When cis-but-2-ene is treated with `Br_(2)` in `"CCl"_(4)` medium the product formed will be

Options

A. (2R, 3S) dibromobutane
B. (2R, 3R) dibromobutane
C. (2S, 3S) dibromobutane
D. Mixture of (2R, 3R) and (2S, 3S) dibromobutane

Answer

To solve the question regarding the reaction of cis-but-2-ene with Br₂ in CCl₄ medium, we will follow these steps:

### Step 1: Identify the Reactant
The reactant given is cis-but-2-ene. The structure of cis-but-2-ene can be represented as follows:

```
CH3
|
CH3-C=C-CH2
|
H
```

### Step 2: Understand the Reaction Conditions
The reaction is carried out in the presence of Br₂ and CCl₄. CCl₄ is a non-polar solvent, which facilitates the reaction by allowing the bromine molecule to remain intact and not dissociate prematurely.

### Step 3: Mechanism of Bromination
When cis-but-2-ene reacts with Br₂, the following mechanism occurs:

1. **Formation of Bromonium Ion**: The double bond of cis-but-2-ene attacks one of the bromine atoms, leading to the formation of a bromonium ion. This step involves the formation of a cyclic structure where one bromine atom is temporarily bonded to both carbon atoms of the double bond.

2. **Nucleophilic Attack**: The other bromine atom (Br⁻) acts as a nucleophile and attacks the more substituted carbon of the bromonium ion. This can occur from either the front or the back side of the bromonium ion.

### Step 4: Determine the Products
Since the attack can occur from either side, we will have two stereoisomers:

1. **Front Side Attack**: This will lead to one stereoisomer where the bromine atoms are on the same side (cis configuration).
2. **Back Side Attack**: This will lead to another stereoisomer where the bromine atoms are on opposite sides (trans configuration).

### Step 5: Identify the Final Products
The final products of the reaction will be:
- 2R,3R-Dibromobutane (from front side attack)
- 2S,3S-Dibromobutane (from back side attack)

### Step 6: Conclusion
Since both products are formed, the correct answer to the question is that the product formed will be a mixture of 2R,3R-Dibromobutane and 2S,3S-Dibromobutane.

Thus, the answer is: **A mixture of 2R,3R-Dibromobutane and 2S,3S-Dibromobutane.**

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