Problem 45 - Arihant Objective Approach to Organic Chemistry for IIT JEE and NEET all Medical Entrances Part 4

Question

Dacron is polymer of : (a) glycol and formaldehyde (b) glycol and phenol (c) glycol and phthalic acid (d) glycol and terephthalic acid

Step-by-Step Solution

Answer

Dacron is a polymer of glycol and terephthalic acid (option d).

Step 1: Understand the Polymer

The exercise asks about Dacron, which is a synthetic polymer. Dacron is known to be a type of polyester, specifically polyethylene terephthalate (PET). To solve this, we need to identify the monomer units that form Dacron.

Step 2: Identify Monomer Components

Polyesters like Dacron are typically formed through a condensation reaction between diols (glycols) and dicarboxylic acids. Knowing this, we need to find which option pairs a glycol with a suitable dicarboxylic acid to form a polyester.

Step 3: Analyze Options

Consider each pair: - (a) Glycol and formaldehyde: Formaldehyde is not a dicarboxylic acid, so they do not form a polyester. - (b) Glycol and phenol: Phenol is not a dicarboxylic acid, so they do not form a polyester. - (c) Glycol and phthalic acid: Phthalic acid can form a polyester with glycol, but it is not the specific pairing for Dacron. - (d) Glycol and terephthalic acid: This pair forms polyethylene terephthalate, which is Dacron.

Step 4: Determine the Correct Answer

Based on the analysis in Step 3, the pair of glycol and terephthalic acid (option d) correctly describes the monomer units that form the polymer Dacron. Therefore, the correct answer is option (d).

Key Concepts

Synthetic Polymers

Synthetic polymers are man-made chains of molecules engineered to possess certain desirable properties. These materials include plastics, fibers, and resins that are widespread in everyday products.
Unlike natural polymers such as proteins and cellulose, synthetic polymers are typically designed in a lab. They offer versatility in wearing properties ranging from stiffness to elasticity.

• Created chemically, usually from petrochemical sources.
• Involves polymerization processes - either addition or condensation.
• Used in industries like packaging, textiles, and electronics.

Understanding synthetic polymers is crucial for innovation in countless applications like biodegradable materials and advanced textiles.

Polyester

Polyesters are a category of polymers formed through ester linkage. In simpler terms, they are made by reacting an alcohol with an acid, eliminating a small molecule like water. Among the many polyester types, polyethylene terephthalate (PET) is quite famous. It is employed extensively in textiles and plastic bottles.
Polyesters are primarily known for their durability and resistance to environmental conditions. Polyethylene terephthalate, for instance, ranks highly for its recyclability and sustainability potential. Ulterior features include:

• High tensile strength
• Resistance to stretching and shrinking
• Color retention over long periods

Given these properties, polyesters are ideal for clothing and packaging materials.

Condensation Reaction

A condensation reaction is a chemical process where molecules join together, releasing a smaller molecule such as water in the process. This reaction is essential in forming polymers, especially those like Dacron. In the case of polyesters like Dacron, the reaction typically involves diols (such as glycol) and dicarboxylic acids (like terephthalic acid).
Key aspects include:

• Releases small molecules such as water or methanol.
• Common in the formation of polymers and other complex molecules.
• Critical step in creating strong, durable polymer chains.

Understanding condensation reactions is essential for fields like polymer chemistry and material science, where forming stable and robust materials is pivotal.