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 1: Understand the Reactants
1-Penten-4-yne is an alkyne with a double bond (C=C) and a triple bond (C≡C) in its structure. The structure can be represented as follows:

```
CH2=CH-CH2-C≡C-H
```

### Step 2: Reaction with Bromine
When alkenes and alkynes react with bromine (Br2), they undergo an electrophilic addition reaction. At low temperatures (like -80°C), the reaction tends to proceed with less rearrangement and more selective addition.

### Step 3: Identify the Site of Reaction
In 1-Penten-4-yne, the presence of both double and triple bonds means that bromine can add across these unsaturations. However, since we are using only 1 mole of bromine, we can expect the addition to occur at the double bond (C=C) first, leading to the formation of a dibromide.

### Step 4: Draw the Product
When bromine adds across the double bond of 1-Penten-4-yne, the product formed will be 4,5-dibromo-1-pentene. The structure can be represented as follows:

```
CH2-Br
|
CH-Br
|
CH2-C≡C-H
```

### Step 5: Final Product
The final product of the reaction is 4,5-dibromo-1-pentene.

### Conclusion
Thus, the product formed when 1-Penten-4-yne reacts with 1 mole of bromine at -80°C is 4,5-dibromo-1-pentene.