Talk:Stereoisomerism

Definition

This definition doesn't really distinguish stereoisomerism from other forms of isomerism at all.

like all other topics in chemistry,this is also useful enough and gives brief description.

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yeah, I didn't finish this before I had to log off. It will be similar to structural isomerism. I agree about the uploading images bit.

-- sooodium

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"Stereoisomerism is WHERE..."?? Any definition that begins by saying something "is where" desperately needs work!

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What is the term for isomers resulting from two or more chiral centres, but which are not mirror-images of each other? For example D-glucose and D-galactose?

• They are called diastereoisomers to distinguish them from enantiomers which have only one chiral centre.

See Wiktionary:Stereoisomerism for a less confised definition.

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(Actually, I'm seeing Wiktionary saying that stereoisomerism is synonymous with optical isomerism, which I believe is mistaken. See my comment below. Eub 06:28, 20 October 2005 (UTC) )

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This article is completely wrong. The compounds depicted are geometric isomers. --dlain 20:50, July 10, 2005 (UTC)

They are geometric isomers, yes, but that's still stereoisomerism according the the definition I'm familiar with. See for example this IUPAC page that describes cis-trans isomers as stereoisomeric: http://goldbook.iupac.org/goldbook/C01093.html Is there another definition in use that we should explain?

The page might more clearly enumerate the different kinds of stereoisomerism, though.

Eub 06:28, 20 October 2005 (UTC)

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Now, from what I gather, no, the way I am sure, sources by my side, we have these structures:

• Stereoisomers
  • Geometric isomers
  • Optical isomers
• Structural isomers
  • Position isomers
  • Function isomers

The PA 02:00, 8 December 2005 (UTC)

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I made some changes to the page which really makes it clear that stereoisomerism = geometric isomerism + optical isomerism. I also added the bibliography of where I took those informations. (I also have my book by my side, but it's my school manual, in french... not too handy to put a reference to since people will want to verify online mostly). This article would actually be more fit as a definition than an encyclopedic article. At least, that's what I think. Now to decide wether the part on geometric isomerism should eb moved to the actual page on that subject... Opinions?

The PA 02:38, 8 December 2005 (UTC)

The definition is really broad, but failed to account all the isomers in this scope. Psvo277 (talk) 23:21, 12 April 2019 (UTC)

Overlapping/confused classifications

There's a whole lot of conflation of classes of stereoisomerism here. Amino acids, described as enantiomeric, are in the diastereomer/cis-trans section instead of the optical isomer section—that section even explicitly describes the source of their stereoisomerism. Diastereomeric is categorized with cis-trans but then the sole example of termed "diastereomeric" is (rightly) placed in the optical isomer secion instead.

Does this page need to exist on its own? It seems it serves mainly as a stepping-stone from the Stereochemistry page to articles about specific types of stereochemistry. A sort of annotated table-of-contents. Except it's incomplete vs the children and moderately muddled in its own right. Maybe scrap this page and add to the Stereochemistry page a section listing the types of stereoisomerism (matched to the chart on that page)? Each could have a one-sentence summary noting what distinguishes that type, and be linked to the page for that type (if such a page exists). DMacks 07:01, 10 February 2006 (UTC)

• I expect an encyclopedia to a have an entry on stereoisomerism, that is why the article should stay as it is. The line containing the reference to amino acids should indeed be removed. Just piling all the content in one article does not solve anything, the problem is that much of the content that should be in the pages is still missing. So lets focus on adding quality content and not focus on moving around chunks of existing content V8rik 17:39, 10 February 2006 (UTC)

• • Merging takes several seconds. I added the merge tag. Why? Because stereochemistry is the definition, and stereoisomerism has the examples. Stereoisomer redirects to the -ism page. 203.218.87.192 01:41, 9 April 2006 (UTC)

label of d and l forms

In the tartaric acid example isn't the label wrong? Doesn't the L form go with Levoroatatory? —The preceding unsigned comment was added by 67.133.62.41 (talk) 00:10, 16 February 2007 (UTC).

