Problem 80 - Chemistry The Central Science

Question

Write the chemical equation that represents the formation of (a) polychloroprene from chloroprene (polychloroprene is used in highway-pavement seals, expansion joints, conveyor belts, and wire and cable jackets); (b) polyacrylonitrile from acrylonitrile (polyacrylonitrile is used in home furnishings, craft yarns, clothing, and many other items).

Step-by-Step Solution

Answer

The chemical equations for the formation of polychloroprene from chloroprene and polyacrylonitrile from acrylonitrile are as follows: a) Polychloroprene: \[\text{n} \ \text{CH}_2= \text{C}(\text{Cl})\text{-CH=CH}_2 \rightarrow [-\text{CH}_2 - \text{C}(\text{Cl})\text{-CH}-\text{CH}_2 -]_n\] b) Polyacrylonitrile: \[\text{n} \ \text{CH}_2= \text{CH} - \text{C}\equiv\text{N} \rightarrow [-\text{CH}_2 -\text{CH}-\text{C}\equiv\text{N}-]_n\]

Step 1: Write the chemical structure of chloroprene

Chloroprene has the following chemical structure: \[\text{CH}_2= \text{C}(\text{Cl})\text{-CH=CH}_2\]

Step 2: Represent the polymerization reaction

To represent the polymerization reaction, we illustrate the process in which the double bond between the carbons in chloroprene molecules break and links up with other chloroprene molecules to form polychloroprene. Thus, the chemical equation for this process is: \[\text{n} \ \text{CH}_2= \text{C}(\text{Cl})\text{-CH=CH}_2 \rightarrow [-\text{CH}_2 - \text{C}(\text{Cl})\text{-CH}-\text{CH}_2 -]_n\] b) Formation of polyacrylonitrile from acrylonitrile:

Step 1: Write the chemical structure of acrylonitrile

Acrylonitrile has the following chemical structure: \[\text{CH}_2= \text{CH}-\text{C}\equiv\text{N}\]

Step 2: Represent the polymerization reaction

To represent the polymerization reaction, we demonstrate the process in which the double bond between the carbons in acrylonitrile molecules breaks and connects with other acrylonitrile molecules to form polyacrylonitrile. Thus, the chemical equation for this process is: \[\text{n} \ \text{CH}_2= \text{CH} - \text{C}\equiv\text{N} \rightarrow [-\text{CH}_2 -\text{CH}-\text{C}\equiv\text{N}-]_n\] Now we have the chemical equations that represent the formation of polychloroprene from chloroprene and polyacrylonitrile from acrylonitrile.

Key Concepts

Polychloroprene

Polychloroprene is a synthetic rubber known for its versatility and durability. It is derived from the polymerization of chloroprene. This process involves the repetitive linking of small units, known as monomers, into a long chain, forming the polymer.

• Chloroprene's chemical structure is \[\text{CH}_2= \text{C}(\text{Cl})\text{-CH=CH}_2\]
• During polymerization, the double bonds in chloroprene break. This allows each molecule to connect with others, forming long chains of polychloroprene.
• The resulting chemical equation for polychloroprene formation is:\[\text{n} \ \text{CH}_2= \text{C}(\text{Cl})\text{-CH=CH}_2 \rightarrow [-\text{CH}_2 - \text{C}(\text{Cl})\text{-CH}-\text{CH}_2 -]_n\]

Polychloroprene is widely used due to its excellent weather resistance and resilience. You can find it in products like wetsuits, gaskets, and even some medical devices.

Polyacrylonitrile

Polyacrylonitrile, or PAN, is another remarkable polymer primarily used in producing synthetic fibers. The basis of polyacrylonitrile is the polymerization of acrylonitrile. This substance is known for its strength and resistance to chemicals and UV rays.

• Acrylonitrile's chemical structure is \[\text{CH}_2= \text{CH}-\text{C}\equiv\text{N}\]
• Just like with chloroprene, the double bonds in acrylonitrile break during polymerization. This allows molecules to link and form long polymer chains.
• The chemical reaction for this transformation of acrylonitrile into polyacrylonitrile is: \[\text{n} \ \text{CH}_2= \text{CH} - \text{C}\equiv\text{N} \rightarrow [-\text{CH}_2 -\text{CH}-\text{C}\equiv\text{N}-]_n\]

Polyacrylonitrile is often used in textiles, thanks to its strength and lightweight nature, and is extensively used in creating carbon fibers, which are crucial in advanced engineering applications.

Chemical Equation

A chemical equation is an essential tool in chemistry for depicting chemical reactions. It provides a concise way to show how reactants transform into products. Let's break it down a bit:

• A chemical equation always begins with the reactants, the starting substances in the reaction.
• The equation uses an arrow pointing to the right to indicate the transformation process.
• Products, the substances formed as a result of the reaction, are listed on the right side.
• In polymerization, like with polychloroprene and polyacrylonitrile, the repeating structure of the polymer is depicted within square brackets and is followed by a subscript 'n' to symbolize the many units in the chain.

Understanding these basic concepts helps in grasping more complex chemical reactions and the significance of accurately representing them. A good grasp of chemical equations allows chemists to predict reaction outcomes and make important modifications to processes.