To address the global challenge of plastic accumulation in the environment, biodegradable polyesters such as polylactic acid (PLA) are used as sustainable alternatives to traditional plastics.
PLA is produced via the condensation polymerisation of lactic acid (2-hydroxypropanoic acid), shown below:
Which of the following represents the correct repeating unit of polylactic acid (PLA)?
−[O−CH(CH3)−CO]n−-\left[ \text{O}-\text{CH}(\text{CH}_3)-\text{CO} \right]_n-−[O−CH(CH3)−CO]n−
−[O−CH2−CH2−CO]n−-\left[ \text{O}-\text{CH}_2-\text{CH}_2-\text{CO} \right]_n-−[O−CH2−CH2−CO]n−
−[O−CH(CH3)−CH2−CO]n−-\left[ \text{O}-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CO} \right]_n-−[O−CH(CH3)−CH2−CO]n−
−[CH2−CH(CH3)]n−-\left[ \text{CH}_2-\text{CH}(\text{CH}_3) \right]_n-−[CH2−CH(CH3)]n−