Problem 52 - Arihant Objective Approach to Organic Chemistry for IIT JEE and NEET all Medical Entrances Part 4

Question

A condensation polymer among the following polymers is: (a) teflon (b) polystyrene (c) PVC (d) dacron

Step-by-Step Solution

Answer

Dacron is the condensation polymer among the options.

Step 1: Identify Condensation Polymers

Condensation polymers are formed by a series of condensation reactions, usually involving the loss of small molecules like water or methanol. Key features of condensation polymers include the presence of functional groups such as esters, amides, or urethanes in the polymer backbone.

Step 2: Evaluate Options

Let's examine each polymer: - Teflon is a polymer of tetrafluoroethylene, formed by addition polymerization, not condensation. - Polystyrene is formed by the polymerization of styrene, also through an addition process. - PVC, or polyvinyl chloride, is formed by the addition polymerization of vinyl chloride. - Dacron, also known as PET (polyethylene terephthalate), is a polyester formed through the condensation of terephthalic acid and ethylene glycol, producing water as a byproduct.

Step 3: Identify the Correct Polymer

Based on the analysis, Dacron (PET) is the only polymer in the list formed through a condensation polymerization process, where ester linkages are created and small molecules (water) are released.

Key Concepts

Polymerization

Polymerization is a chemical process where small molecules, called monomers, are joined together to form longer chains known as polymers.
This process can create various materials with unique properties, ranging from plastic to rubber.
There are different types of polymerization, mainly classified into two categories.

• Addition Polymerization: In this type of polymerization, monomers add together without the loss of any small molecules. The entire monomer becomes part of the polymer, and common examples include polyethylene and polystyrene.
• Condensation Polymerization: Unlike addition polymerization, this involves the loss of small molecules such as water or methanol during the formation of each bond. This type creates polymers like polyesters and polyamides.

Understanding these processes helps in identifying how specific polymers are formed and why they have particular physical and chemical properties.

Functional Groups

Functional groups are specific groups of atoms within molecules responsible for the characteristic chemical reactions of those molecules.
They are crucial in the formation of polymers, particularly in the case of condensation polymerization. Examples of functional groups are:

• Hydroxyl Group (-OH): Found in alcohols and serves as a significant functional group in the formation of esters and polyesters.
• Carboxyl Group (-COOH): Found in carboxylic acids, this group is essential in forming ester linkages in polyesters.
• Amine Group (-NH₂): Present in amines and integral in forming amide linkages in proteins and polyamides.

These groups react with each other, often eliminating small molecules like water, to form the backbone of various polymers. For instance, when a carboxyl group reacts with a hydroxyl group, an ester linkage is formed, resulting in the creation of polyester.

Polyester

Polyesters are a type of polymer formed through condensation polymerization, where esters constitute the primary linkages in the polymer chain.
One well-known polyester is PET, or polyethylene terephthalate, commonly used in the textile industry under the brand name Dacron. Polyesters are created when a diol (a molecule with two hydroxyl groups) reacts with a dicarboxylic acid.
During this reaction, ester linkages form, and water is released as a byproduct. As a result, a strong, durable material that is resistant to many chemicals is produced.
Polyesters are valuable because they:

• Are lightweight, making them ideal for fabrics and fibers.
• Have high resistance to stretching and shrinking.
• Boast good resistance to most chemicals and withstand environmental degradation.

Due to these properties, polyesters are extensively used in clothing, packaging, and many other consumer products.

Addition Polymerization

Addition polymerization is a type of polymerization in which monomers form polymers without losing any molecules in the process.
Unlike condensation polymerization, where small molecules like water are eliminated, addition polymerization essentially stacks the entire monomer molecules to form a long chain. Common features of addition polymerization include:

• Usually involves monomers that contain double bonds, such as ethylene for making polyethylene.
• Produces no byproducts, making the process efficient and straightforward.
• Results in the rapid formation of polymers, useful for industrial applications.

Aside from its efficiency, addition polymerization allows for the creation of polymers like PVC, polystyrene, and Teflon, which are integral in various industries due to their desirable properties such as insulation, flexibility, and resistance to chemical reactions.