How can I recognize enantiomers?

Enantiomers are pairs of molecules that are non-superimposable mirror images of each other. They have the same molecular formula and connectivity of atoms but differ in their spatial arrangement. One common method to recognize enantiomers is by examining their stereochemistry, specifically their chirality.

Chirality refers to the property of a molecule that cannot be superimposed on its mirror image. If a molecule contains an asymmetric carbon atom (also known as a chiral center), where four different substituents are attached to the carbon, it will exist in two enantiomeric forms.

To recognize enantiomers:

1. Identify chiral centers in the molecule.
2. Draw or visualize the mirror image of the molecule.
3. Compare the spatial arrangement of substituents around each chiral center. If the mirror image cannot be overlapped with the original molecule, they are enantiomers.

Another method is to use Fischer projections or wedge-dash diagrams to represent the three-dimensional arrangement of atoms around the chiral centers. Enantiomers will have opposite configurations at each chiral center.

Additionally, enantiomers rotate plane-polarized light in opposite directions. This property, known as optical activity, can be measured using a polarimeter. If a compound rotates plane-polarized light to the right (clockwise), its enantiomer will rotate it to the left (counterclockwise) by an equal amount.