Editing Enantiomer

{{short description|Stereoisomers that are nonsuperposable mirror images of each other}}
{{About|the concept in chemistry|a discussion of enantiomers in mathematics|Chirality (mathematics)}}
[[File:Milchsäure Enantiomerenpaar.svg|thumb|(''S'')-(+)-[[lactic acid]] (left) and (''R'')-(–)-lactic acid (right) are nonsuperimposable mirror images of each other.]]

In [[chemistry]], an '''enantiomer''' ([[Help:IPA/English|/ɪˈnænti.əmər, ɛ-, -oʊ-/]]<ref>{{Cite web |title=Enantiomer: Definition & Meaning |url=https://www.dictionary.com/browse/enantiomer |access-date=2024-04-26 |website=Dictionary.com |language=en}}</ref> [[Help:Pronunciation respelling key|''ih-NAN-tee-ə-mər'']]), also known as an '''optical isomer''',<ref>{{Cite journal |last=Chemistry (IUPAC) |first=The International Union of Pure and Applied |title=IUPAC - optical isomers (O04308) |url=https://goldbook.iupac.org/terms/view/O04308 |access-date=2022-11-17 |website=goldbook.iupac.org|doi=10.1351/goldbook.O04308 |doi-access=free }}</ref> '''antipode''',<ref>{{Cite journal |last=Chemistry (IUPAC) |first=The International Union of Pure and Applied |title=IUPAC - antipodes (A00403) |url=https://goldbook.iupac.org/terms/view/A00403 |access-date=2022-11-17 |website=goldbook.iupac.org|doi=10.1351/goldbook.A00403 |doi-access=free }}</ref> or '''optical antipode''',<ref>{{Cite journal |last=Chemistry (IUPAC) |first=The International Union of Pure and Applied |title=IUPAC - optical antipodes (O04304) |url=https://goldbook.iupac.org/terms/view/O04304 |access-date=2022-11-17 |website=goldbook.iupac.org|doi=10.1351/goldbook.O04304 |doi-access=free }}</ref> is one of a pair of molecular entities which are mirror images of each other and non-superposable. 

Enantiomer molecules are like right and left hands: one cannot be superposed onto the other without first being converted to its mirror image.<ref>{{Cite journal |last1=McConathy |first1=Jonathan |last2=Owens |first2=Michael J. |date=2003 |title=Stereochemistry in Drug Action |journal=Primary Care Companion to the Journal of Clinical Psychiatry |volume=5 |issue=2 |pages=70–73 |doi=10.4088/pcc.v05n0202 |issn=1523-5998 |pmid=15156233|pmc=353039 }}</ref> It is solely a relationship of [[chirality (chemistry)|chirality]] and the permanent three-dimensional relationships among molecules or other chemical structures: no amount of re-orientation of a molecule as a whole or [[conformational isomerism|conformational]] change converts one chemical into its enantiomer. Chemical structures with chirality rotate plane-polarized light.<ref>{{Cite web |title=Chirality and Optical Activity |url=https://chemed.chem.purdue.edu/genchem/topicreview/bp/1organic/chirality.html#:~:text=Once%20techniques%20were%20developed%20to,that%20results%20from%20its%20structure. |access-date=2022-11-17 |website=chemed.chem.purdue.edu}}</ref> A mixture of equal amounts of each enantiomer, a ''[[racemic mixture]]'' or a ''racemate'', does not rotate light.<ref>{{Cite journal |last=Chemistry (IUPAC) |first=The International Union of Pure and Applied |title=IUPAC - racemic (R05026) |url=https://goldbook.iupac.org/terms/view/R05026 |access-date=2022-11-17 |website=goldbook.iupac.org|doi=10.1351/goldbook.R05026 |doi-access=free }}</ref><ref>{{Cite journal |last=Chemistry (IUPAC) |first=The International Union of Pure and Applied |title=IUPAC - racemate (R05025) |url=https://goldbook.iupac.org/terms/view/R05025 |access-date=2022-11-17 |website=goldbook.iupac.org|doi=10.1351/goldbook.R05025 |doi-access=free }}</ref><ref>{{Cite web |last=Weber |first=Erin |title=Library Guides: CHEM 221: Stereochemistry / Isomerism |url=https://libraryguides.salisbury.edu/Chem221/stereochemistry_isomerism |access-date=2022-11-17 |website=libraryguides.salisbury.edu |language=en}}</ref>

