Talk:Chirality (chemistry)

Sugars

The comment about the natural chirality of sugars may be incorrect. The entry on [Optical Rotation] states that there are natural sugars of both chirality.

Are the Pictures correct?

Using the "CORN" method for amino acids, is the picture in the left hand really an L-amino acid, and is the picture in the right hand, really a D-amino acid?? BillChia (talk) 13:23, 24 February 2010 (UTC)BillChia, 24 February 2010.[reply]

I think the lower right hand figure about the C1 C2 chiral and achiral example molecules is wrong. The example molecule does not have a C2 axis. You would need to have all X terminations (or at least 2 X on one side and Y on the other). As is it has no symmetry, though it is deceptively close to a S4 operation. — Preceding unsigned comment added by Mjv500 (talk • contribs) 15:54, 15 July 2020 (UTC)[reply]

It does have a C₂ axis, just like hydrogen peroxide. See http://www.chemspider.com/Chemical-Structure.49724.html or https://www.chemtube3d.com/symhoohc2/, for example. The point group of all these molecules is C₂. --Ben (talk) 21:11, 15 July 2020 (UTC)[reply]

Why

No mention of what explanations are being hypthesised for the right-handedness of biology. Two I know of are

it just turned out that way
the weak nuclear force makes one way more low energy that the other

Pmurray bigpond.com 06:03, 12 September 2005 (UTC)[reply]

Yes

Biology is right handed? NPR's Science Friday said all multicellular life on Earth uses "left-handed" amino acids.--64.107.201.150 19:49, 29 June 2006 (UTC)[reply]

Different parts of "biology" (as a whole) have different handedness (assuming that means "sign of optical rotation" or "correspondence to certain stereocenters"?). The Chirality article doesn't describe biology as being any particular handedness, so when someone finally answers the question, just have to make sure to avoid introducing any such generality. DMacks 02:02, 6 July 2006 (UTC)[reply]

It should probably be amended that ALL amino acids are L type rather than just most. from Chiral Recognition in the Gas Phase, Powis p23. The only possible exception would be from Cysteine where the chirality is impeded by steric hindrence from the bulky sulphur group. 128.243.253.116 (talk) 22:31, 3 May 2011 (UTC)[reply]

Merge?

Would it make sense to merge material from Enantiomer? --Tabor 18:22, 18 October 2005 (UTC)[reply]

I think so, I will add the proposed merge template to both pages. --Aaronsharpe 11:12, 22 June 2007 (UTC)[reply]

this merge proposal is not valid, you cannot have merge discussions lasting 1.5 years. tag removed V8rik 19:39, 22 June 2007 (UTC)[reply]

I have put the tags back and if no one comes up with a good reson not to I will complete the merge in the next few days. TomViza (talk) 19:56, 3 June 2008 (UTC)[reply]

If you merge enantiomer into this article, you should merge diastereomer and atropisomerism, as these are all examples of chirality in chemistry. One cannot discuss diastereomers without first discussing enantiomers anyway. You could actually merge enantiomer and diastereomer into the stereochemistry article instead, which IMO would make more sense. There is no reason to only merge enantiomer into chirality, as there are many other forms of chirality in chemistry. Endtothemeans (talk) 03:34, 8 June 2008 (UTC)[reply]

Perhaps logically that is correct, but only the two articles that I have suggested to merge have large overlaps in terms of their current content. How about the following: move all of the content from here relating to enantiomerism into that article and have this article simply be a short one with links to enantiomer, diastereomer and atropisomerism? TomViza (talk) 16:50, 9 June 2008 (UTC)[reply]

This would work. There is no need for an explanation of enantiomers in an article on chirality in chemistry...they can just be linked. Endtothemeans (talk) 02:04, 21 June 2008 (UTC)[reply]

General issues

Alterations and restructuring are needed to properly represent use and meaning of the word chirality. Please join the multi-disciplinary discussion on Talk:Chirality. --Cigno 22:15, 15 November 2005 (UTC)[reply]

Wrong word?

Surely the word is asymmetry, not dissymmetry. I was also taught that the correct terms were laevorotatory and dextrorotatory. 21:01, 19 December 2005 (UTC)

- OED. dissymmetry: Symmetry between two objects, disposed in opposite directions, such as the right and left hands or feet, or between crystals alike in all respects, save that their angles lie opposite ways. Bueller 007 (talk) 06:40, 19 November 2008 (UTC)[reply]

Bueller is right regarding dissymetry. Apparently dissymetry and asymmetry do not mean the same thing and in this case it is the former which we want to use. Levorotary vs laevorotary is interesting. Again, I am not a linguist, so I do not know if this comes from simplifying words (like encyclopaedia → encyclopedia), however in this particular case it could be annoying to people who know Latin (I am not one of them), because it looks like levo in latin means I lift or I raise, whereas laevo is dative case of laevus which means left or on the left side, among others. Waydot (talk) 10:01, 12 December 2013 (UTC)[reply]

poorly executed content move

Content of optical isomerism has been moved to chirality (chemistry), and optical isomer is now the redirect. The result is that many links to this article are now disabled. Please consider fixing the links or better revert the process as chirality (chemistry) is not an elegant name for an article. V8rik 21:54, 6 April 2006 (UTC)[reply]

"Elegant name"? Encyclopedias are simple, understandable, and concise, but elegant? I think it confuses the layman far more to attempt to understand how optics is related to chirality, than it is to simply explain the concept using the hand example (which is not very clearly explained in the article). I also think a three dimensional image would help greatly (in place of the 2d one that is currently there; it doesn't show the tetrahedral shape of the molecules). Fuzzform 06:06, 14 May 2006 (UTC)[reply]

Isotopes

Is it possible to have this property using isotopes? Suppose in the Alanine molecule the H3C methyl group is replaced with Deuterium instead of hydrogen, does this create an optical isomer? —The preceding unsigned comment was added by 12.10.127.58 (talk • contribs) .

In a glycine molecule where the methylene group is CHD instead of CH₂, that carbon is a chiral center, and the molecule has two possible enantiomers. DMacks 20:36, 1 June 2006 (UTC)[reply]

Not all L

The article says:

[...] the D/L system remains in common use in certain areas of biochemistry, such as amino acid and carbohydrate chemistry, because it is convenient to have the same chiral label for all of the commonly-occurring structures of a given type of structure in higher organisms. In the D/L system, they are all L;

They are not all L; there are lots of D's. Or do I misunderstand the sentence? There's for example D-Glyceraldehyde 3-phosphate at a prominent position in glycolysis. AxelBoldt 23:57, 22 September 2006 (UTC)[reply]

I think this is probably a very poor attempt at pointing out that in the living, human body; the chiral ratio of amino acids is actively shifted to make L-amino acids dominant (90% L, 10% D); and conversely D-monosaccharides are dominant. Only the L-forms of amino acids are active in humans, only the D-forms of monosaccharides are active in humans, so the body keeps that gradient there. After you die, the ratio naturally switches back to 50:50.--KX36 20:07, 3 February 2007 (UTC)[reply]

Some dodgy stuff in here

There is an implication that all enantiomers are optically active - which is rubbish. Also the term is asymmetric, not dissymmetric - Look up most major textbooks it will use that term

Arguably the R & S nomenclature is the most important so surely that should be placed ahead of the d/l and D/L paragraphs - although I am saying this as a chemist rather than as a biologist

Stui 194.72.70.114 13:02, 4 October 2006 (UTC)[reply]

OED. dissymmetry: Symmetry between two objects, disposed in opposite directions, such as the right and left hands or feet, or between crystals alike in all respects, save that their angles lie opposite ways. Bueller 007 (talk) 06:40, 19 November 2008 (UTC)[reply]

Rule surrounding C

The rule where if a tetrahedrally-bonded C has 4 different substituents, then it is chiral applies to any tetrahedrally-bonded element, although C is the most common example. This is according to my university textbook. Mike.lifeguard 00:07, 6 November 2006 (UTC)[reply]

It's true. The article here notes that C is a simple example, and it's the case most wikipedia readers will likely encounter or be likely to recognize or are here to learn about. But actually, it's not even limited to atoms that have 4 bonds, and it's not even limited to atom-centered things at all...see BINAP for example. DMacks 16:43, 6 November 2006 (UTC)[reply]

D-L Chirality Notation Error

I changed the content of the article because it was just plain wrong!

