Atropoisomers are a type of stereoisomer where the molecules differ in their spatial arrangement due to hindered rotation around a single bond. Some synonyms for atropoisomer include axial chirality, planar chirality, topological chirality, and rotational isomerism. These terms describe the same concept of atropoisomerism, where the chirality is determined by the relative orientation of groups on a molecule. Atropoisomers have important applications in medicinal chemistry, as they often display different biological activities and pharmacokinetic properties. Understanding atropoisomerism is crucial for the design and synthesis of new drug molecules and can lead to improved efficacy and lower toxicity.