cis-2-butene`overset(HBr)underset("Peroxide")(to)`product, Product of the reaction is:

Options

A. Racemic
B. Diastereomers
C. Meso
D. Pure enantiomers

Explanation

To determine the product of the reaction of cis-2-butene with HBr in the presence of peroxide, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactant is cis-2-butene, which has the structure:
\[ \text{CH}_3-\text{CH}=\text{CH}-\text{CH}_3 \]
- In the cis configuration, the two methyl (CH₃) groups are on the same side of the double bond.

2. **Understand the Reaction Conditions**:
- The reaction occurs in the presence of peroxide, which indicates that a free radical mechanism will be involved.

3. **Free Radical Mechanism**:
- In the presence of peroxide, HBr will dissociate into H• (hydrogen radical) and Br• (bromine radical).
- The double bond in cis-2-butene will undergo homolysis, forming two radicals: a carbon radical and a hydrogen radical.

4. **Formation of Radicals**:
- The double bond can break in such a way that either carbon can become a radical. This leads to the formation of two possible radicals:
- CH₃-CH•-CH₂-CH₃ (with a radical on the second carbon)
- CH₃-CH₂-CH•-CH₃ (with a radical on the third carbon)

5. **Radical Combination**:
- The H• radical can add to one of the carbon radicals formed, while the Br• radical can add to the other carbon.
- Due to the symmetry of cis-2-butene, both combinations will yield the same product:
- CH₃-CH(Br)-CH₂-CH₃

6. **Chirality and Optical Activity**:
- The product has one chiral center at the carbon that is bonded to the bromine atom. This means that the product will be optically active.
- The presence of a chiral center allows for the formation of two enantiomers (mirror images).

7. **Final Product**:
- The final product of the reaction is 2-bromobutane, which exists as a racemic mixture of two enantiomers due to the presence of the chiral center.

### Conclusion:
The product of the reaction of cis-2-butene with HBr in the presence of peroxide is a racemic mixture of 2-bromobutane, which is optically active due to the presence of a chiral carbon.