STUDENT SPACE · TOPIC 2

Condensation polymers

Identify ester and amide linkages and deduce monomers.

The essentials

A dicarboxylic acid has two –COOH groups. A diol has two –OH groups. A diamine has two –NH₂ groups.
A dicarboxylic acid reacts with a diamine to form a polyamide. Nylon contains –C(=O)–NH– links.
A dicarboxylic acid reacts with a diol to form a polyester. PET contains –C(=O)–O– links.
Break an ester or amide link. Restore OH to the carbonyl carbon and H to the O or N on the other side.

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Which linkage distinguishes a polyester from a polyamide?

Need a hint for Question 1?

Locate the carbonyl carbon, then inspect the next atom in the chain.

Check Question 1

Polyester: –COO–. Polyamide: –CONH–.

Write the linkage in nylon and name its two monomer types.

Need a hint for Question 2?

Identify the atoms in an amide link and the reactive ends needed.

Check Question 2

–C(=O)–NH–. A diamine and a dicarboxylic acid.

Explain why ethanol and ethanoic acid make an ester but cannot build a long polyester chain by themselves.

Need a hint for Question 3?

Long chains require monomers that can join at both ends.

Check Question 3

Each has only one relevant functional group, so they cannot repeatedly link at two ends.

Use Lesson 2 in your worksheet for written practice. Your teacher will discuss those answers in class.