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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.
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.
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)
No mention of what explanations are being hypthesised for the right-handedness of biology. Two I know of are
Pmurray bigpond.com 06:03, 12 September 2005 (UTC)
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)
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)
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)
Would it make sense to merge material from Enantiomer? -- Tabor 18:22, 18 October 2005 (UTC)
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)
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)
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)
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)
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)
"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)
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) .
The article says:
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)
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)
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)
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).
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)
You are right. Sorry about that!
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
A para in the article says:
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)
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)
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)
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)
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)
"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)
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)
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)
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
From the article:
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)
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 Cs-symmetric. So the analogy to hands is flawed. We are however prochiral. Am I missing something?-- Smokefoot ( talk) 16:16, 20 December 2008 (UTC)
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)
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)
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)
Should the chirality of phosphorus (as in sarin) be included? Whoop whoop pull up Bitching Betty | Averted crashes 21:45, 3 August 2011 (UTC)
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)
Do all sugars have chirality? Or is it only for monosaccharides? 173.17.169.171 ( talk) 08:28, 6 March 2012 (UTC)
Dear Editors,
The article currently states the following in the RS section of the Naming conventions:
This disagrees with the standard definition (see, e.g., Voet and Voet).
A suggested correction follows:
Thank you
Mewalloffice ( talk) 19:10, 17 April 2012 (UTC)
User:Rifleman 82 disagrees with my edit, but I do not understand why there should be pictures of both Δ and Λ conformationsisomers. Indeed, if it should, then which design is preferable?
Incnis Mrsi (
talk)
15:13, 7 March 2013 (UTC)
Why don't you use the following:
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)
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)
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)
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)
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)
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)
An interesting discussion of how amino acids might have become (mostly?) homochiral. Also good examples of clear, simple language:
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)
I am moving the extended comments from editor leProf and putting them here. The long list of tags is distracting. "Multiple issues:
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."
My concerns for this particular page:
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)
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)
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.
(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)
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)
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.
{{
cite book}}
: Cite uses deprecated parameter |authors=
(
help){{
cite book}}
: Cite uses deprecated parameter |authors=
(
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.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.
{{
cite book}}
: |journal=
ignored (
help)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)
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 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.
References
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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)
It's got axial chirality.-- Smokefoot ( talk) 11:04, 13 August 2019 (UTC)
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)
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)
@ Christian75: In the section "Stereogenic centers", I had written
It was changed to
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)
@ Christian75:The article now says
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)
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)
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)
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)
@ 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)
Thank you, @ Michael D. Turnbull:. I removed the text.
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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.
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.
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)
No mention of what explanations are being hypthesised for the right-handedness of biology. Two I know of are
Pmurray bigpond.com 06:03, 12 September 2005 (UTC)
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)
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)
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)
Would it make sense to merge material from Enantiomer? -- Tabor 18:22, 18 October 2005 (UTC)
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)
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)
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)
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)
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)
"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)
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) .
The article says:
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)
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)
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)
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).
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)
You are right. Sorry about that!
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
A para in the article says:
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)
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)
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)
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)
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)
"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)
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)
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)
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
From the article:
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)
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 Cs-symmetric. So the analogy to hands is flawed. We are however prochiral. Am I missing something?-- Smokefoot ( talk) 16:16, 20 December 2008 (UTC)
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)
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)
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)
Should the chirality of phosphorus (as in sarin) be included? Whoop whoop pull up Bitching Betty | Averted crashes 21:45, 3 August 2011 (UTC)
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)
Do all sugars have chirality? Or is it only for monosaccharides? 173.17.169.171 ( talk) 08:28, 6 March 2012 (UTC)
Dear Editors,
The article currently states the following in the RS section of the Naming conventions:
This disagrees with the standard definition (see, e.g., Voet and Voet).
A suggested correction follows:
Thank you
Mewalloffice ( talk) 19:10, 17 April 2012 (UTC)
User:Rifleman 82 disagrees with my edit, but I do not understand why there should be pictures of both Δ and Λ conformationsisomers. Indeed, if it should, then which design is preferable?
Incnis Mrsi (
talk)
15:13, 7 March 2013 (UTC)
Why don't you use the following:
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)
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)
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)
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)
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)
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)
An interesting discussion of how amino acids might have become (mostly?) homochiral. Also good examples of clear, simple language:
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)
I am moving the extended comments from editor leProf and putting them here. The long list of tags is distracting. "Multiple issues:
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."
My concerns for this particular page:
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)
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)
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.
(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)
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)
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.
{{
cite book}}
: Cite uses deprecated parameter |authors=
(
help){{
cite book}}
: Cite uses deprecated parameter |authors=
(
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.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.
{{
cite book}}
: |journal=
ignored (
help)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)
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 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.
References
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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)
It's got axial chirality.-- Smokefoot ( talk) 11:04, 13 August 2019 (UTC)
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)
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)
@ Christian75: In the section "Stereogenic centers", I had written
It was changed to
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)
@ Christian75:The article now says
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)
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)
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)
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)
@ 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)
Thank you, @ Michael D. Turnbull:. I removed the text.