Editing Stereoisomerism (section)

==Diastereomers==
{{Main|Diastereomer}}
'''Diastereomers''' are stereoisomers not related through a reflection operation.<ref>{{cite web |url= https://iupac.qmul.ac.uk/stereo/DE.html#07 |title= Basic Terminology of Stereochemistry (IUPAC Recommendations 1996): Diastereoisomerism }}</ref> They are not mirror images of each other. These include [[meso compound]]s, [[Cis–trans isomerism|''cis''–''trans'' isomers]], [[E–Z notation|E-Z isomers]], and non-enantiomeric [[optical isomers]]. Diastereomers seldom have the same physical properties. In the example shown below, the meso form of tartaric acid forms a diastereomeric pair with both levo- and dextro-tartaric acids, which form an enantiomeric pair.

{| cellpadding="5" cellspacing="0"
|-
| align="center" width="150" style="border-right:1px dashed black;" |
[[Image:L-tartaric acid.png]]
| align="center" width="150" style="border-right:1px solid black;" | [[Image:D-tartaric acid.png]]
| align="center" width="270" |  [[Image:Meso-Weinsäure Spiegel.svg|150px]]
|-
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(natural) tartaric acid<br /><small>L</small>-tartaric acid<br /><small>L</small>-(+)-tartaric acid<br />levo-tartaric acid
| align="center" valign="bottom" style="border-right:1px solid black;" |
<small>D</small>-tartaric acid<br /><small>D</small>-(-)-tartaric acid<br />dextro-tartaric acid<br />
| align="center" valign="middle" |
meso-tartaric acid
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| align="center" colspan="2" valign="bottom" style="border-right:1px solid black;" |
(1:1)<br /><small>DL</small>-tartaric acid<br />"racemic acid"
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|}

The <small>D</small>- and <small>L</small>- labeling of the isomers above is not the same as the ''d''- and ''l''- labeling more commonly seen, explaining why these may appear reversed to those familiar with only the latter naming convention.

A [[Fischer projection]] can be used to differentiate between L- and D- molecules [[Chirality (chemistry)]]. For instance, by definition, in a Fischer projection the penultimate carbon of D-sugars are depicted with hydrogen on the left and hydroxyl on the right. L-sugars will be shown with the hydrogen on the right and the hydroxyl on the left.

The other refers to [[Optical rotation]], when looking at the source of light, the rotation of the plane of polarization may be either to the right (dextrorotary — d-rotary, represented by (+), clockwise), or to the left (levorotary — l-rotary, represented by (−), counter-clockwise) depending on which stereoisomer is dominant. For instance, sucrose and camphor are d-rotary whereas cholesterol is l-rotary.