Problem 87 - Chemistry The Central Science In Si Units

Question

An addition polymerization forms the polymer originally used as Saran" wrap. It has the following structure \(\pm \mathrm{CCl}_{2}-\mathrm{CH}_{2}+_{n}\). Draw the structure of the monomer.

Step-by-Step Solution

Answer

The monomer is vinylidene chloride, \( ext{CCl}_2= ext{CH}_2\).

Step 1: Understanding the Polymer Structure

The given polymer structure is \( ext{CCl}_2- ext{CH}_2\) repeated \(n\) times. This means that the polymer is made by repeating a basic unit, known as a monomer, consisting of a \( ext{CCl}_2\) group bonded directly to a \( ext{CH}_2\) group. The key task is to identify what smaller molecule these parts come from to make this repeating structure.

Step 2: Identifying the Monomer

Since each monomer unit in the polymer contains one \( ext{CCl}_2\) and one \( ext{CH}_2\), we need a simple molecule that can form these bonds through polymerization. The monomer for this polymer can be reconstructed by 'reversible breaking' of the double bond to join the same atoms as seen in the polymer structure, resulting in the monomer: vinylidene chloride, which is \( ext{CCl}_2= ext{CH}_2\).

Step 3: Drawing the Monomer

We now need to draw the structure of vinylidene chloride. The structure of the monomer will have a double bond between a carbon with two chlorine atoms (\( ext{CCl}_2\)) and a carbon with two hydrogen atoms (\( ext{CH}_2\)) in the form \( ext{CCl}_2= ext{CH}_2\).

Key Concepts

Polymer Structure

In the world of chemistry, understanding the concept of a polymer structure is fundamental. Polymers are large molecules made up of repeating units called monomers. These monomers are like the building blocks of the polymer structure. When you look at a polymer such as the one used in Saran wrap, the repeating pattern of monomers is vital. The structure provided \( \text{CCl}_2-\text{CH}_2 \) implies that this specific polymer is formed through addition polymerization. This process involves linking monomers with unsaturated bonds, typically double bonds, to form a long chain.
When these monomers are joined via addition polymerization, they create a larger macromolecule with specific properties suitable for applications like food wrapping. Understanding how these monomer units connect and repeat in the chain aids in comprehending the unique characteristics of the resulting polymer.

Monomer Identification

Monomer identification is a pivotal step in understanding how polymers are formed. Each monomer unit in a polymer can often be traced back to a simple molecule from which it originates. In the case of the polymer mentioned, the task is to determine which small molecule can be transformed into the described monomer unit \( \text{CCl}_2-\text{CH}_2 \).

By examining the polymer’s structure, one can reverse-engineer it to identify the monomer. During addition polymerization, the double bonds in the monomer break to link with adjacent monomer units. Thus, the simple monomer molecule for our polymer is vinylidene chloride. This molecule \( \text{CCl}_2=\text{CH}_2 \) contains the necessary double bond between carbons to allow for polymerization. Every time the polymer is produced, this monomer is the repeating element, establishing each repeating section of the longer polymer chain.

Vinylidene Chloride

Vinylidene chloride is a critical monomer in many polymer chemistry applications, especially in the creation of polymers such as Saran wrap. In its monomer form, vinylidene chloride has a structure of \( \text{CCl}_2=\text{CH}_2 \), with a double bond connecting the carbon atoms. This double bond is essential for the process of polymerization, as it allows the molecules to link together when the bond is broken.

The presence of two chlorine atoms bonded to one of the carbons differentiates vinylidene chloride from other similar compounds. This structure imparts specific characteristics upon the polymer formed, including durability and a protective barrier against gases and moisture.

• **Key Features**:
  
  • Double bond for polymerization.
  • Two chlorine atoms for enhanced stability.
• **Applications**:
  Primarily used in food packaging for its ability to create a tight seal and protect the contents.

Understanding the role and significance of vinylidene chloride in polymer science highlights its importance in creating everyday materials with specialized use-cases.