Problem 88 - Chemistry The Central Science In Si Units

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

Chloroprene polymerizes to form polychloroprene, and acrylonitrile polymerizes to form polyacrylonitrile.

Step 1: Understand the Monomers

First, identify the chemical structure of the monomers involved. Chloroprene has the formula \( \text{C}_4\text{H}_5\text{Cl} \), and acrylonitrile is \( \text{C}_3\text{H}_3\text{N} \). These are the starting materials for their respective polymerizations.

Step 2: Formation of Polychloroprene

Polychloroprene is formed through the polymerization of chloroprene. The chemical equation is represented as:\[ n \text{C}_4\text{H}_5\text{Cl} \rightarrow [-\text{C}_4\text{H}_5\text{Cl}-]_n \]where \( n \) represents the number of repeating units in the polymer chain.

Step 3: Formation of Polyacrylonitrile

Polyacrylonitrile is formed through the polymerization of acrylonitrile. The chemical equation is represented as:\[ n \text{C}_3\text{H}_3\text{N} \rightarrow [-\text{C}_3\text{H}_3\text{N}-]_n \]This shows that each acrylonitrile monomer units joins together forming a long chain polymer.

Step 4: Summary of the Polymerization Processes

In both processes, the monomers undergo a reaction to form a polymer by linking multiple monomer molecules. Polychloroprene forms from chloroprene monomers, and polyacrylonitrile forms from acrylonitrile monomers. The general form of the chemical equation shows a repeating unit for each polymer.

Key Concepts

Chemical Equation

A chemical equation is a symbolic way of presenting a chemical reaction. It includes the reactants, which are the starting substances, and the products, which are formed as a result of the reaction. In the context of polymerization, the chemical equation represents how monomers, which are small molecules, link together to form polymers, which are long chains of molecules. By balancing both sides of a chemical equation, we ensure the law of conservation of mass is respected, meaning the same number of each type of atom is present on both sides of the equation. The chemical equations for polymerization, like those for polychloroprene and polyacrylonitrile, often use "n" to denote the number of monomer units that join to form the polymer.

Chloroprene

Chloroprene is a chemical compound with the formula \( \text{C}_4\text{H}_5\text{Cl} \). It is an unsaturated monomer used to make polychloroprene through polymerization. Polychloroprene is a type of synthetic rubber known for its elasticity and resistance to chemicals, heat, and aging. This makes it suitable for products like seals in highways and jackets for cables and wires.

• Chloroprene’s structure allows it to easily form chemical bonds with other monomers, creating long polymer chains.
• The process involves linking the double-bonded carbon atoms with other monomer units to form a stable polymer.

Acrylonitrile

Acrylonitrile, denoted \( \text{C}_3\text{H}_3\text{N} \), is an organic compound used widely in the production of polymers like polyacrylonitrile. It is a volatile, colorless liquid with a distinct odor.

• Its ability to create strong chemical bonds makes it an ideal candidate for polymerization.
• During the polymerization process, acrylonitrile molecules join together to form polyacrylonitrile, which has uses ranging from fibers for clothing to components in home furnishings.

The presence of the nitrile group in acrylonitrile gives the resultant polymer increased strength and thermal stability.

Monomer

Monomers are the basic building blocks of polymers. They are small, single molecules that can join with other monomers through chemical reactions to form a polymer.

• In the case of chloroprene and acrylonitrile, each serves as the monomer for its respective polymer.
• The monomers contain functional groups that participate in polymerization, allowing them to link together forming extensive chains.

The versatility of monomers is key to creating a wide variety of synthetic materials with diverse properties. When monomers link up, they display characteristics vastly different from their original form, which is the basis for many industrial applications.

Polymer

Polymers are large molecules composed of repeating structural units known as monomers. They can form naturally, like cellulose, or synthetically, like plastics. Through polymerization, monomers are chemically bonded to form the polymer structure.

• Polychloroprene and polyacrylonitrile are examples of synthetic polymers formed from chloroprene and acrylonitrile, respectively.
• These polymers have unique properties that make them useful in various applications, from clothing and constructions to transportation and home goods.

The polymerization process allows for customization of polymer characteristics, such as flexibility, durability, and resistance to environmental factors.