It said that after putting the lowest priority group at the back, if the remaining constituents were counterclockwise it was D config. If clockwise L config.

This is wrong!!

If a chiral molecule has a counter-clockwise configuration it is L (corresponding to S in Organic Chemistry) If a chiral molecule has a clockwise configuration it is D (corresponding to R in Organic Chemistry)

Just letting everyone know I fixed that. —The preceding unsigned comment was added by MikeMurko (talk • contribs) 00:19, 3 December 2006 (UTC).[reply]

I'm affraid it was right the first time and I changed it back. You can check this one yourself. Find yourself a picture of for example D-Alanine, turn the hydrogen away from the viewer and the order COOH R NH2 is counterclockwise! —The preceding unsigned comment was added by 62.253.240.3 (talk)

Looking at the (claimed to be) L-(S)-alanine image on the alanine page, R is the methyl group, H is in the back, and I see (COOH)-(R)-(NH₂) running counter-clockwise. This also seems to agree with the L-(S) stereochemical assignments on the glyceraldehyde page per the description of the origin of the L/R nomenclature (NH₂ instead of OH, methyl instead of methylcarbinol). DMacks 02:13, 3 May 2007 (UTC)[reply]

You are right. Sorry about that!

counter clockwise w. r. to...

suggest adding "counterclockwise as viewed against the direction of propagation" or something similar regarding polarization rotation under the History section, in addition to that in the optical activity naming convention section. Angelafit 06:07, 3 December 2006 (UTC)angelafit[reply]

Letter example - huh?

A para in the article says:

By contrast, the operation of superimposition is trivial for a non-chiral mirror image (e.g., the letter "A"). Because letters such as "A" are not three-dimensional, though, no chiral letters exist to demonstrate the contrary.

Doesn't "L" 'demonstrate the contrary'? (i.e., it's chiral.) If that's not what the para is about, it needs fuller explanation. -R. S. Shaw 18:37, 11 March 2007 (UTC)[reply]

Superposition vs Superimposition

One or more anonymous users (get a user account!) feel that this article should use superposition and not superimposition to explain chirality. I know that McMurry, March etc. use superimposable but what the heck is the difference between the two!. Is is one of those flammable / inflammable thingies that non-native English speakers always mess up or a UK vs US English difference? Any ideas? V8rik 17:53, 6 November 2007 (UTC)[reply]

The plain-English definitions (i.e., Wiktionary) suggest that superposition might be more appropriate than superimposition since we're usually talking about things not images. But the former seems to talk more about arbitrary stacking whereas the latter seems more about having some certain alignment (which is what we care about). And we're looking more for a technical term than a linguistic solution I think? I've only ever heard "superposition" in this context as part of the slow-motion revert war here. DMacks 03:37, 7 November 2007 (UTC)[reply]

Hi DMacks, thanks for your comment. I am assuming for now that you would be in favor of the term superimposition. So the IM in imposition stems from IMage? I did not realize that until now. I will wait and see if there are more comments otherwise I switch back the article. V8rik 17:42, 7 November 2007 (UTC)[reply]

Yes, I'm in favor of "superimposition" both in my mind and because we can support it with McMurry, Wade, Streitwieser/Heathcock/Kosower, and Morrison & Boyd. I'd actually never noticed the "IM" word-root similarity:) DMacks 17:48, 7 November 2007 (UTC)[reply]

Made a switch back V8rik 17:31, 9 November 2007 (UTC)[reply]

Slow motion revert war indeed. IUPAC uses "non-superposable". (IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "enantiomer". doi:10.1351/goldbook.E02069.html) --Rifleman 82 (talk) 06:28, 30 June 2008 (UTC)[reply]

Just for the heck of it, here's the Google Books Popularity Contest result: enantiomer superposed, 61 hits; enantiomer superimposed, 322 hits. In my opinion, both are equally valid. I don't know if it is due to regional differences or if it is random, though. --Itub (talk) 09:59, 30 June 2008 (UTC)[reply]

There's no debate. "Superimpose" is flatly wrong. ANY two objects can be "superimposed". "Superimpose" just means "putting one thing on top of another". Further, if you "superimpose" something onto something else, both are typically *still visible*. There is no nuance of "exact fit". "Superpose" is a geometric term and it specifically means "transfer one into the space occupied by the other two show that they coincide". Enantiomers are ***non-superposable*** mirror images of one another. IUPAC is correct. Bueller 007 (talk) 06:29, 19 November 2008 (UTC)[reply]

It's not likely that the non-technical audience will appreciate, or even understand the distinction. Please continue to clarify and simplify (within reason). Kortoso (talk) 23:08, 13 December 2013 (UTC)[reply]

"Superimpose" is not wrong. The Oxford English Dictionary says explicitly that both terms can mean "bring into coincidence" and both can also mean "place over" (Etymologically, both words, in Latin, meant "place above" in various senses - "super" = "above", "-pose" (-ponere) = "to place", "-im-" = "in/on" (see O.E.D.)). lifeform (talk) 23:18, 3 May 2014 (UTC)[reply]

The textbook, Organic Chemistry by Solomons and Fryhle, 10th edition, wiley states that " To be supersuperposable is different than to be superimposable . Any two objects could be superimposedsimply by putting one object on top of other, whether or not the objects are same. To superpose two objects (as in the superposition ) means, on the other hand, that all parts of each object much coincide. The condition of superposability must be met for two things to be identical . " RIT RAJARSHI (talk) 15:37, 16 July 2016 (UTC)[reply]

D/L typesetting

I notice that all of the instances of "D" and "L" are wrapped in <small> tags. If they're supposed to be in smallcaps, we should use <span style="font-variant:small-caps"> instead: small-caps. I didn't convert over myself because I'm not certain this is what the small tags were intended to accomplish. Bryan Derksen (talk) 05:38, 23 November 2007 (UTC)[reply]

The D and L in this context are indeed intended to be small caps. <small> is heck of a lot easier to type than a longer, er "span" of text. DMacks (talk) 16:34, 24 November 2007 (UTC)[reply]

There is now a {{sc|FOO}} template that produces FOO. (One of the very few "good" templates in Wikipedia: among other qualities, it does make editing easier, it can be immediately and completely learned from a single example, and does not generate more visible text than the template call itself.) --Jorge Stolfi (talk) 22:29, 1 February 2020 (UTC)[reply]

Ibuprofen

Ibuprofen is another example of a chiral molecule. One entantiomer has pain relieving effects while the other is inactive. Also, if I remember correctly, the body can convert the inactive form to the active form, which extends the duration of the pain relieving effect of the drug.

