Problem 135 - Chemistry: An Atoms-Focused Approach

Question

Draw the carbon-skeleton structure of the condensation polymer of \(\mathrm{H}_{2} \mathrm{N}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{COOH} .\) How does this polymer compare with nylon- \(6 ?\)

Step-by-Step Solution

Answer

Answer: Both polymers are similar in that they have amide bonds as their repeating units. The main difference between the two polymers is the length of the carbon chain between the amine and carboxylic acid groups in the repeating unit. The polymer formed by \(\mathrm{H}_{2} \mathrm{N}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{COOH}\) has a longer carbon chain with 6 methylene groups, while nylon-6 has 5 methylene groups in its structure.

Step 1: Drawing the monomer structure

First, let's draw the structure of the given compound, \(\mathrm{H}_{2} \mathrm{N}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{COOH}\). This compound has an amine group (NH2) at one end and a carboxylic acid group (COOH) at the other end. The structure is as follows: ``` H H H H H H H | | | | | | | -NH2 -C-C-C-C-C-C-COOH H H H H H H O | H ```

Step 2: Condensation polymerization process

Next, let's understand how the condensation polymerization process works. In this process, two monomers combine with the elimination of a small molecule, such as water. In this case, when two \(\mathrm{H}_{2} \mathrm{N}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{COOH}\) molecules combine, the -OH from a carboxylic acid group reacts with one -H from the amine group of another monomer, releasing a water molecule (H2O) and forming an amide bond.

Step 3: Drawing the polymer structure

In order to draw the polymer structure, we'll represent the repeating amide bond and the length of the carbon chain. This can be represented as follows: ``` H H H H H H H | | | | | | | -NH2 -C-C-C-C-C-C-C H H H H H H \\ -N-C-C-C-C-C-C-C H H H H H H H | O ``` The carbon chain length is given by \(n = 6\), so we can represent it in shorthand, where the brackets and 'n' denote the repeating unit: ``` [-NH - (CH2)6 - CO -] n ```

Step 4: Comparing this polymer with nylon-6

Now, let's compare this polymer with nylon-6. Nylon-6 is formed by the condensation polymerization of caprolactam, which has the following structure: ``` H H H H H H | | | | | | O=C-C-C-C-C-C-N H H H H H H ``` When caprolactam undergoes ring-opening polymerization, it forms the nylon-6 polymer chain: ``` [-NH - (CH2)5 - CO -] n ``` Based on the comparison between the resulting polymers, it can be concluded that both polymers are quite similar, with the main difference being the length of the carbon chain between the amine and carboxylic acid groups in the repeating unit. Our polymer has a longer carbon chain (6 methylene groups) compared to nylon-6 (5 methylene groups).