Addition of `Br_2` to cis-2-butene would give a product which is:

Options

A. achiral
B. racemic
C. meso
D. optically active

Explanation

To solve the question regarding the addition of \( Br_2 \) to cis-2-butene, we can follow these steps:

### Step 1: Understand the Structure of cis-2-butene
Cis-2-butene has the following structure:
```
CH3
|
CH3-C=C-H
|
H
```
In this structure, the two methyl groups (CH3) are on the same side of the double bond.

**Hint:** Identify the arrangement of substituents around the double bond to understand the stereochemistry.

### Step 2: Reaction with Bromine
When cis-2-butene reacts with bromine (\( Br_2 \)), the addition occurs via an anti-addition mechanism. This means that the bromine atoms will add to opposite sides of the double bond.

**Hint:** Remember that bromine adds across the double bond in an anti manner, which is crucial for determining the stereochemistry of the product.

### Step 3: Formation of the Product
The anti-addition of bromine to cis-2-butene will lead to the formation of a dibromide product. The resulting structure will have one bromine atom added to one carbon of the double bond and the other bromine atom added to the adjacent carbon, but on the opposite side.

The product can be represented as:
```
CH3
|
CH3-C-Br
|
Br
```
This product has a plane of symmetry, making it a meso compound.

**Hint:** Look for symmetry in the product structure to determine if it is meso or not.

### Step 4: Identify the Type of Product
Since the product formed is a meso compound, it is not optically active because it has an internal plane of symmetry. Therefore, it does not rotate plane-polarized light.

**Hint:** Recall that meso compounds are typically optically inactive due to their symmetry.

### Conclusion
The addition of \( Br_2 \) to cis-2-butene results in a meso compound, which is the correct answer to the question.

**Final Answer:** The product is a meso compound.

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