Problem 84 - Advanced Problems in Organic Chemistry for Competitive Examinations

Question

Which of the following sets contains only addition polymers? (a) Bakelite, PVC, polyethylene (b) Polyethylene, PVC, acrilon (c) Buna-S, nylon, polybutadine (d) Polyethylene, polypropylene, terylene

Step-by-Step Solution

Answer

The correct set is (b) Polyethylene, PVC, acrilon.

Step 1: Understanding Addition Polymers

Addition polymers are formed by the polymerization of monomers having double or triple bonds through a process where these monomers add together without the loss of any molecules. Generally, this type of polymerization involves alkenes.

Step 2: Reviewing Options for Addition Polymers

Evaluate each of the options to identify if they are addition polymers. Examine the starting monomers for each polymer to determine if they involve addition polymerization.

Step 3: Option Analysis: (a)

Bakelite is a phenol-formaldehyde resin, classified as a condensation polymer, not an addition polymer. Hence, option (a) does not contain only addition polymers.

Step 4: Option Analysis: (b)

Polyethylene and PVC are both addition polymers formed from ethene and vinyl chloride, respectively. Acrilon (acrylonitrile-based) is also polymerized by addition, making option (b) consist of only addition polymers.

Step 5: Option Analysis: (c)

Buna-S is an emulsion polymer formed from butadiene. Nylon is a condensation polymer, specifically from diamines and diacids, and not an addition polymer. Hence, option (c) does not contain only addition polymers.

Step 6: Option Analysis: (d)

Polyethylene and polypropylene are addition polymers, as they polymerize from ethene and propene. However, terylene (polyester) is formed via condensation, not addition polymerization, making option (d) incorrect.

Step 7: Identifying the Correct Option

Based on the analysis, option (b) contains only addition polymers: polyethylene, PVC, and acrilon (acrylonitrile-based polymer).

Key Concepts

Polymerization

Polymerization is a fascinating chemical process where small molecules called monomers join together to form a large chain-like molecule known as a polymer. This transformation is key in creating materials with durable and versatile properties. There are two main types of polymerization: addition polymerization and condensation polymerization.

In addition polymerization, monomers with double or triple bonds are added together, forming polymers without the loss of any other molecules. This process primarily involves alkenes, a type of hydrocarbon. It's like linking together building blocks without anything being cut away.

Condensation polymerization, on the other hand, involves the joining of monomers with the elimination of small molecules such as water or methanol. This type of reaction is common in the formation of polyesters and polyamides and is more like assembling parts where some pieces are trimmed or shaped to fit.

Condensation Polymers

Condensation polymers form through a step-growth polymerization where each step leads to the creation of small by-products like water. These polymers arise when bifunctional or polyfunctional monomers react. Examples of condensation polymers include nylon and terylene.

Nylon, for instance, results from the reaction between diamines and diacids. Every time a bond forms, a water molecule is released. This is different from addition polymerization, where no by-products are formed.

Condensation polymers are used in everyday items such as clothing, carpets, and even car parts. They are valuable because their strength and flexibility can be adjusted based on the monomers used and the conditions of the reaction.

Alkenes Polymerization

Alkenes polymerization is a common method in addition polymerization where the focus is on monomers with carbon-carbon double bonds. These alkenes can open up their double bonds to link together, forming long and sturdy polymers.

Polyethylene and polypropylene are perfect examples. They begin as ethene and propene, respectively, both simple alkenes. During polymerization, these molecules connect in a way similar to snapping together pieces of a chain.

Addition polymers derived from alkenes are found everywhere, from the plastic bags we use daily to the insulation on electrical wires. Their ease of production and wide range of applications make them integral to modern life. The process efficiently turns simple, reactive monomers into complex, useful materials without generating harmful by-products.