Problem 85 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following monomers gives the polymer neoprene on polymerization? (a) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{Cl}\) (b) \(\mathrm{CCl}_{2}=\mathrm{CCl}_{2}\) (c)C=CC(=C)Cl (d) \(\mathrm{CF}_{2}=\mathrm{CF}_{2}\)

Step-by-Step Solution

Answer

Option (c) is the correct answer, as it represents chloroprene.

Step 1: Identifying Neoprene Monomer

Neoprene is a synthetic rubber obtained through the polymerization of chloroprene, which is 2-chloro-1,3-butadiene. The chemical structure of this monomer is important to identify among the options given.

Step 2: Analyzing Option (a)

Option (a) \( \mathrm{CH}_{2}=\mathrm{CH}-\mathrm{Cl} \) is vinyl chloride. Polymerizing vinyl chloride gives polyvinyl chloride (PVC), not neoprene.

Step 3: Analyzing Option (b)

Option (b) \( \mathrm{CCl}_{2}=\mathrm{CCl}_{2} \) is tetrachloroethylene. It does not yield neoprene upon polymerization, as it's not chloroprene.

Step 4: Analyzing Option (c)

Option (c) represents chloroprene (2-chloro-1,3-butadiene). The SMILES code indicates a structure with a double bond and a chlorine atom, matching the necessary configuration for neoprene formation.

Step 5: Analyzing Option (d)

Option (d) \( \mathrm{CF}_{2}=\mathrm{CF}_{2} \) is tetrafluoroethylene, used in making polytetrafluoroethylene (PTFE). It doesn't form neoprene.

Step 6: Conclusion

Since option (c) matches the structure of the monomer chloroprene, it is the correct choice for forming neoprene.

Key Concepts

Chloroprene

Chloroprene is a critical component in the creation of neoprene, a type of synthetic rubber. Its chemical name is 2-chloro-1,3-butadiene. This compound is an organic molecule characterized by the presence of a double bond and a chlorine atom in its structure.

Chloroprene is derived from butadiene, and through slight modification by adding a chlorine atom, it transforms into the monomer known for producing neoprene.

• It has a chemical formula of C₄H₅Cl.
• The unique arrangement of atoms allows it to undergo polymerization to form the rubbery material called neoprene.

The ability of chloroprene to polymerize into a stable rubber makes it valuable in various industries, ranging from automotive manufacturing to consumer goods.

Polymerization

Polymerization is a chemical process where small molecules called monomers combine to form a larger, complex structure known as a polymer. In the case of neoprene, the monomer chloroprene undergoes this transformation through a specific type of polymerization.

During polymerization, the double bond in the chloroprene monomer reacts under certain conditions, leading to the formation of long chains and eventually, a solid material with elastic properties: neoprene. Some key aspects include:

• Initiation: A chemical initiator starts the reaction, causing the chloroprene molecules to open their double bonds.
• Propagation: The open bonds enable the monomers to link together, forming long, repeating units.
• Termination: The process concludes when the polymer reaches desired properties, stopping the reaction.

Understanding polymerization is crucial, as it determines the final attributes of the synthetic rubber.

Synthetic Rubber

Synthetic rubber is manufactured through the polymerization of various monomers, creating materials with elastic properties similar to natural rubber. Neoprene is one such synthetic rubber produced by polymerizing chloroprene.

The synthesis of neoprene exemplifies how chemical engineering advances can replace natural materials and meet specific industrial needs:

• Durability: Neoprene is resilient, making it ideal for products like wetsuits and weather-resistant materials.
• Versatility: It can be used in adhesives, gaskets, and various molded items.
• Resistance: Neoprene offers excellent resistance to oils, chemicals, and temperature variations.

These characteristics make synthetic rubbers like neoprene essential in modern manufacturing and consumer products.

Monomer Identification

Identifying the correct monomer is a crucial first step in producing any synthetic material. For neoprene, the correct monomer is chloroprene, known scientifically as 2-chloro-1,3-butadiene.

When evaluating potential monomers, it is important to look at the structural formula. Option (c) in the exercise, represented in a SMILES structure, accurately depicts chloroprene. This structure features:

• A double bond present in butadiene derivatives.
• A chlorine atom substituting one hydrogen atom, which is essential for chloroprene.

By comparing these features against other options, the correct monomer can be selected to ensure the successful polymerization process leading to neoprene.