Which of the following tests could be performed to distinguish between `1`-butyene and `2`-butyene?

Options

A. `Ag^(+)//NH_(3)`
B. `Br_(2)//C Cl_(4)`
C. `H_(2)//Pt`
D. `Hg^(+2)//H_(2)SO_(4)`

Answer

To distinguish between 1-butyene and 2-butyene, we can perform a simple laboratory test using bromine water or potassium permanganate (KMnO4) solution. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understand the Structures**:
- 1-butyene (C4H8) is a terminal alkene, meaning it has a double bond at the end of the carbon chain.
- 2-butyene (C4H8) is a non-terminal alkene with the double bond between the second and third carbon atoms.

2. **Select a Test**:
- We can use bromine water (Br2 in water) or potassium permanganate (KMnO4) as a reagent to distinguish between the two alkenes.

3. **Perform the Bromine Water Test**:
- Add a few drops of bromine water to separate samples of 1-butyene and 2-butyene.
- Observe any color change. Bromine water is brown in color.

4. **Observe the Results**:
- 1-butyene will decolorize bromine water quickly due to its higher reactivity as a terminal alkene.
- 2-butyene will also decolorize bromine water, but the reaction may be slower compared to 1-butyene.

5. **Perform the Potassium Permanganate Test**:
- Add a few drops of dilute KMnO4 solution to separate samples of 1-butyene and 2-butyene.
- Observe any color change. KMnO4 is purple in color.

6. **Observe the Results**:
- 1-butyene will react with KMnO4 and lead to the formation of a brown precipitate (MnO2), indicating a reaction.
- 2-butyene will also react, but the rate and extent of the reaction may differ.

7. **Conclusion**:
- By comparing the rates of decolorization of bromine water and the reaction with KMnO4, we can distinguish between 1-butyene and 2-butyene. The faster reaction of 1-butyene indicates its terminal nature.