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 (d) isoprene.

Step 1: Understand the Question

The question asks us to identify which of the given compounds is the monomer that forms natural rubber.

Step 2: List the Options

We have four options to consider: (a) butadiene, (b) ethyne, (c) styrene, and (d) isoprene. We need to know which of these compounds is used to make natural rubber.

Step 3: Identify the Monomer of Natural Rubber

Natural rubber is primarily composed of polyisoprene, where 'poly-' indicates that many isoprene units are joined together to form the rubber. Thus, the correct monomer is isoprene.

Step 4: Select the Correct Option

Among the given options, (d) isoprene is the chemical compound that polymerizes to form natural rubber.

Key Concepts

The Role of Isoprene in Natural Rubber

Natural rubber is a fascinating material that finds its applications in various daily products like tires and elastic bands. At the heart of natural rubber is a chemical compound called isoprene. Isoprene is a simple hydrocarbon with the formula \( C_5H_8 \). It serves as the primary building block or monomer for natural rubber.

Isoprene is a key element because it has the unique ability to join together with other isoprene molecules. This property allows it to form long chains or polymers, which give rubber its characteristic elasticity and strength. Without isoprene, the natural rubber could not exist in its familiar form.

• Isoprene gives natural rubber its flexibility.
• The structure of isoprene enables the process of polymerization, which is vital for the formation of rubber.
• Without the polymerization of isoprene, we wouldn't have natural rubber as we know it.

Understanding Polymerization

Polymerization is the process that transforms small molecules called monomers, like isoprene, into long, repeating chains called polymers. It is a fundamental chemical reaction for creating rubber and many other materials. In the context of natural rubber, polymerization involves the joining of multiple isoprene molecules.

During polymerization, the double bonds in isoprene open up, allowing each molecule to connect with another. This creates a chain, known as polyisoprene, a complex structure giving natural rubber its essential properties.

Polyisoprene chains are very long, which contributes to the strength and flexibility of natural rubber. This is what makes it so useful in everyday applications, from the elasticity in rubber bands to the durability required by vehicle tires.

• Polymerization is essential for converting monomers like isoprene into useful materials.
• It transforms individual isoprene units into polyisoprene, forming natural rubber.
• This process gives natural rubber its physical properties, which are so valued in different industries.

Monomer Identification: Finding the Right Building Block

Identifying the correct monomer is crucial in understanding and producing polymers. In the case of natural rubber, isoprene is the specific monomer that is required. Knowing what a monomer is and how to identify it can simplify understanding how complex structures like rubber are formed.

A monomer is the simplest unit that can join with other similar molecules through polymerization. Isoprene's structure allows it to serve this function effectively. It provides the foundational block for creating the polymer chain that leads to natural rubber.

When identifying monomers, it's important to understand the properties of the compound in question—its structure, ability to form bonds, and compatibility with polymerization. Isoprene meets all these criteria, making it the correct choice for the monomer of natural rubber.

• Monomer identification is key to understanding material formation.
• Isoprene acts as the monomer for natural rubber due to its specific structural properties.
• The right monomer determines the properties and utilities of the resulting polymer.