Problem 20 - A Complete Resource Book in Chemistry for JEE Main

Question

Natural rubber is a polymer of (a) butadiene (b) ethyne (c) styrene (d) isoprene

Step-by-Step Solution

Answer

Natural rubber is a polymer of isoprene.

Step 1: Identifying the Problem

We are asked to identify the compound of which natural rubber is a polymer. The four options given are different types of organic compounds or monomers: butadiene, ethyne, styrene, and isoprene.

Step 2: Understanding Key Terms

A polymer is a substance composed of large molecules formed by the bonding of many smaller units called monomers. Natural rubber is made by polymerizing a specific monomer.

Step 3: Recall Natural Rubber Composition

Natural rubber primarily consists of the polymer 'polyisoprene,' which is derived from the monomer 'isoprene.'

Step 4: Solution through Elimination

By identifying options that are the least likely candidates, we see that butadiene, ethyne, and styrene are not the monomers for natural rubber. Ethyne (a type of alkyne) and styrene (related to synthetic polystyrene) do not relate to natural rubber formation.

Step 5: Verifying the Answer

Cross-check with known chemical structures or textbooks: natural rubber is indeed composed of cis-1,4-polyisoprene, making isoprene the correct monomer among the options provided.

Key Concepts

Polymers

Many materials around us, from plastics to proteins, are made of polymers. Polymers are giant molecules, often resembling chains, where many smaller units, called monomers, are linked together. These building blocks bond in repeating patterns to form vast, complex structures.

• Natural and synthetic polymers exist.
• Examples include rubber, nylon, and DNA.
• Properties such as elasticity or strength vary based on the monomers used.

Understanding polymers helps us make better materials and understand complex biological processes. Adjusting the monomers or their arrangement leads to diverse properties, making polymers incredibly versatile.

Monomers

Monomers are the fundamental building blocs of polymers. They are the smaller, simpler molecules that bind in repeating patterns to create complex, large polymer structures.

• Monomers dictate the properties of the resulting polymer.
• Simple structural changes can significantly alter polymer function.
• Common monomers include isoprene, ethene, and amino acids.

In natural rubber, the monomer is isoprene. When many isoprene units join, they form polyisoprene, giving rubber its unique characteristics like elasticity.

Polyisoprene

Polyisoprene is the main component of natural rubber. This polymer, made up of many isoprene units, features a unique structure that affects its properties.

• Cis-1,4-polyisoprene is the specific structure in natural rubber.
• This arrangement gives rubber its elasticity and strength.
• Different arrangements of isoprene lead to synthetic variants with distinct characteristics.

The ability to stretch and return to its original shape makes polyisoprene invaluable for a range of products, including tires and elastic bands.

Organic Chemistry

Organic chemistry is the branch of chemistry dedicated to studying carbon-containing compounds. This field covers varied substances, from small molecules like ethanol to large ones like DNA.

• Central concepts include bonding, structure, and reactivity of carbon compounds.
• Key functional groups determine properties and reactions.
• Polymer chemistry is a vital part of organic chemistry, influencing both industrial applications and biological studies.

Understanding organic chemistry is crucial for myriad applications, whether developing new materials or dissecting complex biochemical processes. It intrigues with the diversity and versatility of carbon compounds.