epimerisaation

Epimerisation is a chemical process where a molecule undergoes a change in the stereochemical configuration at one specific chiral center, while the configurations of all other chiral centers remain unchanged. This results in the formation of an epimer, which is a stereoisomer that differs from the original molecule at only one chiral center. Epimerisation typically occurs under conditions that promote the temporary formation of a planar intermediate, such as an enol or enolate, at the carbon atom undergoing inversion. Acidic or basic catalysis is often employed to facilitate this process. The equilibrium between the epimers is usually established, meaning both the original molecule and its epimer are present, with the ratio determined by their relative thermodynamic stabilities. This phenomenon is particularly relevant in carbohydrate chemistry, where it is observed in sugars like glucose and mannose, which are epimers at the C-2 position. Understanding epimerisation is crucial in organic synthesis and biochemistry, as it can impact the biological activity and chemical properties of molecules.