Animated Solution for Chemistry - Polymers: Match List-I with List-II. $\begin{array}{ll}\text{List-I}& \text{List-II}\\ \text{(Monomer Unit)}& \text{(Polymer)}\\ \text{A. Caprolactum}& \text{1. Natural rubber}\\ \text{B. 2-chloro buta-1,3-diene}& \text{2. Buna-N}\\ \text{C. Isoprene}& \text{3. Nylon-6}\\ \text{D. Acrylonitrile}& \text{4. Neoprene}\end{array}$ Choose the correct answer from the options given below

Matching Monomers to Polymers

Welcome to a classic journey through the world of macromolecules! In chemistry, polymers are ubiquitous, forming everything from the clothes we wear to the tires on our vehicles. For competitive exams like JEE, mastering the names, structures, and corresponding polymers of various monomers is an absolute necessity. It is a high-yield topic where memory directly translates to marks.

In this specific problem, we are presented with a matrix match. We have a list of four distinct monomers and we need to pair them perfectly with their resulting polymers. Let's break down each molecule and understand the chemistry behind its transformation.

First on our list is Caprolactum. If you look at its chemical structure, caprolactum is a seven-membered cyclic amide. It contains a continuous chain of five $-{\text{CH}}_2-$ groups, one carbonyl group ($-\text{C}=\text{O}$), and one amine group ($-\text{NH}-$).

When caprolactum is heated with water at high temperatures (around $533\text{ K}$), it undergoes a fascinating process called ring-opening polymerization. The water hydrolyzes the amide bond, breaking the ring open to form an amino acid intermediate (aminocaproic acid). These linear molecules then undergo condensation polymerization, linking head-to-tail to form a long, continuous chain.

The resulting polymer is Nylon-6. The number '6' is a direct reference to the fact that its monomeric unit, caprolactum, contains exactly six carbon atoms. Therefore, we can confidently match A $\to$ 3.

Chloroprene

Next, we encounter 2-chloro buta-1,3-diene. This molecule is a diene, meaning it has two double bonds, with a chlorine atom attached to the second carbon. In the industrial world, this molecule is famously known by its common name: Chloroprene.

Chloroprene undergoes free-radical addition polymerization. During this process, the double bonds shift, and the molecules link together to form a highly resilient synthetic rubber known as Neoprene. Neoprene is highly resistant to chemical degradation and maintains its flexibility over a wide temperature range, making it ideal for wetsuits and electrical insulation.

Thus, our second match is firmly established: B $\to$ 4.

Isoprene

Our third monomer is Isoprene. Its formal IUPAC name is 2-methylbuta-1,3-diene. Notice the structural similarity to chloroprene? The only difference is that the chlorine atom has been replaced by a methyl group ($-{\text{CH}}_3$).

Isoprene is the fundamental building block of Natural rubber. When isoprene polymerizes in nature (within the sap of rubber trees), it forms a polymer where all the double bonds have a specific geometric arrangement: the cis configuration. This means the polymer chain continues on the same side of the double bond.

This specific geometry, known chemically as cis-1,4-polyisoprene, prevents the polymer chains from packing tightly together, giving natural rubber its characteristic stretchiness and elasticity. Hence, we match C $\to$ 1.

Acrylonitrile

Finally, we look at Acrylonitrile, which has the chemical formula ${\text{CH}}_2=\text{CH}-\text{CN}$. This monomer is unique in our list because, in this context, it doesn't polymerize alone.

Acrylonitrile is copolymerized with 1,3-butadiene. When these two different monomers join forces in the presence of a peroxide catalyst, they form a highly durable synthetic rubber called Buna-N (also known as Nitrile rubber).

The nomenclature here is a great memory aid: 'Bu' stands for butadiene, 'na' stands for sodium (which was historically used as a catalyst), and the crucial 'N' stands for Nitrile, pointing directly to the acrylonitrile monomer. Therefore, our final match is D $\to$ 2.

Let's bring all our logical deductions together:

A. Caprolactum forms 3. Nylon-6 B. 2-chloro buta-1,3-diene forms 4. Neoprene C. Isoprene forms 1. Natural rubber D. Acrylonitrile forms 2. Buna-N

This gives us the sequence: A $\to$ 3, B $\to$ 4, C $\to$ 1, D $\to$ 2.

Scanning through the given options, we see that this sequence perfectly matches option (d). By understanding the structures and the stories behind these molecules, what seems like a pure memorization task becomes a logical and rewarding exercise in chemical deduction.