KingHanneman (talk) 04:12, 1 February 2008 (UTC)KingHanneman[reply]

Yup. See the "Stereochemistry" section of the Ibuprofen article for more info. DMacks (talk) 10:21, 3 February 2008 (UTC)[reply]

Comment on the origin of homochirality

From the article:

"The origin of this homochirality in biology is the subject of much debate. Most scientists believe that Earth life's choice of chirality was purely random, and that if carbon-based life forms exist elsewhere in the universe, their chemistry could theoretically have opposite chirality."

I was under the impression that the weak interaction is often suspected as having a role in the origin of homochirality, based partially on indicative experiments involving crystal growth like those of Compton and Pagni (sorry, I don't have a cite off the top of my head). I realize that it's still very speculative to believe this with regards to amino acids in particular, but I wonder whether it's significant enough to comment on in the article? (chemistry isn't my area, so I cannot say)

Even if the hypothesis involving the weak interaction isn't significant enough to include here, the assertion that "most scientists" believe the origin of Earth-bound life's homochirality to be purely random seems misleading. There are certainly plenty who believe it could be the result of natural physical laws. -- 98.26.182.245 (talk) 22:45, 13 October 2008 (UTC)[reply]

Are hands really chiral?

Amputated hands represent a pair of enantiomers. But while still attached to the body, and ignoring our blemishes and the "enantioselective" placement of organs, the hands are not chiral since we are C_s-symmetric. So the analogy to hands is flawed. We are however prochiral. Am I missing something?--Smokefoot (talk) 16:16, 20 December 2008 (UTC)[reply]

agree but analogies will only take you that far. The concept of chirality should be explained on the chirality page itself. As long as you say hands are each others mirror images that is okay. To say (as the article suggests) that a hand is chiral is taking it too far. Are we also homochiral as the heart is always on the left side of the body? V8rik (talk) 20:47, 21 December 2008 (UTC)[reply]

It is not unreasonable to use an analogy when describing a technical topic. Perhaps the word "example" leads readers to assume that hands are actually chiral. Kortoso (talk) 23:11, 13 December 2013 (UTC)[reply]

There is no inconsistency and one need not resort to surgery. A single hand is definitely a chiral object. The whole human body (ignoring internal organs and "accidental" shape variations) is not chiral. A pair of hands from the same individual may or may not be chiral, depending on how they are arranged in space. That is a common situation in chemistry: a molecule with chiral parts may be not chiral as a whole. --Jorge Stolfi (talk) 22:37, 1 February 2020 (UTC)[reply]

Greek IPA /cheir/

The term chirality is derived from the Greek word for hand, χειρ-(/cheir/). I'm know this is improper IPA (which is what one uses inside phonological brackets "/ /"), so I'm guessing that the original editor was simply putting the standard romanization in parentheses. Therefore, I've edited out the brackets. 99.141.180.36 (talk) 02:02, 10 June 2009 (UTC)[reply]

The pronunciation "cheir" seems to be that of Modern Greek, but is neither the Ancient Greek pronunciation, nor the pronunciation from which English /kaɪˈræl/ derived.
From various internet sources, it seems that the (conjectural) Ancient Greek pronunciation was /kʰěːr/ with a hard /kʰ/ sound like in English "keep". By the 4th century CE the Koine pronunciaton was /xir/ where /x/ is a hard "h" sound, as in Scottish "loch" or German "nacht". By the 10th century it became /çir/ where /ç/ is the sound of "ch" in German "nicht"; which seems to be the Modern Greek one.
The English pronunciation of "chiral", with a hard "k" sound, must have come from a possibly inaccurate "Scholar's Greek" pronunciation, something like /kʰeiːr/ or /kʰaiːr/, that was in use by Western European scholars and scientists a couple centuries ago; possibly the (assumed) Homeric Greek pronunciation used in Classics studies.
(Likewise, the pronunciation of Latin generally used in Romance countries, since the Middle Ages, is quite different from that used in English-speaking ones; and both are surely different from that of the Ancient Romans.)
So, which pronunciation should be given? Ideally we should find the true origin of English "chiral"=/kaɪˈræl/ ("Western European Scholar's Greek"?) and give its pronunciation. Failing that, it may be OK to say "from Ancient Greek χείρ"; but its pronunciation should be given as /kʰěːr/ (in IPA) or "ker" (in English-like spelling), rather than "cheir". --Jorge Stolfi (talk) 01:54, 2 February 2020 (UTC)[reply]

@Jorge Stolfi: In Modern Greek it's /çir/, not "cheir". There may have been a point in time when the χ was pronounced /x/ while the ειρ was still pronounced /ěːr/ or /ějr/ — I don't think we really know which change occurred first. I doubt that scholars pronounced the χ like a hard k, it's just that the k sound is the usual way to pronounce words that had a χ in Greek, like "Christ" or "architecture", or the word "scholar" itself. The only exception I can think of in English is the word "cherub", which normally should be pronounced "kerub". Eric Kvaalen (talk) 12:33, 11 May 2021 (UTC)[reply]

"chiral center" vs. "chirality center"

I've seen both, is there any difference? Is it worth mentioning? —Preceding unsigned comment added by 173.250.142.56 (talk) 01:45, 1 February 2011 (UTC)[reply]

Superposition vs Superimposition again

I found in the the first two paragraphs of the introduction part of the article an incorrect wording :-"non-superposable mirror image".So I corrected it to "non-superimposable".Superposable has a totally different meaning in physics and mathematics.Please check article on Superposition Principle for verification. — Preceding unsigned comment added by Ichgab (talk • contribs) 07:35, 11 June 2011 (UTC) The correction to superimposable was done by me User Ichgab.I forgot to sign my comment.Sorry for the mistake.Ichgab (talk) 07:47, 11 June 2011 (UTC)[reply]

I have undone this change per the WP:RS noted in the #Superposition vs Superimposition discussion earlier on this talk-page. As a chemistry article, IUPAC is more authoritative than physics/math technical meanings in their fields (and your change was not supported by that cite given in the article). I have added a heading...because this was filed under '"chiral center" vs. "chirality center"', it's no wonder nobody else noticed or bothered to respond at the time to your separate issue. I have added an additional IUPAC ref that specifically defines "Superposition" as it is used in chemistry to help clarify its meaning in this field. It's definitely different than the superposition principle, so I have removed the link to that target. DMacks (talk) 13:53, 22 January 2012 (UTC)[reply]

Is there another way to describe this without resorting to technical terms that require their own definitions? Kortoso (talk) 23:13, 13 December 2013 (UTC)[reply]

Chirality of phosphorus

Should the chirality of phosphorus (as in sarin) be included? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:45, 3 August 2011 (UTC)[reply]

