Defining Enantiomers
Enantiomers are a specific type of stereoisomer, characterized as non-superimposable mirror images of each other. This means that while they reflect each other perfectly, no amount of rotation or translation can make one enantiomer perfectly overlap the other.
The Role of Chirality
The existence of enantiomers is fundamentally linked to a molecule possessing chirality. A molecule is chiral if it contains a chiral center—typically a carbon atom bonded to four distinct groups—creating an asymmetry that prevents its mirror image from being identical.
Thalidomide: A Stark Example
The drug Thalidomide offers a critical illustration: one enantiomer was effective as a sedative for morning sickness, while its mirror image caused severe birth defects. This demonstrates how subtle molecular differences can lead to drastically different biological effects.
Importance in Biological Systems and Drugs
Enantiomers are incredibly important in fields like pharmaceuticals and biochemistry because biological systems (such as enzymes and receptors) are often chiral themselves. They interact selectively with only one enantiomer, leading to unique pharmacological responses, varied potency, or unexpected toxicity for the other.