Enantiomers are non-superimposable mirror images of each other, with the same chemical formula but different three-dimensional structures. They can rotate plane-polarized light in opposite directions and are classified based on their rotational direction or structural orientation. Enantiomers can have different effects in chemical reactions and biological systems, and can be found together in racemic mixtures.
An enantiomer is a molecule that is a non-superimposable mirror image of another molecule. Resembling a person’s right and left hand, the two molecules look alike but differ in orientation. Enantiomers are isomers, which means they contain the same chemical formula but a different structure. Also within that category are stereoisomers, meaning that the bonds between the atoms in each molecule are the same but the three-dimensional arrangement of the atoms is different.
One of the defining characteristics of an enantiomer is the fact that it can rotate plane-polarized light. When light is plane polarized, its waves are oriented in a plane which then passes through a mixture of the enantiomeric compound. While one enantiomer will rotate light waves passing through it in one direction, the other enantiomer will rotate it in the opposite direction by the exact same magnitude. This is due to the physical structure of the molecules and their specific orientation.
Enantiomers can be classified based on the rotational direction of light or the physical orientation of the atoms in each molecule. There is no definitive relationship between the two naming systems, but they are used depending on the context of the classification. Compounds are said to be dol compounds, or (+) or (-) compounds, depending on the direction in which they rotate plane-polarized light. The letters correspond to the words dextrorotatory and levorotatory, meaning clockwise and counterclockwise, respectively.
The second classification method for an enantiomer depends on the structural orientation of the atoms around the central atom, where the bond difference occurs. This atom is often a carbon atom, known as a chiral carbon. When categorizing using this method, the molecule is oriented such that the smallest atom is positioned away from the observer, while the other three atoms are oriented in a triangle. The direction is determined by starting with the atom of heaviest weight and moving around the triangle in order of decreasing weight. Clockwise directions correspond to R-enantiomeric compounds, while counterclockwise directions refer to S compounds.
Enantiomeric compounds will respond differently in some chemical reactions, especially when mixed with other enantiomers. Various enzymes and signaling molecules occur in one enantiomeric form and the other enantiomer will not elicit the same effects. Enantiomers are sometimes formed together in what is known as a racemic mixture, in which there will be no rotation of plane-polarized light because each compound will cancel out the other.
Protect your devices with Threat Protection by NordVPN