The article should definitely note the general idea that a lone-pair can be considered a substituent (or at least consume a geometric position like one), and therefore give a stereocenter. The "Chirality of amines" section is a start, but it focuses on the transient nature due to rapid inversion, not the fact that each single state is chiral. Probably best to put the idea of chirality for molecules like RR'RN and RR'RP and RR'SO in the "Stereogenic centers" section (including how to name them R/S, etc.). Then separately can have some commentary on the fact that some chiral molecules can invert under standard conditions (pulling together the conformational-changes from "Stereogenic centers" and the amine-inversion idea). There was a discussion on the science ref-desk within the past month or two about barriers to inversion of P and N centers, I think with some links to other WP articles and/or literature sources. DMacks (talk) 02:45, 4 August 2011 (UTC)[reply]

Naming conventions

It states that " it is labeled R (for Rectus, Latin for right), if it decreases in counterclockwise direction, it is S (for Sinister, Latin for left)." That is incorrect. rectus means straight (such as rectus abdominis), right in latin is dexter. Where does the R come from then? — Preceding unsigned comment added by 86.135.11.19 (talk) 14:59, 15 January 2012 (UTC)[reply]

good point, R is from Rectus (straight, correct) the text should be changed V8rik (talk) 22:13, 15 January 2012 (UTC)[reply]

In English, "right" can mean "correct", but it can also refer to the side opposite "left". In Latin, "rectus" seems to refer to the former, "dexter" the latter, though "right" is a 100% acceptable translation of both words—the problem is that "right" has multiple meanings. Is this as simple as a very old conflation of terms? Or is "rectus" really an additional word for the side opposite left in Latin (even though "dexter" has that covered)? 70.172.214.70 (talk) 04:58, 23 June 2013 (UTC)[reply]

I also spotted this ... imperfection. R must come from Rectus, there is no doubt about it. This looks wrong to some of us, because there's apparently a pair of right and wrong and another pair of right and left. I am not a linguist but this must be related to the fact that most of the population is right-handed. Right side is the good side, while left side is the bad side. Right in English has several meanings, in Latin sinister has that property. It could help perfectionists to change the translation to something which includes correct. Waydot (talk) 09:53, 12 December 2013 (UTC)[reply]

Here is a quote from a 1793 book in latin that uses "recta vel sinistra" ("to the right or to the left"?). So "rectus" it may have been acceptable synonym of "dexter", at least in Medieval Latin -- which is where scientific "Latin" terms are usually taken from. --Jorge Stolfi (talk) 22:49, 1 February 2020 (UTC)[reply]

Chiral sugars?

Do all sugars have chirality? Or is it only for monosaccharides? 173.17.169.171 (talk) 08:28, 6 March 2012 (UTC)[reply]

Almost any sugar that has at least one stereocenter is chiral. A polysaccharide is simply a polymer of monosaccharides, and forming a polymer does not change the chiral fact of the individual monomers within it. If your left and right gloves are chiral, a shopping cart full of gloves is just a whole lot of chirality. DMacks (talk) 16:21, 6 March 2012 (UTC)[reply]
In theory, one could connect an even number of monosaccharides to make an achiral molecule. For example, by connecting a D-glucose to an L-glucose by a 3-3' bond that replaces two hydrogens (or two hydroxyls). The resulting molecule would have a plane of symmetry. But I don't see how to do that with normal glycoside bonds. --Jorge Stolfi (talk) 22:56, 1 February 2020 (UTC)[reply]

@Jorge Stolfi and DMacks: Dihydroxyacetone is a three-carbon sugar that is not chiral. In principle you could have other ketoses that would not be chiral if there are an odd number of carbon atoms and the ketone group is on the central atom. In that case there would be chiral forms but alwo "meso" forms that would not be chiral. But as far as I know, ketoses always have the ketone group on the carbon next to the end. Eric Kvaalen (talk) 12:33, 11 May 2021 (UTC)[reply]

3-Pentulose and 3-hexulose are known. DMacks (talk) 13:47, 11 May 2021 (UTC)[reply]

And 3-heptulose and 4-heptulose and 5-nonulose. Several stereoisomers of 3-pentulose, 4-heptulose, and 5-nonulose are meso compounds. DMacks (talk) 03:47, 12 May 2021 (UTC)[reply]

@DMacks: Thanks. I wonder, do those ketoses exist naturally? I mean, I suppose you could make any ketose you wanted synthetically. By the way, I learn'd recently that there were many unsuccessful attempts to synthesize sucrose (from glucose and fructose) before it was finally achieved in 1953. I wonder whether the problem was to cause the condensation, or to get the right isomer. Eric Kvaalen (talk) 08:04, 15 May 2021 (UTC)[reply]

Error in RS section of Naming conventions

Dear Editors,

The article currently states the following in the RS section of the Naming conventions:

If the center is oriented so that the lowest-priority of the four is pointed away from a viewer, the viewer will then see two possibilities: If the priority of the remaining three substituents increases in clockwise direction, it is labeled R (for Rectus, Latin for right), if it increases in counterclockwise direction, it is S (for Sinister, Latin for left).

This disagrees with the standard definition (see, e.g., Voet and Voet).

A suggested correction follows:

If the center is oriented so that the lowest-priority of the four is pointed away from a viewer, the viewer will then see two possibilities: If the priority of the remaining three substituents decreases in a clockwise direction, it is labeled R (for Rectus, Latin for right), if it decreases in a counterclockwise direction, it is S (for Sinister, Latin for left).

Thank you

Mewalloffice (talk) 19:10, 17 April 2012 (UTC)[reply]

Thanks for spotting the error. It is is the result of vandalism (21 March 2012). It is already corrected.

Δ and Λ complexes

User:Rifleman 82 disagrees with my edit, but I do not understand why there should be pictures of both Δ and Λ ~~conformations~~isomers. Indeed, if it should, then which design is preferable? Incnis Mrsi (talk) 15:13, 7 March 2013 (UTC)[reply]

Why don't you use the following:

Λ-[Fe(ox)₃]³⁻
Δ-[Fe(ox)₃]³⁻

Showing both delta and lambda enantiomers highlights how chirality can exist apart from tetrahedral carbon compounds, the latter of which, is the most common. --Rifleman 82 (talk) 15:23, 7 March 2013 (UTC)[reply]

(edit conflict) "Stereoisomers" not "conformations". But anyway, the whole point of this article is to discuss and illustrate the idea of chirality, and especially the differences among stereoisomers. Only having a picture of one possibility and then saying "and there's another" does not help anyone who does not already understand the key aspect of the difference or to illustrate the quick definition of the "other" symbol. But I also think File:Énantiomères octaèdriques.jpg might be too oversimplified, since it doesn't help if you don't really understand the molecules being represented. Maybe the [Fe(ox)₃]^3– 3D-balls images from Complex (chemistry)#Optical isomerism would be better here? DMacks (talk) 15:28, 7 March 2013 (UTC)[reply]

I do not object against any picture but JPEG, and any changes but destruction of typography fixes and wikification already made by me. Incnis Mrsi (talk) 15:56, 7 March 2013 (UTC)[reply]

We have indeed been moving away from JPEG to PNG or SVG images, but JPEG images should not be removed unless an equally good replacement is available. --Rifleman 82 (talk) 16:10, 7 March 2013 (UTC)[reply]

And agree with this statement too. A JPEG is better than nothing and better than an image that doesn't illustrate the appropriate/relevant content. File format is *not* the most important aspect of an article. DMacks (talk) 16:29, 7 March 2013 (UTC)[reply]

What could illustrate this downscaled heap of muck? Incompetence of the creator and low quality of contributions of the user who placed it here, IMHO. I do not think that this loathsome image could really help to understand the 3D structure of complexes even accurately remade in SVG but with exactly same graphical features. Incnis Mrsi (talk) 16:51, 7 March 2013 (UTC)[reply]

There are two equilateral triangles in this graphic (either enantiomer), and they mark the face formed by three vertexes of the octahedral metal complex. The round lines join two vertices together; they represent a chelating ligand. By seeing how the "propeller" rotates, you can assign delta or lambda symmetry to the compound. Some chemists prefer such a representation that omits the central metal atom, but I'm not a fan. --Rifleman 82 (talk) 17:09, 7 March 2013 (UTC)[reply]

Chiral molecules with different properties?

