A synthetic rubber is not obtained from the polymerization of?

Analysis of the Question

The question asks us to identify which of the listed substances is not a monomer used in the production of synthetic rubber. To solve this, we need to understand the process of polymerization and the chemical structures required to form rubber-like polymers.

Concept Explanation

• Polymerization: This is a chemical process where small molecules called monomers react together to form a long, chain-like molecule called a polymer.
• Synthetic Rubber: Synthetic rubbers are elastomers (polymers with elastic properties) produced by the polymerization of unsaturated hydrocarbons, typically dienes (compounds with two double bonds).
• The Requirement: For a substance to undergo addition polymerization to form rubber, it must contain a carbon-carbon double bond (alkene) or multiple double bonds (dienes).

Step-by-Step Solution

1. Analyze Neoprene (Option A): Neoprene is a synthetic rubber produced by the polymerization of chloroprene (2-chloro-1,3-butadiene). It is a well-known synthetic rubber.
2. Analyze Isoprene (Option B): Isoprene (2-methyl-1,3-butadiene) is the monomer unit of natural rubber. Synthetic versions of polyisoprene are also produced as synthetic rubbers.
3. Analyze Butadiene (Option C): 1,3-butadiene is a fundamental monomer used in the production of various synthetic rubbers, such as Styrene-Butadiene Rubber (SBR) and Polybutadiene.
4. Analyze Hexane (Option D): Hexane ($C_6H_{14}$) is an alkane. Alkanes are saturated hydrocarbons, meaning they contain only single covalent bonds between carbon atoms. Because they lack the double bonds necessary for addition polymerization, they cannot act as monomers to form synthetic rubber.

Conclusion

Since hexane is a saturated alkane and lacks the double bonds required for polymerization, it cannot be used to produce synthetic rubber.

Exam Tip

When you see questions about polymerization, look for the suffix "-ene" or "-diene." These indicate the presence of double bonds, which are the "hooks" that allow molecules to link together. Saturated compounds ending in "-ane" (like hexane, propane, or ethane) generally do not undergo addition polymerization.