Problem 91 - Advanced Problems in Organic Chemistry for Competitive Examinations

Question

Polythene is a resin obtained by polymerisation of (a) butadiene (b) ethylene (c) styrene (d) isoprene

Step-by-Step Solution

Answer

Polythene is a resin obtained by polymerization of ethylene (b).

Step 1: Understand Polymerization

To solve this question, we need to understand what polymerization is. Polymerization is the process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. The key is identifying the correct monomer.

Step 2: Identify Polythene

Polythene, also known as polyethylene, is one of the most common plastic materials used worldwide. It is created through the polymerization process of a specific monomer.

Step 3: Look at the Options

Let's examine the options given: (a) butadiene, (b) ethylene, (c) styrene, (d) isoprene. Among these, one of these is responsible for forming polythene.

Step 4: Select the Correct Monomer

Polythene is produced by the polymerization of ethylene (b). Ethylene, a hydrocarbon compound with the formula C₂H₄, polymerizes to form polyethylene.

Key Concepts

Understanding Polythene

Polythene, often known as polyethylene, is a type of plastic that is extremely versatile and commonly used across many industries. It is found in everyday objects, ranging from plastic bags to water bottles and even as an insulating layer in cables.
Polythene is produced through a chemical process known as polymerization, where small molecules called monomers join together to form longer chains, constituting a polymer.

• Lightweight and durable, making it ideal for packaging materials.
• Resistant to moisture and chemicals, which increases its versatility.
• Available in both low-density (LDPE) and high-density (HDPE) forms, each with unique properties and applications.

Understanding how polythene is produced can help in appreciating its varied uses and innovations in creating more sustainable plastic alternatives.

The Role of Ethylene

Ethylene is the primary raw material, or monomer, used in the production of polythene through polymerization. Ethylene itself is a hydrocarbon that is both colorless and flammable.
Its chemical formula is C\(_2\)H\(_4\), and it is an unsaturated molecule, which means it has a double bond between two carbon atoms. This double bond allows ethylene molecules to link together efficiently during polymerization become extremely long chains:

• Source: Ethylene is derived from natural gas and petroleum.
• Ease of polymerization: It polymerizes easily under pressure and temperature to form polyethylene.
• By forming stable and strong bonds, ethylene enables the production of varied plastics with custom attributes.

Understanding ethylene's chemical properties and behavior is crucial for comprehending how everyday materials are manufactured.

Concept of Monomers

Monomers are the building blocks of polymers. They are small, simple molecular compounds that can join together to create polymer chains.
In the context of polythene formation, ethylene acts as the monomer, where numerous ethylene molecules combine to form the plastic material we use daily.

• Monomers are typically reactive thanks to functional groups or double bonds.
• Each polymer's properties depend heavily on the type and structure of the monomer used.
• By altering the arrangement or type of monomer, polymers with a wide variety of properties can be synthesized, suitable for different applications.

Recognizing the role of monomers helps explain the vast diversity found within synthetic materials and their applications.