyl bromide from n-propyl bromide is **C) Boiling with aqueous KOH followed by acidification with dilute HNO3 and addition of AgNO3**.