Organic Chemistry MCAT Practice Exam 2026 - Free MCAT Practice Questions and Study Guide

Enantiomers are a specific type of stereoisomer that are non-superimposable mirror images of each other, and this characteristic arises from chirality. Chirality is defined by the presence of chiral centers—typically carbon atoms bonded to four different substituents. This unique arrangement leads to two distinct configurations that cannot be aligned with one another, much like left and right hands.

This property of chirality is what fundamentally differentiates enantiomers; despite having the same molecular formula and connectivity, their spatial arrangement results in different optical activities. One enantiomer will rotate plane-polarized light in one direction (clockwise, or dextrorotatory), while the other will do so in the opposite direction (counterclockwise, or levorotatory).

The other choices do not capture this essential characteristic of enantiomers. Isomerism refers more broadly to molecules with the same molecular formula but different arrangements, while polyvalency pertains to the ability of an atom to form multiple bonds and does not specifically relate to enantiomers. Hydrophobicity deals with the affinity of a compound for water and how it interacts with aqueous environments, which also does not directly address the defining features of enantiomers. Thus, chirality