I'm curious as to if there are chemicals with different melting points, or such, when flipped. I mean it doesn't seem like there would be according to simple valance electron theory, but then again, He3/He4 are very different beasts when isolated (spin-related cause).

I'm curious as to if some trios of atoms have a preferred relative orientation. Think of particle physics and the layout of the brain where globally it seems they're reflections but locally they might not be. They turn out to only be good approximations.71.196.246.113 (talk) 19:21, 9 March 2013 (UTC)[reply]

In their pure forms and when not mixed with other chiral compounds, two enantiomers have the same melting point and such as each other because whatever their preferred relative orientation, it's a relative orientation. The mirror image would have the same relative orientation, just in the opposite direction. Diastereomers could be as different as any two unrelated compounds (except for same molecular weight) precisely because of different relative orientations. DMacks (talk) 20:55, 9 March 2013 (UTC)[reply]

I do not think that something like this is possible under typical circumstances because both electromagnetic and nuclear force are P-invariant. Though, it is perfectly possible under the same external influence which is not P-invariant. I can easily imagine two chiral isomers which have different properties if irradiated by the same circularly-polarized light. Or, say, under superposed electric and magnetic fields which are not perpendicular – parities of E and H fields are positive and negative respectively. Incnis Mrsi (talk) 21:09, 9 March 2013 (UTC)[reply]

Yes, I was thinking of the magnetic and spin properties. A neat (and lethal) thing is that H2 has biologically different effects than the H1 that is in most water molecules. For microbes, it slows them down to about half speed (twice as much energy needed to move the same number of hydrogen atoms?) but for animals... does a lot more than just slow us. Another thing that seems odd at first sight is that helium actually becomes toxic at high enough depths. I think it was related to neuron connections? I actually doubt too many if any molecules will have detectable differences in melting points but I'm willing to bet that muons or something will react differently. μ+SR and μ-SR (Muon/Mu Meson/Mu-Electron bombardment) is an interesting technology. Not everything can be done at places like the CERN LHC. We need smaller-hadron colliders, too! ;) Too bad there's no practical way to do Muon-chemistry in electronics. I could see a lot of potential applications. 71.196.246.113 (talk) 19:45, 10 March 2013 (UTC)[reply]

Deuterium is toxic because it has different chemistry, it's C-H bonds are slightly stronger than those of normal hydrogen and enzymes have a very hard time dealing with that (see Heavy water. I think helium toxicity (HPNS) is caused by it building up in the tissues to such a point that it becomes disruptive (similar to Nitrogen narcosis).Project Osprey (talk) 20:18, 10 March 2013 (UTC)[reply]

Lede

Tried to clean up the lede so it was clearer to the uninitiated. If the result is technically inaccurate, please help. Kortoso (talk) 23:16, 13 December 2013 (UTC)[reply]

"Most" amino acids are L

If the "rule" is supposed to be L amino and R sugar (in fact in many sources we see "all"), then what are the exceptions? Where do we encounter R aminos and L sugars? Archaea? Kortoso (talk) 23:24, 13 December 2013 (UTC)[reply]

How life turned left

An interesting discussion of how amino acids might have become (mostly?) homochiral. Also good examples of clear, simple language:

http://www.nasa.gov/topics/solarsystem/features/life-turned-left.html Kortoso (talk) 23:33, 13 December 2013 (UTC)[reply]

All life needs to be modified

This article Chirality_(chemistry) has it that "all life on Earth being homochiral". Perhaps that phrase should be modified a bit then to mark what is actually homochiral in "all life"? Amino acids, proteins and sugar , yes. Higher level structures of DNA, perhaps not so much. I suspect one could modify it to either "all amino acids , proteins and sugars" or perhaps "all primary level chirality of molecules" or something to that effect, but I am not qualified to make the change right now. Star Lord - 星王 (talk) 15:24, 28 March 2014 (UTC)[reply]

Higher level structures are just a composite/effect, not an independent nature. The helicity (screw-thread direction) of the double-strand of each form of DNA always has the same handedness, or at least different stabilities and biochemical interactions when both directions are possible (see Nucleic acid double helix#Helix geometries). This higher-level handedness is due to the atomic chirality details. Same with other macromolecular details, such as the direction of a protein alpha-helix (see Alpha helix#Geometry and hydrogen bonding). DMacks (talk) 16:11, 28 March 2014 (UTC)[reply]

le Prof's comments, moved from article

I am moving the extended comments from editor leProf and putting them here. The long list of tags is distracting. "Multiple issues:

inadequate lead
refimprove
page numbers needed

This is a central, critically important, highly in-referenced WP article, but it has become, at many places, a very weakly sourced hodgepodge of information unlike any authoritative source. Moreover, it has become poorly sectioned, and presents poorly paragraphed text. Because this has now gone on for some time, experts in organic, inorganic, and other chemical specialties are needed to take Eliel and other authoritative sources and decide on an organization, then remove trivial and unsourced/otherwise dubious content, and organize and fill in the rest with quality material in encyclopedic fashion (removing poor and partial sources as you go."

Agreed that the article needs help. One comment: in Wikipedia-Chem do not often cite page numbers for books. Doing so would be ideal, but we are dealing with reality not ideality. i.e., we are lucky to have Eliel cited, much less the page number. Let's just get good book sources as your suggest but pushing for pagination is too much.

One further comment, why dont you dig into the nomenclature section and fix it? You are probably better qualified than most of us, and you know what you want.--Smokefoot (talk) 15:42, 6 February 2016 (UTC)[reply]

This article is one of several articles defaced recently. Wikipedia provides a lot of tags and any child can add any number of tags to any page. These tags tend to stay on that page for a long time: interested readers are discouraged to continue reading and editors are reluctant to improve the page.