Stereoisomers include both enantiomers and [[diastereomer]]s. Diastereomers, like enantiomers, share the same molecular formula and are also non-superimposable onto each other; however, they are not mirror images of each other.<ref>{{March6th}}</ref>

==Naming conventions==
{{Main|Absolute configuration}}

There are three common naming conventions for specifying one of the two enantiomers (the [[absolute configuration]]) of a given chiral molecule: the R/S system is based on the geometry of the molecule; the (+)- and (−)- system (also written using the obsolete equivalents ''d''- and ''l''-) is based on its [[optical rotation]] properties; and the <small>D</small>/<small>L</small> system is based on the molecule's relationship to enantiomers of [[glyceraldehyde]].

The R/S system is based on the molecule's geometry with respect to a chiral center.<ref name=":0">{{Cite journal |last=Brewster |first=James H. |date=December 1986 |title=The distinction of diastereomers in the Cahn-Ingold-Prelog (RS) notation |url=https://pubs.acs.org/doi/abs/10.1021/jo00375a001 |journal=The Journal of Organic Chemistry |language=en |volume=51 |issue=25 |pages=4751–4753 |doi=10.1021/jo00375a001 |issn=0022-3263}}</ref> The R/S system is assigned to a molecule based on the priority rules assigned by [[Cahn–Ingold–Prelog priority rules]], in which the group or atom with the largest atomic number is assigned the highest priority and the group or atom with the smallest atomic number is assigned the lowest priority.

The (+) or (−) symbol is used to specify a molecule's [[optical rotation]] — the direction in which the polarization of light rotates as it passes through a solution containing the molecule.<ref>{{Cite journal |last1=Caldwell |first1=John |last2=Wainer |first2=Irving W. |date=December 2001 |title=Stereochemistry: definitions and a note on nomenclature |url=https://onlinelibrary.wiley.com/doi/10.1002/hup.334 |journal=Human Psychopharmacology: Clinical and Experimental |language=en |volume=16 |issue=S2 |pages=S105–S107 |doi=10.1002/hup.334 |pmid=12404716 |s2cid=12367578 |issn=0885-6222}}</ref> When a molecule is denoted dextrorotatory, it rotates the plane of polarized light clockwise and can also be denoted as (+).<ref name=":0" /> When it is denoted as levorotatory, it rotates the plane of polarized light counterclockwise and can also be denoted as (−).<ref name=":0" /> 

The Latin words for ''left'' are ''laevus'' and ''sinister'', and the word for ''right'' is ''dexter'' (or ''rectus'' in the sense of correct or virtuous). The English word ''right'' is a [[cognate]] of ''rectus''. This is the origin of the D/L and R/S notations, and the employment of prefixes [[Dextrorotation and levorotation|''levo-'' and ''dextro-'']] in [[Systematic name|common names]].

The prefix ''ar-'', from the Latin ''recto'' (right), is applied to the right-handed version; ''es-'', from the Latin ''sinister'' (left), to the left-handed molecule. Example: [[ketamine]], [[arketamine]], [[esketamine]].<ref>{{Cite journal|url=https://doi.org/10.1001/jamanetworkopen.2021.5731|title=Evaluation of Trials Comparing Single-Enantiomer Drugs to Their Racemic Precursors: A Systematic Review|first1=Aaron S.|last1=Long|first2=Audrey D.|last2=Zhang|first3=Caitlin E.|last3=Meyer|first4=Alexander C.|last4=Egilman|first5=Joseph S.|last5=Ross|first6=Joshua D.|last6=Wallach|date=May 6, 2021|journal=JAMA Network Open|volume=4|issue=5|pages=e215731|via=Silverchair|doi=10.1001/jamanetworkopen.2021.5731|pmid=33956134 |pmc=8103227}}</ref>

