Addition of bromine to cis-3 hexene gives

Options

A. racemic dibromide
B. a mixture of diastereomeric dibromides
C. optically active dibromide
D. meso dibromide

Answer

To determine the product of the addition of bromine to cis-3-hexene, we can follow these steps:

### Step 1: Identify the Structure of Cis-3-Hexene
Cis-3-hexene has the following structure:
- It is an alkene with a double bond between the 3rd and 4th carbon atoms.
- The "cis" configuration means that the two alkyl groups (ethyl and methyl) are on the same side of the double bond.

### Step 2: Understand the Mechanism of Bromine Addition
When bromine (Br2) is added to an alkene, the reaction proceeds via a bromonium ion intermediate. The double bond attacks one of the bromine atoms, leading to the formation of a cyclic bromonium ion.

### Step 3: Formation of the Bromonium Ion
- The double bond in cis-3-hexene attacks one of the bromine atoms, forming a bromonium ion.
- This intermediate has a three-membered ring structure with a positive charge on the bromine.

### Step 4: Nucleophilic Attack
- The bromide ion (Br-) then attacks the bromonium ion.
- Due to the three-dimensional nature of the bromonium ion, the attack can occur from the opposite side of the bromonium ion (backside attack), leading to anti-addition.

### Step 5: Draw the Products
- The attack from the top side of the bromonium ion will yield one product, while the attack from the bottom side will yield another product.
- Both products will be enantiomers of each other due to the stereochemistry of the addition.

### Step 6: Conclusion
The addition of bromine to cis-3-hexene results in the formation of a racemic mixture of 2,3-dibromo-hexane, which consists of two enantiomers.

### Final Product
The final product of the addition of bromine to cis-3-hexene is a racemic mixture of 2,3-dibromo-hexane.

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