Biodegradable polyesters

1 mark · Normal

Which of the following shows the correct displayed formula for the repeat unit of polylactic acid (PLA)?

Show answer

Correct option: —[O—CH(CH3)—CO]—

Common mistakes: Choosing a structure that has not lost water; Selecting a structure that is not polyester

Show mark scheme and worked solution

Marking points

A1 · 1 mark · Chooses the correct displayed repeat unit: —[O—CH(CH3)—CO]—

Worked solution

Polylactic acid formed from lactic acid monomers links via the formation of the —O—CH(CH3)—CO— repeat unit as water is lost on polymerisation.