Talk:Chirality (chemistry)

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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.

Contents

[edit] Why

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

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

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)

[edit] Merge?

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

I think so, I will add the proposed merge template to both pages. --Aaronsharpe 11:12, 22 June 2007 (UTC)
  • this merge proposal is not valid, you cannot have merge discussions lasting 1.5 years. tag removed V8rik 19:39, 22 June 2007 (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)

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)

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)

[edit] 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)

[edit] 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)

[edit] 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)

"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)

[edit] 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)

[edit] 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)

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)

[edit] 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)

[edit] 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)

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)

[edit] 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).


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!

[edit] 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

[edit] 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)

[edit] 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)

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)

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)
  • Made a switch back V8rik 17:31, 9 November 2007 (UTC)

[edit] 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)

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)

[edit] 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

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