Problem 60 - Chemistry in Focus

Question

Give the structure of the condensation copolymer made from the following monomers: \(\mathrm{HOOCCH} \mathrm{CH}_{2} \mathrm{COOH}\) and \(\mathrm{H}_{2} \mathrm{NCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\)

Step-by-Step Solution

Answer

The structure of the condensation copolymer is \(-[\mathrm{NHCH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2} \mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CONHCH}CH_{2}]-\).

Step 1: Identify the functional groups

Identify the functional groups in the monomers that can react with each other to form a copolymer. The first monomer, \(\mathrm{HOOCCHCH}_{2}\mathrm{COOH}\), contains two carboxylic acid groups (-COOH), while the second monomer, \(\mathrm{H}_{2}\mathrm{NCH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2} \mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}_{2}\), has two amino groups (-NH2).

Step 2: Determine the reaction type

Determine the type of reaction that will occur between the functional groups. Here, the carboxylic acid groups can react with the amino groups to form an amide bond through a condensation reaction, releasing water as a by-product.

Step 3: Write the polymer structure

Connect the monomers by replacing an H from the -NH2 group and an OH from the -COOH group with a covalent bond to form the amide linkage (-CONH-). The repeating unit of the copolymer will be: \(-[\mathrm{NHCH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2} \mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CONHCH}CH_{2}]-\).

Key Concepts

Copolymerization

Copolymerization refers to the chemical process where two or more different types of monomers polymerize to form a copolymer. Imagine building a multicolored chain using only red and blue chain links - you need to join them systematically to form a pattern. Similarly, in copolymerization, the monomers with distinct chemical properties are linked together, resulting in a material that displays combined properties of the original components. This copolymer will have unique physical and chemical characteristics based on the types and arrangement of its monomers.

For example, a copolymer made from a monomer with a carboxylic acid group and another with an amino group results in a product with properties different from those of a polymer made from one type of monomer alone. The diverse uses of copolymers range from creating flexible plastics to manufacturing fabrics used in sports apparel.

Amide Bond Formation

Amide bond formation is a fundamental chemical reaction, particularly in the synthesis of proteins and certain types of polymers. This bond is also the backbone of proteins, connecting amino acids in long chains. To form an amide bond, a carboxylic acid group \textrm{(-COOH)} reacts with an amino group \textrm{(-NH\(_2\))}, typically resulting in the release of a water molecule - a process known as condensation. The resulting \textrm{(-CONH-)} linkage is strong and gives structural stability to molecules. In polymers like the condensation copolymer example provided, the regularity of amide bond formation leads to the creation of a robust and stable chain that contributes to the desirable properties of materials such as nylon, one of the most well-known synthetic polymers.

Functional Groups in Polymers

Functional groups in polymers are specific groupings of atoms within a molecule that dictate how a polymer behaves in chemical reactions. These groups give polymers their unique characteristics, such as solubility, melting point, and reactivity. Common functional groups include hydroxyl \textrm{(-OH)}, amino \textrm{(-NH\(_2\))}, carboxylic acid \textrm{(-COOH)}, and many others.

In the context of polymer science, functional groups are like individual personalities that dictate how monomers interact with each other. They are the active sites where chemical reactions occur, leading to the formation of long chains or three-dimensional networks. A polymer's properties are highly dependent on the nature and arrangement of its functional groups, making an understanding of these groups crucial for customizing materials for specific applications.

Carboxylic Acid and Amino Group Reaction

The reaction between a carboxylic acid and an amino group is a type of condensation reaction and is fundamental to the structure of various polymers and biomolecules. When these two groups react, they form an amide bond accompanied by the release of a water molecule.

Think of this reaction as a handshake between two monomers, where the carboxylic acid group (\textrm{-COOH}) offers an \textrm{OH} and the amino group (\textrm{-NH\(_2\)}) offers an \textrm{H} to the mix, resulting in water (\textrm{H\(_2\)O}) and the formation of a solid bond (\textrm{-CONH-}). This process can repeat over and over, leading to a long chain, or polymer, with repeating amide links. Such reactions are not only essential in producing synthetic polymers but also occur in biological systems, highlighting the importance of this chemistry in both the industrial and natural worlds.