Problem 6 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The two monomers for the synthesis of nylon 6,6 are : [Main Jan. 12, 2019 (II)] (a) \(\mathrm{HOOC}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{COOH}, \mathrm{H}_{2} \mathrm{~N}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{NH}_{2}\) (b) \(\mathrm{HOOC}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{COOH}, \mathrm{H}_{2} \mathrm{~N}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{NH}_{2}\) (c) \(\mathrm{HOOC}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{COOH}, \mathrm{H}_{2} \mathrm{~N}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{NH}_{2}\) \text { (d) } \mathrm{HOOC}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{COOH}, \mathrm{H}_{2} \mathrm{~N}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{NH}_{2}

Step-by-Step Solution

Answer

The correct monomers are option (b): Adipic acid and hexamethylenediamine.

Step 1: Understand Nylon 6,6 Synthesis

Nylon 6,6 is synthesized through a condensation polymerization reaction, primarily involving two different types of monomers: hexamethylenediamine (a diamine) and adipic acid (a dicarboxylic acid).

Step 2: Identify the Structure of Hexamethylenediamine

Hexamethylenediamine is characterized by having 6 carbon atoms in a straight chain, ending with amine groups. Its chemical structure is denoted as \(\mathrm{H}_2 \mathrm{~N}(\mathrm{CH}_2)_6 \mathrm{NH}_2\).

Step 3: Identify the Structure of Adipic Acid

Adipic acid also has a straight chain of 6 carbon atoms, ending with carboxylic acid groups. It is represented as \(\mathrm{HOOC}(\mathrm{CH}_2)_4 \mathrm{COOH}\).

Step 4: Match with Given Options

Among the choices, option (b) lists the correct monomers for nylon 6,6 as \(\mathrm{HOOC}(\mathrm{CH}_2)_6 \mathrm{COOH}\) and \(\mathrm{H}_2 \mathrm{~N}(\mathrm{CH}_2)_6 \mathrm{NH}_2\). This matches adipic acid and hexamethylenediamine.

Key Concepts

Condensation Polymerization

Nylon 6,6 is created through a chemical process known as condensation polymerization. This type of polymerization involves the joining of monomers while simultaneously releasing small molecules as by-products, commonly water. The specific reaction we focus on here occurs between two monomers: hexamethylenediamine and adipic acid.

In the case of nylon 6,6, each molecule of hexamethylenediamine has two amine groups at each end, while each adipic acid molecule has two carboxylic groups. During the polymerization reaction, the amine group on the hexamethylenediamine reacts with the carboxylic group on the adipic acid. This reaction forms a strong amide bond and releases a molecule of water.

As this reaction repeats, long chains of nylon-6,6 are formed, characterized by the repeating pattern of -CO-(CH₂)₄-CO-NH-(CH₂)₆-NH-. This builds up into the strong material used in textiles and various other applications. Therefore, understanding condensation polymerization is crucial for grasping how such a versatile and durable material as nylon 6,6 is synthesized.

Hexamethylenediamine

Hexamethylenediamine is a key monomer used in the synthesis of nylon 6,6. Recognized by its chemical formula \( ext{H}_2 ext{N}( ext{CH}_2)_6 ext{NH}_2\), this compound comprises six carbon atoms forming a straight chain, flanked by amine (\