== Chirality centers ==
[[File:Meso-Weins%C3%A4ure_Spiegel.svg|thumb|150px|[[Fischer projection]] of meso-tartaric acid]]
The asymmetric atom is called a '''chirality center''',<ref>{{GoldBookRef|title=''chirality centre''|file=C01060}}</ref><ref name="Wade 2006">{{cite journal | last=Wade | first=LeRoy G. | title=Precision in Stereochemical Terminology | journal=J. Chem. Educ. | volume=83 | issue=12 | year=2006 | issn=0021-9584 | doi=10.1021/ed083p1793 | page=1793| bibcode=2006JChEd..83.1793W }}</ref> a type of [[stereocenter]]. A chirality center is also called a ''chiral center''<ref name="Karras 2018">{{cite thesis |last=Karras |first=Manfred |date=2018 |title="Synthesis of Enantiomerically Pure Helical Aromatics Such As NHC Ligands and Their Use in Asymmetric Catalysis |type=PhD |publisher=Charles University |url=https://dspace.cuni.cz/handle/20.500.11956/104319 |access-date=6 August 2021}}</ref><ref name="Eliel 1994">{{Cite book|title=Stereochemistry of organic compounds|last1=Eliel |first1=Ernest L.|date=1994|publisher=Wiley|last2=Wilen |first2=Samuel H. |last3=Mander |first3=Lewis N.|isbn=0471016705|location=New York|oclc=27642721}}</ref><ref name="Clayden 2012">{{cite book | last1=Clayden | first1=Jonathan | last2=Greeves | first2=Nick | last3=Warren | first3=Stuart G. | title=Organic chemistry | publisher=Oxford University Press | publication-place=Oxford | date=2012 | isbn=978-0-19-927029-3 | oclc=761379371 | page=}}</ref> or an ''asymmetric center''.<ref>{{GoldBookRef|title=''asymmetric centre''|file=A00480}}</ref> Some sources use the terms ''stereocenter'', ''stereogenic center'', ''stereogenic atom'' or ''stereogen'' to refer exclusively to a chirality center,<ref name="Karras 2018" /><ref name="Clayden 2012" /><ref name="Clark 2021">{{cite book | last1=Clark | first1=Andrew | last2=Kitson | first2=Russell R. A. | last3=Mistry | first3=Nimesh | last4=Taylor | first4=Paul | last5=Taylor | first5=Matthew | last6=Lloyd | first6=Michael | last7=Akamune | first7=Caroline | title=Introduction to stereochemistry | publication-place=Cambridge, UK | date=2021 | isbn=978-1-78801-315-4 | oclc=1180250839}}</ref> while others use the terms more broadly to refer also to centers that result in [[diastereomers]] (stereoisomers that are not enantiomers).<ref name="Wade 2006" /><ref>{{GoldBookRef|title=''stereogenic unit (stereogen/stereoelement)''|file=S05980}}</ref><ref name="Mislow 1984">{{cite journal | last1=Mislow | first1=Kurt | last2=Siegel | first2=Jay | title=Stereoisomerism and local chirality | journal=J. Am. Chem. Soc. | volume=106 | issue=11 | year=1984 | issn=0002-7863 | doi=10.1021/ja00323a043 | pages=3319–3328| bibcode=1984JAChS.106.3319M }}</ref>

Compounds that contain exactly one (or any odd number) of asymmetric atoms are always chiral. However, compounds that contain an even number of asymmetric atoms sometimes lack chirality because they are arranged in mirror-symmetric pairs, and are known as [[Meso compound|''meso'' compounds]]. For instance, ''meso'' [[tartaric acid]] (shown on the right) has two asymmetric carbon atoms, but it does not exhibit enantiomerism because there is a  mirror symmetry plane. Conversely, there exist forms of chirality that do not require asymmetric atoms, such as [[Axial chirality|axial]], [[Planar chirality|planar]], and [[Helical chirality|helical]] chirality.<ref name="Karras 2018" />{{Rp|pg. 3}}

