Iso -butylene can be converted into tert -butyl bromide by its reaction with

Options

A. HBr
B. `Br_(2)`
C. HBr in the presence of peroxides
D. HOBr

Answer

To convert isobutylene into tert-butyl bromide, we need to follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of Isobutylene**:
- Isobutylene (also known as 2-methylpropene) has the structure:
\[ \text{CH}_2=C(\text{CH}_3)\text{CH}_3 \]
- This structure indicates that isobutylene has a double bond between the first carbon (CH2) and the second carbon (C) which is attached to two methyl groups (CH3).

2. **Identify the Desired Product**:
- The target product is tert-butyl bromide, which has the structure:
\[ \text{(CH}_3)_3\text{CBr} \]
- This indicates that the bromine atom is attached to a tertiary carbon that is bonded to three other carbon atoms.

3. **Analyze the Reaction Conditions**:
- We have four options for reagents: A) HBr, B) Br2, C) HBr in the presence of peroxides, D) HOBr.
- We need to determine which of these will lead to the formation of tert-butyl bromide.

4. **Evaluate Each Reagent**:
- **Option A: HBr**:
- When isobutylene reacts with HBr, it dissociates into H+ and Br-.
- According to Markovnikov's rule, the H+ will add to the carbon with more hydrogen atoms, leading to the formation of a tertiary carbocation.
- The Br- will then attack this tertiary carbocation, resulting in tert-butyl bromide.
- **Conclusion**: This option is correct.

- **Option B: Br2**:
- The reaction with Br2 would lead to the formation of a dibromo compound, where bromine atoms would add across the double bond.
- **Conclusion**: This option is incorrect.

- **Option C: HBr in the presence of peroxides**:
- In the presence of peroxides, the reaction follows a radical mechanism, leading to anti-Markovnikov addition.
- This would result in the bromine attaching to the primary carbon instead of the tertiary carbon.
- **Conclusion**: This option is incorrect.

- **Option D: HOBr**:
- HOBr would not lead to the formation of tert-butyl bromide due to the presence of oxygen, which complicates the reaction and does not favor the formation of the desired product.
- **Conclusion**: This option is incorrect.

5. **Final Answer**:
- The correct reagent for converting isobutylene into tert-butyl bromide is **A) HBr**.