My concerns for this particular page:

Why is the expert needed: what inaccuracies do exist? Deal with them or explain yourself on the talk-page rather than just complain
With regard to the naming conventions: what is the irrelevant information? One purpose of Wikipedia is to actually explain a concept: I do not see any how-to content
Sources: why not find those sources that this page is consistent with and include them as a reference rather than just complain. It is really not a lot of work
Why complain about page-needed? Pointless dull labour, do the work yourself
Why introduce an empty section "Methods and practices". Do the work yourself, do not expect others to do the work for you
Do not expect a reference when a topic like enantiomeric excess is mentioned: this topic has a page of its own with references on that particular page
What is the deal with the "Further reading" section: do not patronise your fellow editors. They know what a library looks like. If you feel that the current Wikipedia page is consistent with any of these texts include them as a reference. V8rik (talk) 22:20, 6 February 2016 (UTC)[reply]

If we're seriously contemplating major changes to this page then I think we need to contemplate merging Enantiomer, Diastereomer and Stereocenter into this article. I know you're first thought is probably "No. Those pages are far too developed" but just take a moment and look at them; the amount of duplicated content between here and there is going to be huge. --Project Osprey (talk) 10:41, 7 February 2016 (UTC)[reply]

Exactly the wrong approach, the creation of huge ugly articles. Think of the 95% of those readers arriving on this page, what do they want to take away from it? Not enantiomers or stereogenic lone pairs! The specialised stuff should not belong on this general-interest page but on one of the specialised pages, there is no need for content duplication, a lot of the current content on this page could be scrapped because it already exists in the specialist pages for example naming conventions and Stereogenic centers. The section "Stereogenic lone pairs" could be handled by lone pair as well. Important pages do not need to be big pages V8rik (talk) 19:22, 7 February 2016 (UTC)[reply]

I often do not agree with V8rik on merging etc, but in this case, maybe he's on to something: that Chirality focus on what chirality is and that the fairly short article facilitate shunting readers to the the subtopics. The spirit of what Osprey is asking about is what are these other topics? We could possibly devise an ideal outline:

symmetry criteria; dissymmetic vs asym; decent in symmetry CH₄ → CH₃X → CH₂XY → CHXYZ?
history focused on Pasteur and Werner (organic is not central)
the 'cosmic' question about the origin of D-amino acids, etc
example gallery with comments: amino acids, thalidomide? quartz? [Ru(bipy)₃]²⁺, a helicene
Where would we guide readers to resolution, enantiomers & racemates & meso, ways to describe absolute configuration?

I have started some of these changes today, if you two think that these changes are a bad idea, then revert.

--Smokefoot (talk) 20:54, 7 February 2016 (UTC)[reply]

Not one of those two people already discussing here yet, but I support your offloading of the RS/DL/+– nomenclature details to Absolute configuration. That's a pretty specialized aspect that does need a bunch of space for the technical details, but is not critical to understanding the idea of chirality itself. DMacks (talk) 22:17, 7 February 2016 (UTC)[reply]

The more advice (or shoveling) the better. BTW, although LeProf can be annoying with his tagging, he did real content work on many articles recently (in addition to excessive tagging), so he is not all talk. --Smokefoot (talk) 22:25, 7 February 2016 (UTC)[reply]

Even after 10 years of editing the central issue of big articles vs dedicated articles has not been settled. Not good. I stay away from articles with excessive tagging so for this article you are on your own. On the other hand it is nice to be able to collaborate with people on an article or set of articles so I will help out where I can on some of the related articles V8rik (talk) 22:50, 8 February 2016 (UTC)[reply]

On mentioning handedness

Currently (and the article is seeing a lot of change at the moment) this article describes chirality solely in terms of molecular symmetry. I feel this is starting from a far too advanced point. Even undergrads struggle with such descriptions and they already know what chirality is. Standard practice is to begin with a description based on human hands and I feel strongly that we should have a brief paragraph on this - if only for the lay readers. --Project Osprey (talk) 22:33, 6 February 2016 (UTC)[reply]

I agree that we need to be careful, approachability is one of the real challenges. My feeling is that the elementary explanations should be near the lede but they should be couched in chemistry. The article is about chemistry, not about chirality in general. Hence my abrupt (apologies) removal of the discussion about hands. Further comments (without solutions):

The symmetry perspective is absolute and concise, can't beat that. It can seem rigid or opaque, and maybe we need to work on that angle. It might be worth finding a similar drawing of a chiral molecule to illustrate symmetry elements withing a dissymmetric molecule.
The area of chirality is packed with terminology (racemic, enantio..., dissy- vs asym.., ). The article needs a concise summary of these terms.
The area of chirality is also packed with ways of describing configuration. Hopefully LeProf will prove that he can write by tackling this aspect.

Overall, I hope that we hear from a lot of editors about how to tackle this tricky but core topic.--Smokefoot (talk) 04:02, 7 February 2016 (UTC)[reply]

Hmm...Well I'll hold of for now until other editors chime in (hopefully). I do agree that we're going to need more pictures though. This is a visual phenomenon after-all. --Project Osprey (talk) 10:52, 7 February 2016 (UTC)[reply]

Restoration of disambiguation note

I've restored the disambiguation note that was recently removed by user Smokefoot on the grounds that it "seems obscure". That is, the note that says: "L-form" redirects here. For the bacterial strains, see L-form bacteria.

Just in case this is controversial, here are my reasons.

It is plausible that a reader looking for information on L-form bacteria might type "L-form" into the URL. One of the functions of the redirect system is to facilitate that kind of shorthand.

Wikipedia better meets its objectives if readers can serendipitously discover new information, as they can in a print encyclopaedia. Disambiguation notes are a good way to facilitate this.

In my experience it is not common practise to remove disambiguation notes simply because the topic insufficiently well known.

(For the record, I have an account but choose not to use it. No need to reply to this parenthetical aside.)

14.2.35.204 (talk) 11:31, 18 March 2016 (UTC)[reply]

Moved from article

The following resources and comments for editors was placed within the article, but it is more appropriate here. -- Ed (Edgar181) 17:20, 16 May 2016 (UTC)[reply]

Further reading

The following are principle sources for the developing content in this article, that contain further information that may be of interest to readers. In the books listed, the material on chirality appears throughout, and so page numbers should be given for specific ideas and quotations drawn from them that are introduced above.

A high quality introductory to intermediate textbook of organic chemistry: Organic Chemistry (2nd ed.). Oxford, UK: Oxford University Press. 2012. pp. 319f, 432, 604np, 653, 746int, 803ketals, 839, 846f. ISBN 0199270295. Retrieved 2 February 2016. {{cite book}}: Unknown parameter |authors= ignored (help)
A seminal, authoritative work on modern organic stereochemistry: "Chirality in Molecules Devoid of Chiral Centers (Chapter 14)". Stereochemistry of Organic Compounds (1st ed.). New York, NY, USA: Wiley & Sons. 1994. ISBN 0471016705. Retrieved 2 February 2016. {{cite book}}: Unknown parameter |authors= ignored (help) For a further but less stable source of the same text that provides access to the relevant material, see Stereochemistry of Organic Compounds. ISBN 9780471016700., same access date.
An important brief expert comment on misuse of stereochemical terms: Eliel, E.L. (1997). "Infelicitous Stereochemical Nomenclatures". chirality. 9: 428–430. Retrieved 5 February 2016. Quoting: 'Misuse of current stereochemical terms is discussed, including terms that should be avoided altogether and replaced by other, standard ones. The reasons for using the proper terms and avoiding the infelicitous ones are pointed out.' For a further but less stable source of the same text that provides access to the relevant material, see [1], same access date.
A recent review providing definitions, examples, and history: Gal, Joseph (2013). "Molecular Chirality: Language, History, and Significance". Differentiation of Enantiomers I. Topics in Current Chemistry. Vol. 340. pp. 1–20. Retrieved 5 February 2016. {{cite book}}: |journal= ignored (help)

Moved from article

I'm moving the following comment for editors which was placed in the "Methods and practices" section to here. -- Ed (Edgar181) 17:23, 16 May 2016 (UTC)[reply]

One or more sections, again with reference to Eliel, describing the methods and tools used in determining structure, generally, and then determining chiroptical properties, and absolute and relative configuration, and methods and tools for characterizing and quantifying enantiomers and diastereomers in mixtures, for resolution and racemization, for studying topicity and prochirality with special emphasis on NMR), and for stereoselective synthesis (stub referencing main article).

