Problem 118 - A Complete Resource Book in Chemistry for JEE Main

Question

Buna \(-\mathrm{N}\) synthetic rubber is copolymer of: (a) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}\) and \(\mathrm{H}_{5} \mathrm{C}_{6}-\mathrm{CH}=\mathrm{CH}_{2}\) (b) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CN}\) and \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}\) (c) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CN}\) and C=CC(=C)C C=CC(=C)Cl (d) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{C}=\mathrm{CH}_{2}\) and \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}\)

Step-by-Step Solution

Answer

Buna N is made from (b) Acrylonitrile and Butadiene.

Step 1: Understanding Buna N Rubber

Buna N, also known as Nitrile rubber, is a synthetic rubber copolymer composed of acrylonitrile and butadiene monomers. This rubber is known for its resistance to oils and is commonly used in various industrial applications.

Step 2: Identifying the Monomers in Buna N Rubber

The two monomers that constitute Buna N rubber are: Acrylonitrile (CH_2=CH-CN) and Butadiene (CH_2=CH-CH=CH_2). The acrylonitrile provides resistance to oils, while butadiene contributes to the rubber's flexibility.

Step 3: Analysis of Given Options

We need to match the monomer pair for Buna N rubber with the given options. - Option (a) involves 1,3-butadiene and styrene, which is used in making Styrene-butadiene rubber (SBR), not Buna N. - Option (b) contains Acrylonitrile and 1,3-butadiene, which matches the components of Buna N rubber. - Option (c) contains Acrylonitrile and Isoprene (C=CC(=C)C), which is not used for Buna N. - Option (d) contains two butadiene molecules, which do not combine to form Buna N.

Step 4: Conclusion

From the analysis, Option (b) correctly lists the monomers that form Buna N synthetic rubber: Acrylonitrile (CH_2=CH-CN) and 1,3-Butadiene (CH_2=CH-CH=CH_2). Therefore, the correct answer is Option (b).

Key Concepts

Buna N Rubber

Buna N Rubber, also known as Nitrile rubber, is a versatile synthetic rubber that is highly valued for its excellent resistance to oils, fuels, and other chemicals. It is widely used in the automotive and aerospace industries, as well as in various industrial applications such as seals, hoses, and gaskets.

The resistance to oils makes Buna N an ideal material for uses where contact with oils is frequent, such as in fuel tanks or hydraulic systems. This rubber’s durability ensures reliability in harsh conditions, which is paramount for these environments.

• Widely used in the automotive and aerospace industries
• Excellent oil and chemical resistance
• Common applications include seals, hoses, and gaskets

Overall, the widespread use of Buna N Rubber in critical industries brings attention to its importance as a material that balances flexibility and chemical resistance.

Copolymer Composition

The composition of a copolymer significantly determines its properties and uses. Copolymers like Buna N are composed of two or more monomers, which combine to create a material that benefits from the properties of each component.

In the case of Buna N Rubber, the copolymer consists of acrylonitrile and butadiene. Each monomer contributes distinct characteristics: acrylonitrile is responsible for chemical resistance, while butadiene adds flexibility and resilience to the rubber.

• Copolymer of two or more monomers
• Acrylonitrile provides oil and chemical resistance
• Butadiene offers flexibility

This combination makes Buna N ideal for products requiring both flexibility and resistance, showing how copolymer composition can be strategically used to achieve specific material properties.

Acrylonitrile and Butadiene

Acrylonitrile and Butadiene are the fundamental building blocks of Buna N Rubber. Understanding these monomers helps explain why this copolymer is so effective.

Acrylonitrile, represented chemically as \( ext{CH}_2= ext{CH}- ext{CN}\), provides significant resistance to solvents, oils, and other chemicals. It is this resistance that makes Buna N fixtures dependable in environments exposed to these elements.

• Acrylonitrile (\( ext{CH}_2= ext{CH}- ext{CN}\)) makes the copolymer resistant.

On the other hand, Butadiene, with the chemical structure \( ext{CH}_2= ext{CH}- ext{CH}= ext{CH}_2\), imparts elasticity and flexibility to the rubber. This flexibility is essential for applications where tension and movement are frequent, allowing the material to maintain integrity under stress.

• Butadiene (\( ext{CH}_2= ext{CH}- ext{CH}= ext{CH}_2\)) provides elasticity and flexibility.

Together, these monomers create a material that is not only resistant to harsh chemicals but also adaptable enough to be molded into various applications without sacrificing performance.