Question

The monomer unit of polyvinyl chloride has the formula (a) \(\mathrm{CH}_{3}-\mathrm{CH}_{2} \mathrm{Cl}\) (b) \(\mathrm{CH}_{2}=\mathrm{CH}_{2}\) (c) \(\mathrm{CHCl}=\mathrm{CHCl}\) (d) \(\mathrm{CH}_{2}=\mathrm{CHCl}\)

Short answer

The monomer unit of PVC is \(\mathrm{CH}_{2}=\mathrm{CHCl}\), option (d).

Step-by-step solution

Understanding the Question

The problem asks for the chemical formula of the monomer unit of polyvinyl chloride (PVC). Monomer units are the building blocks of polymers.

Knowing Polyvinyl Chloride

Polyvinyl chloride, or PVC, is a polymer created from the polymerization of vinyl chloride monomers. Therefore, to find the monomer of PVC, we must know the structure of vinyl chloride.

Analyzing the Choices

We are given four chemical formulas:(a) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}\mathrm{Cl}\) - This is ethyl chloride, not vinyl chloride.(b) \(\mathrm{CH}_{2}=\mathrm{CH}_{2}\) - This is ethylene, with no chlorine atom involved.(c) \(\mathrm{CHCl}=\mathrm{CHCl}\) - This is not a vinyl chloride structure; it has two carbon atoms but with one chlorine on each carbon.(d) \(\mathrm{CH}_{2}=\mathrm{CHCl}\) - This is vinyl chloride, with a double bond and one chlorine atom on the second carbon.

Choosing the Correct Monomer

Option (d) \(\mathrm{CH}_{2}=\mathrm{CHCl}\) represents the correct structure for the vinyl chloride monomer. It consists of a double bond between two carbon atoms, with one chlorine atom attached to one of the carbons.

Key concepts

Vinyl Chloride

Vinyl chloride is a critical component in the world of chemistry as it serves as the foundational building block for polyvinyl chloride (PVC). It is a colorless gas with a distinct sweet smell, commonly used in manufacturing. The significance of vinyl chloride lies in its role as a monomer—a small molecule that, when linked together with identical molecules, forms a polymer. In the case of vinyl chloride, it polymerizes to create PVC, a versatile and widely used plastic. The structure of vinyl chloride, with the chemical formula \( \mathrm{CH}_{2}=\mathrm{CHCl} \), is characterized by a double bond between two carbon atoms, with a chlorine atom bonded to one of these carbons. This specific arrangement is what facilitates its ability to form long chains in the polymerization process.

Chemical Formula

The chemical formula is like a blueprint for understanding a chemical compound. It specifies the types and numbers of atoms in the smallest unit of the substance.
For vinyl chloride, the chemical formula is crucial in identifying it among other compounds.
In the exercise, multiple options represent different chemical structures, but only \( \mathrm{CH}_{2}=\mathrm{CHCl} \) correctly represents vinyl chloride.

• (a) \( \mathrm{CH}_{3}-\mathrm{CH}_{2}\mathrm{Cl} \) is ethyl chloride, lacking the defining double bond of vinyl chloride.
• (b) \( \mathrm{CH}_{2}=\mathrm{CH}_{2} \) is ethylene, which does not include chlorine.
• (c) \( \mathrm{CHCl}=\mathrm{CHCl} \) showcases two Cl atoms, deviating from the singular Cl of vinyl chloride.
• (d) \( \mathrm{CH}_{2}=\mathrm{CHCl} \) has the double bond and Cl placement that defines vinyl chloride.

Understanding the correct chemical formula helps in accurately identifying the compound and predicting its behavior in chemical reactions.

Polymerization

Polymerization is the chemical process where small molecules called monomers join together to form a larger compound known as a polymer. The magic of polymerization lies in its ability to create complex structures from simpler units. In the case of vinyl chloride, polymerization transforms it into polyvinyl chloride (PVC).
This process involves breaking the double bond between the carbon atoms in vinyl chloride, allowing these molecules to link together in a repeated chain.

• During polymerization, catalysts or heat might be applied to initiate or speed up the reaction.
• The resulting polymer chain is strong and durable, a property that is essential for materials like PVC, used in products ranging from pipes to clothing.

This transformation is a fundamental reaction in creating plastics and showcases the versatility and importance of monomers like vinyl chloride.

PVC Structure

The structure of polyvinyl chloride (PVC) reveals much about its properties and applications. PVC is a thermoplastic polymer, meaning it becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
The formation of PVC involves individual vinyl chloride units linking together through polymerization, where the double bonds open and connect in long chains.
This unique structure imparts several key characteristics to PVC:

• It is highly durable and resistant to environmental degradation.
• PVC is resistant to water and chemicals, making it suitable for a wide range of applications, including pipes, window frames, and clothing.
• It can be transparent or colored, flexible or rigid, depending on the processing and additives used.

The versatility of the PVC structure allows it to be tailored for specific uses, providing valuable materials across diverse industries.