Ace the MCAT Organic Chemistry Exam 2026 – Unleash Your Chemistry Genius!

The correct answer identifies the two main types of stereoisomers as enantiomers and diastereomers, which is a foundational concept in stereochemistry.

Enantiomers are pairs of stereoisomers that are non-superimposable mirror images of each other, much like left and right hands. They possess identical physical properties in a symmetric environment, yet they can have drastically different chemical behavior, particularly in chiral environments—such as biological systems—where they can interact differently with other chiral molecules. This property is crucial in the pharmaceutical industry, where often only one enantiomer is therapeutically active or safe.

Diastereomers, on the other hand, are stereoisomers that are not mirror images of each other. They often differ in multiple stereocenters and as such, can exhibit varying physical and chemical properties. Unlike enantiomers, diastereomers may have different boiling points, melting points, and reactivities, which makes them significant in synthetic organic chemistry and reactions.

The other options provided do not accurately classify stereoisomers. Structural isomers (often referred to as constitutional isomers) involve compounds with the same molecular formula but different connectivity of their atoms, and thus do not qualify as stereoisomers. Geometr