Achiral/needs better definition

Achiral redirects to this article as a whole, e.g. from xylitol, but the only definition is an example embedded in a table under Definition. The latter is so terse and the language so technical that even I, as a BSc in Chemistry, have trouble following it. Either achiral should have its own stub, or the definition of chiral needs to be clarified and include achiral, and redirects on achiral should link to the Definition section.

As so many compounds, especially biologically active compounds and drugs, are chiral, the article is likely to be read by those unfamiliar with current technical language and stereoisomer diagrams, and needs clarification. WP is a general cyclodaedia, not an advanced chemistry dictionary.
I also tend to agree with the usage 'asymmetric'. 'Dissymetric' may be technically correct, but is controversial^[1] and unfamiliar to many. D Anthony Patriarche (talk) 23:27, 23 September 2017 (UTC)[reply]

I also agree. This article as written is nothing but confusing, and then jargon. So it is absolutely worthless. Definitions are just flat-out wrong, starting with the "mirror image" statement. Needs a complete re-write. 98.194.39.86 (talk) 13:32, 4 August 2018 (UTC)[reply]

References

^ "Do "asymmetric" and "dissymmetric" have different meaning?". English Language & Usage Stack Exchange. Retrieved 23 September 2017.

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Chiral molecule used as example is not chiral

The allene used as example as chiral molecule with a C₂ axis in "Molecular symmetry and chirality" table (section: Definition) is not chiral, as it contains an S₄ axis. --MarcoCappelletti (talk) 10:26, 13 August 2019 (UTC)[reply]

Attempted S₄ operation for ABCCCAB, which is axially chiral.

It's got axial chirality.--Smokefoot (talk) 11:04, 13 August 2019 (UTC)[reply]

Agree with --MarcoCappelletti , this molecule contain S₄ symmetry (n-fold rotation followed by reflection in plane perpendicular to axis) and is thus not chiral. Axel Fredrik (talk) 18:59, 13 August 2019 (UTC)[reply]

@Dirac66: @DMacks: Allene derivatives of the type RR'C=C=CRR' have axial chirality. They lack an S_n axis. That point is what I tried to demonstrate with the drawing above where S₄ does not generate the same structure, it generates an enantiomer. Visualization of the effect is tricky, and for that reason often discussed. Maybe I am incorrect, but then so is allene and the corresponding German article.--Smokefoot (talk) 19:07, 13 August 2019 (UTC)[reply]

It is called axial chirality. Chirality of allene derivatives was investigated (theoretically) by J. H. van 't Hoff in 1875. The main chemical thing about allene are its π-bonds – they bind atoms rigidly and the molecule lacks a usual conformational freedom characteristic for ⋯C–C–C⋯ chains. One can deem the molecule a rigid body for the purposes of symmetry. Allene’s symmetry group is [2,2]⁺, a subgroup of the regular tetrahedron’s group consisting of identity and three 180° rotations. If even a tetrahedron having all four vertices distinguished is chiral, then a rigid >C=C=C·· thing more certainly is so. Incnis Mrsi (talk) 20:05, 13 August 2019 (UTC)[reply]

I agree with Smokefoot that the molecule drawn above is chiral and does not have an S₄ axis. However this diagram would be clearer if A' and B' were written as A and B, which would eliminate the need for the parenthetical comment "(ignoring A vs A' etc.)".

As for the diagram in the Definition section of the article, the drawing of the relevant molecule (row C₂, column chiral) also needs improvement. Specifically, the C₂ axis should not be in the plane of the article (i.e. of the computer screen) but rather at 45° to the screen. Or else the C₂ axis can be left alone and the four substituents rotated 45° about the C=C=C axis.

Since I lack the software to redraw the diagrams, I will have to leave these suggestions for someone else. Dirac66 (talk) 00:05, 14 August 2019 (UTC)[reply]

Indeed, allenes of type (A)(B)C=C=C(X)(Y) are chiral (where A≠B and X≠Y). I added a cite to Allene#Symmetry for the first theoretical (by van 't Hof) and experimental (for 1,3-dinaphthyl-1,3-diphenylallene) reports of it. DMacks (talk) 05:52, 16 August 2019 (UTC)[reply]

"Different groups" versus "Distinct atoms"

@Christian75: In the section "Stereogenic centers", I had written

Many chiral molecules have point chirality, namely a single stereogenic center that coincides with an atom. This atom usually has four or more bonds to distinct atoms

It was changed to

Many chiral molecules have point chirality, namely a single stereogenic center that coincides with an atom. This atom usually has four or more bonds to different groups

This passage is not precise anyway; it is a "usually" sort of claim. The point of saying "distinct atoms" was to exclude multiple bonds to the same atom, as in acetylene. On the other hand, "different groups" is not precise either, because a carbon in a pyranose ring (say) is connected to only three groups (one of them divalent).
I wish this paragraph could be made more precise, but I don't see how to do that without making it inaccessible to the general reader. Suggestions? --Jorge Stolfi (talk) 23:32, 1 February 2020 (UTC)[reply]

Stereogenic centers x stereogenic atoms

@Christian75:The article now says

While the presence of a stereogenic atom describes the great majority of chiral molecules, many variations and exceptions exist. For instance it is not necessary for the chiral substance to have a stereogenic atom.

The definition of "stereogenic center" (whose article sorely needs cleanup, by the way) says that a stereogenic center need not be an atom. While the presence of a stereogenic atom is not necessary, a stereogenic center is, no? If so, this article should say so.
... Or is the concept of "stereogenic center" a bogus one? Achirality requires a reflection across a plane that leaves the molecule unchanged apart from a rotation. If the rotation can be null, that plane is a (proper) "symmetry plane"; if it must be not null, the point where the axis cuts the plane is a (generalized) "symmetry center", and any plane through it has the same property. Thus that plane or point can be considered the "source" (more appropriately, the "witness") of the achirality. But chirality means only the absence of such a symmetry plane or center. It does not make sense to say that the absence of such a thing is located in a particular place; does it?
Moreover, in all the examples given next, some stereogenic atoms do seem to exist. In FClBr-adamantane, for example, the carbon connected to F has three other bonds that are not equivalent, because each leads in two C-C steps to a carbon with a different substituent. So the vertex carbons are all stereogenic atoms, no?
All the best, --Jorge Stolfi (talk) 00:09, 2 February 2020 (UTC)[reply]

@Jorge Stolfi: Good point. I have rewritten that sentence and modified the next two. Eric Kvaalen (talk) 12:33, 11 May 2021 (UTC)[reply]

Chiral ethane

The article notes that asymmetrically-substituted amines NRR′R″ are not considered chiral, even though the three bonds are not planar, because of the low interconversion barrier between the two enantiomers. Maybe it should note also that the same can be said of ethane in a state that is neither staggered nor eclipsed: such states are chiral, but they are not considered in chemistry because (I suppose) they are on the slope of an energy valley, with the enantiomer on the other side. Right?
However, it seems possible that some phase of solid ethane has all or some molecules in such a chiral configuration, in racemic ratio or not. If not ethane, there surely must be compounds with this property (dynamically achiral in liquid or gas, chiral in solid). No?
--Jorge Stolfi (talk) 00:22, 2 February 2020 (UTC)[reply]

I don't think rotamers are normally considered chiral, except in the case of atropisomers. --Project Osprey (talk) 00:58, 30 January 2021 (UTC)[reply]

@Jorge Stolfi: Yes, I think it could happen that crystals of a nominally achiral molecule be chiral. I have added a little paragraph about that possibility. In that case, one would usually get a mixture of right-handed and left-handed crystals, but (as noted in the article Chiral resolution) one could get just one kind by seeding the liquid with small crystals of the desired chirality. Eric Kvaalen (talk) 12:33, 11 May 2021 (UTC)[reply]

NRR'R" are certainly chiral in my book but I am a coordination chemist and must deal with the fact that once coordinated, the inversion is often frozen. A recurring case is for secondary amines (RR'NH) like triethylenetetramine.

