35.1.3—The repeat unit of a condensation polymer

A condensation-polymer repeat unit is the smallest section that repeats after the monomers lose a small molecule such as water or HCl. Draw the new covalent link, then show the unreacted atoms at each end.

For a diol/diacid polymer, the repeat contains –O–CO–; for a diamine/diacid polymer, it contains –NH–CO–. Include the correct carbon count from each monomer.

Ethane-1,2-diol + benzene-1,4-dicarboxylic acid gives –OCH₂CH₂OCOC₆H₄CO– as the repeating section.

Do not remove atoms from the carbon skeleton or draw a terminal molecule instead of a repeating unit.