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 2 3 4 (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), (4)-(i). (Caprolactam intended match is not directly available.)

Step 1: Understand each component

First, identify the compounds associated with each item in List I and List II. 1. **Phenol + Formaldehyde**: This combination is known to form Bakelite, a thermosetting polymer. 2. **Terephthalic Acid + Ethylene Glycol**: This combination forms polyester, specifically known as Terylene or Dacron. 3. **Caprolactam**: This compound undergoes polymerization to form Nylon-6, not Nylon-66 which is a common mistake. 4. **Butadiene + Styrene**: This is used to produce Styrene-Butadiene Rubber (SBR), a type of synthetic rubber.

Step 2: Perform initial matching

Based on the understanding from Step 1, make the initial matches: 1. **Phenol + Formaldehyde** — **Bakelite** (ii) 2. **Terephthalic Acid + Ethylene Glycol** — **Terylene** (iv) 3. **Caprolactam** — (There is a mismatch since Caprolactam should match Nylon-6, but no option corresponds directly in List II to only Nylon-66, so it may be left unmatched correctly here or assumed incorrectly aligned with something for test purposes.) 4. **Butadiene + Styrene** — **Synthetic rubber** (i)

Step 3: Evaluate given options

Look at the provided match options in the question and see which option aligns our findings: - Option (a) does not match any conclusions. - Option (b) has **(1) corresponds to (ii) Bakelite**, and **(2) corresponds to (iv) Terylene,** as per our findings. - Even though not a perfect match to all, Option (b) aligns with two known matches and typical test conventions, acknowledging the Caprolactam inconsistency.

Step 4: Confirm the best match

Given the analysis in Steps 1-3, confirm which of the provided answer options matches our deductions: - The correct partial match based on available options and typical test recognition is (b).

Key Concepts

Polymerization

Polymerization is the process of linking small molecules called monomers into larger, more complex structures known as polymers. This process can occur in several ways:

• Addition Polymerization: Monomers add to each other without the loss of any small molecules. Common in forming polymers like polyethylene.
• Condensation Polymerization: Two different monomers join with the loss of a small molecule such as water. Polyester, such as Terylene, forms by condensing terephthalic acid with ethylene glycol.

Polymerization can be initiated by heat, light, or catalysts, each serving to drive the reaction under suitable conditions.
Understanding the type of polymerization is crucial because it affects the polymer's properties like strength, flexibility, and its applications in everyday materials.

Thermosetting Polymers

Thermosetting polymers are materials that irreversibly harden when heated. Once set, they cannot be reshaped by reheating. They are formed by cross-linking polymer chains to create a rigid three-dimensional structure.

• **Bakelite** is a classic example of a thermosetting polymer, created from phenol and formaldehyde. It is known for its strength and heat resistance.
• These polymers do not melt when exposed to high temperatures. Instead, they decompose, making them ideal for high-temperature applications.

Such properties make thermosetting polymers suitable for electrical insulators, kitchenware, and adhesives. Their durability and resistance to deformation set them apart from thermoplastics, which can be reshaped multiple times.

Synthetic Rubber

Synthetic rubber is a man-made alternative to natural rubber, crafted through the polymerization of various monomers.

• **Butadiene** and **Styrene** are commonly used to produce Styrene-Butadiene Rubber (SBR), a popular synthetic rubber.
• Synthetic rubbers like SBR are advantageous due to their resistance to abrasion and aging compared to natural rubber.

Synthetic rubber is widely used in tires, footwear, and various industrial applications.
These rubbers provide consistent quality and can be tailored for specific uses by altering their chemical makeup and processing conditions.

Polyester

Polyester is a category of polymers that includes various materials like fibers and resins, with a common feature being the ester functional group in their main chain.

• **Terylene**, a well-known polyester, is formed by condensing ethylene glycol with terephthalic acid. This process results in strong, durable fibers.
• Polyesters are appreciated for their wrinkle resistance, strength, and quick-drying properties.

They are extensively used in textiles, packaging, and reinforcements for belts and hoses. Polyester textiles are valued for their ability to hold shape and resist shrinking, making them a staple in fashion and home decor.
The versatility of polyester materials stems from their synthetic nature, allowing chemical modification to improve specific properties for diverse applications.