Perhaps related to Jorge's other comment, sodium chlorate crystallizes in a chiral habit. When saturated solutions are stirred and concentrated, typically only one enantiomer precipitates, although which one appears is random. See "Chiral Symmetry Breaking in Sodium Chlorate Crystallizaton" Dilip K. Kondepudi1, Rebecca J. Kaufman1, Nolini Singh, Science 16 Nov 1990, Vol. 250, Issue 4983, pp. 975-976 DOI: 10.1126/science.250.4983.975. BTW our Symmetry breaking article needs help.--Smokefoot (talk) 14:43, 11 May 2021 (UTC)[reply]

@Smokefoot: Interestin'. An even better-known example is sillicon dioxide, which forms chiral quartz. Eric Kvaalen (talk) 08:04, 15 May 2021 (UTC)[reply]

Nomenclature (R/S, L/D)

A Nomenclature section is missing in this article. It should deal with "R/S" and "L/D" symbols.

In S (disambiguation)#Physics and chemistry there is "S, a label that denotes one of two chiral center configurations in the R/S system pointing to "Chirality_(chemistry)#By_configuration:_R-_and_S-" but there is no such section.

And it's very strange, because a can see talks about them, in this page.--Meridiana solare (talk) 00:14, 26 January 2021 (UTC)[reply]

I added a mention about nomenclature, with link to absolute configuration. That article talks about R/S and other systems. DMacks (talk) 00:37, 26 January 2021 (UTC)[reply]

Thank you. But I dare that it's and hard way to follow for users coming from those disambiguating pages: they will look for "R" or "S" or for "L" or "D", not to "absolute configuration", which may be meaningless to them. --Meridiana solare (talk) 18:39, 29 January 2021 (UTC)[reply]

Good point! Updated. DMacks (talk) 18:44, 29 January 2021 (UTC)[reply]

So I think it may be better to point from R (disambiguation), S (disambiguation), L (disambiguation) and D (disambiguation) directly stright to a propoer article. Should absolute configuration be right for all 4 of them? Or Stereocenter?

At rhem moment they point to "chirality (chemistry)#By configuration: R- and S-" , which I suppose that is a no more existing section.--Meridiana solare (talk) 11:48, 31 January 2021 (UTC)[reply]

Are inherent, axial, and planar chirality well defined?

Are the terms "axial chirality", "stereogenic axis", helical chirality, "planar chirality", "stereogenic plane", and "inherent chirality" well defined, or are they loose terms defined only by approximate descriptions and examples? For example, trans-cyclooctene is described here as "commonly cited example of a planar chiral molecule" but it doesn't fit the definition at planar chirality, since it lacks two non-coplanar rings (and what counts as a "ring"?); the cyclooctene article mentions chirality but not planar chirality. On the other hand, BINAP meets the definition for planar chirality but is offered as typical example of axial chirality. The WP articles and sources I have are all vague about these terms when examined closely. "Stereogenic center" and "central chirality" are clear enough, but we should be precise about the other terms somewhere, or mention that they are only loosely defined. –MadeOfAtoms (talk) 01:03, 17 July 2022 (UTC)[reply]

Perhaps regrettably, they are not included in this article itself, and I think they should be. If you have the time please include them. Although I work in asymmetric catalysis, stereochemical terminology is something I am reluctant to edit, because it it notoriously easy to give an incorrect definition. For example, the definition of planar chirality in the planar chirality article is wrong -- there only needs to be one reference plane with a left and right side that are "different" and a part of the molecule that is forced to sit above or below that plane. In the case of trans-cyclooctene, that plane is the plane of the alkene. The Greg Fu type ferrocene derivatives are the most famous examples, but, as trans-cyclooctene shows, they are not the only type of planar chiral molecule. The definition given by Eliel (p. 1121 to 1122) is quite elaborate and difficult to explain. The glossary of Eliel merely defines planar chirality as "chirality resulting from the arrangement of out-of-plane groups with respect to a reference plane." Gawley and Aube is another rigorous resource containing definitions in a glossary. There is a definition of stereogenic plane, but the full definition is also somewhat involved.

I think the articles themselves should definitely have a correct and full definition (from either Gawley and Aube's Principles of Asymmetric Synthesis or Eliel's Stereochemistry of Organic Compounds). However, the degree of rigor that this article should adhere to for these tough definitions is, in my opinion, a topic of debate. If you can give a concise and reasonably rigorous definition, please do so!! Alsosaid1987 (talk) 01:36, 17 July 2022 (UTC)[reply]

When there is a IUPAC Gold Book definition, we should certainly ensure our articles are in line with it. Of the terms mentioned by MadeOfAtoms, I can find only axial chirality, planar chirality and the related stereogenic unit. This suggest to me that the other expressions are more likely to be loosely defined and need further explanation with sources like Eliel or March's Advanced Organic Chemistry (my 4th edition from 1992 has its chapter 4, pages 94–164 devoted to the stereochemistry). Mike Turnbull (talk) 14:15, 17 July 2022 (UTC)[reply]

Thanks Alsosaid1987 and Mike Turnbull for your perspectives and references. The IUPAC definitions are clearer than I realized, now that you mention that Planar chirality § In chemistry is wrong. That article really threw me for a loop. Axial chirality first line also appears vague ~~and wrong~~. Axial chirality and Inherent chirality both claim helical chirality as their own. Thankfully IUPAC's "helicity" is clear enough. Precise rules would be great if they are widely used and accepted, but I mainly want to give at least brief useful definitions here in this article. I have only Mislow, and Clark et al (both "Intro to Stereochemisty") which aren't helping. I'll try to improve the situation and hope you'll be picky about my edits. –MadeOfAtoms (talk) 00:33, 18 July 2022 (UTC)[reply]

Adamantanes

@Halfinjest: I noticed your recent edit to the article. You took out a diagram but left in the text which refers to it, hence leaving readers puzzled. Please could you fix that? The wording does indeed need changing as the example adamantane shown has several stereogenic units: four by my count, one at each tertiary carbon apex. User:Alsosaid1987 may like to chip in as they added the diagram, I think. Mike Turnbull (talk) 10:55, 26 June 2024 (UTC)[reply]

Thank you, @Michael D. Turnbull:. I removed the text.

[1] "Do "asymmetric" and "dissymmetric" have different meaning?". English Language & Usage Stack Exchange. Retrieved 23 September 2017.

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