Question

Identify the monomer of natural rubber.

• A. Isoprene
• B. Polyacrylonitrile
• C. Chloroprene
• D. Tetrafluoroethylene

Hint:

Natural rubber = cis-1,4-polyisoprene, so its monomer is isoprene.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Polymers are large molecules formed by the repeated linkage of smaller units called monomers.
Natural rubber is an addition polymer obtained from latex, which is tapped from rubber trees.
Step 2: Key Formula or Approach:
Recall the chemical composition of common polymers.
Identify the specific small molecule (monomer) that undergoes polymerization to form natural rubber.
Step 3: Detailed Explanation:
Let's review the role of each chemical listed in the options:
(B) Polyacrylonitrile: As the "poly" prefix suggests, this is already a polymer, not a monomer. Its monomer is acrylonitrile. It is used to make synthetic fibers like Orlon.
(C) Chloroprene: This is the monomer used to manufacture a common synthetic rubber called neoprene. Its chemical structure is similar to isoprene but has a chlorine atom instead of a methyl group.
(D) Tetrafluoroethylene: This is the monomer that polymerizes to form Polytetrafluoroethylene (PTFE), widely known by its trade name, Teflon.
(A) Isoprene: The chemical name for isoprene is 2-methyl-1,3-butadiene.
Natural rubber is formed by the stereospecific 1,4-addition polymerization of isoprene units.
Specifically, natural rubber consists almost exclusively of {cis}-1,4-polyisoprene.
Therefore, isoprene is the foundational building block (monomer) of natural rubber.
Step 4: Final Answer:
The monomer of natural rubber is isoprene.