Draw the enantiomer of the molecule shown below. Use a dash or wedge bond to indicate the stereochemistry of substituents on asymmetric centers, where applicable.
The Correct Answer and Explanation is:
Enantiomers are a type of stereoisomer—molecules that have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. Specifically, enantiomers are non-superimposable mirror images of each other, much like left and right hands. This property arises when a molecule contains at least one chiral center: a carbon atom bonded to four different substituents.
In the molecule you referenced, the presence of a bromine (Br) atom attached to a chiral carbon suggests that the carbon is bonded to four distinct groups. To draw the enantiomer, we must invert the configuration at this chiral center. This is done by switching the positions of any two substituents—commonly, the wedge (coming out of the plane) and dash (going into the plane) bonds.
For example, if the original molecule has the Br on a wedge (indicating it projects out toward the viewer), the enantiomer will have the Br on a dash (indicating it projects away from the viewer). The rest of the molecule remains unchanged in connectivity but is mirrored in three-dimensional space.
This inversion changes the molecule’s optical activity. While the original molecule might rotate plane-polarized light to the right (dextrorotatory), its enantiomer will rotate it to the left (levorotatory) by the same magnitude. However, this optical behavior cannot be predicted solely from the structure; it must be determined experimentally.
Enantiomers have identical physical properties (melting point, boiling point, density) but differ in how they interact with other chiral environments, such as enzymes or receptors. This distinction is crucial in fields like pharmaceuticals, where one enantiomer of a drug may be therapeutic while the other is inactive or even harmful.