Even though a chiral molecule lacks reflection (C<sub>s</sub>) and [[improper rotation|rotoreflection]] symmetries (S<sub>2''n''</sub>), it can have other [[Molecular symmetry|molecular symmetries]], and its symmetry is described by one of the chiral [[Point groups in three dimensions|point groups]]: C<sub>''n''</sub>, D<sub>''n''</sub>,  T, O, or I. For example, [[hydrogen peroxide]] is chiral and has C<sub>2</sub> (two-fold rotational) symmetry. A common chiral case is the point group C<sub>1</sub>, meaning no symmetries, which is the case for lactic acid.
{{clear}}

== Examples ==
[[File:(±)-Mecoprop Enantiomers Formulae.png|thumb|300px|left|Structures of the two enantiomeric forms (''S'' left, ''R'' right) of [[mecoprop]]]]
[[Image:Citalopram Structural Formulae.png|thumb|150px|right|Enantiomers of [[citalopram]].  The top is (''R'')-citalopram and the bottom is [[Escitalopram|(''S'')-citalopram]].]]
An example of such an enantiomer is the [[sedative]] [[thalidomide]], which was sold in a number of countries around the world from 1957 until 1961.  It was withdrawn from the market when it was found to cause birth defects.  One enantiomer caused the desirable sedative effects, while the other, unavoidably<ref>{{cite journal|last1=Knoche|first1=B|last2=Blaschke|first2=G|year=1994|title=Investigations on the in vitro racemization of thalidomide by high-performance liquid chromatography|journal=Journal of Chromatography A|volume=666|issue=1–2|pages=235–240|doi=10.1016/0021-9673(94)80385-4}}<!--|access-date=19 October 2015--></ref> present in equal quantities, caused birth defects.<ref>{{Cite book|title=Fundamentals of Biochemistry|page=[https://archive.org/details/fundamentalsofbi00voet_0/page/89 89]|isbn=0-471-21495-7|url=https://archive.org/details/fundamentalsofbi00voet_0/page/89|last1=Voet|first1=Donald|last2=Voet|first2=Judith G.|last3=Pratt|first3=Charlotte W.|year=2006|publisher=Wiley }}</ref>

The [[herbicide]] [[mecoprop]] is a racemic mixture, with the (''R'')-(+)-enantiomer ("Mecoprop-P", "Duplosan KV") possessing the herbicidal activity.<ref>{{ cite journal | journal = Acta Crystallogr. B | volume = 36 | issue = 4 |date=April 1980 | pages = 992–994 | doi = 10.1107/S0567740880005134 | title = (±)-2-(4-Chloro-2-methylphenoxy)propionic acid (mecoprop) |author1=G. Smith |author2=C. H. L. Kennard |author3=A. H. White |author4=P. G. Hodgson | bibcode = 1980AcCrB..36..992S }}</ref>

Another example is <!--Predicate agrees with its subject NOT its complement.--> the antidepressant drugs [[escitalopram]] and [[citalopram]].  Citalopram is a [[racemate]] [1:1 mixture of (''S'')-citalopram and (''R'')-citalopram]; escitalopram [(''S'')-citalopram] is a pure enantiomer.  The dosages for escitalopram are typically 1/2 of those for citalopram. Here, (S)-citalopram is called a [[chiral switch]] of Citalopram.

