Editing Enantiomer (section)

==Enantioselective preparations==
{{See also|chiral resolution|asymmetric synthesis}}
In the absence of an effective enantiomeric environment ([[Precursor (chemistry)|precursor]], chiral [[Catalysis|catalyst]], or [[kinetic resolution]]), separation of a racemic mixture into its enantiomeric components is impossible, although certain racemic mixtures spontaneously crystallize in the form of a ''racemic conglomerate'', in which crystals of the enantiomers are physically segregated and may be separated mechanically. However, most racemates form crystals containing both enantiomers in a 1:1 ratio.

In his pioneering work, [[Louis Pasteur]] was able to isolate the isomers of [[tartaric acid|sodium ammonium tartrate]] because the individual enantiomers crystallize separately from solution.  To be sure, equal amounts of the enantiomorphic crystals are produced, but the two kinds of crystals can be separated with tweezers. This behavior is unusual. A less common method is by [[enantiomer self-disproportionation]].

The second strategy is asymmetric synthesis: the use of various techniques to prepare the desired compound in high [[enantiomeric excess]]. Techniques encompassed include the use of chiral starting materials ([[chiral pool synthesis]]), the use of [[chiral auxiliaries]] and [[chiral catalysts]], and the application of [[asymmetric induction]]. The use of enzymes ([[biocatalysis]]) may also produce the desired compound.

A third strategy is [[Enantioconvergent synthesis]], the synthesis of one enantiomer from a racemic precursor, utilizing both enantiomers. By making use of a chiral catalyist, both enantiomers of the reactant result in a single enantiomer of product.<ref name="Mohr2016">{{cite journal |last1=Mohr |first1=J.T. |last2=Moore |first2=J.T. |last3=Stoltz |first3=B.M. |title=Enantioconvergent catalysis |journal=Beilstein J. Org. Chem. |date=2016 |volume=12 |pages=2038–2045 |doi=10.3762/bjoc.12.192 |pmid=27829909 |pmc=5082454 |url=https://www.beilstein-journals.org/bjoc/articles/12/192 |access-date=4 August 2021}}</ref>

Enantiomers may not be isolable if there is an accessible pathway for racemization (interconversion between enantiomorphs to yield a racemic mixture) at a given temperature and timescale. For example, amines with three distinct substituents are chiral, but with few exceptions (e.g. substituted ''N''-chloroaziridines), they rapidly undergo "[[Nitrogen inversion|umbrella inversion]]"  at room temperature, leading to racemization. If the racemization is fast enough, the molecule can often be treated as an achiral, averaged structure.