The tartaric acid page talks about the different naming issues in effect here. More generally, see Chirality (chemistry)#Naming_conventions to see how your title ("d" and "l" has a different meaning than your question (about "L"). DMacks 01:26, 16 February 2007 (UTC)

While the naming here is technically correct, I think it can be a bit misleading to those who are unaware that there is a difference betwen the D/L naming convention and the d/l convention and this needs to be made clearer. I will add a note referencing the Chirality (chemistry)#Naming_conventions page and anyone here is of course more than welcome to add to it or clean it up a bit, but I think something needs to be said about it. —Preceding unsigned comment added by 75.109.138.241 (talk) 04:07, 28 October 2008 (UTC)

Isn't the naming of the isomers WRONG? The L-(+)-tartaric acid is named LEVO in this figure, when it's really DEXTRO, at least according to the article on tartaric acid. And vice versa. It makes it all very confusing. — Preceding unsigned comment added by Dr Mixe (talk • contribs) 21:19, 14 September 2022 (UTC)

Good eye! This is a new issue, a result of changes by User:Kamdenek on June 11, 2022. I'm out of time to address it. DMacks (talk) 21:43, 14 September 2022 (UTC)

Limonene

It might be illuminating to describe the very different odours of the D- and L- forms of Limonene. Old Aylesburian (talk) 12:53, 5 April 2009 (UTC)

How the body processes (reverse?) stereoisomers

Is there anyone that can tell me whether (reverse?) stereoisomers are processed by the body in an identical fashion? I'm curious because I found out that Lunesta, an expensive and patented sleeping pill, is the reverse stereoisomer of a generic pill that's been available in other countries for years. Historian932 (talk) 15:36, 6 June 2009 (UTC)

Enzymes and other biological molecules almost always occur in only one stereoisomeric form, and rarely do they handle different stereoisomers the same. To put it another way, different stereoisomers of a compound often do not have the same biological effect: they may be metabolized at different rates, bind more or less strongly to a target, bind not-at-all or to entirely different targets, etc. But the difference depends on the molecule and target of interest. Lunesta is a "single enantiomer" (one of two opposite stereoisomers of the structure). It sounds like the previous/European-generic drug Zopiclone was actually the mixture of both lunesta and its opposite (a racemate), not just the reverse, and Lunesta is the one of those two that is the one that actually has an effect. The racemic mixture contains 50% of the other enantiomer, which does not have substantial biological effect at all. That's actually a pretty common situation in the drug industry because it might be easier to manufacture a racemic mixture and just make sure that none of the stereoisomers are toxic rather than to manufacture one enantiomer or to separate one enantiomer from the mixture. If eventually the single enantiomer of interest becomes economically available, it is a separate drug: allows companies to extend their patent rights and market it as "new and improved, now you only need half the dose!". DMacks (talk) 16:14, 6 June 2009 (UTC)

Conformers

Two editors have removed the "Conformers" section, claiming that conformers are not isomers. However, the removed section contains three references that call conformers "conformational isomers". The book Stereochemistry by Karnik and Hasan is cited as saying "Conformations or conformational isomers have different spatial arrangements of atoms of a molecule but have same bond connectivity and the same configuration, if chiral."[1] A chapter from a chemistry course at the University of Calgary says "Conformational isomers (or conformers or rotational isomers or rotamers) are stereoisomers produced by rotation (twisting) about σ bonds, ..."[2] And the Encyclopedia Britannica says "These staggered forms, called “anti” and “gauche,” of 1,2-dideuterioethane are different but are interconverted through rotations around the central carbon-carbon bond and are called “conformational isomers.”"[3] A claim that all these sources are using incorrect nomenclature needs better support rather than unsourced assertions. CodeTalker (talk) 16:41, 9 April 2023 (UTC)

I have reverted the change so that a discussion can take place here before deletion of a substantial section of the article. Qflib, aka KeeYou Flib (talk) 19:05, 9 April 2023 (UTC)