Racemization

Racemization is the conversion of an enantiomerically enriched compound into a mixture with equal amounts of its two enantiomers, eliminating net optical rotation.

Enolization: The formation of an enol or enolate from a carbonyl compound by proton transfer. Enolization makes a carbonyl compound’s alpha carbon planar, allowing reprotonation from either face.
Enantiomer: One of two stereoisomers that are nonsuperimposable mirror images of each other. Racemization changes the proportions of this mirror-image pair.
Enantiomeric excess: The excess proportion of one enantiomer over the other, expressed as a percentage. Racemization lowers enantiomeric excess toward zero as the two forms approach equality.
Epimerization: The conversion of one stereoisomer into another that differs at exactly one stereogenic center. Epimerization changes a selected center, whereas racemization produces both enantiomers in equal amounts.
Carbocation: An organic ion in which a carbon atom bears a positive charge and has only six valence electrons. A planar carbocation can be attacked from either face, scrambling configuration at the charged center.
Chirality (chemistry): The property of an object or molecule that makes it nonsuperimposable on its mirror image. A chiral compound can exist as two enantiomers whose proportions racemization alters.
Chiral resolution: The separation of enantiomers from a mixture using a chiral environment or resolving agent. Resolution can reverse racemization’s practical effect by enriching one enantiomer.
Inversion of configuration: A stereochemical change in which a stereogenic center adopts the opposite spatial configuration. Inversion gives the opposite configuration rather than necessarily creating an equal enantiomer mixture.
S<sub>N</sub>1 reaction: A nucleophilic substitution that proceeds through a carbocation intermediate after the leaving group departs. Its planar intermediate can produce both configurations, often causing partial racemization.
Stereochemistry: The study of the three-dimensional arrangement of atoms in molecules and its chemical consequences. Racemization is a change in molecular stereochemistry without changing molecular connectivity.

Linked from 4 pages