Problem 115 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I List II 1\. Phenol+formaldehyde (i) Synthetic rubber 2\. Terephthalic acid \(+\) (ii) Bakelite ethylene glycol 3\. Caprolactam (iii) Nylon-66 4\. Butadiene \(+\) styrene (iv) Terylene The correct matching is: 1 \(\begin{array}{lll}2 & 3 & 4\end{array}\) (a) (iv) (ii) (iii) (i) (b) (ii) (iv) (iii) (i) (c) (iii) (ii) (i) (iv) (d) (ii) (iii) (iv) (i)

Step-by-Step Solution

Answer

The correct matching is option (b): 1(ii), 2(iv), 3(iii), 4(i).

Step 1: Understanding the Components

We first identify what polymers or materials result from each listed pair combination in List I. Phenol with formaldehyde is known to form Bakelite. Terephthalic acid and ethylene glycol create Terylene, which is a type of polyester. Caprolactam is a monomer for Nylon-6, not to be confused with Nylon-66 (formed from adipic acid and hexamethylene diamine). Butadiene and styrene are used to produce synthetic rubber like SBR (styrene-butadiene rubber).

Step 2: Matching Elements to List II

Now, we match each combination from List I to the correct polymer or material named in List II: - Phenol + formaldehyde matches with Bakelite (ii). - Terephthalic acid + ethylene glycol matches with Terylene (iv). - Caprolactam isn't in List I, so it's ignored. - Butadiene + styrene matches with synthetic rubber (i).

Step 3: Selecting the Correct Answer

From the matching outlined above, we look for an option that matches this pattern: 1(ii), 2(iv), 4(i). The option that matches this sequence is (b).

Key Concepts

Bakelite synthesis

Bakelite is one of the first synthetic plastics ever created and it is produced by the reaction of phenol with formaldehyde. When these two compounds react, they form a thermosetting phenol formaldehyde resin with excellent insulating properties, making it very useful in the electrical industry.
The process for synthesizing Bakelite involves a condensation reaction that occurs in several steps:

• First, phenol and formaldehyde undergo an addition reaction to form an intermediate hydroxymethyl phenol.
• Next, these intermediates undergo polymerization and are transformed into a complex, cross-linked network structure.
• Finally, the polymer solidifies upon heating and becomes insoluble and infusible. This is due to the formation of methylene bridges between aromatic rings, contributing to its rigidity.

Bakelite's heat-resistant and durable nature makes it suitable for kitchenware, electrical insulators, and early fashion accessories like buttons and bangles.

Polyester formation

Polyesters are formed through a polymerization reaction between an acid and an alcohol, commonly known as a condensation reaction. In the case of Terylene (also known as PET or polyethylene terephthalate), the acid used is terephthalic acid, and the alcohol is ethylene glycol.
Terylene synthesis involves the following steps:

• First, ethylene glycol reacts with terephthalic acid to form bis(2-hydroxyethyl) terephthalate.
• This intermediate then goes through a polycondensation reaction, resulting in the long chains of polyester, releasing water as a by-product.
• The resulting polymer chains are then spun into fibers or molded into solid materials.

Terylene is known for its strength, flexibility, and resistance to wrinkles, and it is widely used in textiles, plastic bottles, food packaging, and more.

Synthetic rubber production

Synthetic rubber is an artificial elastomer, mainly produced from petroleum byproducts. The most common type of synthetic rubber is Styrene-Butadiene Rubber (SBR), created through the copolymerization of butadiene and styrene.
Here's how synthetic rubber is produced:

• Butadiene and styrene are polymerized in an emulsion process, which means they are mixed with water and soap to form micelles, where polymerization occurs.
• During polymerization, a rubbery elastic material is formed, which can be processed further.
• The resulting SBR displays qualities similar to natural rubber, being strong, flexible, and resistant to abrasion and wear.

SBR is widely used in manufacturing tires, footwear, and various automotive parts due to its excellent abrasion resistance and aging stability.

Nylon-6 vs Nylon-66

Nylon is a type of polyamide polymer that comes in several types, including the well-known Nylon-6 and Nylon-66. While both are used for similar applications, they have distinct differences stemming from their chemical compositions and the monomers involved.
Nylon-6 is synthesized from caprolactam:

• The caprolactam undergoes a ring-opening polymerization, aided by heat, to form Nylon-6.
• This process involves polymer chains formed from a single type of monomer, giving it slightly different thermal properties compared to Nylon-66.

Nylon-66, on the other hand, is synthesized from adipic acid and hexamethylene diamine:

• These react to form a nylon salt, which undergoes polycondensation to produce the final polymer.
• Nylon-66 typically has greater resistance to heat and wear, making it suitable for more demanding applications.

Both types of nylon are commonly used in textiles, automotive components, and industrial goods due to their strength, durability, and resistance to wear and chemicals.