1-Penten-4-yne reacts with 1 mol bromine at -`80°C` to produce :

Options

A. 4, 4, 5, 5-Tetrabromopentene
B. 1, 2-Dibromo-1, 4-pentadiene
C. 1, 1, 2, 2, 4, 5-hexabromopentane
D. 4, 5-dibromopentyne

Answer

To solve the problem of what product is formed when 1-Penten-4-yne reacts with 1 mole of bromine at -80°C, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of 1-Penten-4-yne**:
- The molecular structure of 1-Penten-4-yne can be drawn as follows:
- It has a total of 5 carbon atoms, with a double bond between the first and second carbon, and a triple bond between the fourth and fifth carbon.
- The structure can be represented as:
```
CH2=CH-CH2-C≡C-CH3
```

2. **Understanding the Reaction with Bromine**:
- The reaction of alkenes and alkynes with bromine is an electrophilic addition reaction.
- At -80°C, the reaction will proceed with a single mole of bromine (Br2), which means that only one bromine atom will add across the multiple bonds.

3. **Determine the Site of Electrophilic Attack**:
- In the case of 1-Penten-4-yne, the electrophilic bromine will preferentially add to the carbon-carbon triple bond (C≡C) because it is more electron-rich compared to the double bond (C=C).
- The addition will occur at the terminal carbon of the triple bond.

4. **Draw the Product Structure**:
- When bromine adds to the triple bond, one of the bromine atoms will attach to one of the carbon atoms involved in the triple bond, resulting in the formation of a double bond.
- The product formed will be:
```
CH2=CH-CH2-C(Br)=C-CH3
```
- This structure can also be represented as 4-bromo-1-pentene.

5. **Final Product**:
- The final product after the reaction is 4-bromo-1-pentene, which can also be referred to as 4-bromopent-1-ene.

### Final Answer:
The product formed from the reaction of 1-Penten-4-yne with 1 mole of bromine at -80°C is **4-bromo-1-pentene**.

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