{{clear}}

== Chiral drugs ==
{{Main articles|Chiral drugs|Enantiopure drug}}
'''Enantiopure compounds''' consist of only one of the two enantiomers.  Enantiopurity is of practical importance since such compositions have improved therapeutic efficacy.<ref>{{Cite journal |last=Ariëns |first=Everardus J. |date=1986 |title=Stereochemistry: A source of problems in medicinal chemistry |url=http://dx.doi.org/10.1002/med.2610060404 |journal=Medicinal Research Reviews |volume=6 |issue=4 |pages=451–466 |doi=10.1002/med.2610060404 |issn=0198-6325 |pmid=3534485 |s2cid=36115871}}</ref> The switch from a racemic drug to an [[enantiopure drug]] is called a [[chiral switch]]. In many cases, the enantiomers have distinct effects. One case is that of Propoxyphene. The enantiomeric pair of propoxyphene is separately sold by Eli Lilly and company. One of the partners is [[dextropropoxyphene]], an [[analgesic]] agent (Darvon) and the other is called [[levopropoxyphene]], an effective [[antitussive]] (Novrad).<ref>{{Cite journal |last=Drayer |first=Dennis E |date=1986 |title=Pharmacodynamic and pharmacokinetic differences between drug enantiomers in humans: An overview |url=http://dx.doi.org/10.1038/clpt.1986.150 |journal=Clinical Pharmacology and Therapeutics |volume=40 |issue=2 |pages=125–133 |doi=10.1038/clpt.1986.150 |issn=0009-9236 |pmid=3731675 |s2cid=33537650}}</ref><ref>{{Cite book |last=Ariens |first=E.J |title=Chiral Separations by HPLC |publisher=Ellis Horwwod |year=1989 |location=Chichester |pages=31–68}}</ref>  It is interesting to note that the trade names of the drugs, DARVON and NOVRAD, also reflect the chemical mirror-image relationship.  In other cases, there may be no clinical benefit to the patient. In some jurisdictions, single-enantiomer drugs are separately patentable from the racemic mixture.<ref>{{cite web |title=European Medicines Agency - - Sepracor Pharmaceuticals Ltd withdraws its marketing authorisation application for Lunivia (eszopiclone) |url=http://www.ema.europa.eu/ema/index.jsp?curl=pages/news_and_events/news/2009/11/news_detail_000083.jsp&jsenabled=true |website=www.ema.europa.eu |date=17 September 2018 |access-date=14 February 2011 |archive-date=1 December 2017 |archive-url=https://web.archive.org/web/20171201043407/http://www.ema.europa.eu/ema/index.jsp?curl=pages%2Fnews_and_events%2Fnews%2F2009%2F11%2Fnews_detail_000083.jsp&jsenabled=true |url-status=dead }}</ref> It is possible that only one of the enantiomers is active. Or, it may be that both are active, in which case separating the mixture has no objective benefits, but extends the drug's patentability.<ref>{{cite book |author=Merrill Goozner |url=https://archive.org/details/800millionpilltr00gooz |title=The $800 Million Pill: The Truth Behind the Cost of New Drugs |publisher=University of California Press |year=2004 |isbn=0-520-23945-8 |format=excerpt}}</ref>

==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.

==Parity violation==
For all intents and purposes, each enantiomer in a pair has the same energy. However, theoretical physics predicts that due to [[parity violation]] of the [[Weak interaction|weak nuclear force]] (the only force in nature that can "tell left from right"), there is actually a ''minute'' difference in energy between enantiomers (on the order of 10<sup>−12</sup> eV or 10<sup>−10</sup> kJ/mol or less) due to the [[weak neutral current]] mechanism. This difference in energy is far smaller than energy changes caused by even small changes in molecular conformation, and far too small to measure by current technology, and is therefore chemically inconsequential.<ref name="Eliel 1994" /><ref>{{Cite book|title=The origin of chirality in the molecules of life: a revision from awareness to the current theories and perspectives of this unsolved problem|last=Albert|first=Guijarro|date=2008|publisher=Royal Society of Chemistry|others=Yus, Miguel.|isbn=9781847558756|location=Cambridge, UK|oclc=319518566}}</ref><ref>{{Cite journal|last1=Stickler|first1=Benjamin A.|last2=Diekmann|first2=Mira|last3=Berger|first3=Robert|last4=Wang|first4=Daqing|date=2021-09-14|title=Enantiomer Superpositions from Matter-Wave Interference of Chiral Molecules|url=https://link.aps.org/doi/10.1103/PhysRevX.11.031056|journal=Physical Review X|language=en|volume=11|issue=3|pages=031056|doi=10.1103/PhysRevX.11.031056|issn=2160-3308|arxiv=2102.06124|bibcode=2021PhRvX..11c1056S |s2cid=231879820 }}</ref> In the sense used by particle physicists, the "true" enantiomer of a molecule, which has exactly the same mass-energy content as the original molecule, is a mirror-image that is also ''built from antimatter'' (antiprotons, antineutrons, and positrons).<ref name="Eliel 1994" /> Throughout this article, "enantiomer" is used only in the chemical sense of compounds of ordinary matter that are not superposable on their mirror image.

