enantioisomerism

Enantioisomerism is a type of stereoisomerism in which a molecule and its mirror image are non-superimposable. These mirror image molecules are called enantiomers. The most common cause of enantioisomerism is the presence of a chiral center, typically a carbon atom bonded to four different substituents. Chirality is a fundamental property in organic chemistry and biochemistry, as many biological molecules, such as amino acids and sugars, exist as enantiomers.

The physical properties of enantiomers, such as melting point, boiling point, and solubility, are identical. However, they differ in their interaction with plane-polarized light. One enantiomer will rotate the plane of polarized light in a clockwise direction (dextrorotatory, denoted by + or d), while its mirror image will rotate it in the counterclockwise direction by the same magnitude (levorotatory, denoted by - or l). This phenomenon is known as optical activity.

Enantiomers also exhibit different biological activities because biological systems, like enzymes and receptors, are often chiral. This means that one enantiomer may be a potent drug while the other is inactive or even harmful. For example, thalidomide, a drug prescribed in the 1950s and 60s, had one enantiomer that was an effective sedative, but the other caused severe birth defects. The separation of enantiomers, known as resolution, is a crucial process in the pharmaceutical industry to ensure the safety and efficacy of chiral drugs.