Question

This section contains multiple choice questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONLY ONE is correct. Polyurethane is a polymerisation product of ethylene glycol and (a) vinyl chloride (b) terephthalic acid (c) acrylonitrile (d) toluene- 2,4 -diisocyanate

Short answer

(a) Vinyl chloride (b) Terephthalic acid (c) Acrylonitrile (d) Toluene-2,4-diisocyanate Answer: (d) Toluene-2,4-diisocyanate

Step-by-step solution

Choice (a): Vinyl chloride

Vinyl chloride is a monomer used in the production of polyvinyl chloride (PVC), a type of plastic. It does not react with ethylene glycol to form polyurethane.

Choice (b): Terephthalic acid

Terephthalic acid is a compound used in the production of polyesters, like polyethylene terephthalate (PET). It does not react with ethylene glycol to form polyurethane.

Choice (c): Acrylonitrile

Acrylonitrile is a monomer used in the production of various polymers, such as polyacrylonitrile and acrylonitrile-butadiene-styrene (ABS). It does not react with ethylene glycol to form polyurethane.

Choice (d): Toluene-2,4-diisocyanate

Toluene-2,4-diisocyanate is a compound that reacts with ethylene glycol (or other polyols) to form polyurethane. This is the correct answer. Therefore, the correct answer is: (d) Toluene-2,4-diisocyanate

Key concepts

Polymerisation Product

Polymerisation is a chemical reaction in which small molecules, known as monomers, combine to form a larger network called a polymer. The formation of a polymerisation product like polyurethane is a result of a specific type of polymerisation called step-growth polymerisation.

Different polymers have diverse properties and applications, depending on the monomers used and the conditions under which the polymerisation occurs. In the synthesis of polyurethane, a key concept is that it requires a diisocyanate and a diol, in this case, ethylene glycol, to undergo a polymerisation reaction. During this process, the -OH (hydroxyl) groups of the ethylene glycol react with the -NCO (isocyanate) groups of the diisocyanate to form urethane linkages.

Understanding this step-by-step reaction helps students grasp how the structure and properties of polyurethanes are derived from its reactive components, which significantly affects its functionality in various applications ranging from foams to elastomers.

Ethylene Glycol

Ethylene glycol, a colorless, sweet-tasting organic compound, plays a pivotal role in the synthesis of polymers like polyurethane. It is a diol, meaning it contains two -OH (hydroxyl) groups that are reactive and able to form strong chemical bonds with other compounds.

In the context of polyurethane synthesis, ethylene glycol serves as the 'backbone' to which other reactive molecules, such as toluene-2,4-diisocyanate, can attach. When combined, ethylene glycol's hydroxyl groups react with the isocyanate groups, creating a polymeric chain known as a polyurethane linkage.

To help students better understand ethylene glycol’s role, it's critical to highlight its molecular structure and reactivity. Commonly used in antifreeze and as an industrial feedstock, ethylene glycol's versatility in forming various polymers makes it a significant substance in the realm of polymer chemistry.

Toluene-2,4-Diisocyanate

Toluene-2,4-diisocyanate, abbreviated as TDI, is a key monomer in the production of polyurethane. This organic compound is characterized by two isocyanate groups marked as -NCO, which are highly reactive and essential for the polymerisation reaction with ethylene glycol.

When TDI reacts with ethylene glycol, the resulting chemical bonds form urethane linkages, which give polyurethane its unique properties. Safety is paramount when handling TDI, as it is a toxic substance that can cause irritation or sensitization. Proper safety measures must be taught to students, emphasizing the importance of careful handling during polyurethane synthesis.

Overall, TDI's chemistry and its pivotal role in creating flexible, durable polyurethane products underscore its significance in material science. Learning how its structure helps form the characteristic urethane bonds is fundamental for students exploring advanced polymer synthesis.