Stereoisomers are molecules with the same atomic connectivity and chemical formula but different atomic arrangements in space. Different biological activity or physical characteristics result from these variations in spatial arrangement. Optical isomerism, in which molecules exist in two forms known as enantiomers that are non-superimposable mirror images of each other, is a significant form of stereoisomerism.In most cases, enantiomers have the same physical characteristics, including solubility, melting and boiling points. But when it comes to polarized light, they behave differently—a process called optical activity. Polarized light rotates clockwise (dextrorotatory) in one enantiomer and counterclockwise (levorotatory) in the other. This characteristic is used to distinguish and describe enantiomers via methods such as polarimetry.Contrarily, pseudo-enantiomers are stereoisomers that have the same physical characteristics and comparable chemical reactivity but differ in their absolute configuration at a chiral center. This is frequently because they have a functional group that is oriented differently in space. Because of their different three-dimensional structures, pseudo-enantiomers might have different biological activities or interactions despite having comparable characteristics.Thalidomide is a well-known example of a pseudo-enantiomer. Originally promoted as a sedative and antiemetic in the late 1950s, this medication unfortunately resulted in serious birth abnormalities when used by expectant mothers. The existence of thalidomide as a racemic combination of two enantiomers, one of which relieves morning sickness and the other of which has teratogenic consequences, was subsequently found. Because these enantiomers differ in their biological function yet have comparable physical features, they are classified as pseudo-enantiomers.In domains like medicinal chemistry, where a molecule's three-dimensional structure greatly influences its biological activity, knowing the difference between stereoisomers and pseudo-enantiomers is essential. By synthesizing or focusing on particular stereoisomers, researchers can create safer and more effective medications by clarifying the connection between structure and activity.To sum up, stereoisomers and pseudo-enantiomers are significant chemical concepts having wide-ranging effects on other scientific fields. Their work contributes to advances in healthcare and other fields by improving our understanding of molecular behavior and becoming a key player in drug discovery and development.