==Quasi-enantiomers==
''Quasi''-enantiomers are molecular species that are not strictly enantiomers, but behave as if they were. In quasi-enantiomers, the majority of the molecule is reflected; however, an atom or group within the molecule is changed to a similar atom or group.<ref name=":1">{{Cite journal |last1=Zhang |first1=Qisheng |last2=Rivkin |first2=Alexey |last3=Curran |first3=Dennis P. |date=2002-05-01 |title=Quasiracemic Synthesis: Concepts and Implementation with a Fluorous Tagging Strategy to Make Both Enantiomers of Pyridovericin and Mappicine |url=https://pubs.acs.org/doi/10.1021/ja025606x |journal=Journal of the American Chemical Society |language=en |volume=124 |issue=20 |pages=5774–5781 |doi=10.1021/ja025606x |pmid=12010052 |bibcode=2002JAChS.124.5774Z |issn=0002-7863}}</ref> Quasi-enantiomers can also be defined as molecules that have the potential to become enantiomers if an atom or group in the molecule were replaced.<ref>{{Cite journal |last1=Zhang |first1=Qisheng |last2=Curran |first2=Dennis P. |date=2005-08-19 |title=Quasienantiomers and Quasiracemates: New Tools for Identification, Analysis, Separation, and Synthesis of Enantiomers |url=https://onlinelibrary.wiley.com/doi/10.1002/chem.200500076 |journal=Chemistry - A European Journal |language=en |volume=11 |issue=17 |pages=4866–4880 |doi=10.1002/chem.200500076 |pmid=15915521 |issn=0947-6539}}</ref> An example of quasi-enantiomers is (''S'')-bromobutane and (''R'')-iodobutane. Under normal conditions, the enantiomers for (''S'')-bromobutane and (''R'')-iodobutane are (''R)-''bromobutane and (''S'')-iodobutane respectively. Quasi-enantiomers also produce quasi-racemates, which are similar to normal racemates (see [[Racemic mixture]]) in that they form an equal mixture of quasi-enantiomers.<ref name=":1" />

Though not considered actual enantiomers, the naming convention for quasi-enantiomers also follows the same trend as enantiomers, when looking at (''R'') and (''S'') configurations - which are considered from a geometrical basis (see [[Cahn–Ingold–Prelog priority rules]]).

Quasi-enantiomers have applications in parallel [[kinetic resolution]].<ref>G.S. Coumbarides, M. Dingjan, J. Eames, A. Flinn, J. Northen and Y. Yohannes, Tetrahedron Lett. 46 (2005), p. 2897er</ref>

==See also==
{{Div col|colwidth=30}}
* [[Chiral switch]]
* [[Crystal system]] <!-- [[Crystal structure]] is very similar but discusses enantiomorphism less -->
* [[Enantiopure drug]]
* [[Atropisomer]]
* [[Chirotechnology]]
* [[Chirality (physics)]]
* [[Diastereomer]]
* [[Dynamic stereochemistry]]
* [[Epimer]]
* [[Homochirality]]
* [[Molecular symmetry]]
* [[Stereochemistry]]
* [[Stereocenter]]
{{Div col end}}

==References==
{{Reflist}}

==External links==
*{{Commons category-inline|Enantiomers}}
*[http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter__3%3a_Conformations_and_Stereochemistry/Section_3.3%3a_Stereoisomerism_%e2%80%93_chirality%2c_stereocenters%2c_enantiomers chemwiki:stereoisomerism]

{{Chiral synthesis}}

[[Category:Stereochemistry]]
[[Category:Isomerism]]