Isobutylene `underset("peroxides")overset(+HBr)rarr` product is :

Options

A. Tertiary butyl bromide
B. Isobutyl bromide
C. Tertiary butyl alcohol
D. Isobutyl alcohol

Answer

To solve the question regarding the reaction of isobutylene with HBr in the presence of peroxides, we will follow these steps:

### Step 1: Identify the Structure of Isobutylene
Isobutylene, also known as 2-methylpropene, has the following structure:
- It consists of three carbon atoms (C) and a double bond between the first and second carbon.
- The structure can be represented as:
```
CH3
|
CH2=C
|
CH3
```

### Step 2: Understand the Reaction Conditions
The reaction involves adding HBr in the presence of peroxides. The presence of peroxides indicates that the reaction will follow a free radical mechanism, leading to anti-Markovnikov addition.

### Step 3: Chain Initiation
In the presence of peroxides, the first step is chain initiation:
- Peroxide undergoes homolytic cleavage to form two RO radicals.
- One of these radicals reacts with HBr, resulting in the formation of a Br radical and an alcohol (ROH).

### Step 4: Chain Propagation
Next, we move to chain propagation:
- The Br radical generated in the previous step will attack the isobutylene.
- The double bond in isobutylene will break, and the Br radical will bond to the carbon that has more hydrogen atoms (due to anti-Markovnikov addition).
- This results in the formation of a more stable tertiary radical.

### Step 5: Formation of the Product
The newly formed radical will then react with another HBr molecule:
- The Br radical will leave, and the hydrogen will attach to the carbon that originally had the double bond.
- This leads to the formation of isobutyl bromide (2-bromobutane).

### Step 6: Final Product
The final product of the reaction is isobutyl bromide, which can be represented as:
```
CH3
|
CH3-C-CH2-Br
```

### Conclusion
The product formed when isobutylene reacts with HBr in the presence of peroxides is **isobutyl bromide**.