Question

Buna-S can be represented as:

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is D

Step 1: Understanding the structure of Buna-S 
Buna-S is a copolymer, meaning it is formed by the polymerization of two distinct monomers: butadiene and styrene. The monomers involved in the copolymerization are as follows: 
Butadiene (\( \text{CH}_2 = \text{CH} - \text{CH} = \text{CH}_2 \))
Styrene (\( \text{C}_6\text{H}_5 - \text{CH} = \text{CH}_2 \)) 
Step 2: Identifying the correct structure 
The polymerization of butadiene and styrene occurs in a 3:1 ratio. This means that for every three units of butadiene, one unit of styrene is incorporated. In the polymerization process, the double bonds in the monomers break and connect, forming the long polymer chain.
Option (1) is incorrect because it does not correctly represent the polymerization process involving styrene. 
Option (2) is the correct representation as it shows the proper copolymerization between butadiene and styrene, with the following structure: \[ \left[ \text{CH}_2 = \text{CH} - \text{CH} = \text{C}_6\text{H}_5 \right]_n \] This structure correctly alternates between the butadiene and styrene units, forming the desired polymer chain. 
Step 3: Finalizing the structure of Buna-S 
In Buna-S, the repeating unit alternates between styrene and butadiene molecules. This arrangement is essential as it determines the material's properties, such as its elasticity, strength, and resistance to wear.
Thus, the correct structure of Buna-S is represented in option (4), and the polymerization of butadiene and styrene produces the copolymer known as Buna-S.