Problem 102 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is a condensation polymer? (a) Polyacrylonitrile (b) Bakelite (c) Glyptal (d) Nylon \(-6,6\)

Step-by-Step Solution

Answer

Bakelite, Glyptal, and Nylon -6,6 are condensation polymers.

Step 1: Understand Condensation Polymerization

Condensation polymerization takes place when monomers join together, releasing small molecules like water or methanol as by-products. This is different from addition polymerization, which does not release by-products.

Step 2: Identify Polymer Types

Examine each option to categorize the type of polymerization process involved: - Polyacrylonitrile is typically formed through addition polymerization. - Bakelite is formed by a condensation reaction involving formaldehyde and phenol, releasing water. - Glyptal is formed through a condensation reaction of phthalic anhydride and glycerol, also releasing water. - Nylon -6,6 definitively forms through the condensation polymerization of hexamethylenediamine and adipic acid, releasing water.

Step 3: List Condensation Polymers

From Step 2, the polymers formed through condensation reactions are Bakelite, Glyptal, and Nylon -6,6. These involve the release of small molecules such as water during their formation.

Key Concepts

Polymerization Process

Polymerization is the process by which small molecules called monomers bond together to form larger complex structures known as polymers. There are two main types of polymerization processes: **condensation polymerization** and **addition polymerization**. Each process leads to the formation of polymers but through different mechanisms. Understanding these processes is fundamental to classifying and synthesizing different types of polymers, like Nylon and Bakelite.

• Condensation Polymerization: This involves the combination of monomers with the elimination of small molecules such as water or methanol.
• Addition Polymerization: Monomers add to each other without the loss of any atoms. The entire monomer becomes part of the polymer.

Polymerization is key in producing materials with a wide range of applications, from everyday plastics to specialized fibers.

Condensation Reaction

A condensation reaction is a chemical process where two molecules join together, usually leading to the release of a smaller molecule such as water. In the context of polymer chemistry, this is crucial for the formation of condensation polymers.

• For example, **Bakelite** and **Glyptal** are formed by condensation reactions that emit water as a by-product.
• Nylon 6,6, a well-known synthetic polymer, is produced from hexamethylenediamine and adipic acid, again releasing water during polymerization.

These reactions are vital not just for making polymers, but also in many biological processes and industries.

Addition Polymerization

Addition polymerization involves monomers joining together without the loss of any small molecules in the process. This is distinct from condensation polymerization, where by-products are released.

• In addition polymerization, monomers typically have double or triple bonds that open up and link together, forming a chain.
• Polyacrylonitrile is an example of a polymer formed this way, where acrylonitrile molecules create strong polymer chains used in fibers and precursors for carbon fibers.

This process is usually faster than condensation polymerization and can help create a variety of different materials used in textiles, packaging, and even medical devices.