Problem 57 - Chemistry The Molecular Science

Question

Draw the structure of the repeating unit in a polymer in which the monomer is (a) 1 -butene. (b) 1,1 -dichloroethylene. (c) vinyl acetate.

Step-by-Step Solution

Answer

(a) [-CH2-CH(CH2-CH3)-], (b) [-CH2-CCl2-], (c) [-CH2-CH(OCOCH3)-]

Step 1: Understand the Monomer Structure

Before creating the polymer structure, we need to know the monomer's structure. The monomer for (a) is 1-butene (CH2=CH-CH2-CH3), for (b) it is 1,1-dichloroethylene (CH2=CCl2), and for (c) it is vinyl acetate (CH2=CHOCOCH3).

Step 2: Draw the Monomer Unit

Draw the structure of each monomer. For 1-butene, it consists of a double bond between the first two carbon atoms. The structure is as follows: CH2=CH-CH2-CH3. For 1,1-dichloroethylene, the chlorine atoms are attached to the second carbon making it CH2=CCl2. For vinyl acetate, the acetate group (OCOCH3) is attached to the vinyl structure CH2=CHOCOCH3.

Step 3: Create the Polymer Chain

Understand that polymerization involves the opening of the double bond in each monomer, allowing them to connect and form long chains. For each monomer, the double bonds convert into single bonds during polymerization.

Step 4: Draw the Repeating Unit for 1-butene

Upon polymerizing 1-butene, the repeating unit becomes: [-CH2-CH(CH2-CH3)-]. The double bond opens, allowing the units to connect, leaving each carbon with only single bonds.

Step 5: Draw the Repeating Unit for 1,1-dichloroethylene

For 1,1-dichloroethylene, polymerization converts the double bond into a single bond forming the repeating unit: [-CH2-CCl2-]. The chlorine atoms remain on the same carbon atom as in the monomer.

Step 6: Draw the Repeating Unit for Vinyl Acetate

In vinyl acetate, polymerization changes the vinyl group from a double bond to a single bond, resulting in the repeating structure: [-CH2-CH(OCOCH3)-]. The acetate group remains attached as in the monomer.

Key Concepts

1-butene

1-butene is a simple alkene that plays an essential role in polymer chemistry. It is a four-carbon linear molecule, identifiable by its double bond between the first two carbon atoms. This structure is usually represented as CH₂=CH-CH₂-CH₃. The presence of a double bond makes it a valuable monomer in forming polymers. During polymerization, this double bond "breaks" to form single bonds, allowing the monomers to link into long chains. This process creates a polymer like polyethylene with a repeating unit denoted as [-CH₂-CH(CH₂-CH₃)-]. Each monomer initially has a reactive double bond, which transforms into single covalent bonds in the polymer, providing stability and new properties, such as flexibility and strength. Polymerized 1-butene gives way to materials used in many applications, including the manufacturing of plastic containers and automotive parts. Understanding the change from monomer to polymer sheds light on the creation of durable materials used in everyday life.

1,1-dichloroethylene

1,1-dichloroethylene, also known as vinylidene chloride, is another pivotal monomer in polymer chemistry. It consists of a two-carbon structure, with the formula CH₂=CCl₂, where two chlorine atoms are bonded to one carbon atom. These atoms significantly affect the chemical behavior, imparting unique properties to the resulting polymer. During the polymerization process, similar to other alkenes, the double bond opens to form a stable and long polymer chain. This reaction leads to the formation of the repeating unit [-CH₂-CCl₂-]. The chlorine atoms remain attached to the same carbon as in the monomer, adding a twist to the polymer's structural integrity and chemical resistance. Polymers formed from 1,1-dichloroethylene are often used in creating materials that require exceptional barrier properties, such as food packaging and chemical-resistant coatings. The presence of chlorine contributes to these properties, enhancing the polymer's utility in various industrial applications.

vinyl acetate

Vinyl acetate is a versatile monomer with a unique structure characterized by its acetate group. The chemical formula of this monomer is CH₂=CHOCOCH₃, where the acetate group (OCOCH₃) is attached to the vinyl structure. This configuration offers specific characteristics useful in forming distinctive polymer products. In its transformation to a polymer, vinyl acetate undergoes a reaction where the double bond is converted to a single bond. This polymerization process yields a repeating unit structured as [-CH₂-CH(OCOCH₃)-]. The acetate group remains part of the polymer backbone, providing functional aspects to the polymer, such as increased flexibility and adhesion properties. Materials derived from vinyl acetate include adhesives and paints, capitalizing on its adhesive properties. When polymerized, vinyl acetate forms polyvinyl acetate (PVA), commonly used in glue, ensuring excellent stickiness and longevity. These properties make vinyl acetate an indispensable component in producing various craft and construction materials.